Add pysh, ply, and codegen to lib/ to prepare for future work

Signed-off-by: Chris Larson <chris_larson@mentor.com>

13 files changed, 9046 insertions, 0 deletions

diff --git a/lib/codegen.py b/lib/codegen.py
new file mode 100644
index 000000000..be772d510
--- /dev/null
+++ b/lib/codegen.py
@@ -0,0 +1,570 @@
+# -*- coding: utf-8 -*-
+"""
+    codegen
+    ~~~~~~~
+
+    Extension to ast that allow ast -> python code generation.
+
+    :copyright: Copyright 2008 by Armin Ronacher.
+    :license: BSD.
+"""
+from ast import *
+
+BOOLOP_SYMBOLS = {
+    And:        'and',
+    Or:         'or'
+}
+
+BINOP_SYMBOLS = {
+    Add:        '+',
+    Sub:        '-',
+    Mult:       '*',
+    Div:        '/',
+    FloorDiv:   '//',
+    Mod:        '%',
+    LShift:     '<<',
+    RShift:     '>>',
+    BitOr:      '|',
+    BitAnd:     '&',
+    BitXor:     '^'
+}
+
+CMPOP_SYMBOLS = {
+    Eq:         '==',
+    Gt:         '>',
+    GtE:        '>=',
+    In:         'in',
+    Is:         'is',
+    IsNot:      'is not',
+    Lt:         '<',
+    LtE:        '<=',
+    NotEq:      '!=',
+    NotIn:      'not in'
+}
+
+UNARYOP_SYMBOLS = {
+    Invert:     '~',
+    Not:        'not',
+    UAdd:       '+',
+    USub:       '-'
+}
+
+ALL_SYMBOLS = {}
+ALL_SYMBOLS.update(BOOLOP_SYMBOLS)
+ALL_SYMBOLS.update(BINOP_SYMBOLS)
+ALL_SYMBOLS.update(CMPOP_SYMBOLS)
+ALL_SYMBOLS.update(UNARYOP_SYMBOLS)
+
+def to_source(node, indent_with=' ' * 4, add_line_information=False):
+    """This function can convert a node tree back into python sourcecode.
+    This is useful for debugging purposes, especially if you're dealing with
+    custom asts not generated by python itself.
+
+    It could be that the sourcecode is evaluable when the AST itself is not
+    compilable / evaluable.  The reason for this is that the AST contains some
+    more data than regular sourcecode does, which is dropped during
+    conversion.
+
+    Each level of indentation is replaced with `indent_with`.  Per default this
+    parameter is equal to four spaces as suggested by PEP 8, but it might be
+    adjusted to match the application's styleguide.
+
+    If `add_line_information` is set to `True` comments for the line numbers
+    of the nodes are added to the output.  This can be used to spot wrong line
+    number information of statement nodes.
+    """
+    generator = SourceGenerator(indent_with, add_line_information)
+    generator.visit(node)
+    return ''.join(generator.result)
+
+
+class SourceGenerator(NodeVisitor):
+    """This visitor is able to transform a well formed syntax tree into python
+    sourcecode.  For more details have a look at the docstring of the
+    `node_to_source` function.
+    """
+
+    def __init__(self, indent_with, add_line_information=False):
+        self.result = []
+        self.indent_with = indent_with
+        self.add_line_information = add_line_information
+        self.indentation = 0
+        self.new_lines = 0
+
+    def write(self, x):
+        if self.new_lines:
+            if self.result:
+                self.result.append('\n' * self.new_lines)
+            self.result.append(self.indent_with * self.indentation)
+            self.new_lines = 0
+        self.result.append(x)
+
+    def newline(self, node=None, extra=0):
+        self.new_lines = max(self.new_lines, 1 + extra)
+        if node is not None and self.add_line_information:
+            self.write('# line: %s' % node.lineno)
+            self.new_lines = 1
+
+    def body(self, statements):
+        self.new_line = True
+        self.indentation += 1
+        for stmt in statements:
+            self.visit(stmt)
+        self.indentation -= 1
+
+    def body_or_else(self, node):
+        self.body(node.body)
+        if node.orelse:
+            self.newline()
+            self.write('else:')
+            self.body(node.orelse)
+
+    def signature(self, node):
+        want_comma = []
+        def write_comma():
+            if want_comma:
+                self.write(', ')
+            else:
+                want_comma.append(True)
+
+        padding = [None] * (len(node.args) - len(node.defaults))
+        for arg, default in zip(node.args, padding + node.defaults):
+            write_comma()
+            self.visit(arg)
+            if default is not None:
+                self.write('=')
+                self.visit(default)
+        if node.vararg is not None:
+            write_comma()
+            self.write('*' + node.vararg)
+        if node.kwarg is not None:
+            write_comma()
+            self.write('**' + node.kwarg)
+
+    def decorators(self, node):
+        for decorator in node.decorator_list:
+            self.newline(decorator)
+            self.write('@')
+            self.visit(decorator)
+
+    # Statements
+
+    def visit_Assign(self, node):
+        self.newline(node)
+        for idx, target in enumerate(node.targets):
+            if idx:
+                self.write(', ')
+            self.visit(target)
+        self.write(' = ')
+        self.visit(node.value)
+
+    def visit_AugAssign(self, node):
+        self.newline(node)
+        self.visit(node.target)
+        self.write(BINOP_SYMBOLS[type(node.op)] + '=')
+        self.visit(node.value)
+
+    def visit_ImportFrom(self, node):
+        self.newline(node)
+        self.write('from %s%s import ' % ('.' * node.level, node.module))
+        for idx, item in enumerate(node.names):
+            if idx:
+                self.write(', ')
+            self.write(item)
+
+    def visit_Import(self, node):
+        self.newline(node)
+        for item in node.names:
+            self.write('import ')
+            self.visit(item)
+
+    def visit_Expr(self, node):
+        self.newline(node)
+        self.generic_visit(node)
+
+    def visit_FunctionDef(self, node):
+        self.newline(extra=1)
+        self.decorators(node)
+        self.newline(node)
+        self.write('def %s(' % node.name)
+        self.signature(node.args)
+        self.write('):')
+        self.body(node.body)
+
+    def visit_ClassDef(self, node):
+        have_args = []
+        def paren_or_comma():
+            if have_args:
+                self.write(', ')
+            else:
+                have_args.append(True)
+                self.write('(')
+
+        self.newline(extra=2)
+        self.decorators(node)
+        self.newline(node)
+        self.write('class %s' % node.name)
+        for base in node.bases:
+            paren_or_comma()
+            self.visit(base)
+        # XXX: the if here is used to keep this module compatible
+        #      with python 2.6.
+        if hasattr(node, 'keywords'):
+            for keyword in node.keywords:
+                paren_or_comma()
+                self.write(keyword.arg + '=')
+                self.visit(keyword.value)
+            if node.starargs is not None:
+                paren_or_comma()
+                self.write('*')
+                self.visit(node.starargs)
+            if node.kwargs is not None:
+                paren_or_comma()
+                self.write('**')
+                self.visit(node.kwargs)
+        self.write(have_args and '):' or ':')
+        self.body(node.body)
+
+    def visit_If(self, node):
+        self.newline(node)
+        self.write('if ')
+        self.visit(node.test)
+        self.write(':')
+        self.body(node.body)
+        while True:
+            else_ = node.orelse
+            if len(else_) == 1 and isinstance(else_[0], If):
+                node = else_[0]
+                self.newline()
+                self.write('elif ')
+                self.visit(node.test)
+                self.write(':')
+                self.body(node.body)
+            else:
+                self.newline()
+                self.write('else:')
+                self.body(else_)
+                break
+
+    def visit_For(self, node):
+        self.newline(node)
+        self.write('for ')
+        self.visit(node.target)
+        self.write(' in ')
+        self.visit(node.iter)
+        self.write(':')
+        self.body_or_else(node)
+
+    def visit_While(self, node):
+        self.newline(node)
+        self.write('while ')
+        self.visit(node.test)
+        self.write(':')
+        self.body_or_else(node)
+
+    def visit_With(self, node):
+        self.newline(node)
+        self.write('with ')
+        self.visit(node.context_expr)
+        if node.optional_vars is not None:
+            self.write(' as ')
+            self.visit(node.optional_vars)
+        self.write(':')
+        self.body(node.body)
+
+    def visit_Pass(self, node):
+        self.newline(node)
+        self.write('pass')
+
+    def visit_Print(self, node):
+        # XXX: python 2.6 only
+        self.newline(node)
+        self.write('print ')
+        want_comma = False
+        if node.dest is not None:
+            self.write(' >> ')
+            self.visit(node.dest)
+            want_comma = True
+        for value in node.values:
+            if want_comma:
+                self.write(', ')
+            self.visit(value)
+            want_comma = True
+        if not node.nl:
+            self.write(',')
+
+    def visit_Delete(self, node):
+        self.newline(node)
+        self.write('del ')
+        for idx, target in enumerate(node):
+            if idx:
+                self.write(', ')
+            self.visit(target)
+
+    def visit_TryExcept(self, node):
+        self.newline(node)
+        self.write('try:')
+        self.body(node.body)
+        for handler in node.handlers:
+            self.visit(handler)
+
+    def visit_TryFinally(self, node):
+        self.newline(node)
+        self.write('try:')
+        self.body(node.body)
+        self.newline(node)
+        self.write('finally:')
+        self.body(node.finalbody)
+
+    def visit_Global(self, node):
+        self.newline(node)
+        self.write('global ' + ', '.join(node.names))
+
+    def visit_Nonlocal(self, node):
+        self.newline(node)
+        self.write('nonlocal ' + ', '.join(node.names))
+
+    def visit_Return(self, node):
+        self.newline(node)
+        self.write('return ')
+        self.visit(node.value)
+
+    def visit_Break(self, node):
+        self.newline(node)
+        self.write('break')
+
+    def visit_Continue(self, node):
+        self.newline(node)
+        self.write('continue')
+
+    def visit_Raise(self, node):
+        # XXX: Python 2.6 / 3.0 compatibility
+        self.newline(node)
+        self.write('raise')
+        if hasattr(node, 'exc') and node.exc is not None:
+            self.write(' ')
+            self.visit(node.exc)
+            if node.cause is not None:
+                self.write(' from ')
+                self.visit(node.cause)
+        elif hasattr(node, 'type') and node.type is not None:
+            self.visit(node.type)
+            if node.inst is not None:
+                self.write(', ')
+                self.visit(node.inst)
+            if node.tback is not None:
+                self.write(', ')
+                self.visit(node.tback)
+
+    # Expressions
+
+    def visit_Attribute(self, node):
+        self.visit(node.value)
+        self.write('.' + node.attr)
+
+    def visit_Call(self, node):
+        want_comma = []
+        def write_comma():
+            if want_comma:
+                self.write(', ')
+            else:
+                want_comma.append(True)
+
+        self.visit(node.func)
+        self.write('(')
+        for arg in node.args:
+            write_comma()
+            self.visit(arg)
+        for keyword in node.keywords:
+            write_comma()
+            self.write(keyword.arg + '=')
+            self.visit(keyword.value)
+        if node.starargs is not None:
+            write_comma()
+            self.write('*')
+            self.visit(node.starargs)
+        if node.kwargs is not None:
+            write_comma()
+            self.write('**')
+            self.visit(node.kwargs)
+        self.write(')')
+
+    def visit_Name(self, node):
+        self.write(node.id)
+
+    def visit_Str(self, node):
+        self.write(repr(node.s))
+
+    def visit_Bytes(self, node):
+        self.write(repr(node.s))
+
+    def visit_Num(self, node):
+        self.write(repr(node.n))
+
+    def visit_Tuple(self, node):
+        self.write('(')
+        idx = -1
+        for idx, item in enumerate(node.elts):
+            if idx:
+                self.write(', ')
+            self.visit(item)
+        self.write(idx and ')' or ',)')
+
+    def sequence_visit(left, right):
+        def visit(self, node):
+            self.write(left)
+            for idx, item in enumerate(node.elts):
+                if idx:
+                    self.write(', ')
+                self.visit(item)
+            self.write(right)
+        return visit
+
+    visit_List = sequence_visit('[', ']')
+    visit_Set = sequence_visit('{', '}')
+    del sequence_visit
+
+    def visit_Dict(self, node):
+        self.write('{')
+        for idx, (key, value) in enumerate(zip(node.keys, node.values)):
+            if idx:
+                self.write(', ')
+            self.visit(key)
+            self.write(': ')
+            self.visit(value)
+        self.write('}')
+
+    def visit_BinOp(self, node):
+        self.visit(node.left)
+        self.write(' %s ' % BINOP_SYMBOLS[type(node.op)])
+        self.visit(node.right)
+
+    def visit_BoolOp(self, node):
+        self.write('(')
+        for idx, value in enumerate(node.values):
+            if idx:
+                self.write(' %s ' % BOOLOP_SYMBOLS[type(node.op)])
+            self.visit(value)
+        self.write(')')
+
+    def visit_Compare(self, node):
+        self.write('(')
+        self.write(node.left)
+        for op, right in zip(node.ops, node.comparators):
+            self.write(' %s %%' % CMPOP_SYMBOLS[type(op)])
+            self.visit(right)
+        self.write(')')
+
+    def visit_UnaryOp(self, node):
+        self.write('(')
+        op = UNARYOP_SYMBOLS[type(node.op)]
+        self.write(op)
+        if op == 'not':
+            self.write(' ')
+        self.visit(node.operand)
+        self.write(')')
+
+    def visit_Subscript(self, node):
+        self.visit(node.value)
+        self.write('[')
+        self.visit(node.slice)
+        self.write(']')
+
+    def visit_Slice(self, node):
+        if node.lower is not None:
+            self.visit(node.lower)
+        self.write(':')
+        if node.upper is not None:
+            self.visit(node.upper)
+        if node.step is not None:
+            self.write(':')
+            if not (isinstance(node.step, Name) and node.step.id == 'None'):
+                self.visit(node.step)
+
+    def visit_ExtSlice(self, node):
+        for idx, item in node.dims:
+            if idx:
+                self.write(', ')
+            self.visit(item)
+
+    def visit_Yield(self, node):
+        self.write('yield ')
+        self.visit(node.value)
+
+    def visit_Lambda(self, node):
+        self.write('lambda ')
+        self.signature(node.args)
+        self.write(': ')
+        self.visit(node.body)
+
+    def visit_Ellipsis(self, node):
+        self.write('Ellipsis')
+
+    def generator_visit(left, right):
+        def visit(self, node):
+            self.write(left)
+            self.visit(node.elt)
+            for comprehension in node.generators:
+                self.visit(comprehension)
+            self.write(right)
+        return visit
+
+    visit_ListComp = generator_visit('[', ']')
+    visit_GeneratorExp = generator_visit('(', ')')
+    visit_SetComp = generator_visit('{', '}')
+    del generator_visit
+
+    def visit_DictComp(self, node):
+        self.write('{')
+        self.visit(node.key)
+        self.write(': ')
+        self.visit(node.value)
+        for comprehension in node.generators:
+            self.visit(comprehension)
+        self.write('}')
+
+    def visit_IfExp(self, node):
+        self.visit(node.body)
+        self.write(' if ')
+        self.visit(node.test)
+        self.write(' else ')
+        self.visit(node.orelse)
+
+    def visit_Starred(self, node):
+        self.write('*')
+        self.visit(node.value)
+
+    def visit_Repr(self, node):
+        # XXX: python 2.6 only
+        self.write('`')
+        self.visit(node.value)
+        self.write('`')
+
+    # Helper Nodes
+
+    def visit_alias(self, node):
+        self.write(node.name)
+        if node.asname is not None:
+            self.write(' as ' + node.asname)
+
+    def visit_comprehension(self, node):
+        self.write(' for ')
+        self.visit(node.target)
+        self.write(' in ')
+        self.visit(node.iter)
+        if node.ifs:
+            for if_ in node.ifs:
+                self.write(' if ')
+                self.visit(if_)
+
+    def visit_excepthandler(self, node):
+        self.newline(node)
+        self.write('except')
+        if node.type is not None:
+            self.write(' ')
+            self.visit(node.type)
+            if node.name is not None:
+                self.write(' as ')
+                self.visit(node.name)
+        self.write(':')
+        self.body(node.body)
diff --git a/lib/ply/__init__.py b/lib/ply/__init__.py
new file mode 100644
index 000000000..853a98554
--- /dev/null
+++ b/lib/ply/__init__.py
@@ -0,0 +1,4 @@
+# PLY package
+# Author: David Beazley (dave@dabeaz.com)
+
+__all__ = ['lex','yacc']
diff --git a/lib/ply/lex.py b/lib/ply/lex.py
new file mode 100644
index 000000000..267ec100f
--- /dev/null
+++ b/lib/ply/lex.py
@@ -0,0 +1,1058 @@
+# -----------------------------------------------------------------------------
+# ply: lex.py
+#
+# Copyright (C) 2001-2009,
+# David M. Beazley (Dabeaz LLC)
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+# 
+# * Redistributions of source code must retain the above copyright notice,
+#   this list of conditions and the following disclaimer.  
+# * Redistributions in binary form must reproduce the above copyright notice, 
+#   this list of conditions and the following disclaimer in the documentation
+#   and/or other materials provided with the distribution.  
+# * Neither the name of the David Beazley or Dabeaz LLC may be used to
+#   endorse or promote products derived from this software without
+#  specific prior written permission. 
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+# -----------------------------------------------------------------------------
+
+__version__    = "3.3"
+__tabversion__ = "3.2"       # Version of table file used
+
+import re, sys, types, copy, os
+
+# This tuple contains known string types
+try:
+    # Python 2.6
+    StringTypes = (types.StringType, types.UnicodeType)
+except AttributeError:
+    # Python 3.0
+    StringTypes = (str, bytes)
+
+# Extract the code attribute of a function. Different implementations
+# are for Python 2/3 compatibility.
+
+if sys.version_info[0] < 3:
+    def func_code(f):
+        return f.func_code
+else:
+    def func_code(f):
+        return f.__code__
+
+# This regular expression is used to match valid token names
+_is_identifier = re.compile(r'^[a-zA-Z0-9_]+$')
+
+# Exception thrown when invalid token encountered and no default error
+# handler is defined.
+
+class LexError(Exception):
+    def __init__(self,message,s):
+         self.args = (message,)
+         self.text = s
+
+# Token class.  This class is used to represent the tokens produced.
+class LexToken(object):
+    def __str__(self):
+        return "LexToken(%s,%r,%d,%d)" % (self.type,self.value,self.lineno,self.lexpos)
+    def __repr__(self):
+        return str(self)
+
+# This object is a stand-in for a logging object created by the 
+# logging module.  
+
+class PlyLogger(object):
+    def __init__(self,f):
+        self.f = f
+    def critical(self,msg,*args,**kwargs):
+        self.f.write((msg % args) + "\n")
+
+    def warning(self,msg,*args,**kwargs):
+        self.f.write("WARNING: "+ (msg % args) + "\n")
+
+    def error(self,msg,*args,**kwargs):
+        self.f.write("ERROR: " + (msg % args) + "\n")
+
+    info = critical
+    debug = critical
+
+# Null logger is used when no output is generated. Does nothing.
+class NullLogger(object):
+    def __getattribute__(self,name):
+        return self
+    def __call__(self,*args,**kwargs):
+        return self
+
+# -----------------------------------------------------------------------------
+#                        === Lexing Engine ===
+#
+# The following Lexer class implements the lexer runtime.   There are only
+# a few public methods and attributes:
+#
+#    input()          -  Store a new string in the lexer
+#    token()          -  Get the next token
+#    clone()          -  Clone the lexer
+#
+#    lineno           -  Current line number
+#    lexpos           -  Current position in the input string
+# -----------------------------------------------------------------------------
+
+class Lexer:
+    def __init__(self):
+        self.lexre = None             # Master regular expression. This is a list of
+                                      # tuples (re,findex) where re is a compiled
+                                      # regular expression and findex is a list
+                                      # mapping regex group numbers to rules
+        self.lexretext = None         # Current regular expression strings
+        self.lexstatere = {}          # Dictionary mapping lexer states to master regexs
+        self.lexstateretext = {}      # Dictionary mapping lexer states to regex strings
+        self.lexstaterenames = {}     # Dictionary mapping lexer states to symbol names
+        self.lexstate = "INITIAL"     # Current lexer state
+        self.lexstatestack = []       # Stack of lexer states
+        self.lexstateinfo = None      # State information
+        self.lexstateignore = {}      # Dictionary of ignored characters for each state
+        self.lexstateerrorf = {}      # Dictionary of error functions for each state
+        self.lexreflags = 0           # Optional re compile flags
+        self.lexdata = None           # Actual input data (as a string)
+        self.lexpos = 0               # Current position in input text
+        self.lexlen = 0               # Length of the input text
+        self.lexerrorf = None         # Error rule (if any)
+        self.lextokens = None         # List of valid tokens
+        self.lexignore = ""           # Ignored characters
+        self.lexliterals = ""         # Literal characters that can be passed through
+        self.lexmodule = None         # Module
+        self.lineno = 1               # Current line number
+        self.lexoptimize = 0          # Optimized mode
+
+    def clone(self,object=None):
+        c = copy.copy(self)
+
+        # If the object parameter has been supplied, it means we are attaching the
+        # lexer to a new object.  In this case, we have to rebind all methods in
+        # the lexstatere and lexstateerrorf tables.
+
+        if object:
+            newtab = { }
+            for key, ritem in self.lexstatere.items():
+                newre = []
+                for cre, findex in ritem:
+                     newfindex = []
+                     for f in findex:
+                         if not f or not f[0]:
+                             newfindex.append(f)
+                             continue
+                         newfindex.append((getattr(object,f[0].__name__),f[1]))
+                newre.append((cre,newfindex))
+                newtab[key] = newre
+            c.lexstatere = newtab
+            c.lexstateerrorf = { }
+            for key, ef in self.lexstateerrorf.items():
+                c.lexstateerrorf[key] = getattr(object,ef.__name__)
+            c.lexmodule = object
+        return c
+
+    # ------------------------------------------------------------
+    # writetab() - Write lexer information to a table file
+    # ------------------------------------------------------------
+    def writetab(self,tabfile,outputdir=""):
+        if isinstance(tabfile,types.ModuleType):
+            return
+        basetabfilename = tabfile.split(".")[-1]
+        filename = os.path.join(outputdir,basetabfilename)+".py"
+        tf = open(filename,"w")
+        tf.write("# %s.py. This file automatically created by PLY (version %s). Don't edit!\n" % (tabfile,__version__))
+        tf.write("_tabversion   = %s\n" % repr(__version__))
+        tf.write("_lextokens    = %s\n" % repr(self.lextokens))
+        tf.write("_lexreflags   = %s\n" % repr(self.lexreflags))
+        tf.write("_lexliterals  = %s\n" % repr(self.lexliterals))
+        tf.write("_lexstateinfo = %s\n" % repr(self.lexstateinfo))
+
+        tabre = { }
+        # Collect all functions in the initial state
+        initial = self.lexstatere["INITIAL"]
+        initialfuncs = []
+        for part in initial:
+            for f in part[1]:
+                if f and f[0]:
+                    initialfuncs.append(f)
+
+        for key, lre in self.lexstatere.items():
+             titem = []
+             for i in range(len(lre)):
+                  titem.append((self.lexstateretext[key][i],_funcs_to_names(lre[i][1],self.lexstaterenames[key][i])))
+             tabre[key] = titem
+
+        tf.write("_lexstatere   = %s\n" % repr(tabre))
+        tf.write("_lexstateignore = %s\n" % repr(self.lexstateignore))
+
+        taberr = { }
+        for key, ef in self.lexstateerrorf.items():
+             if ef:
+                  taberr[key] = ef.__name__
+             else:
+                  taberr[key] = None
+        tf.write("_lexstateerrorf = %s\n" % repr(taberr))
+        tf.close()
+
+    # ------------------------------------------------------------
+    # readtab() - Read lexer information from a tab file
+    # ------------------------------------------------------------
+    def readtab(self,tabfile,fdict):
+        if isinstance(tabfile,types.ModuleType):
+            lextab = tabfile
+        else:
+            if sys.version_info[0] < 3:
+                exec("import %s as lextab" % tabfile)
+            else:
+                env = { }
+                exec("import %s as lextab" % tabfile, env,env)
+                lextab = env['lextab']
+
+        if getattr(lextab,"_tabversion","0.0") != __version__:
+            raise ImportError("Inconsistent PLY version")
+
+        self.lextokens      = lextab._lextokens
+        self.lexreflags     = lextab._lexreflags
+        self.lexliterals    = lextab._lexliterals
+        self.lexstateinfo   = lextab._lexstateinfo
+        self.lexstateignore = lextab._lexstateignore
+        self.lexstatere     = { }
+        self.lexstateretext = { }
+        for key,lre in lextab._lexstatere.items():
+             titem = []
+             txtitem = []
+             for i in range(len(lre)):
+                  titem.append((re.compile(lre[i][0],lextab._lexreflags | re.VERBOSE),_names_to_funcs(lre[i][1],fdict)))
+                  txtitem.append(lre[i][0])
+             self.lexstatere[key] = titem
+             self.lexstateretext[key] = txtitem
+        self.lexstateerrorf = { }
+        for key,ef in lextab._lexstateerrorf.items():
+             self.lexstateerrorf[key] = fdict[ef]
+        self.begin('INITIAL')
+
+    # ------------------------------------------------------------
+    # input() - Push a new string into the lexer
+    # ------------------------------------------------------------
+    def input(self,s):
+        # Pull off the first character to see if s looks like a string
+        c = s[:1]
+        if not isinstance(c,StringTypes):
+            raise ValueError("Expected a string")
+        self.lexdata = s
+        self.lexpos = 0
+        self.lexlen = len(s)
+
+    # ------------------------------------------------------------
+    # begin() - Changes the lexing state
+    # ------------------------------------------------------------
+    def begin(self,state):
+        if not state in self.lexstatere:
+            raise ValueError("Undefined state")
+        self.lexre = self.lexstatere[state]
+        self.lexretext = self.lexstateretext[state]
+        self.lexignore = self.lexstateignore.get(state,"")
+        self.lexerrorf = self.lexstateerrorf.get(state,None)
+        self.lexstate = state
+
+    # ------------------------------------------------------------
+    # push_state() - Changes the lexing state and saves old on stack
+    # ------------------------------------------------------------
+    def push_state(self,state):
+        self.lexstatestack.append(self.lexstate)
+        self.begin(state)
+
+    # ------------------------------------------------------------
+    # pop_state() - Restores the previous state
+    # ------------------------------------------------------------
+    def pop_state(self):
+        self.begin(self.lexstatestack.pop())
+
+    # ------------------------------------------------------------
+    # current_state() - Returns the current lexing state
+    # ------------------------------------------------------------
+    def current_state(self):
+        return self.lexstate
+
+    # ------------------------------------------------------------
+    # skip() - Skip ahead n characters
+    # ------------------------------------------------------------
+    def skip(self,n):
+        self.lexpos += n
+
+    # ------------------------------------------------------------
+    # opttoken() - Return the next token from the Lexer
+    #
+    # Note: This function has been carefully implemented to be as fast
+    # as possible.  Don't make changes unless you really know what
+    # you are doing
+    # ------------------------------------------------------------
+    def token(self):
+        # Make local copies of frequently referenced attributes
+        lexpos    = self.lexpos
+        lexlen    = self.lexlen
+        lexignore = self.lexignore
+        lexdata   = self.lexdata
+
+        while lexpos < lexlen:
+            # This code provides some short-circuit code for whitespace, tabs, and other ignored characters
+            if lexdata[lexpos] in lexignore:
+                lexpos += 1
+                continue
+
+            # Look for a regular expression match
+            for lexre,lexindexfunc in self.lexre:
+                m = lexre.match(lexdata,lexpos)
+                if not m: continue
+
+                # Create a token for return
+                tok = LexToken()
+                tok.value = m.group()
+                tok.lineno = self.lineno
+                tok.lexpos = lexpos
+
+                i = m.lastindex
+                func,tok.type = lexindexfunc[i]
+
+                if not func:
+                   # If no token type was set, it's an ignored token
+                   if tok.type:
+                      self.lexpos = m.end()
+                      return tok
+                   else:
+                      lexpos = m.end()
+                      break
+
+                lexpos = m.end()
+
+                # If token is processed by a function, call it
+
+                tok.lexer = self      # Set additional attributes useful in token rules
+                self.lexmatch = m
+                self.lexpos = lexpos
+
+                newtok = func(tok)
+
+                # Every function must return a token, if nothing, we just move to next token
+                if not newtok:
+                    lexpos    = self.lexpos         # This is here in case user has updated lexpos.
+                    lexignore = self.lexignore      # This is here in case there was a state change
+                    break
+
+                # Verify type of the token.  If not in the token map, raise an error
+                if not self.lexoptimize:
+                    if not newtok.type in self.lextokens:
+                        raise LexError("%s:%d: Rule '%s' returned an unknown token type '%s'" % (
+                            func_code(func).co_filename, func_code(func).co_firstlineno,
+                            func.__name__, newtok.type),lexdata[lexpos:])
+
+                return newtok
+            else:
+                # No match, see if in literals
+                if lexdata[lexpos] in self.lexliterals:
+                    tok = LexToken()
+                    tok.value = lexdata[lexpos]
+                    tok.lineno = self.lineno
+                    tok.type = tok.value
+                    tok.lexpos = lexpos
+                    self.lexpos = lexpos + 1
+                    return tok
+
+                # No match. Call t_error() if defined.
+                if self.lexerrorf:
+                    tok = LexToken()
+                    tok.value = self.lexdata[lexpos:]
+                    tok.lineno = self.lineno
+                    tok.type = "error"
+                    tok.lexer = self
+                    tok.lexpos = lexpos
+                    self.lexpos = lexpos
+                    newtok = self.lexerrorf(tok)
+                    if lexpos == self.lexpos:
+                        # Error method didn't change text position at all. This is an error.
+                        raise LexError("Scanning error. Illegal character '%s'" % (lexdata[lexpos]), lexdata[lexpos:])
+                    lexpos = self.lexpos
+                    if not newtok: continue
+                    return newtok
+
+                self.lexpos = lexpos
+                raise LexError("Illegal character '%s' at index %d" % (lexdata[lexpos],lexpos), lexdata[lexpos:])
+
+        self.lexpos = lexpos + 1
+        if self.lexdata is None:
+             raise RuntimeError("No input string given with input()")
+        return None
+
+    # Iterator interface
+    def __iter__(self):
+        return self
+
+    def next(self):
+        t = self.token()
+        if t is None:
+            raise StopIteration
+        return t
+
+    __next__ = next
+
+# -----------------------------------------------------------------------------
+#                           ==== Lex Builder ===
+#
+# The functions and classes below are used to collect lexing information
+# and build a Lexer object from it.
+# -----------------------------------------------------------------------------
+
+# -----------------------------------------------------------------------------
+# get_caller_module_dict()
+#
+# This function returns a dictionary containing all of the symbols defined within
+# a caller further down the call stack.  This is used to get the environment
+# associated with the yacc() call if none was provided.
+# -----------------------------------------------------------------------------
+
+def get_caller_module_dict(levels):
+    try:
+        raise RuntimeError
+    except RuntimeError:
+        e,b,t = sys.exc_info()
+        f = t.tb_frame
+        while levels > 0:
+            f = f.f_back                   
+            levels -= 1
+        ldict = f.f_globals.copy()
+        if f.f_globals != f.f_locals:
+            ldict.update(f.f_locals)
+
+        return ldict
+
+# -----------------------------------------------------------------------------
+# _funcs_to_names()
+#
+# Given a list of regular expression functions, this converts it to a list
+# suitable for output to a table file
+# -----------------------------------------------------------------------------
+
+def _funcs_to_names(funclist,namelist):
+    result = []
+    for f,name in zip(funclist,namelist):
+         if f and f[0]:
+             result.append((name, f[1]))
+         else:
+             result.append(f)
+    return result
+
+# -----------------------------------------------------------------------------
+# _names_to_funcs()
+#
+# Given a list of regular expression function names, this converts it back to
+# functions.
+# -----------------------------------------------------------------------------
+
+def _names_to_funcs(namelist,fdict):
+     result = []
+     for n in namelist:
+          if n and n[0]:
+              result.append((fdict[n[0]],n[1]))
+          else:
+              result.append(n)
+     return result
+
+# -----------------------------------------------------------------------------
+# _form_master_re()
+#
+# This function takes a list of all of the regex components and attempts to
+# form the master regular expression.  Given limitations in the Python re
+# module, it may be necessary to break the master regex into separate expressions.
+# -----------------------------------------------------------------------------
+
+def _form_master_re(relist,reflags,ldict,toknames):
+    if not relist: return []
+    regex = "|".join(relist)
+    try:
+        lexre = re.compile(regex,re.VERBOSE | reflags)
+
+        # Build the index to function map for the matching engine
+        lexindexfunc = [ None ] * (max(lexre.groupindex.values())+1)
+        lexindexnames = lexindexfunc[:]
+
+        for f,i in lexre.groupindex.items():
+            handle = ldict.get(f,None)
+            if type(handle) in (types.FunctionType, types.MethodType):
+                lexindexfunc[i] = (handle,toknames[f])
+                lexindexnames[i] = f
+            elif handle is not None:
+                lexindexnames[i] = f
+                if f.find("ignore_") > 0:
+                    lexindexfunc[i] = (None,None)
+                else:
+                    lexindexfunc[i] = (None, toknames[f])
+        
+        return [(lexre,lexindexfunc)],[regex],[lexindexnames]
+    except Exception:
+        m = int(len(relist)/2)
+        if m == 0: m = 1
+        llist, lre, lnames = _form_master_re(relist[:m],reflags,ldict,toknames)
+        rlist, rre, rnames = _form_master_re(relist[m:],reflags,ldict,toknames)
+        return llist+rlist, lre+rre, lnames+rnames
+
+# -----------------------------------------------------------------------------
+# def _statetoken(s,names)
+#
+# Given a declaration name s of the form "t_" and a dictionary whose keys are
+# state names, this function returns a tuple (states,tokenname) where states
+# is a tuple of state names and tokenname is the name of the token.  For example,
+# calling this with s = "t_foo_bar_SPAM" might return (('foo','bar'),'SPAM')
+# -----------------------------------------------------------------------------
+
+def _statetoken(s,names):
+    nonstate = 1
+    parts = s.split("_")
+    for i in range(1,len(parts)):
+         if not parts[i] in names and parts[i] != 'ANY': break
+    if i > 1:
+       states = tuple(parts[1:i])
+    else:
+       states = ('INITIAL',)
+
+    if 'ANY' in states:
+       states = tuple(names)
+
+    tokenname = "_".join(parts[i:])
+    return (states,tokenname)
+
+
+# -----------------------------------------------------------------------------
+# LexerReflect()
+#
+# This class represents information needed to build a lexer as extracted from a
+# user's input file.
+# -----------------------------------------------------------------------------
+class LexerReflect(object):
+    def __init__(self,ldict,log=None,reflags=0):
+        self.ldict      = ldict
+        self.error_func = None
+        self.tokens     = []
+        self.reflags    = reflags
+        self.stateinfo  = { 'INITIAL' : 'inclusive'}
+        self.files      = {}
+        self.error      = 0
+
+        if log is None:
+            self.log = PlyLogger(sys.stderr)
+        else:
+            self.log = log
+
+    # Get all of the basic information
+    def get_all(self):
+        self.get_tokens()
+        self.get_literals()
+        self.get_states()
+        self.get_rules()
+        
+    # Validate all of the information
+    def validate_all(self):
+        self.validate_tokens()
+        self.validate_literals()
+        self.validate_rules()
+        return self.error
+
+    # Get the tokens map
+    def get_tokens(self):
+        tokens = self.ldict.get("tokens",None)
+        if not tokens:
+            self.log.error("No token list is defined")
+            self.error = 1
+            return
+
+        if not isinstance(tokens,(list, tuple)):
+            self.log.error("tokens must be a list or tuple")
+            self.error = 1
+            return
+        
+        if not tokens:
+            self.log.error("tokens is empty")
+            self.error = 1
+            return
+
+        self.tokens = tokens
+
+    # Validate the tokens
+    def validate_tokens(self):
+        terminals = {}
+        for n in self.tokens:
+            if not _is_identifier.match(n):
+                self.log.error("Bad token name '%s'",n)
+                self.error = 1
+            if n in terminals:
+                self.log.warning("Token '%s' multiply defined", n)
+            terminals[n] = 1
+
+    # Get the literals specifier
+    def get_literals(self):
+        self.literals = self.ldict.get("literals","")
+
+    # Validate literals
+    def validate_literals(self):
+        try:
+            for c in self.literals:
+                if not isinstance(c,StringTypes) or len(c) > 1:
+                    self.log.error("Invalid literal %s. Must be a single character", repr(c))
+                    self.error = 1
+                    continue
+
+        except TypeError:
+            self.log.error("Invalid literals specification. literals must be a sequence of characters")
+            self.error = 1
+
+    def get_states(self):
+        self.states = self.ldict.get("states",None)
+        # Build statemap
+        if self.states:
+             if not isinstance(self.states,(tuple,list)):
+                  self.log.error("states must be defined as a tuple or list")
+                  self.error = 1
+             else:
+                  for s in self.states:
+                        if not isinstance(s,tuple) or len(s) != 2:
+                               self.log.error("Invalid state specifier %s. Must be a tuple (statename,'exclusive|inclusive')",repr(s))
+                               self.error = 1
+                               continue
+                        name, statetype = s
+                        if not isinstance(name,StringTypes):
+                               self.log.error("State name %s must be a string", repr(name))
+                               self.error = 1
+                               continue
+                        if not (statetype == 'inclusive' or statetype == 'exclusive'):
+                               self.log.error("State type for state %s must be 'inclusive' or 'exclusive'",name)
+                               self.error = 1
+                               continue
+                        if name in self.stateinfo:
+                               self.log.error("State '%s' already defined",name)
+                               self.error = 1
+                               continue
+                        self.stateinfo[name] = statetype
+
+    # Get all of the symbols with a t_ prefix and sort them into various
+    # categories (functions, strings, error functions, and ignore characters)
+
+    def get_rules(self):
+        tsymbols = [f for f in self.ldict if f[:2] == 't_' ]
+
+        # Now build up a list of functions and a list of strings
+
+        self.toknames = { }        # Mapping of symbols to token names
+        self.funcsym =  { }        # Symbols defined as functions
+        self.strsym =   { }        # Symbols defined as strings
+        self.ignore   = { }        # Ignore strings by state
+        self.errorf   = { }        # Error functions by state
+
+        for s in self.stateinfo:
+             self.funcsym[s] = []
+             self.strsym[s] = []
+
+        if len(tsymbols) == 0:
+            self.log.error("No rules of the form t_rulename are defined")
+            self.error = 1
+            return
+
+        for f in tsymbols:
+            t = self.ldict[f]
+            states, tokname = _statetoken(f,self.stateinfo)
+            self.toknames[f] = tokname
+
+            if hasattr(t,"__call__"):
+                if tokname == 'error':
+                    for s in states:
+                        self.errorf[s] = t
+                elif tokname == 'ignore':
+                    line = func_code(t).co_firstlineno
+                    file = func_code(t).co_filename
+                    self.log.error("%s:%d: Rule '%s' must be defined as a string",file,line,t.__name__)
+                    self.error = 1
+                else:
+                    for s in states: 
+                        self.funcsym[s].append((f,t))
+            elif isinstance(t, StringTypes):
+                if tokname == 'ignore':
+                    for s in states:
+                        self.ignore[s] = t
+                    if "\\" in t:
+                        self.log.warning("%s contains a literal backslash '\\'",f)
+
+                elif tokname == 'error':
+                    self.log.error("Rule '%s' must be defined as a function", f)
+                    self.error = 1
+                else:
+                    for s in states: 
+                        self.strsym[s].append((f,t))
+            else:
+                self.log.error("%s not defined as a function or string", f)
+                self.error = 1
+
+        # Sort the functions by line number
+        for f in self.funcsym.values():
+            if sys.version_info[0] < 3:
+                f.sort(lambda x,y: cmp(func_code(x[1]).co_firstlineno,func_code(y[1]).co_firstlineno))
+            else:
+                # Python 3.0
+                f.sort(key=lambda x: func_code(x[1]).co_firstlineno)
+
+        # Sort the strings by regular expression length
+        for s in self.strsym.values():
+            if sys.version_info[0] < 3:
+                s.sort(lambda x,y: (len(x[1]) < len(y[1])) - (len(x[1]) > len(y[1])))
+            else:
+                # Python 3.0
+                s.sort(key=lambda x: len(x[1]),reverse=True)
+
+    # Validate all of the t_rules collected 
+    def validate_rules(self):
+        for state in self.stateinfo:
+            # Validate all rules defined by functions
+
+            
+
+            for fname, f in self.funcsym[state]:
+                line = func_code(f).co_firstlineno
+                file = func_code(f).co_filename
+                self.files[file] = 1
+
+                tokname = self.toknames[fname]
+                if isinstance(f, types.MethodType):
+                    reqargs = 2
+                else:
+                    reqargs = 1
+                nargs = func_code(f).co_argcount
+                if nargs > reqargs:
+                    self.log.error("%s:%d: Rule '%s' has too many arguments",file,line,f.__name__)
+                    self.error = 1
+                    continue
+
+                if nargs < reqargs:
+                    self.log.error("%s:%d: Rule '%s' requires an argument", file,line,f.__name__)
+                    self.error = 1
+                    continue
+
+                if not f.__doc__:
+                    self.log.error("%s:%d: No regular expression defined for rule '%s'",file,line,f.__name__)
+                    self.error = 1
+                    continue
+
+                try:
+                    c = re.compile("(?P<%s>%s)" % (fname,f.__doc__), re.VERBOSE | self.reflags)
+                    if c.match(""):
+                        self.log.error("%s:%d: Regular expression for rule '%s' matches empty string", file,line,f.__name__)
+                        self.error = 1
+                except re.error:
+                    _etype, e, _etrace = sys.exc_info()
+                    self.log.error("%s:%d: Invalid regular expression for rule '%s'. %s", file,line,f.__name__,e)
+                    if '#' in f.__doc__:
+                        self.log.error("%s:%d. Make sure '#' in rule '%s' is escaped with '\\#'",file,line, f.__name__)
+                    self.error = 1
+
+            # Validate all rules defined by strings
+            for name,r in self.strsym[state]:
+                tokname = self.toknames[name]
+                if tokname == 'error':
+                    self.log.error("Rule '%s' must be defined as a function", name)
+                    self.error = 1
+                    continue
+
+                if not tokname in self.tokens and tokname.find("ignore_") < 0:
+                    self.log.error("Rule '%s' defined for an unspecified token %s",name,tokname)
+                    self.error = 1
+                    continue
+
+                try:
+                    c = re.compile("(?P<%s>%s)" % (name,r),re.VERBOSE | self.reflags)
+                    if (c.match("")):
+                         self.log.error("Regular expression for rule '%s' matches empty string",name)
+                         self.error = 1
+                except re.error:
+                    _etype, e, _etrace = sys.exc_info()
+                    self.log.error("Invalid regular expression for rule '%s'. %s",name,e)
+                    if '#' in r:
+                         self.log.error("Make sure '#' in rule '%s' is escaped with '\\#'",name)
+                    self.error = 1
+
+            if not self.funcsym[state] and not self.strsym[state]:
+                self.log.error("No rules defined for state '%s'",state)
+                self.error = 1
+
+            # Validate the error function
+            efunc = self.errorf.get(state,None)
+            if efunc:
+                f = efunc
+                line = func_code(f).co_firstlineno
+                file = func_code(f).co_filename
+                self.files[file] = 1
+
+                if isinstance(f, types.MethodType):
+                    reqargs = 2
+                else:
+                    reqargs = 1
+                nargs = func_code(f).co_argcount
+                if nargs > reqargs:
+                    self.log.error("%s:%d: Rule '%s' has too many arguments",file,line,f.__name__)
+                    self.error = 1
+
+                if nargs < reqargs:
+                    self.log.error("%s:%d: Rule '%s' requires an argument", file,line,f.__name__)
+                    self.error = 1
+
+        for f in self.files:
+            self.validate_file(f)
+
+
+    # -----------------------------------------------------------------------------
+    # validate_file()
+    #
+    # This checks to see if there are duplicated t_rulename() functions or strings
+    # in the parser input file.  This is done using a simple regular expression
+    # match on each line in the given file.  
+    # -----------------------------------------------------------------------------
+
+    def validate_file(self,filename):
+        import os.path
+        base,ext = os.path.splitext(filename)
+        if ext != '.py': return         # No idea what the file is. Return OK
+
+        try:
+            f = open(filename)
+            lines = f.readlines()
+            f.close()
+        except IOError:
+            return                      # Couldn't find the file.  Don't worry about it
+
+        fre = re.compile(r'\s*def\s+(t_[a-zA-Z_0-9]*)\(')
+        sre = re.compile(r'\s*(t_[a-zA-Z_0-9]*)\s*=')
+
+        counthash = { }
+        linen = 1
+        for l in lines:
+            m = fre.match(l)
+            if not m:
+                m = sre.match(l)
+            if m:
+                name = m.group(1)
+                prev = counthash.get(name)
+                if not prev:
+                    counthash[name] = linen
+                else:
+                    self.log.error("%s:%d: Rule %s redefined. Previously defined on line %d",filename,linen,name,prev)
+                    self.error = 1
+            linen += 1
+            
+# -----------------------------------------------------------------------------
+# lex(module)
+#
+# Build all of the regular expression rules from definitions in the supplied module
+# -----------------------------------------------------------------------------
+def lex(module=None,object=None,debug=0,optimize=0,lextab="lextab",reflags=0,nowarn=0,outputdir="", debuglog=None, errorlog=None):
+    global lexer
+    ldict = None
+    stateinfo  = { 'INITIAL' : 'inclusive'}
+    lexobj = Lexer()
+    lexobj.lexoptimize = optimize
+    global token,input
+
+    if errorlog is None:
+        errorlog = PlyLogger(sys.stderr)
+
+    if debug:
+        if debuglog is None:
+            debuglog = PlyLogger(sys.stderr)
+
+    # Get the module dictionary used for the lexer
+    if object: module = object
+
+    if module:
+        _items = [(k,getattr(module,k)) for k in dir(module)]
+        ldict = dict(_items)
+    else:
+        ldict = get_caller_module_dict(2)
+
+    # Collect parser information from the dictionary
+    linfo = LexerReflect(ldict,log=errorlog,reflags=reflags)
+    linfo.get_all()
+    if not optimize:
+        if linfo.validate_all():
+            raise SyntaxError("Can't build lexer")
+
+    if optimize and lextab:
+        try:
+            lexobj.readtab(lextab,ldict)
+            token = lexobj.token
+            input = lexobj.input
+            lexer = lexobj
+            return lexobj
+
+        except ImportError:
+            pass
+
+    # Dump some basic debugging information
+    if debug:
+        debuglog.info("lex: tokens   = %r", linfo.tokens)
+        debuglog.info("lex: literals = %r", linfo.literals)
+        debuglog.info("lex: states   = %r", linfo.stateinfo)
+
+    # Build a dictionary of valid token names
+    lexobj.lextokens = { }
+    for n in linfo.tokens:
+        lexobj.lextokens[n] = 1
+
+    # Get literals specification
+    if isinstance(linfo.literals,(list,tuple)):
+        lexobj.lexliterals = type(linfo.literals[0])().join(linfo.literals)
+    else:
+        lexobj.lexliterals = linfo.literals
+
+    # Get the stateinfo dictionary
+    stateinfo = linfo.stateinfo
+
+    regexs = { }
+    # Build the master regular expressions
+    for state in stateinfo:
+        regex_list = []
+
+        # Add rules defined by functions first
+        for fname, f in linfo.funcsym[state]:
+            line = func_code(f).co_firstlineno
+            file = func_code(f).co_filename
+            regex_list.append("(?P<%s>%s)" % (fname,f.__doc__))
+            if debug:
+                debuglog.info("lex: Adding rule %s -> '%s' (state '%s')",fname,f.__doc__, state)
+
+        # Now add all of the simple rules
+        for name,r in linfo.strsym[state]:
+            regex_list.append("(?P<%s>%s)" % (name,r))
+            if debug:
+                debuglog.info("lex: Adding rule %s -> '%s' (state '%s')",name,r, state)
+
+        regexs[state] = regex_list
+
+    # Build the master regular expressions
+
+    if debug:
+        debuglog.info("lex: ==== MASTER REGEXS FOLLOW ====")
+
+    for state in regexs:
+        lexre, re_text, re_names = _form_master_re(regexs[state],reflags,ldict,linfo.toknames)
+        lexobj.lexstatere[state] = lexre
+        lexobj.lexstateretext[state] = re_text
+        lexobj.lexstaterenames[state] = re_names
+        if debug:
+            for i in range(len(re_text)):
+                debuglog.info("lex: state '%s' : regex[%d] = '%s'",state, i, re_text[i])
+
+    # For inclusive states, we need to add the regular expressions from the INITIAL state
+    for state,stype in stateinfo.items():
+        if state != "INITIAL" and stype == 'inclusive':
+             lexobj.lexstatere[state].extend(lexobj.lexstatere['INITIAL'])
+             lexobj.lexstateretext[state].extend(lexobj.lexstateretext['INITIAL'])
+             lexobj.lexstaterenames[state].extend(lexobj.lexstaterenames['INITIAL'])
+
+    lexobj.lexstateinfo = stateinfo
+    lexobj.lexre = lexobj.lexstatere["INITIAL"]
+    lexobj.lexretext = lexobj.lexstateretext["INITIAL"]
+    lexobj.lexreflags = reflags
+
+    # Set up ignore variables
+    lexobj.lexstateignore = linfo.ignore
+    lexobj.lexignore = lexobj.lexstateignore.get("INITIAL","")
+
+    # Set up error functions
+    lexobj.lexstateerrorf = linfo.errorf
+    lexobj.lexerrorf = linfo.errorf.get("INITIAL",None)
+    if not lexobj.lexerrorf:
+        errorlog.warning("No t_error rule is defined")
+
+    # Check state information for ignore and error rules
+    for s,stype in stateinfo.items():
+        if stype == 'exclusive':
+              if not s in linfo.errorf:
+                   errorlog.warning("No error rule is defined for exclusive state '%s'", s)
+              if not s in linfo.ignore and lexobj.lexignore:
+                   errorlog.warning("No ignore rule is defined for exclusive state '%s'", s)
+        elif stype == 'inclusive':
+              if not s in linfo.errorf:
+                   linfo.errorf[s] = linfo.errorf.get("INITIAL",None)
+              if not s in linfo.ignore:
+                   linfo.ignore[s] = linfo.ignore.get("INITIAL","")
+
+    # Create global versions of the token() and input() functions
+    token = lexobj.token
+    input = lexobj.input
+    lexer = lexobj
+
+    # If in optimize mode, we write the lextab
+    if lextab and optimize:
+        lexobj.writetab(lextab,outputdir)
+
+    return lexobj
+
+# -----------------------------------------------------------------------------
+# runmain()
+#
+# This runs the lexer as a main program
+# -----------------------------------------------------------------------------
+
+def runmain(lexer=None,data=None):
+    if not data:
+        try:
+            filename = sys.argv[1]
+            f = open(filename)
+            data = f.read()
+            f.close()
+        except IndexError:
+            sys.stdout.write("Reading from standard input (type EOF to end):\n")
+            data = sys.stdin.read()
+
+    if lexer:
+        _input = lexer.input
+    else:
+        _input = input
+    _input(data)
+    if lexer:
+        _token = lexer.token
+    else:
+        _token = token
+
+    while 1:
+        tok = _token()
+        if not tok: break
+        sys.stdout.write("(%s,%r,%d,%d)\n" % (tok.type, tok.value, tok.lineno,tok.lexpos))
+
+# -----------------------------------------------------------------------------
+# @TOKEN(regex)
+#
+# This decorator function can be used to set the regex expression on a function
+# when its docstring might need to be set in an alternative way
+# -----------------------------------------------------------------------------
+
+def TOKEN(r):
+    def set_doc(f):
+        if hasattr(r,"__call__"):
+            f.__doc__ = r.__doc__
+        else:
+            f.__doc__ = r
+        return f
+    return set_doc
+
+# Alternative spelling of the TOKEN decorator
+Token = TOKEN
+
diff --git a/lib/ply/yacc.py b/lib/ply/yacc.py
new file mode 100644
index 000000000..6168fd9a0
--- /dev/null
+++ b/lib/ply/yacc.py
@@ -0,0 +1,3276 @@
+# -----------------------------------------------------------------------------
+# ply: yacc.py
+#
+# Copyright (C) 2001-2009,
+# David M. Beazley (Dabeaz LLC)
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+# 
+# * Redistributions of source code must retain the above copyright notice,
+#   this list of conditions and the following disclaimer.  
+# * Redistributions in binary form must reproduce the above copyright notice, 
+#   this list of conditions and the following disclaimer in the documentation
+#   and/or other materials provided with the distribution.  
+# * Neither the name of the David Beazley or Dabeaz LLC may be used to
+#   endorse or promote products derived from this software without
+#  specific prior written permission. 
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+# -----------------------------------------------------------------------------
+#
+# This implements an LR parser that is constructed from grammar rules defined
+# as Python functions. The grammer is specified by supplying the BNF inside
+# Python documentation strings.  The inspiration for this technique was borrowed
+# from John Aycock's Spark parsing system.  PLY might be viewed as cross between
+# Spark and the GNU bison utility.
+#
+# The current implementation is only somewhat object-oriented. The
+# LR parser itself is defined in terms of an object (which allows multiple
+# parsers to co-exist).  However, most of the variables used during table
+# construction are defined in terms of global variables.  Users shouldn't
+# notice unless they are trying to define multiple parsers at the same
+# time using threads (in which case they should have their head examined).
+#
+# This implementation supports both SLR and LALR(1) parsing.  LALR(1)
+# support was originally implemented by Elias Ioup (ezioup@alumni.uchicago.edu),
+# using the algorithm found in Aho, Sethi, and Ullman "Compilers: Principles,
+# Techniques, and Tools" (The Dragon Book).  LALR(1) has since been replaced
+# by the more efficient DeRemer and Pennello algorithm.
+#
+# :::::::: WARNING :::::::
+#
+# Construction of LR parsing tables is fairly complicated and expensive.
+# To make this module run fast, a *LOT* of work has been put into
+# optimization---often at the expensive of readability and what might
+# consider to be good Python "coding style."   Modify the code at your
+# own risk!
+# ----------------------------------------------------------------------------
+
+__version__    = "3.3"
+__tabversion__ = "3.2"       # Table version
+
+#-----------------------------------------------------------------------------
+#                     === User configurable parameters ===
+#
+# Change these to modify the default behavior of yacc (if you wish)
+#-----------------------------------------------------------------------------
+
+yaccdebug   = 0                # Debugging mode.  If set, yacc generates a
+                               # a 'parser.out' file in the current directory
+
+debug_file  = 'parser.out'     # Default name of the debugging file
+tab_module  = 'parsetab'       # Default name of the table module
+default_lr  = 'LALR'           # Default LR table generation method
+
+error_count = 3                # Number of symbols that must be shifted to leave recovery mode
+
+yaccdevel   = 0                # Set to True if developing yacc.  This turns off optimized
+                               # implementations of certain functions.
+
+resultlimit = 40               # Size limit of results when running in debug mode.
+
+pickle_protocol = 0            # Protocol to use when writing pickle files
+
+import re, types, sys, os.path
+
+# Compatibility function for python 2.6/3.0
+if sys.version_info[0] < 3:
+    def func_code(f):
+        return f.func_code
+else:
+    def func_code(f):
+        return f.__code__
+
+# Compatibility
+try:
+    MAXINT = sys.maxint
+except AttributeError:
+    MAXINT = sys.maxsize
+
+# Python 2.x/3.0 compatibility.
+def load_ply_lex():
+    if sys.version_info[0] < 3:
+        import lex
+    else:
+        import ply.lex as lex
+    return lex
+
+# This object is a stand-in for a logging object created by the 
+# logging module.   PLY will use this by default to create things
+# such as the parser.out file.  If a user wants more detailed
+# information, they can create their own logging object and pass
+# it into PLY.
+
+class PlyLogger(object):
+    def __init__(self,f):
+        self.f = f
+    def debug(self,msg,*args,**kwargs):
+        self.f.write((msg % args) + "\n")
+    info     = debug
+
+    def warning(self,msg,*args,**kwargs):
+        self.f.write("WARNING: "+ (msg % args) + "\n")
+
+    def error(self,msg,*args,**kwargs):
+        self.f.write("ERROR: " + (msg % args) + "\n")
+
+    critical = debug
+
+# Null logger is used when no output is generated. Does nothing.
+class NullLogger(object):
+    def __getattribute__(self,name):
+        return self
+    def __call__(self,*args,**kwargs):
+        return self
+        
+# Exception raised for yacc-related errors
+class YaccError(Exception):   pass
+
+# Format the result message that the parser produces when running in debug mode.
+def format_result(r):
+    repr_str = repr(r)
+    if '\n' in repr_str: repr_str = repr(repr_str)
+    if len(repr_str) > resultlimit:
+        repr_str = repr_str[:resultlimit]+" ..."
+    result = "<%s @ 0x%x> (%s)" % (type(r).__name__,id(r),repr_str)
+    return result
+
+
+# Format stack entries when the parser is running in debug mode
+def format_stack_entry(r):
+    repr_str = repr(r)
+    if '\n' in repr_str: repr_str = repr(repr_str)
+    if len(repr_str) < 16:
+        return repr_str
+    else:
+        return "<%s @ 0x%x>" % (type(r).__name__,id(r))
+
+#-----------------------------------------------------------------------------
+#                        ===  LR Parsing Engine ===
+#
+# The following classes are used for the LR parser itself.  These are not
+# used during table construction and are independent of the actual LR
+# table generation algorithm
+#-----------------------------------------------------------------------------
+
+# This class is used to hold non-terminal grammar symbols during parsing.
+# It normally has the following attributes set:
+#        .type       = Grammar symbol type
+#        .value      = Symbol value
+#        .lineno     = Starting line number
+#        .endlineno  = Ending line number (optional, set automatically)
+#        .lexpos     = Starting lex position
+#        .endlexpos  = Ending lex position (optional, set automatically)
+
+class YaccSymbol:
+    def __str__(self):    return self.type
+    def __repr__(self):   return str(self)
+
+# This class is a wrapper around the objects actually passed to each
+# grammar rule.   Index lookup and assignment actually assign the
+# .value attribute of the underlying YaccSymbol object.
+# The lineno() method returns the line number of a given
+# item (or 0 if not defined).   The linespan() method returns
+# a tuple of (startline,endline) representing the range of lines
+# for a symbol.  The lexspan() method returns a tuple (lexpos,endlexpos)
+# representing the range of positional information for a symbol.
+
+class YaccProduction:
+    def __init__(self,s,stack=None):
+        self.slice = s
+        self.stack = stack
+        self.lexer = None
+        self.parser= None
+    def __getitem__(self,n):
+        if n >= 0: return self.slice[n].value
+        else: return self.stack[n].value
+
+    def __setitem__(self,n,v):
+        self.slice[n].value = v
+
+    def __getslice__(self,i,j):
+        return [s.value for s in self.slice[i:j]]
+
+    def __len__(self):
+        return len(self.slice)
+
+    def lineno(self,n):
+        return getattr(self.slice[n],"lineno",0)
+
+    def set_lineno(self,n,lineno):
+        self.slice[n].lineno = lineno
+
+    def linespan(self,n):
+        startline = getattr(self.slice[n],"lineno",0)
+        endline = getattr(self.slice[n],"endlineno",startline)
+        return startline,endline
+
+    def lexpos(self,n):
+        return getattr(self.slice[n],"lexpos",0)
+
+    def lexspan(self,n):
+        startpos = getattr(self.slice[n],"lexpos",0)
+        endpos = getattr(self.slice[n],"endlexpos",startpos)
+        return startpos,endpos
+
+    def error(self):
+       raise SyntaxError
+
+
+# -----------------------------------------------------------------------------
+#                               == LRParser ==
+#
+# The LR Parsing engine.
+# -----------------------------------------------------------------------------
+
+class LRParser:
+    def __init__(self,lrtab,errorf):
+        self.productions = lrtab.lr_productions
+        self.action      = lrtab.lr_action
+        self.goto        = lrtab.lr_goto
+        self.errorfunc   = errorf
+
+    def errok(self):
+        self.errorok     = 1
+
+    def restart(self):
+        del self.statestack[:]
+        del self.symstack[:]
+        sym = YaccSymbol()
+        sym.type = '$end'
+        self.symstack.append(sym)
+        self.statestack.append(0)
+
+    def parse(self,input=None,lexer=None,debug=0,tracking=0,tokenfunc=None):
+        if debug or yaccdevel:
+            if isinstance(debug,int):
+                debug = PlyLogger(sys.stderr)
+            return self.parsedebug(input,lexer,debug,tracking,tokenfunc)
+        elif tracking:
+            return self.parseopt(input,lexer,debug,tracking,tokenfunc)
+        else:
+            return self.parseopt_notrack(input,lexer,debug,tracking,tokenfunc)
+        
+
+    # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+    # parsedebug().
+    #
+    # This is the debugging enabled version of parse().  All changes made to the
+    # parsing engine should be made here.   For the non-debugging version,
+    # copy this code to a method parseopt() and delete all of the sections
+    # enclosed in:
+    #
+    #      #--! DEBUG
+    #      statements
+    #      #--! DEBUG
+    #
+    # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+    def parsedebug(self,input=None,lexer=None,debug=None,tracking=0,tokenfunc=None):
+        lookahead = None                 # Current lookahead symbol
+        lookaheadstack = [ ]             # Stack of lookahead symbols
+        actions = self.action            # Local reference to action table (to avoid lookup on self.)
+        goto    = self.goto              # Local reference to goto table (to avoid lookup on self.)
+        prod    = self.productions       # Local reference to production list (to avoid lookup on self.)
+        pslice  = YaccProduction(None)   # Production object passed to grammar rules
+        errorcount = 0                   # Used during error recovery 
+
+        # --! DEBUG
+        debug.info("PLY: PARSE DEBUG START")
+        # --! DEBUG
+
+        # If no lexer was given, we will try to use the lex module
+        if not lexer:
+            lex = load_ply_lex()
+            lexer = lex.lexer
+
+        # Set up the lexer and parser objects on pslice
+        pslice.lexer = lexer
+        pslice.parser = self
+
+        # If input was supplied, pass to lexer
+        if input is not None:
+            lexer.input(input)
+
+        if tokenfunc is None:
+           # Tokenize function
+           get_token = lexer.token
+        else:
+           get_token = tokenfunc
+
+        # Set up the state and symbol stacks
+
+        statestack = [ ]                # Stack of parsing states
+        self.statestack = statestack
+        symstack   = [ ]                # Stack of grammar symbols
+        self.symstack = symstack
+
+        pslice.stack = symstack         # Put in the production
+        errtoken   = None               # Err token
+
+        # The start state is assumed to be (0,$end)
+
+        statestack.append(0)
+        sym = YaccSymbol()
+        sym.type = "$end"
+        symstack.append(sym)
+        state = 0
+        while 1:
+            # Get the next symbol on the input.  If a lookahead symbol
+            # is already set, we just use that. Otherwise, we'll pull
+            # the next token off of the lookaheadstack or from the lexer
+
+            # --! DEBUG
+            debug.debug('')
+            debug.debug('State  : %s', state)
+            # --! DEBUG
+
+            if not lookahead:
+                if not lookaheadstack:
+                    lookahead = get_token()     # Get the next token
+                else:
+                    lookahead = lookaheadstack.pop()
+                if not lookahead:
+                    lookahead = YaccSymbol()
+                    lookahead.type = "$end"
+
+            # --! DEBUG
+            debug.debug('Stack  : %s',
+                        ("%s . %s" % (" ".join([xx.type for xx in symstack][1:]), str(lookahead))).lstrip())
+            # --! DEBUG
+
+            # Check the action table
+            ltype = lookahead.type
+            t = actions[state].get(ltype)
+
+            if t is not None:
+                if t > 0:
+                    # shift a symbol on the stack
+                    statestack.append(t)
+                    state = t
+                    
+                    # --! DEBUG
+                    debug.debug("Action : Shift and goto state %s", t)
+                    # --! DEBUG
+
+                    symstack.append(lookahead)
+                    lookahead = None
+
+                    # Decrease error count on successful shift
+                    if errorcount: errorcount -=1
+                    continue
+
+                if t < 0:
+                    # reduce a symbol on the stack, emit a production
+                    p = prod[-t]
+                    pname = p.name
+                    plen  = p.len
+
+                    # Get production function
+                    sym = YaccSymbol()
+                    sym.type = pname       # Production name
+                    sym.value = None
+
+                    # --! DEBUG
+                    if plen:
+                        debug.info("Action : Reduce rule [%s] with %s and goto state %d", p.str, "["+",".join([format_stack_entry(_v.value) for _v in symstack[-plen:]])+"]",-t)
+                    else:
+                        debug.info("Action : Reduce rule [%s] with %s and goto state %d", p.str, [],-t)
+                        
+                    # --! DEBUG
+
+                    if plen:
+                        targ = symstack[-plen-1:]
+                        targ[0] = sym
+
+                        # --! TRACKING
+                        if tracking:
+                           t1 = targ[1]
+                           sym.lineno = t1.lineno
+                           sym.lexpos = t1.lexpos
+                           t1 = targ[-1]
+                           sym.endlineno = getattr(t1,"endlineno",t1.lineno)
+                           sym.endlexpos = getattr(t1,"endlexpos",t1.lexpos)
+
+                        # --! TRACKING
+
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+                        # The code enclosed in this section is duplicated 
+                        # below as a performance optimization.  Make sure
+                        # changes get made in both locations.
+
+                        pslice.slice = targ
+                        
+                        try:
+                            # Call the grammar rule with our special slice object
+                            del symstack[-plen:]
+                            del statestack[-plen:]
+                            p.callable(pslice)
+                            # --! DEBUG
+                            debug.info("Result : %s", format_result(pslice[0]))
+                            # --! DEBUG
+                            symstack.append(sym)
+                            state = goto[statestack[-1]][pname]
+                            statestack.append(state)
+                        except SyntaxError:
+                            # If an error was set. Enter error recovery state
+                            lookaheadstack.append(lookahead)
+                            symstack.pop()
+                            statestack.pop()
+                            state = statestack[-1]
+                            sym.type = 'error'
+                            lookahead = sym
+                            errorcount = error_count
+                            self.errorok = 0
+                        continue
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+    
+                    else:
+
+                        # --! TRACKING
+                        if tracking:
+                           sym.lineno = lexer.lineno
+                           sym.lexpos = lexer.lexpos
+                        # --! TRACKING
+
+                        targ = [ sym ]
+
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+                        # The code enclosed in this section is duplicated 
+                        # above as a performance optimization.  Make sure
+                        # changes get made in both locations.
+
+                        pslice.slice = targ
+
+                        try:
+                            # Call the grammar rule with our special slice object
+                            p.callable(pslice)
+                            # --! DEBUG
+                            debug.info("Result : %s", format_result(pslice[0]))
+                            # --! DEBUG
+                            symstack.append(sym)
+                            state = goto[statestack[-1]][pname]
+                            statestack.append(state)
+                        except SyntaxError:
+                            # If an error was set. Enter error recovery state
+                            lookaheadstack.append(lookahead)
+                            symstack.pop()
+                            statestack.pop()
+                            state = statestack[-1]
+                            sym.type = 'error'
+                            lookahead = sym
+                            errorcount = error_count
+                            self.errorok = 0
+                        continue
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+                if t == 0:
+                    n = symstack[-1]
+                    result = getattr(n,"value",None)
+                    # --! DEBUG
+                    debug.info("Done   : Returning %s", format_result(result))
+                    debug.info("PLY: PARSE DEBUG END")
+                    # --! DEBUG
+                    return result
+
+            if t == None:
+
+                # --! DEBUG
+                debug.error('Error  : %s',
+                            ("%s . %s" % (" ".join([xx.type for xx in symstack][1:]), str(lookahead))).lstrip())
+                # --! DEBUG
+
+                # We have some kind of parsing error here.  To handle
+                # this, we are going to push the current token onto
+                # the tokenstack and replace it with an 'error' token.
+                # If there are any synchronization rules, they may
+                # catch it.
+                #
+                # In addition to pushing the error token, we call call
+                # the user defined p_error() function if this is the
+                # first syntax error.  This function is only called if
+                # errorcount == 0.
+                if errorcount == 0 or self.errorok:
+                    errorcount = error_count
+                    self.errorok = 0
+                    errtoken = lookahead
+                    if errtoken.type == "$end":
+                        errtoken = None               # End of file!
+                    if self.errorfunc:
+                        global errok,token,restart
+                        errok = self.errok        # Set some special functions available in error recovery
+                        token = get_token
+                        restart = self.restart
+                        if errtoken and not hasattr(errtoken,'lexer'):
+                            errtoken.lexer = lexer
+                        tok = self.errorfunc(errtoken)
+                        del errok, token, restart   # Delete special functions
+
+                        if self.errorok:
+                            # User must have done some kind of panic
+                            # mode recovery on their own.  The
+                            # returned token is the next lookahead
+                            lookahead = tok
+                            errtoken = None
+                            continue
+                    else:
+                        if errtoken:
+                            if hasattr(errtoken,"lineno"): lineno = lookahead.lineno
+                            else: lineno = 0
+                            if lineno:
+                                sys.stderr.write("yacc: Syntax error at line %d, token=%s\n" % (lineno, errtoken.type))
+                            else:
+                                sys.stderr.write("yacc: Syntax error, token=%s" % errtoken.type)
+                        else:
+                            sys.stderr.write("yacc: Parse error in input. EOF\n")
+                            return
+
+                else:
+                    errorcount = error_count
+
+                # case 1:  the statestack only has 1 entry on it.  If we're in this state, the
+                # entire parse has been rolled back and we're completely hosed.   The token is
+                # discarded and we just keep going.
+
+                if len(statestack) <= 1 and lookahead.type != "$end":
+                    lookahead = None
+                    errtoken = None
+                    state = 0
+                    # Nuke the pushback stack
+                    del lookaheadstack[:]
+                    continue
+
+                # case 2: the statestack has a couple of entries on it, but we're
+                # at the end of the file. nuke the top entry and generate an error token
+
+                # Start nuking entries on the stack
+                if lookahead.type == "$end":
+                    # Whoa. We're really hosed here. Bail out
+                    return
+
+                if lookahead.type != 'error':
+                    sym = symstack[-1]
+                    if sym.type == 'error':
+                        # Hmmm. Error is on top of stack, we'll just nuke input
+                        # symbol and continue
+                        lookahead = None
+                        continue
+                    t = YaccSymbol()
+                    t.type = 'error'
+                    if hasattr(lookahead,"lineno"):
+                        t.lineno = lookahead.lineno
+                    t.value = lookahead
+                    lookaheadstack.append(lookahead)
+                    lookahead = t
+                else:
+                    symstack.pop()
+                    statestack.pop()
+                    state = statestack[-1]       # Potential bug fix
+
+                continue
+
+            # Call an error function here
+            raise RuntimeError("yacc: internal parser error!!!\n")
+
+    # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+    # parseopt().
+    #
+    # Optimized version of parse() method.  DO NOT EDIT THIS CODE DIRECTLY.
+    # Edit the debug version above, then copy any modifications to the method
+    # below while removing #--! DEBUG sections.
+    # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+
+    def parseopt(self,input=None,lexer=None,debug=0,tracking=0,tokenfunc=None):
+        lookahead = None                 # Current lookahead symbol
+        lookaheadstack = [ ]             # Stack of lookahead symbols
+        actions = self.action            # Local reference to action table (to avoid lookup on self.)
+        goto    = self.goto              # Local reference to goto table (to avoid lookup on self.)
+        prod    = self.productions       # Local reference to production list (to avoid lookup on self.)
+        pslice  = YaccProduction(None)   # Production object passed to grammar rules
+        errorcount = 0                   # Used during error recovery 
+
+        # If no lexer was given, we will try to use the lex module
+        if not lexer:
+            lex = load_ply_lex()
+            lexer = lex.lexer
+        
+        # Set up the lexer and parser objects on pslice
+        pslice.lexer = lexer
+        pslice.parser = self
+
+        # If input was supplied, pass to lexer
+        if input is not None:
+            lexer.input(input)
+
+        if tokenfunc is None:
+           # Tokenize function
+           get_token = lexer.token
+        else:
+           get_token = tokenfunc
+
+        # Set up the state and symbol stacks
+
+        statestack = [ ]                # Stack of parsing states
+        self.statestack = statestack
+        symstack   = [ ]                # Stack of grammar symbols
+        self.symstack = symstack
+
+        pslice.stack = symstack         # Put in the production
+        errtoken   = None               # Err token
+
+        # The start state is assumed to be (0,$end)
+
+        statestack.append(0)
+        sym = YaccSymbol()
+        sym.type = '$end'
+        symstack.append(sym)
+        state = 0
+        while 1:
+            # Get the next symbol on the input.  If a lookahead symbol
+            # is already set, we just use that. Otherwise, we'll pull
+            # the next token off of the lookaheadstack or from the lexer
+
+            if not lookahead:
+                if not lookaheadstack:
+                    lookahead = get_token()     # Get the next token
+                else:
+                    lookahead = lookaheadstack.pop()
+                if not lookahead:
+                    lookahead = YaccSymbol()
+                    lookahead.type = '$end'
+
+            # Check the action table
+            ltype = lookahead.type
+            t = actions[state].get(ltype)
+
+            if t is not None:
+                if t > 0:
+                    # shift a symbol on the stack
+                    statestack.append(t)
+                    state = t
+
+                    symstack.append(lookahead)
+                    lookahead = None
+
+                    # Decrease error count on successful shift
+                    if errorcount: errorcount -=1
+                    continue
+
+                if t < 0:
+                    # reduce a symbol on the stack, emit a production
+                    p = prod[-t]
+                    pname = p.name
+                    plen  = p.len
+
+                    # Get production function
+                    sym = YaccSymbol()
+                    sym.type = pname       # Production name
+                    sym.value = None
+
+                    if plen:
+                        targ = symstack[-plen-1:]
+                        targ[0] = sym
+
+                        # --! TRACKING
+                        if tracking:
+                           t1 = targ[1]
+                           sym.lineno = t1.lineno
+                           sym.lexpos = t1.lexpos
+                           t1 = targ[-1]
+                           sym.endlineno = getattr(t1,"endlineno",t1.lineno)
+                           sym.endlexpos = getattr(t1,"endlexpos",t1.lexpos)
+
+                        # --! TRACKING
+
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+                        # The code enclosed in this section is duplicated 
+                        # below as a performance optimization.  Make sure
+                        # changes get made in both locations.
+
+                        pslice.slice = targ
+                        
+                        try:
+                            # Call the grammar rule with our special slice object
+                            del symstack[-plen:]
+                            del statestack[-plen:]
+                            p.callable(pslice)
+                            symstack.append(sym)
+                            state = goto[statestack[-1]][pname]
+                            statestack.append(state)
+                        except SyntaxError:
+                            # If an error was set. Enter error recovery state
+                            lookaheadstack.append(lookahead)
+                            symstack.pop()
+                            statestack.pop()
+                            state = statestack[-1]
+                            sym.type = 'error'
+                            lookahead = sym
+                            errorcount = error_count
+                            self.errorok = 0
+                        continue
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+    
+                    else:
+
+                        # --! TRACKING
+                        if tracking:
+                           sym.lineno = lexer.lineno
+                           sym.lexpos = lexer.lexpos
+                        # --! TRACKING
+
+                        targ = [ sym ]
+
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+                        # The code enclosed in this section is duplicated 
+                        # above as a performance optimization.  Make sure
+                        # changes get made in both locations.
+
+                        pslice.slice = targ
+
+                        try:
+                            # Call the grammar rule with our special slice object
+                            p.callable(pslice)
+                            symstack.append(sym)
+                            state = goto[statestack[-1]][pname]
+                            statestack.append(state)
+                        except SyntaxError:
+                            # If an error was set. Enter error recovery state
+                            lookaheadstack.append(lookahead)
+                            symstack.pop()
+                            statestack.pop()
+                            state = statestack[-1]
+                            sym.type = 'error'
+                            lookahead = sym
+                            errorcount = error_count
+                            self.errorok = 0
+                        continue
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+                if t == 0:
+                    n = symstack[-1]
+                    return getattr(n,"value",None)
+
+            if t == None:
+
+                # We have some kind of parsing error here.  To handle
+                # this, we are going to push the current token onto
+                # the tokenstack and replace it with an 'error' token.
+                # If there are any synchronization rules, they may
+                # catch it.
+                #
+                # In addition to pushing the error token, we call call
+                # the user defined p_error() function if this is the
+                # first syntax error.  This function is only called if
+                # errorcount == 0.
+                if errorcount == 0 or self.errorok:
+                    errorcount = error_count
+                    self.errorok = 0
+                    errtoken = lookahead
+                    if errtoken.type == '$end':
+                        errtoken = None               # End of file!
+                    if self.errorfunc:
+                        global errok,token,restart
+                        errok = self.errok        # Set some special functions available in error recovery
+                        token = get_token
+                        restart = self.restart
+                        if errtoken and not hasattr(errtoken,'lexer'):
+                            errtoken.lexer = lexer
+                        tok = self.errorfunc(errtoken)
+                        del errok, token, restart   # Delete special functions
+
+                        if self.errorok:
+                            # User must have done some kind of panic
+                            # mode recovery on their own.  The
+                            # returned token is the next lookahead
+                            lookahead = tok
+                            errtoken = None
+                            continue
+                    else:
+                        if errtoken:
+                            if hasattr(errtoken,"lineno"): lineno = lookahead.lineno
+                            else: lineno = 0
+                            if lineno:
+                                sys.stderr.write("yacc: Syntax error at line %d, token=%s\n" % (lineno, errtoken.type))
+                            else:
+                                sys.stderr.write("yacc: Syntax error, token=%s" % errtoken.type)
+                        else:
+                            sys.stderr.write("yacc: Parse error in input. EOF\n")
+                            return
+
+                else:
+                    errorcount = error_count
+
+                # case 1:  the statestack only has 1 entry on it.  If we're in this state, the
+                # entire parse has been rolled back and we're completely hosed.   The token is
+                # discarded and we just keep going.
+
+                if len(statestack) <= 1 and lookahead.type != '$end':
+                    lookahead = None
+                    errtoken = None
+                    state = 0
+                    # Nuke the pushback stack
+                    del lookaheadstack[:]
+                    continue
+
+                # case 2: the statestack has a couple of entries on it, but we're
+                # at the end of the file. nuke the top entry and generate an error token
+
+                # Start nuking entries on the stack
+                if lookahead.type == '$end':
+                    # Whoa. We're really hosed here. Bail out
+                    return
+
+                if lookahead.type != 'error':
+                    sym = symstack[-1]
+                    if sym.type == 'error':
+                        # Hmmm. Error is on top of stack, we'll just nuke input
+                        # symbol and continue
+                        lookahead = None
+                        continue
+                    t = YaccSymbol()
+                    t.type = 'error'
+                    if hasattr(lookahead,"lineno"):
+                        t.lineno = lookahead.lineno
+                    t.value = lookahead
+                    lookaheadstack.append(lookahead)
+                    lookahead = t
+                else:
+                    symstack.pop()
+                    statestack.pop()
+                    state = statestack[-1]       # Potential bug fix
+
+                continue
+
+            # Call an error function here
+            raise RuntimeError("yacc: internal parser error!!!\n")
+
+    # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+    # parseopt_notrack().
+    #
+    # Optimized version of parseopt() with line number tracking removed. 
+    # DO NOT EDIT THIS CODE DIRECTLY. Copy the optimized version and remove
+    # code in the #--! TRACKING sections
+    # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+    def parseopt_notrack(self,input=None,lexer=None,debug=0,tracking=0,tokenfunc=None):
+        lookahead = None                 # Current lookahead symbol
+        lookaheadstack = [ ]             # Stack of lookahead symbols
+        actions = self.action            # Local reference to action table (to avoid lookup on self.)
+        goto    = self.goto              # Local reference to goto table (to avoid lookup on self.)
+        prod    = self.productions       # Local reference to production list (to avoid lookup on self.)
+        pslice  = YaccProduction(None)   # Production object passed to grammar rules
+        errorcount = 0                   # Used during error recovery 
+
+        # If no lexer was given, we will try to use the lex module
+        if not lexer:
+            lex = load_ply_lex()
+            lexer = lex.lexer
+        
+        # Set up the lexer and parser objects on pslice
+        pslice.lexer = lexer
+        pslice.parser = self
+
+        # If input was supplied, pass to lexer
+        if input is not None:
+            lexer.input(input)
+
+        if tokenfunc is None:
+           # Tokenize function
+           get_token = lexer.token
+        else:
+           get_token = tokenfunc
+
+        # Set up the state and symbol stacks
+
+        statestack = [ ]                # Stack of parsing states
+        self.statestack = statestack
+        symstack   = [ ]                # Stack of grammar symbols
+        self.symstack = symstack
+
+        pslice.stack = symstack         # Put in the production
+        errtoken   = None               # Err token
+
+        # The start state is assumed to be (0,$end)
+
+        statestack.append(0)
+        sym = YaccSymbol()
+        sym.type = '$end'
+        symstack.append(sym)
+        state = 0
+        while 1:
+            # Get the next symbol on the input.  If a lookahead symbol
+            # is already set, we just use that. Otherwise, we'll pull
+            # the next token off of the lookaheadstack or from the lexer
+
+            if not lookahead:
+                if not lookaheadstack:
+                    lookahead = get_token()     # Get the next token
+                else:
+                    lookahead = lookaheadstack.pop()
+                if not lookahead:
+                    lookahead = YaccSymbol()
+                    lookahead.type = '$end'
+
+            # Check the action table
+            ltype = lookahead.type
+            t = actions[state].get(ltype)
+
+            if t is not None:
+                if t > 0:
+                    # shift a symbol on the stack
+                    statestack.append(t)
+                    state = t
+
+                    symstack.append(lookahead)
+                    lookahead = None
+
+                    # Decrease error count on successful shift
+                    if errorcount: errorcount -=1
+                    continue
+
+                if t < 0:
+                    # reduce a symbol on the stack, emit a production
+                    p = prod[-t]
+                    pname = p.name
+                    plen  = p.len
+
+                    # Get production function
+                    sym = YaccSymbol()
+                    sym.type = pname       # Production name
+                    sym.value = None
+
+                    if plen:
+                        targ = symstack[-plen-1:]
+                        targ[0] = sym
+
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+                        # The code enclosed in this section is duplicated 
+                        # below as a performance optimization.  Make sure
+                        # changes get made in both locations.
+
+                        pslice.slice = targ
+                        
+                        try:
+                            # Call the grammar rule with our special slice object
+                            del symstack[-plen:]
+                            del statestack[-plen:]
+                            p.callable(pslice)
+                            symstack.append(sym)
+                            state = goto[statestack[-1]][pname]
+                            statestack.append(state)
+                        except SyntaxError:
+                            # If an error was set. Enter error recovery state
+                            lookaheadstack.append(lookahead)
+                            symstack.pop()
+                            statestack.pop()
+                            state = statestack[-1]
+                            sym.type = 'error'
+                            lookahead = sym
+                            errorcount = error_count
+                            self.errorok = 0
+                        continue
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+    
+                    else:
+
+                        targ = [ sym ]
+
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+                        # The code enclosed in this section is duplicated 
+                        # above as a performance optimization.  Make sure
+                        # changes get made in both locations.
+
+                        pslice.slice = targ
+
+                        try:
+                            # Call the grammar rule with our special slice object
+                            p.callable(pslice)
+                            symstack.append(sym)
+                            state = goto[statestack[-1]][pname]
+                            statestack.append(state)
+                        except SyntaxError:
+                            # If an error was set. Enter error recovery state
+                            lookaheadstack.append(lookahead)
+                            symstack.pop()
+                            statestack.pop()
+                            state = statestack[-1]
+                            sym.type = 'error'
+                            lookahead = sym
+                            errorcount = error_count
+                            self.errorok = 0
+                        continue
+                        # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+
+                if t == 0:
+                    n = symstack[-1]
+                    return getattr(n,"value",None)
+
+            if t == None:
+
+                # We have some kind of parsing error here.  To handle
+                # this, we are going to push the current token onto
+                # the tokenstack and replace it with an 'error' token.
+                # If there are any synchronization rules, they may
+                # catch it.
+                #
+                # In addition to pushing the error token, we call call
+                # the user defined p_error() function if this is the
+                # first syntax error.  This function is only called if
+                # errorcount == 0.
+                if errorcount == 0 or self.errorok:
+                    errorcount = error_count
+                    self.errorok = 0
+                    errtoken = lookahead
+                    if errtoken.type == '$end':
+                        errtoken = None               # End of file!
+                    if self.errorfunc:
+                        global errok,token,restart
+                        errok = self.errok        # Set some special functions available in error recovery
+                        token = get_token
+                        restart = self.restart
+                        if errtoken and not hasattr(errtoken,'lexer'):
+                            errtoken.lexer = lexer
+                        tok = self.errorfunc(errtoken)
+                        del errok, token, restart   # Delete special functions
+
+                        if self.errorok:
+                            # User must have done some kind of panic
+                            # mode recovery on their own.  The
+                            # returned token is the next lookahead
+                            lookahead = tok
+                            errtoken = None
+                            continue
+                    else:
+                        if errtoken:
+                            if hasattr(errtoken,"lineno"): lineno = lookahead.lineno
+                            else: lineno = 0
+                            if lineno:
+                                sys.stderr.write("yacc: Syntax error at line %d, token=%s\n" % (lineno, errtoken.type))
+                            else:
+                                sys.stderr.write("yacc: Syntax error, token=%s" % errtoken.type)
+                        else:
+                            sys.stderr.write("yacc: Parse error in input. EOF\n")
+                            return
+
+                else:
+                    errorcount = error_count
+
+                # case 1:  the statestack only has 1 entry on it.  If we're in this state, the
+                # entire parse has been rolled back and we're completely hosed.   The token is
+                # discarded and we just keep going.
+
+                if len(statestack) <= 1 and lookahead.type != '$end':
+                    lookahead = None
+                    errtoken = None
+                    state = 0
+                    # Nuke the pushback stack
+                    del lookaheadstack[:]
+                    continue
+
+                # case 2: the statestack has a couple of entries on it, but we're
+                # at the end of the file. nuke the top entry and generate an error token
+
+                # Start nuking entries on the stack
+                if lookahead.type == '$end':
+                    # Whoa. We're really hosed here. Bail out
+                    return
+
+                if lookahead.type != 'error':
+                    sym = symstack[-1]
+                    if sym.type == 'error':
+                        # Hmmm. Error is on top of stack, we'll just nuke input
+                        # symbol and continue
+                        lookahead = None
+                        continue
+                    t = YaccSymbol()
+                    t.type = 'error'
+                    if hasattr(lookahead,"lineno"):
+                        t.lineno = lookahead.lineno
+                    t.value = lookahead
+                    lookaheadstack.append(lookahead)
+                    lookahead = t
+                else:
+                    symstack.pop()
+                    statestack.pop()
+                    state = statestack[-1]       # Potential bug fix
+
+                continue
+
+            # Call an error function here
+            raise RuntimeError("yacc: internal parser error!!!\n")
+
+# -----------------------------------------------------------------------------
+#                          === Grammar Representation ===
+#
+# The following functions, classes, and variables are used to represent and
+# manipulate the rules that make up a grammar. 
+# -----------------------------------------------------------------------------
+
+import re
+
+# regex matching identifiers
+_is_identifier = re.compile(r'^[a-zA-Z0-9_-]+$')
+
+# -----------------------------------------------------------------------------
+# class Production:
+#
+# This class stores the raw information about a single production or grammar rule.
+# A grammar rule refers to a specification such as this:
+#
+#       expr : expr PLUS term 
+#
+# Here are the basic attributes defined on all productions
+#
+#       name     - Name of the production.  For example 'expr'
+#       prod     - A list of symbols on the right side ['expr','PLUS','term']
+#       prec     - Production precedence level
+#       number   - Production number.
+#       func     - Function that executes on reduce
+#       file     - File where production function is defined
+#       lineno   - Line number where production function is defined
+#
+# The following attributes are defined or optional.
+#
+#       len       - Length of the production (number of symbols on right hand side)
+#       usyms     - Set of unique symbols found in the production
+# -----------------------------------------------------------------------------
+
+class Production(object):
+    reduced = 0
+    def __init__(self,number,name,prod,precedence=('right',0),func=None,file='',line=0):
+        self.name     = name
+        self.prod     = tuple(prod)
+        self.number   = number
+        self.func     = func
+        self.callable = None
+        self.file     = file
+        self.line     = line
+        self.prec     = precedence
+
+        # Internal settings used during table construction
+        
+        self.len  = len(self.prod)   # Length of the production
+
+        # Create a list of unique production symbols used in the production
+        self.usyms = [ ]             
+        for s in self.prod:
+            if s not in self.usyms:
+                self.usyms.append(s)
+
+        # List of all LR items for the production
+        self.lr_items = []
+        self.lr_next = None
+
+        # Create a string representation
+        if self.prod:
+            self.str = "%s -> %s" % (self.name," ".join(self.prod))
+        else:
+            self.str = "%s -> <empty>" % self.name
+
+    def __str__(self):
+        return self.str
+
+    def __repr__(self):
+        return "Production("+str(self)+")"
+
+    def __len__(self):
+        return len(self.prod)
+
+    def __nonzero__(self):
+        return 1
+
+    def __getitem__(self,index):
+        return self.prod[index]
+            
+    # Return the nth lr_item from the production (or None if at the end)
+    def lr_item(self,n):
+        if n > len(self.prod): return None
+        p = LRItem(self,n)
+
+        # Precompute the list of productions immediately following.  Hack. Remove later
+        try:
+            p.lr_after = Prodnames[p.prod[n+1]]
+        except (IndexError,KeyError):
+            p.lr_after = []
+        try:
+            p.lr_before = p.prod[n-1]
+        except IndexError:
+            p.lr_before = None
+
+        return p
+    
+    # Bind the production function name to a callable
+    def bind(self,pdict):
+        if self.func:
+            self.callable = pdict[self.func]
+
+# This class serves as a minimal standin for Production objects when
+# reading table data from files.   It only contains information
+# actually used by the LR parsing engine, plus some additional
+# debugging information.
+class MiniProduction(object):
+    def __init__(self,str,name,len,func,file,line):
+        self.name     = name
+        self.len      = len
+        self.func     = func
+        self.callable = None
+        self.file     = file
+        self.line     = line
+        self.str      = str
+    def __str__(self):
+        return self.str
+    def __repr__(self):
+        return "MiniProduction(%s)" % self.str
+
+    # Bind the production function name to a callable
+    def bind(self,pdict):
+        if self.func:
+            self.callable = pdict[self.func]
+
+
+# -----------------------------------------------------------------------------
+# class LRItem
+#
+# This class represents a specific stage of parsing a production rule.  For
+# example: 
+#
+#       expr : expr . PLUS term 
+#
+# In the above, the "." represents the current location of the parse.  Here
+# basic attributes:
+#
+#       name       - Name of the production.  For example 'expr'
+#       prod       - A list of symbols on the right side ['expr','.', 'PLUS','term']
+#       number     - Production number.
+#
+#       lr_next      Next LR item. Example, if we are ' expr -> expr . PLUS term'
+#                    then lr_next refers to 'expr -> expr PLUS . term'
+#       lr_index   - LR item index (location of the ".") in the prod list.
+#       lookaheads - LALR lookahead symbols for this item
+#       len        - Length of the production (number of symbols on right hand side)
+#       lr_after    - List of all productions that immediately follow
+#       lr_before   - Grammar symbol immediately before
+# -----------------------------------------------------------------------------
+
+class LRItem(object):
+    def __init__(self,p,n):
+        self.name       = p.name
+        self.prod       = list(p.prod)
+        self.number     = p.number
+        self.lr_index   = n
+        self.lookaheads = { }
+        self.prod.insert(n,".")
+        self.prod       = tuple(self.prod)
+        self.len        = len(self.prod)
+        self.usyms      = p.usyms
+
+    def __str__(self):
+        if self.prod:
+            s = "%s -> %s" % (self.name," ".join(self.prod))
+        else:
+            s = "%s -> <empty>" % self.name
+        return s
+
+    def __repr__(self):
+        return "LRItem("+str(self)+")"
+
+# -----------------------------------------------------------------------------
+# rightmost_terminal()
+#
+# Return the rightmost terminal from a list of symbols.  Used in add_production()
+# -----------------------------------------------------------------------------
+def rightmost_terminal(symbols, terminals):
+    i = len(symbols) - 1
+    while i >= 0:
+        if symbols[i] in terminals:
+            return symbols[i]
+        i -= 1
+    return None
+
+# -----------------------------------------------------------------------------
+#                           === GRAMMAR CLASS ===
+#
+# The following class represents the contents of the specified grammar along
+# with various computed properties such as first sets, follow sets, LR items, etc.
+# This data is used for critical parts of the table generation process later.
+# -----------------------------------------------------------------------------
+
+class GrammarError(YaccError): pass
+
+class Grammar(object):
+    def __init__(self,terminals):
+        self.Productions  = [None]  # A list of all of the productions.  The first
+                                    # entry is always reserved for the purpose of
+                                    # building an augmented grammar
+
+        self.Prodnames    = { }     # A dictionary mapping the names of nonterminals to a list of all
+                                    # productions of that nonterminal.
+
+        self.Prodmap      = { }     # A dictionary that is only used to detect duplicate
+                                    # productions.
+
+        self.Terminals    = { }     # A dictionary mapping the names of terminal symbols to a
+                                    # list of the rules where they are used.
+
+        for term in terminals:
+            self.Terminals[term] = []
+
+        self.Terminals['error'] = []
+
+        self.Nonterminals = { }     # A dictionary mapping names of nonterminals to a list
+                                    # of rule numbers where they are used.
+
+        self.First        = { }     # A dictionary of precomputed FIRST(x) symbols
+
+        self.Follow       = { }     # A dictionary of precomputed FOLLOW(x) symbols
+
+        self.Precedence   = { }     # Precedence rules for each terminal. Contains tuples of the
+                                    # form ('right',level) or ('nonassoc', level) or ('left',level)
+
+        self.UsedPrecedence = { }   # Precedence rules that were actually used by the grammer.
+                                    # This is only used to provide error checking and to generate
+                                    # a warning about unused precedence rules.
+
+        self.Start = None           # Starting symbol for the grammar
+
+
+    def __len__(self):
+        return len(self.Productions)
+
+    def __getitem__(self,index):
+        return self.Productions[index]
+
+    # -----------------------------------------------------------------------------
+    # set_precedence()
+    #
+    # Sets the precedence for a given terminal. assoc is the associativity such as
+    # 'left','right', or 'nonassoc'.  level is a numeric level.
+    #
+    # -----------------------------------------------------------------------------
+
+    def set_precedence(self,term,assoc,level):
+        assert self.Productions == [None],"Must call set_precedence() before add_production()"
+        if term in self.Precedence:
+            raise GrammarError("Precedence already specified for terminal '%s'" % term)
+        if assoc not in ['left','right','nonassoc']:
+            raise GrammarError("Associativity must be one of 'left','right', or 'nonassoc'")
+        self.Precedence[term] = (assoc,level)
+ 
+    # -----------------------------------------------------------------------------
+    # add_production()
+    #
+    # Given an action function, this function assembles a production rule and
+    # computes its precedence level.
+    #
+    # The production rule is supplied as a list of symbols.   For example,
+    # a rule such as 'expr : expr PLUS term' has a production name of 'expr' and
+    # symbols ['expr','PLUS','term'].
+    #
+    # Precedence is determined by the precedence of the right-most non-terminal
+    # or the precedence of a terminal specified by %prec.
+    #
+    # A variety of error checks are performed to make sure production symbols
+    # are valid and that %prec is used correctly.
+    # -----------------------------------------------------------------------------
+
+    def add_production(self,prodname,syms,func=None,file='',line=0):
+
+        if prodname in self.Terminals:
+            raise GrammarError("%s:%d: Illegal rule name '%s'. Already defined as a token" % (file,line,prodname))
+        if prodname == 'error':
+            raise GrammarError("%s:%d: Illegal rule name '%s'. error is a reserved word" % (file,line,prodname))
+        if not _is_identifier.match(prodname):
+            raise GrammarError("%s:%d: Illegal rule name '%s'" % (file,line,prodname))
+
+        # Look for literal tokens 
+        for n,s in enumerate(syms):
+            if s[0] in "'\"":
+                 try:
+                     c = eval(s)
+                     if (len(c) > 1):
+                          raise GrammarError("%s:%d: Literal token %s in rule '%s' may only be a single character" % (file,line,s, prodname))
+                     if not c in self.Terminals:
+                          self.Terminals[c] = []
+                     syms[n] = c
+                     continue
+                 except SyntaxError:
+                     pass
+            if not _is_identifier.match(s) and s != '%prec':
+                raise GrammarError("%s:%d: Illegal name '%s' in rule '%s'" % (file,line,s, prodname))
+        
+        # Determine the precedence level
+        if '%prec' in syms:
+            if syms[-1] == '%prec':
+                raise GrammarError("%s:%d: Syntax error. Nothing follows %%prec" % (file,line))
+            if syms[-2] != '%prec':
+                raise GrammarError("%s:%d: Syntax error. %%prec can only appear at the end of a grammar rule" % (file,line))
+            precname = syms[-1]
+            prodprec = self.Precedence.get(precname,None)
+            if not prodprec:
+                raise GrammarError("%s:%d: Nothing known about the precedence of '%s'" % (file,line,precname))
+            else:
+                self.UsedPrecedence[precname] = 1
+            del syms[-2:]     # Drop %prec from the rule
+        else:
+            # If no %prec, precedence is determined by the rightmost terminal symbol
+            precname = rightmost_terminal(syms,self.Terminals)
+            prodprec = self.Precedence.get(precname,('right',0)) 
+            
+        # See if the rule is already in the rulemap
+        map = "%s -> %s" % (prodname,syms)
+        if map in self.Prodmap:
+            m = self.Prodmap[map]
+            raise GrammarError("%s:%d: Duplicate rule %s. " % (file,line, m) +
+                               "Previous definition at %s:%d" % (m.file, m.line))
+
+        # From this point on, everything is valid.  Create a new Production instance
+        pnumber  = len(self.Productions)
+        if not prodname in self.Nonterminals:
+            self.Nonterminals[prodname] = [ ]
+
+        # Add the production number to Terminals and Nonterminals
+        for t in syms:
+            if t in self.Terminals:
+                self.Terminals[t].append(pnumber)
+            else:
+                if not t in self.Nonterminals:
+                    self.Nonterminals[t] = [ ]
+                self.Nonterminals[t].append(pnumber)
+
+        # Create a production and add it to the list of productions
+        p = Production(pnumber,prodname,syms,prodprec,func,file,line)
+        self.Productions.append(p)
+        self.Prodmap[map] = p
+
+        # Add to the global productions list
+        try:
+            self.Prodnames[prodname].append(p)
+        except KeyError:
+            self.Prodnames[prodname] = [ p ]
+        return 0
+
+    # -----------------------------------------------------------------------------
+    # set_start()
+    #
+    # Sets the starting symbol and creates the augmented grammar.  Production 
+    # rule 0 is S' -> start where start is the start symbol.
+    # -----------------------------------------------------------------------------
+
+    def set_start(self,start=None):
+        if not start:
+            start = self.Productions[1].name
+        if start not in self.Nonterminals:
+            raise GrammarError("start symbol %s undefined" % start)
+        self.Productions[0] = Production(0,"S'",[start])
+        self.Nonterminals[start].append(0)
+        self.Start = start
+
+    # -----------------------------------------------------------------------------
+    # find_unreachable()
+    #
+    # Find all of the nonterminal symbols that can't be reached from the starting
+    # symbol.  Returns a list of nonterminals that can't be reached.
+    # -----------------------------------------------------------------------------
+
+    def find_unreachable(self):
+        
+        # Mark all symbols that are reachable from a symbol s
+        def mark_reachable_from(s):
+            if reachable[s]:
+                # We've already reached symbol s.
+                return
+            reachable[s] = 1
+            for p in self.Prodnames.get(s,[]):
+                for r in p.prod:
+                    mark_reachable_from(r)
+
+        reachable   = { }
+        for s in list(self.Terminals) + list(self.Nonterminals):
+            reachable[s] = 0
+
+        mark_reachable_from( self.Productions[0].prod[0] )
+
+        return [s for s in list(self.Nonterminals)
+                        if not reachable[s]]
+    
+    # -----------------------------------------------------------------------------
+    # infinite_cycles()
+    #
+    # This function looks at the various parsing rules and tries to detect
+    # infinite recursion cycles (grammar rules where there is no possible way
+    # to derive a string of only terminals).
+    # -----------------------------------------------------------------------------
+
+    def infinite_cycles(self):
+        terminates = {}
+
+        # Terminals:
+        for t in self.Terminals:
+            terminates[t] = 1
+
+        terminates['$end'] = 1
+
+        # Nonterminals:
+
+        # Initialize to false:
+        for n in self.Nonterminals:
+            terminates[n] = 0
+
+        # Then propagate termination until no change:
+        while 1:
+            some_change = 0
+            for (n,pl) in self.Prodnames.items():
+                # Nonterminal n terminates iff any of its productions terminates.
+                for p in pl:
+                    # Production p terminates iff all of its rhs symbols terminate.
+                    for s in p.prod:
+                        if not terminates[s]:
+                            # The symbol s does not terminate,
+                            # so production p does not terminate.
+                            p_terminates = 0
+                            break
+                    else:
+                        # didn't break from the loop,
+                        # so every symbol s terminates
+                        # so production p terminates.
+                        p_terminates = 1
+
+                    if p_terminates:
+                        # symbol n terminates!
+                        if not terminates[n]:
+                            terminates[n] = 1
+                            some_change = 1
+                        # Don't need to consider any more productions for this n.
+                        break
+
+            if not some_change:
+                break
+
+        infinite = []
+        for (s,term) in terminates.items():
+            if not term:
+                if not s in self.Prodnames and not s in self.Terminals and s != 'error':
+                    # s is used-but-not-defined, and we've already warned of that,
+                    # so it would be overkill to say that it's also non-terminating.
+                    pass
+                else:
+                    infinite.append(s)
+
+        return infinite
+
+
+    # -----------------------------------------------------------------------------
+    # undefined_symbols()
+    #
+    # Find all symbols that were used the grammar, but not defined as tokens or
+    # grammar rules.  Returns a list of tuples (sym, prod) where sym in the symbol
+    # and prod is the production where the symbol was used. 
+    # -----------------------------------------------------------------------------
+    def undefined_symbols(self):
+        result = []
+        for p in self.Productions:
+            if not p: continue
+
+            for s in p.prod:
+                if not s in self.Prodnames and not s in self.Terminals and s != 'error':
+                    result.append((s,p))
+        return result
+
+    # -----------------------------------------------------------------------------
+    # unused_terminals()
+    #
+    # Find all terminals that were defined, but not used by the grammar.  Returns
+    # a list of all symbols.
+    # -----------------------------------------------------------------------------
+    def unused_terminals(self):
+        unused_tok = []
+        for s,v in self.Terminals.items():
+            if s != 'error' and not v:
+                unused_tok.append(s)
+
+        return unused_tok
+
+    # ------------------------------------------------------------------------------
+    # unused_rules()
+    #
+    # Find all grammar rules that were defined,  but not used (maybe not reachable)
+    # Returns a list of productions.
+    # ------------------------------------------------------------------------------
+
+    def unused_rules(self):
+        unused_prod = []
+        for s,v in self.Nonterminals.items():
+            if not v:
+                p = self.Prodnames[s][0]
+                unused_prod.append(p)
+        return unused_prod
+
+    # -----------------------------------------------------------------------------
+    # unused_precedence()
+    #
+    # Returns a list of tuples (term,precedence) corresponding to precedence
+    # rules that were never used by the grammar.  term is the name of the terminal
+    # on which precedence was applied and precedence is a string such as 'left' or
+    # 'right' corresponding to the type of precedence. 
+    # -----------------------------------------------------------------------------
+
+    def unused_precedence(self):
+        unused = []
+        for termname in self.Precedence:
+            if not (termname in self.Terminals or termname in self.UsedPrecedence):
+                unused.append((termname,self.Precedence[termname][0]))
+                
+        return unused
+
+    # -------------------------------------------------------------------------
+    # _first()
+    #
+    # Compute the value of FIRST1(beta) where beta is a tuple of symbols.
+    #
+    # During execution of compute_first1, the result may be incomplete.
+    # Afterward (e.g., when called from compute_follow()), it will be complete.
+    # -------------------------------------------------------------------------
+    def _first(self,beta):
+
+        # We are computing First(x1,x2,x3,...,xn)
+        result = [ ]
+        for x in beta:
+            x_produces_empty = 0
+
+            # Add all the non-<empty> symbols of First[x] to the result.
+            for f in self.First[x]:
+                if f == '<empty>':
+                    x_produces_empty = 1
+                else:
+                    if f not in result: result.append(f)
+
+            if x_produces_empty:
+                # We have to consider the next x in beta,
+                # i.e. stay in the loop.
+                pass
+            else:
+                # We don't have to consider any further symbols in beta.
+                break
+        else:
+            # There was no 'break' from the loop,
+            # so x_produces_empty was true for all x in beta,
+            # so beta produces empty as well.
+            result.append('<empty>')
+
+        return result
+
+    # -------------------------------------------------------------------------
+    # compute_first()
+    #
+    # Compute the value of FIRST1(X) for all symbols
+    # -------------------------------------------------------------------------
+    def compute_first(self):
+        if self.First:
+            return self.First
+
+        # Terminals:
+        for t in self.Terminals:
+            self.First[t] = [t]
+
+        self.First['$end'] = ['$end']
+
+        # Nonterminals:
+
+        # Initialize to the empty set:
+        for n in self.Nonterminals:
+            self.First[n] = []
+
+        # Then propagate symbols until no change:
+        while 1:
+            some_change = 0
+            for n in self.Nonterminals:
+                for p in self.Prodnames[n]:
+                    for f in self._first(p.prod):
+                        if f not in self.First[n]:
+                            self.First[n].append( f )
+                            some_change = 1
+            if not some_change:
+                break
+        
+        return self.First
+
+    # ---------------------------------------------------------------------
+    # compute_follow()
+    #
+    # Computes all of the follow sets for every non-terminal symbol.  The
+    # follow set is the set of all symbols that might follow a given
+    # non-terminal.  See the Dragon book, 2nd Ed. p. 189.
+    # ---------------------------------------------------------------------
+    def compute_follow(self,start=None):
+        # If already computed, return the result
+        if self.Follow:
+            return self.Follow
+
+        # If first sets not computed yet, do that first.
+        if not self.First:
+            self.compute_first()
+
+        # Add '$end' to the follow list of the start symbol
+        for k in self.Nonterminals:
+            self.Follow[k] = [ ]
+
+        if not start:
+            start = self.Productions[1].name
+
+        self.Follow[start] = [ '$end' ]
+
+        while 1:
+            didadd = 0
+            for p in self.Productions[1:]:
+                # Here is the production set
+                for i in range(len(p.prod)):
+                    B = p.prod[i]
+                    if B in self.Nonterminals:
+                        # Okay. We got a non-terminal in a production
+                        fst = self._first(p.prod[i+1:])
+                        hasempty = 0
+                        for f in fst:
+                            if f != '<empty>' and f not in self.Follow[B]:
+                                self.Follow[B].append(f)
+                                didadd = 1
+                            if f == '<empty>':
+                                hasempty = 1
+                        if hasempty or i == (len(p.prod)-1):
+                            # Add elements of follow(a) to follow(b)
+                            for f in self.Follow[p.name]:
+                                if f not in self.Follow[B]:
+                                    self.Follow[B].append(f)
+                                    didadd = 1
+            if not didadd: break
+        return self.Follow
+
+
+    # -----------------------------------------------------------------------------
+    # build_lritems()
+    #
+    # This function walks the list of productions and builds a complete set of the
+    # LR items.  The LR items are stored in two ways:  First, they are uniquely
+    # numbered and placed in the list _lritems.  Second, a linked list of LR items
+    # is built for each production.  For example:
+    #
+    #   E -> E PLUS E
+    #
+    # Creates the list
+    #
+    #  [E -> . E PLUS E, E -> E . PLUS E, E -> E PLUS . E, E -> E PLUS E . ]
+    # -----------------------------------------------------------------------------
+
+    def build_lritems(self):
+        for p in self.Productions:
+            lastlri = p
+            i = 0
+            lr_items = []
+            while 1:
+                if i > len(p):
+                    lri = None
+                else:
+                    lri = LRItem(p,i)
+                    # Precompute the list of productions immediately following
+                    try:
+                        lri.lr_after = self.Prodnames[lri.prod[i+1]]
+                    except (IndexError,KeyError):
+                        lri.lr_after = []
+                    try:
+                        lri.lr_before = lri.prod[i-1]
+                    except IndexError:
+                        lri.lr_before = None
+
+                lastlri.lr_next = lri
+                if not lri: break
+                lr_items.append(lri)
+                lastlri = lri
+                i += 1
+            p.lr_items = lr_items
+
+# -----------------------------------------------------------------------------
+#                            == Class LRTable ==
+#
+# This basic class represents a basic table of LR parsing information.  
+# Methods for generating the tables are not defined here.  They are defined
+# in the derived class LRGeneratedTable.
+# -----------------------------------------------------------------------------
+
+class VersionError(YaccError): pass
+
+class LRTable(object):
+    def __init__(self):
+        self.lr_action = None
+        self.lr_goto = None
+        self.lr_productions = None
+        self.lr_method = None
+
+    def read_table(self,module):
+        if isinstance(module,types.ModuleType):
+            parsetab = module
+        else:
+            if sys.version_info[0] < 3:
+                exec("import %s as parsetab" % module)
+            else:
+                env = { }
+                exec("import %s as parsetab" % module, env, env)
+                parsetab = env['parsetab']
+
+        if parsetab._tabversion != __tabversion__:
+            raise VersionError("yacc table file version is out of date")
+
+        self.lr_action = parsetab._lr_action
+        self.lr_goto = parsetab._lr_goto
+
+        self.lr_productions = []
+        for p in parsetab._lr_productions:
+            self.lr_productions.append(MiniProduction(*p))
+
+        self.lr_method = parsetab._lr_method
+        return parsetab._lr_signature
+
+    def read_pickle(self,filename):
+        try:
+            import cPickle as pickle
+        except ImportError:
+            import pickle
+
+        in_f = open(filename,"rb")
+
+        tabversion = pickle.load(in_f)
+        if tabversion != __tabversion__:
+            raise VersionError("yacc table file version is out of date")
+        self.lr_method = pickle.load(in_f)
+        signature      = pickle.load(in_f)
+        self.lr_action = pickle.load(in_f)
+        self.lr_goto   = pickle.load(in_f)
+        productions    = pickle.load(in_f)
+
+        self.lr_productions = []
+        for p in productions:
+            self.lr_productions.append(MiniProduction(*p))
+
+        in_f.close()
+        return signature
+
+    # Bind all production function names to callable objects in pdict
+    def bind_callables(self,pdict):
+        for p in self.lr_productions:
+            p.bind(pdict)
+    
+# -----------------------------------------------------------------------------
+#                           === LR Generator ===
+#
+# The following classes and functions are used to generate LR parsing tables on 
+# a grammar.
+# -----------------------------------------------------------------------------
+
+# -----------------------------------------------------------------------------
+# digraph()
+# traverse()
+#
+# The following two functions are used to compute set valued functions
+# of the form:
+#
+#     F(x) = F'(x) U U{F(y) | x R y}
+#
+# This is used to compute the values of Read() sets as well as FOLLOW sets
+# in LALR(1) generation.
+#
+# Inputs:  X    - An input set
+#          R    - A relation
+#          FP   - Set-valued function
+# ------------------------------------------------------------------------------
+
+def digraph(X,R,FP):
+    N = { }
+    for x in X:
+       N[x] = 0
+    stack = []
+    F = { }
+    for x in X:
+        if N[x] == 0: traverse(x,N,stack,F,X,R,FP)
+    return F
+
+def traverse(x,N,stack,F,X,R,FP):
+    stack.append(x)
+    d = len(stack)
+    N[x] = d
+    F[x] = FP(x)             # F(X) <- F'(x)
+
+    rel = R(x)               # Get y's related to x
+    for y in rel:
+        if N[y] == 0:
+             traverse(y,N,stack,F,X,R,FP)
+        N[x] = min(N[x],N[y])
+        for a in F.get(y,[]):
+            if a not in F[x]: F[x].append(a)
+    if N[x] == d:
+       N[stack[-1]] = MAXINT
+       F[stack[-1]] = F[x]
+       element = stack.pop()
+       while element != x:
+           N[stack[-1]] = MAXINT
+           F[stack[-1]] = F[x]
+           element = stack.pop()
+
+class LALRError(YaccError): pass
+
+# -----------------------------------------------------------------------------
+#                             == LRGeneratedTable ==
+#
+# This class implements the LR table generation algorithm.  There are no
+# public methods except for write()
+# -----------------------------------------------------------------------------
+
+class LRGeneratedTable(LRTable):
+    def __init__(self,grammar,method='LALR',log=None):
+        if method not in ['SLR','LALR']:
+            raise LALRError("Unsupported method %s" % method)
+
+        self.grammar = grammar
+        self.lr_method = method
+
+        # Set up the logger
+        if not log:
+            log = NullLogger()
+        self.log = log
+
+        # Internal attributes
+        self.lr_action     = {}        # Action table
+        self.lr_goto       = {}        # Goto table
+        self.lr_productions  = grammar.Productions    # Copy of grammar Production array
+        self.lr_goto_cache = {}        # Cache of computed gotos
+        self.lr0_cidhash   = {}        # Cache of closures
+
+        self._add_count    = 0         # Internal counter used to detect cycles
+
+        # Diagonistic information filled in by the table generator
+        self.sr_conflict   = 0
+        self.rr_conflict   = 0
+        self.conflicts     = []        # List of conflicts
+
+        self.sr_conflicts  = []
+        self.rr_conflicts  = []
+
+        # Build the tables
+        self.grammar.build_lritems()
+        self.grammar.compute_first()
+        self.grammar.compute_follow()
+        self.lr_parse_table()
+
+    # Compute the LR(0) closure operation on I, where I is a set of LR(0) items.
+
+    def lr0_closure(self,I):
+        self._add_count += 1
+
+        # Add everything in I to J
+        J = I[:]
+        didadd = 1
+        while didadd:
+            didadd = 0
+            for j in J:
+                for x in j.lr_after:
+                    if getattr(x,"lr0_added",0) == self._add_count: continue
+                    # Add B --> .G to J
+                    J.append(x.lr_next)
+                    x.lr0_added = self._add_count
+                    didadd = 1
+
+        return J
+
+    # Compute the LR(0) goto function goto(I,X) where I is a set
+    # of LR(0) items and X is a grammar symbol.   This function is written
+    # in a way that guarantees uniqueness of the generated goto sets
+    # (i.e. the same goto set will never be returned as two different Python
+    # objects).  With uniqueness, we can later do fast set comparisons using
+    # id(obj) instead of element-wise comparison.
+
+    def lr0_goto(self,I,x):
+        # First we look for a previously cached entry
+        g = self.lr_goto_cache.get((id(I),x),None)
+        if g: return g
+
+        # Now we generate the goto set in a way that guarantees uniqueness
+        # of the result
+
+        s = self.lr_goto_cache.get(x,None)
+        if not s:
+            s = { }
+            self.lr_goto_cache[x] = s
+
+        gs = [ ]
+        for p in I:
+            n = p.lr_next
+            if n and n.lr_before == x:
+                s1 = s.get(id(n),None)
+                if not s1:
+                    s1 = { }
+                    s[id(n)] = s1
+                gs.append(n)
+                s = s1
+        g = s.get('$end',None)
+        if not g:
+            if gs:
+                g = self.lr0_closure(gs)
+                s['$end'] = g
+            else:
+                s['$end'] = gs
+        self.lr_goto_cache[(id(I),x)] = g
+        return g
+
+    # Compute the LR(0) sets of item function
+    def lr0_items(self):
+
+        C = [ self.lr0_closure([self.grammar.Productions[0].lr_next]) ]
+        i = 0
+        for I in C:
+            self.lr0_cidhash[id(I)] = i
+            i += 1
+
+        # Loop over the items in C and each grammar symbols
+        i = 0
+        while i < len(C):
+            I = C[i]
+            i += 1
+
+            # Collect all of the symbols that could possibly be in the goto(I,X) sets
+            asyms = { }
+            for ii in I:
+                for s in ii.usyms:
+                    asyms[s] = None
+
+            for x in asyms:
+                g = self.lr0_goto(I,x)
+                if not g:  continue
+                if id(g) in self.lr0_cidhash: continue
+                self.lr0_cidhash[id(g)] = len(C)
+                C.append(g)
+
+        return C
+
+    # -----------------------------------------------------------------------------
+    #                       ==== LALR(1) Parsing ====
+    #
+    # LALR(1) parsing is almost exactly the same as SLR except that instead of
+    # relying upon Follow() sets when performing reductions, a more selective
+    # lookahead set that incorporates the state of the LR(0) machine is utilized.
+    # Thus, we mainly just have to focus on calculating the lookahead sets.
+    #
+    # The method used here is due to DeRemer and Pennelo (1982).
+    #
+    # DeRemer, F. L., and T. J. Pennelo: "Efficient Computation of LALR(1)
+    #     Lookahead Sets", ACM Transactions on Programming Languages and Systems,
+    #     Vol. 4, No. 4, Oct. 1982, pp. 615-649
+    #
+    # Further details can also be found in:
+    #
+    #  J. Tremblay and P. Sorenson, "The Theory and Practice of Compiler Writing",
+    #      McGraw-Hill Book Company, (1985).
+    #
+    # -----------------------------------------------------------------------------
+
+    # -----------------------------------------------------------------------------
+    # compute_nullable_nonterminals()
+    #
+    # Creates a dictionary containing all of the non-terminals that might produce
+    # an empty production.
+    # -----------------------------------------------------------------------------
+
+    def compute_nullable_nonterminals(self):
+        nullable = {}
+        num_nullable = 0
+        while 1:
+           for p in self.grammar.Productions[1:]:
+               if p.len == 0:
+                    nullable[p.name] = 1
+                    continue
+               for t in p.prod:
+                    if not t in nullable: break
+               else:
+                    nullable[p.name] = 1
+           if len(nullable) == num_nullable: break
+           num_nullable = len(nullable)
+        return nullable
+
+    # -----------------------------------------------------------------------------
+    # find_nonterminal_trans(C)
+    #
+    # Given a set of LR(0) items, this functions finds all of the non-terminal
+    # transitions.    These are transitions in which a dot appears immediately before
+    # a non-terminal.   Returns a list of tuples of the form (state,N) where state
+    # is the state number and N is the nonterminal symbol.
+    #
+    # The input C is the set of LR(0) items.
+    # -----------------------------------------------------------------------------
+
+    def find_nonterminal_transitions(self,C):
+         trans = []
+         for state in range(len(C)):
+             for p in C[state]:
+                 if p.lr_index < p.len - 1:
+                      t = (state,p.prod[p.lr_index+1])
+                      if t[1] in self.grammar.Nonterminals:
+                            if t not in trans: trans.append(t)
+             state = state + 1
+         return trans
+
+    # -----------------------------------------------------------------------------
+    # dr_relation()
+    #
+    # Computes the DR(p,A) relationships for non-terminal transitions.  The input
+    # is a tuple (state,N) where state is a number and N is a nonterminal symbol.
+    #
+    # Returns a list of terminals.
+    # -----------------------------------------------------------------------------
+
+    def dr_relation(self,C,trans,nullable):
+        dr_set = { }
+        state,N = trans
+        terms = []
+
+        g = self.lr0_goto(C[state],N)
+        for p in g:
+           if p.lr_index < p.len - 1:
+               a = p.prod[p.lr_index+1]
+               if a in self.grammar.Terminals:
+                   if a not in terms: terms.append(a)
+
+        # This extra bit is to handle the start state
+        if state == 0 and N == self.grammar.Productions[0].prod[0]:
+           terms.append('$end')
+
+        return terms
+
+    # -----------------------------------------------------------------------------
+    # reads_relation()
+    #
+    # Computes the READS() relation (p,A) READS (t,C).
+    # -----------------------------------------------------------------------------
+
+    def reads_relation(self,C, trans, empty):
+        # Look for empty transitions
+        rel = []
+        state, N = trans
+
+        g = self.lr0_goto(C[state],N)
+        j = self.lr0_cidhash.get(id(g),-1)
+        for p in g:
+            if p.lr_index < p.len - 1:
+                 a = p.prod[p.lr_index + 1]
+                 if a in empty:
+                      rel.append((j,a))
+
+        return rel
+
+    # -----------------------------------------------------------------------------
+    # compute_lookback_includes()
+    #
+    # Determines the lookback and includes relations
+    #
+    # LOOKBACK:
+    #
+    # This relation is determined by running the LR(0) state machine forward.
+    # For example, starting with a production "N : . A B C", we run it forward
+    # to obtain "N : A B C ."   We then build a relationship between this final
+    # state and the starting state.   These relationships are stored in a dictionary
+    # lookdict.
+    #
+    # INCLUDES:
+    #
+    # Computes the INCLUDE() relation (p,A) INCLUDES (p',B).
+    #
+    # This relation is used to determine non-terminal transitions that occur
+    # inside of other non-terminal transition states.   (p,A) INCLUDES (p', B)
+    # if the following holds:
+    #
+    #       B -> LAT, where T -> epsilon and p' -L-> p
+    #
+    # L is essentially a prefix (which may be empty), T is a suffix that must be
+    # able to derive an empty string.  State p' must lead to state p with the string L.
+    #
+    # -----------------------------------------------------------------------------
+
+    def compute_lookback_includes(self,C,trans,nullable):
+
+        lookdict = {}          # Dictionary of lookback relations
+        includedict = {}       # Dictionary of include relations
+
+        # Make a dictionary of non-terminal transitions
+        dtrans = {}
+        for t in trans:
+            dtrans[t] = 1
+
+        # Loop over all transitions and compute lookbacks and includes
+        for state,N in trans:
+            lookb = []
+            includes = []
+            for p in C[state]:
+                if p.name != N: continue
+
+                # Okay, we have a name match.  We now follow the production all the way
+                # through the state machine until we get the . on the right hand side
+
+                lr_index = p.lr_index
+                j = state
+                while lr_index < p.len - 1:
+                     lr_index = lr_index + 1
+                     t = p.prod[lr_index]
+
+                     # Check to see if this symbol and state are a non-terminal transition
+                     if (j,t) in dtrans:
+                           # Yes.  Okay, there is some chance that this is an includes relation
+                           # the only way to know for certain is whether the rest of the
+                           # production derives empty
+
+                           li = lr_index + 1
+                           while li < p.len:
+                                if p.prod[li] in self.grammar.Terminals: break      # No forget it
+                                if not p.prod[li] in nullable: break
+                                li = li + 1
+                           else:
+                                # Appears to be a relation between (j,t) and (state,N)
+                                includes.append((j,t))
+
+                     g = self.lr0_goto(C[j],t)               # Go to next set
+                     j = self.lr0_cidhash.get(id(g),-1)     # Go to next state
+
+                # When we get here, j is the final state, now we have to locate the production
+                for r in C[j]:
+                     if r.name != p.name: continue
+                     if r.len != p.len:   continue
+                     i = 0
+                     # This look is comparing a production ". A B C" with "A B C ."
+                     while i < r.lr_index:
+                          if r.prod[i] != p.prod[i+1]: break
+                          i = i + 1
+                     else:
+                          lookb.append((j,r))
+            for i in includes:
+                 if not i in includedict: includedict[i] = []
+                 includedict[i].append((state,N))
+            lookdict[(state,N)] = lookb
+
+        return lookdict,includedict
+
+    # -----------------------------------------------------------------------------
+    # compute_read_sets()
+    #
+    # Given a set of LR(0) items, this function computes the read sets.
+    #
+    # Inputs:  C        =  Set of LR(0) items
+    #          ntrans   = Set of nonterminal transitions
+    #          nullable = Set of empty transitions
+    #
+    # Returns a set containing the read sets
+    # -----------------------------------------------------------------------------
+
+    def compute_read_sets(self,C, ntrans, nullable):
+        FP = lambda x: self.dr_relation(C,x,nullable)
+        R =  lambda x: self.reads_relation(C,x,nullable)
+        F = digraph(ntrans,R,FP)
+        return F
+
+    # -----------------------------------------------------------------------------
+    # compute_follow_sets()
+    #
+    # Given a set of LR(0) items, a set of non-terminal transitions, a readset,
+    # and an include set, this function computes the follow sets
+    #
+    # Follow(p,A) = Read(p,A) U U {Follow(p',B) | (p,A) INCLUDES (p',B)}
+    #
+    # Inputs:
+    #            ntrans     = Set of nonterminal transitions
+    #            readsets   = Readset (previously computed)
+    #            inclsets   = Include sets (previously computed)
+    #
+    # Returns a set containing the follow sets
+    # -----------------------------------------------------------------------------
+
+    def compute_follow_sets(self,ntrans,readsets,inclsets):
+         FP = lambda x: readsets[x]
+         R  = lambda x: inclsets.get(x,[])
+         F = digraph(ntrans,R,FP)
+         return F
+
+    # -----------------------------------------------------------------------------
+    # add_lookaheads()
+    #
+    # Attaches the lookahead symbols to grammar rules.
+    #
+    # Inputs:    lookbacks         -  Set of lookback relations
+    #            followset         -  Computed follow set
+    #
+    # This function directly attaches the lookaheads to productions contained
+    # in the lookbacks set
+    # -----------------------------------------------------------------------------
+
+    def add_lookaheads(self,lookbacks,followset):
+        for trans,lb in lookbacks.items():
+            # Loop over productions in lookback
+            for state,p in lb:
+                 if not state in p.lookaheads:
+                      p.lookaheads[state] = []
+                 f = followset.get(trans,[])
+                 for a in f:
+                      if a not in p.lookaheads[state]: p.lookaheads[state].append(a)
+
+    # -----------------------------------------------------------------------------
+    # add_lalr_lookaheads()
+    #
+    # This function does all of the work of adding lookahead information for use
+    # with LALR parsing
+    # -----------------------------------------------------------------------------
+
+    def add_lalr_lookaheads(self,C):
+        # Determine all of the nullable nonterminals
+        nullable = self.compute_nullable_nonterminals()
+
+        # Find all non-terminal transitions
+        trans = self.find_nonterminal_transitions(C)
+
+        # Compute read sets
+        readsets = self.compute_read_sets(C,trans,nullable)
+
+        # Compute lookback/includes relations
+        lookd, included = self.compute_lookback_includes(C,trans,nullable)
+
+        # Compute LALR FOLLOW sets
+        followsets = self.compute_follow_sets(trans,readsets,included)
+
+        # Add all of the lookaheads
+        self.add_lookaheads(lookd,followsets)
+
+    # -----------------------------------------------------------------------------
+    # lr_parse_table()
+    #
+    # This function constructs the parse tables for SLR or LALR
+    # -----------------------------------------------------------------------------
+    def lr_parse_table(self):
+        Productions = self.grammar.Productions
+        Precedence  = self.grammar.Precedence
+        goto   = self.lr_goto         # Goto array
+        action = self.lr_action       # Action array
+        log    = self.log             # Logger for output
+
+        actionp = { }                 # Action production array (temporary)
+        
+        log.info("Parsing method: %s", self.lr_method)
+
+        # Step 1: Construct C = { I0, I1, ... IN}, collection of LR(0) items
+        # This determines the number of states
+
+        C = self.lr0_items()
+
+        if self.lr_method == 'LALR':
+            self.add_lalr_lookaheads(C)
+
+        # Build the parser table, state by state
+        st = 0
+        for I in C:
+            # Loop over each production in I
+            actlist = [ ]              # List of actions
+            st_action  = { }
+            st_actionp = { }
+            st_goto    = { }
+            log.info("")
+            log.info("state %d", st)
+            log.info("")
+            for p in I:
+                log.info("    (%d) %s", p.number, str(p))
+            log.info("")
+
+            for p in I:
+                    if p.len == p.lr_index + 1:
+                        if p.name == "S'":
+                            # Start symbol. Accept!
+                            st_action["$end"] = 0
+                            st_actionp["$end"] = p
+                        else:
+                            # We are at the end of a production.  Reduce!
+                            if self.lr_method == 'LALR':
+                                laheads = p.lookaheads[st]
+                            else:
+                                laheads = self.grammar.Follow[p.name]
+                            for a in laheads:
+                                actlist.append((a,p,"reduce using rule %d (%s)" % (p.number,p)))
+                                r = st_action.get(a,None)
+                                if r is not None:
+                                    # Whoa. Have a shift/reduce or reduce/reduce conflict
+                                    if r > 0:
+                                        # Need to decide on shift or reduce here
+                                        # By default we favor shifting. Need to add
+                                        # some precedence rules here.
+                                        sprec,slevel = Productions[st_actionp[a].number].prec
+                                        rprec,rlevel = Precedence.get(a,('right',0))
+                                        if (slevel < rlevel) or ((slevel == rlevel) and (rprec == 'left')):
+                                            # We really need to reduce here.
+                                            st_action[a] = -p.number
+                                            st_actionp[a] = p
+                                            if not slevel and not rlevel:
+                                                log.info("  ! shift/reduce conflict for %s resolved as reduce",a)
+                                                self.sr_conflicts.append((st,a,'reduce'))
+                                            Productions[p.number].reduced += 1
+                                        elif (slevel == rlevel) and (rprec == 'nonassoc'):
+                                            st_action[a] = None
+                                        else:
+                                            # Hmmm. Guess we'll keep the shift
+                                            if not rlevel:
+                                                log.info("  ! shift/reduce conflict for %s resolved as shift",a)
+                                                self.sr_conflicts.append((st,a,'shift'))
+                                    elif r < 0:
+                                        # Reduce/reduce conflict.   In this case, we favor the rule
+                                        # that was defined first in the grammar file
+                                        oldp = Productions[-r]
+                                        pp = Productions[p.number]
+                                        if oldp.line > pp.line:
+                                            st_action[a] = -p.number
+                                            st_actionp[a] = p
+                                            chosenp,rejectp = pp,oldp
+                                            Productions[p.number].reduced += 1
+                                            Productions[oldp.number].reduced -= 1
+                                        else:
+                                            chosenp,rejectp = oldp,pp
+                                        self.rr_conflicts.append((st,chosenp,rejectp))
+                                        log.info("  ! reduce/reduce conflict for %s resolved using rule %d (%s)", a,st_actionp[a].number, st_actionp[a])
+                                    else:
+                                        raise LALRError("Unknown conflict in state %d" % st)
+                                else:
+                                    st_action[a] = -p.number
+                                    st_actionp[a] = p
+                                    Productions[p.number].reduced += 1
+                    else:
+                        i = p.lr_index
+                        a = p.prod[i+1]       # Get symbol right after the "."
+                        if a in self.grammar.Terminals:
+                            g = self.lr0_goto(I,a)
+                            j = self.lr0_cidhash.get(id(g),-1)
+                            if j >= 0:
+                                # We are in a shift state
+                                actlist.append((a,p,"shift and go to state %d" % j))
+                                r = st_action.get(a,None)
+                                if r is not None:
+                                    # Whoa have a shift/reduce or shift/shift conflict
+                                    if r > 0:
+                                        if r != j:
+                                            raise LALRError("Shift/shift conflict in state %d" % st)
+                                    elif r < 0:
+                                        # Do a precedence check.
+                                        #   -  if precedence of reduce rule is higher, we reduce.
+                                        #   -  if precedence of reduce is same and left assoc, we reduce.
+                                        #   -  otherwise we shift
+                                        rprec,rlevel = Productions[st_actionp[a].number].prec
+                                        sprec,slevel = Precedence.get(a,('right',0))
+                                        if (slevel > rlevel) or ((slevel == rlevel) and (rprec == 'right')):
+                                            # We decide to shift here... highest precedence to shift
+                                            Productions[st_actionp[a].number].reduced -= 1
+                                            st_action[a] = j
+                                            st_actionp[a] = p
+                                            if not rlevel:
+                                                log.info("  ! shift/reduce conflict for %s resolved as shift",a)
+                                                self.sr_conflicts.append((st,a,'shift'))
+                                        elif (slevel == rlevel) and (rprec == 'nonassoc'):
+                                            st_action[a] = None
+                                        else:
+                                            # Hmmm. Guess we'll keep the reduce
+                                            if not slevel and not rlevel:
+                                                log.info("  ! shift/reduce conflict for %s resolved as reduce",a)
+                                                self.sr_conflicts.append((st,a,'reduce'))
+
+                                    else:
+                                        raise LALRError("Unknown conflict in state %d" % st)
+                                else:
+                                    st_action[a] = j
+                                    st_actionp[a] = p
+
+            # Print the actions associated with each terminal
+            _actprint = { }
+            for a,p,m in actlist:
+                if a in st_action:
+                    if p is st_actionp[a]:
+                        log.info("    %-15s %s",a,m)
+                        _actprint[(a,m)] = 1
+            log.info("")
+            # Print the actions that were not used. (debugging)
+            not_used = 0
+            for a,p,m in actlist:
+                if a in st_action:
+                    if p is not st_actionp[a]:
+                        if not (a,m) in _actprint:
+                            log.debug("  ! %-15s [ %s ]",a,m)
+                            not_used = 1
+                            _actprint[(a,m)] = 1
+            if not_used:
+                log.debug("")
+
+            # Construct the goto table for this state
+
+            nkeys = { }
+            for ii in I:
+                for s in ii.usyms:
+                    if s in self.grammar.Nonterminals:
+                        nkeys[s] = None
+            for n in nkeys:
+                g = self.lr0_goto(I,n)
+                j = self.lr0_cidhash.get(id(g),-1)
+                if j >= 0:
+                    st_goto[n] = j
+                    log.info("    %-30s shift and go to state %d",n,j)
+
+            action[st] = st_action
+            actionp[st] = st_actionp
+            goto[st] = st_goto
+            st += 1
+
+
+    # -----------------------------------------------------------------------------
+    # write()
+    #
+    # This function writes the LR parsing tables to a file
+    # -----------------------------------------------------------------------------
+
+    def write_table(self,modulename,outputdir='',signature=""):
+        basemodulename = modulename.split(".")[-1]
+        filename = os.path.join(outputdir,basemodulename) + ".py"
+        try:
+            f = open(filename,"w")
+
+            f.write("""
+# %s
+# This file is automatically generated. Do not edit.
+_tabversion = %r
+
+_lr_method = %r
+
+_lr_signature = %r
+    """ % (filename, __tabversion__, self.lr_method, signature))
+
+            # Change smaller to 0 to go back to original tables
+            smaller = 1
+
+            # Factor out names to try and make smaller
+            if smaller:
+                items = { }
+
+                for s,nd in self.lr_action.items():
+                   for name,v in nd.items():
+                      i = items.get(name)
+                      if not i:
+                         i = ([],[])
+                         items[name] = i
+                      i[0].append(s)
+                      i[1].append(v)
+
+                f.write("\n_lr_action_items = {")
+                for k,v in items.items():
+                    f.write("%r:([" % k)
+                    for i in v[0]:
+                        f.write("%r," % i)
+                    f.write("],[")
+                    for i in v[1]:
+                        f.write("%r," % i)
+
+                    f.write("]),")
+                f.write("}\n")
+
+                f.write("""
+_lr_action = { }
+for _k, _v in _lr_action_items.items():
+   for _x,_y in zip(_v[0],_v[1]):
+      if not _x in _lr_action:  _lr_action[_x] = { }
+      _lr_action[_x][_k] = _y
+del _lr_action_items
+""")
+
+            else:
+                f.write("\n_lr_action = { ");
+                for k,v in self.lr_action.items():
+                    f.write("(%r,%r):%r," % (k[0],k[1],v))
+                f.write("}\n");
+
+            if smaller:
+                # Factor out names to try and make smaller
+                items = { }
+
+                for s,nd in self.lr_goto.items():
+                   for name,v in nd.items():
+                      i = items.get(name)
+                      if not i:
+                         i = ([],[])
+                         items[name] = i
+                      i[0].append(s)
+                      i[1].append(v)
+
+                f.write("\n_lr_goto_items = {")
+                for k,v in items.items():
+                    f.write("%r:([" % k)
+                    for i in v[0]:
+                        f.write("%r," % i)
+                    f.write("],[")
+                    for i in v[1]:
+                        f.write("%r," % i)
+
+                    f.write("]),")
+                f.write("}\n")
+
+                f.write("""
+_lr_goto = { }
+for _k, _v in _lr_goto_items.items():
+   for _x,_y in zip(_v[0],_v[1]):
+       if not _x in _lr_goto: _lr_goto[_x] = { }
+       _lr_goto[_x][_k] = _y
+del _lr_goto_items
+""")
+            else:
+                f.write("\n_lr_goto = { ");
+                for k,v in self.lr_goto.items():
+                    f.write("(%r,%r):%r," % (k[0],k[1],v))
+                f.write("}\n");
+
+            # Write production table
+            f.write("_lr_productions = [\n")
+            for p in self.lr_productions:
+                if p.func:
+                    f.write("  (%r,%r,%d,%r,%r,%d),\n" % (p.str,p.name, p.len, p.func,p.file,p.line))
+                else:
+                    f.write("  (%r,%r,%d,None,None,None),\n" % (str(p),p.name, p.len))
+            f.write("]\n")
+            f.close()
+
+        except IOError:
+            e = sys.exc_info()[1]
+            sys.stderr.write("Unable to create '%s'\n" % filename)
+            sys.stderr.write(str(e)+"\n")
+            return
+
+
+    # -----------------------------------------------------------------------------
+    # pickle_table()
+    #
+    # This function pickles the LR parsing tables to a supplied file object
+    # -----------------------------------------------------------------------------
+
+    def pickle_table(self,filename,signature=""):
+        try:
+            import cPickle as pickle
+        except ImportError:
+            import pickle
+        outf = open(filename,"wb")
+        pickle.dump(__tabversion__,outf,pickle_protocol)
+        pickle.dump(self.lr_method,outf,pickle_protocol)
+        pickle.dump(signature,outf,pickle_protocol)
+        pickle.dump(self.lr_action,outf,pickle_protocol)
+        pickle.dump(self.lr_goto,outf,pickle_protocol)
+
+        outp = []
+        for p in self.lr_productions:
+            if p.func:
+                outp.append((p.str,p.name, p.len, p.func,p.file,p.line))
+            else:
+                outp.append((str(p),p.name,p.len,None,None,None))
+        pickle.dump(outp,outf,pickle_protocol)
+        outf.close()
+
+# -----------------------------------------------------------------------------
+#                            === INTROSPECTION ===
+#
+# The following functions and classes are used to implement the PLY
+# introspection features followed by the yacc() function itself.
+# -----------------------------------------------------------------------------
+
+# -----------------------------------------------------------------------------
+# get_caller_module_dict()
+#
+# This function returns a dictionary containing all of the symbols defined within
+# a caller further down the call stack.  This is used to get the environment
+# associated with the yacc() call if none was provided.
+# -----------------------------------------------------------------------------
+
+def get_caller_module_dict(levels):
+    try:
+        raise RuntimeError
+    except RuntimeError:
+        e,b,t = sys.exc_info()
+        f = t.tb_frame
+        while levels > 0:
+            f = f.f_back                   
+            levels -= 1
+        ldict = f.f_globals.copy()
+        if f.f_globals != f.f_locals:
+            ldict.update(f.f_locals)
+
+        return ldict
+
+# -----------------------------------------------------------------------------
+# parse_grammar()
+#
+# This takes a raw grammar rule string and parses it into production data
+# -----------------------------------------------------------------------------
+def parse_grammar(doc,file,line):
+    grammar = []
+    # Split the doc string into lines
+    pstrings = doc.splitlines()
+    lastp = None
+    dline = line
+    for ps in pstrings:
+        dline += 1
+        p = ps.split()
+        if not p: continue
+        try:
+            if p[0] == '|':
+                # This is a continuation of a previous rule
+                if not lastp:
+                    raise SyntaxError("%s:%d: Misplaced '|'" % (file,dline))
+                prodname = lastp
+                syms = p[1:]
+            else:
+                prodname = p[0]
+                lastp = prodname
+                syms   = p[2:]
+                assign = p[1]
+                if assign != ':' and assign != '::=':
+                    raise SyntaxError("%s:%d: Syntax error. Expected ':'" % (file,dline))
+
+            grammar.append((file,dline,prodname,syms))
+        except SyntaxError:
+            raise
+        except Exception:
+            raise SyntaxError("%s:%d: Syntax error in rule '%s'" % (file,dline,ps.strip()))
+
+    return grammar
+
+# -----------------------------------------------------------------------------
+# ParserReflect()
+#
+# This class represents information extracted for building a parser including
+# start symbol, error function, tokens, precedence list, action functions,
+# etc.
+# -----------------------------------------------------------------------------
+class ParserReflect(object):
+    def __init__(self,pdict,log=None):
+        self.pdict      = pdict
+        self.start      = None
+        self.error_func = None
+        self.tokens     = None
+        self.files      = {}
+        self.grammar    = []
+        self.error      = 0
+
+        if log is None:
+            self.log = PlyLogger(sys.stderr)
+        else:
+            self.log = log
+
+    # Get all of the basic information
+    def get_all(self):
+        self.get_start()
+        self.get_error_func()
+        self.get_tokens()
+        self.get_precedence()
+        self.get_pfunctions()
+        
+    # Validate all of the information
+    def validate_all(self):
+        self.validate_start()
+        self.validate_error_func()
+        self.validate_tokens()
+        self.validate_precedence()
+        self.validate_pfunctions()
+        self.validate_files()
+        return self.error
+
+    # Compute a signature over the grammar
+    def signature(self):
+        try:
+            from hashlib import md5
+        except ImportError:
+            from md5 import md5
+        try:
+            sig = md5()
+            if self.start:
+                sig.update(self.start.encode('latin-1'))
+            if self.prec:
+                sig.update("".join(["".join(p) for p in self.prec]).encode('latin-1'))
+            if self.tokens:
+                sig.update(" ".join(self.tokens).encode('latin-1'))
+            for f in self.pfuncs:
+                if f[3]:
+                    sig.update(f[3].encode('latin-1'))
+        except (TypeError,ValueError):
+            pass
+        return sig.digest()
+
+    # -----------------------------------------------------------------------------
+    # validate_file()
+    #
+    # This method checks to see if there are duplicated p_rulename() functions
+    # in the parser module file.  Without this function, it is really easy for
+    # users to make mistakes by cutting and pasting code fragments (and it's a real
+    # bugger to try and figure out why the resulting parser doesn't work).  Therefore,
+    # we just do a little regular expression pattern matching of def statements
+    # to try and detect duplicates.
+    # -----------------------------------------------------------------------------
+
+    def validate_files(self):
+        # Match def p_funcname(
+        fre = re.compile(r'\s*def\s+(p_[a-zA-Z_0-9]*)\(')
+
+        for filename in self.files.keys():
+            base,ext = os.path.splitext(filename)
+            if ext != '.py': return 1          # No idea. Assume it's okay.
+
+            try:
+                f = open(filename)
+                lines = f.readlines()
+                f.close()
+            except IOError:
+                continue
+
+            counthash = { }
+            for linen,l in enumerate(lines):
+                linen += 1
+                m = fre.match(l)
+                if m:
+                    name = m.group(1)
+                    prev = counthash.get(name)
+                    if not prev:
+                        counthash[name] = linen
+                    else:
+                        self.log.warning("%s:%d: Function %s redefined. Previously defined on line %d", filename,linen,name,prev)
+
+    # Get the start symbol
+    def get_start(self):
+        self.start = self.pdict.get('start')
+
+    # Validate the start symbol
+    def validate_start(self):
+        if self.start is not None:
+            if not isinstance(self.start,str):
+                self.log.error("'start' must be a string")
+
+    # Look for error handler
+    def get_error_func(self):
+        self.error_func = self.pdict.get('p_error')
+
+    # Validate the error function
+    def validate_error_func(self):
+        if self.error_func:
+            if isinstance(self.error_func,types.FunctionType):
+                ismethod = 0
+            elif isinstance(self.error_func, types.MethodType):
+                ismethod = 1
+            else:
+                self.log.error("'p_error' defined, but is not a function or method")
+                self.error = 1
+                return
+
+            eline = func_code(self.error_func).co_firstlineno
+            efile = func_code(self.error_func).co_filename
+            self.files[efile] = 1
+
+            if (func_code(self.error_func).co_argcount != 1+ismethod):
+                self.log.error("%s:%d: p_error() requires 1 argument",efile,eline)
+                self.error = 1
+
+    # Get the tokens map
+    def get_tokens(self):
+        tokens = self.pdict.get("tokens",None)
+        if not tokens:
+            self.log.error("No token list is defined")
+            self.error = 1
+            return
+
+        if not isinstance(tokens,(list, tuple)):
+            self.log.error("tokens must be a list or tuple")
+            self.error = 1
+            return
+        
+        if not tokens:
+            self.log.error("tokens is empty")
+            self.error = 1
+            return
+
+        self.tokens = tokens
+
+    # Validate the tokens
+    def validate_tokens(self):
+        # Validate the tokens.
+        if 'error' in self.tokens:
+            self.log.error("Illegal token name 'error'. Is a reserved word")
+            self.error = 1
+            return
+
+        terminals = {}
+        for n in self.tokens:
+            if n in terminals:
+                self.log.warning("Token '%s' multiply defined", n)
+            terminals[n] = 1
+
+    # Get the precedence map (if any)
+    def get_precedence(self):
+        self.prec = self.pdict.get("precedence",None)
+
+    # Validate and parse the precedence map
+    def validate_precedence(self):
+        preclist = []
+        if self.prec:
+            if not isinstance(self.prec,(list,tuple)):
+                self.log.error("precedence must be a list or tuple")
+                self.error = 1
+                return
+            for level,p in enumerate(self.prec):
+                if not isinstance(p,(list,tuple)):
+                    self.log.error("Bad precedence table")
+                    self.error = 1
+                    return
+
+                if len(p) < 2:
+                    self.log.error("Malformed precedence entry %s. Must be (assoc, term, ..., term)",p)
+                    self.error = 1
+                    return
+                assoc = p[0]
+                if not isinstance(assoc,str):
+                    self.log.error("precedence associativity must be a string")
+                    self.error = 1
+                    return
+                for term in p[1:]:
+                    if not isinstance(term,str):
+                        self.log.error("precedence items must be strings")
+                        self.error = 1
+                        return
+                    preclist.append((term,assoc,level+1))
+        self.preclist = preclist
+
+    # Get all p_functions from the grammar
+    def get_pfunctions(self):
+        p_functions = []
+        for name, item in self.pdict.items():
+            if name[:2] != 'p_': continue
+            if name == 'p_error': continue
+            if isinstance(item,(types.FunctionType,types.MethodType)):
+                line = func_code(item).co_firstlineno
+                file = func_code(item).co_filename
+                p_functions.append((line,file,name,item.__doc__))
+
+        # Sort all of the actions by line number
+        p_functions.sort()
+        self.pfuncs = p_functions
+
+
+    # Validate all of the p_functions
+    def validate_pfunctions(self):
+        grammar = []
+        # Check for non-empty symbols
+        if len(self.pfuncs) == 0:
+            self.log.error("no rules of the form p_rulename are defined")
+            self.error = 1
+            return 
+        
+        for line, file, name, doc in self.pfuncs:
+            func = self.pdict[name]
+            if isinstance(func, types.MethodType):
+                reqargs = 2
+            else:
+                reqargs = 1
+            if func_code(func).co_argcount > reqargs:
+                self.log.error("%s:%d: Rule '%s' has too many arguments",file,line,func.__name__)
+                self.error = 1
+            elif func_code(func).co_argcount < reqargs:
+                self.log.error("%s:%d: Rule '%s' requires an argument",file,line,func.__name__)
+                self.error = 1
+            elif not func.__doc__:
+                self.log.warning("%s:%d: No documentation string specified in function '%s' (ignored)",file,line,func.__name__)
+            else:
+                try:
+                    parsed_g = parse_grammar(doc,file,line)
+                    for g in parsed_g:
+                        grammar.append((name, g))
+                except SyntaxError:
+                    e = sys.exc_info()[1]
+                    self.log.error(str(e))
+                    self.error = 1
+
+                # Looks like a valid grammar rule
+                # Mark the file in which defined.
+                self.files[file] = 1
+
+        # Secondary validation step that looks for p_ definitions that are not functions
+        # or functions that look like they might be grammar rules.
+
+        for n,v in self.pdict.items():
+            if n[0:2] == 'p_' and isinstance(v, (types.FunctionType, types.MethodType)): continue
+            if n[0:2] == 't_': continue
+            if n[0:2] == 'p_' and n != 'p_error':
+                self.log.warning("'%s' not defined as a function", n)
+            if ((isinstance(v,types.FunctionType) and func_code(v).co_argcount == 1) or
+                (isinstance(v,types.MethodType) and func_code(v).co_argcount == 2)):
+                try:
+                    doc = v.__doc__.split(" ")
+                    if doc[1] == ':':
+                        self.log.warning("%s:%d: Possible grammar rule '%s' defined without p_ prefix",
+                                         func_code(v).co_filename, func_code(v).co_firstlineno,n)
+                except Exception:
+                    pass
+
+        self.grammar = grammar
+
+# -----------------------------------------------------------------------------
+# yacc(module)
+#
+# Build a parser
+# -----------------------------------------------------------------------------
+
+def yacc(method='LALR', debug=yaccdebug, module=None, tabmodule=tab_module, start=None, 
+         check_recursion=1, optimize=0, write_tables=1, debugfile=debug_file,outputdir='',
+         debuglog=None, errorlog = None, picklefile=None):
+
+    global parse                 # Reference to the parsing method of the last built parser
+
+    # If pickling is enabled, table files are not created
+
+    if picklefile:
+        write_tables = 0
+
+    if errorlog is None:
+        errorlog = PlyLogger(sys.stderr)
+
+    # Get the module dictionary used for the parser
+    if module:
+        _items = [(k,getattr(module,k)) for k in dir(module)]
+        pdict = dict(_items)
+    else:
+        pdict = get_caller_module_dict(2)
+
+    # Collect parser information from the dictionary
+    pinfo = ParserReflect(pdict,log=errorlog)
+    pinfo.get_all()
+
+    if pinfo.error:
+        raise YaccError("Unable to build parser")
+
+    # Check signature against table files (if any)
+    signature = pinfo.signature()
+
+    # Read the tables
+    try:
+        lr = LRTable()
+        if picklefile:
+            read_signature = lr.read_pickle(picklefile)
+        else:
+            read_signature = lr.read_table(tabmodule)
+        if optimize or (read_signature == signature):
+            try:
+                lr.bind_callables(pinfo.pdict)
+                parser = LRParser(lr,pinfo.error_func)
+                parse = parser.parse
+                return parser
+            except Exception:
+                e = sys.exc_info()[1]
+                errorlog.warning("There was a problem loading the table file: %s", repr(e))
+    except VersionError:
+        e = sys.exc_info()
+        errorlog.warning(str(e))
+    except Exception:
+        pass
+
+    if debuglog is None:
+        if debug:
+            debuglog = PlyLogger(open(debugfile,"w"))
+        else:
+            debuglog = NullLogger()
+
+    debuglog.info("Created by PLY version %s (http://www.dabeaz.com/ply)", __version__)
+
+
+    errors = 0
+
+    # Validate the parser information
+    if pinfo.validate_all():
+        raise YaccError("Unable to build parser")
+    
+    if not pinfo.error_func:
+        errorlog.warning("no p_error() function is defined")
+
+    # Create a grammar object
+    grammar = Grammar(pinfo.tokens)
+
+    # Set precedence level for terminals
+    for term, assoc, level in pinfo.preclist:
+        try:
+            grammar.set_precedence(term,assoc,level)
+        except GrammarError:
+            e = sys.exc_info()[1]
+            errorlog.warning("%s",str(e))
+
+    # Add productions to the grammar
+    for funcname, gram in pinfo.grammar:
+        file, line, prodname, syms = gram
+        try:
+            grammar.add_production(prodname,syms,funcname,file,line)
+        except GrammarError:
+            e = sys.exc_info()[1]
+            errorlog.error("%s",str(e))
+            errors = 1
+
+    # Set the grammar start symbols
+    try:
+        if start is None:
+            grammar.set_start(pinfo.start)
+        else:
+            grammar.set_start(start)
+    except GrammarError:
+        e = sys.exc_info()[1]
+        errorlog.error(str(e))
+        errors = 1
+
+    if errors:
+        raise YaccError("Unable to build parser")
+
+    # Verify the grammar structure
+    undefined_symbols = grammar.undefined_symbols()
+    for sym, prod in undefined_symbols:
+        errorlog.error("%s:%d: Symbol '%s' used, but not defined as a token or a rule",prod.file,prod.line,sym)
+        errors = 1
+
+    unused_terminals = grammar.unused_terminals()
+    if unused_terminals:
+        debuglog.info("")
+        debuglog.info("Unused terminals:")
+        debuglog.info("")
+        for term in unused_terminals:
+            errorlog.warning("Token '%s' defined, but not used", term)
+            debuglog.info("    %s", term)
+
+    # Print out all productions to the debug log
+    if debug:
+        debuglog.info("")
+        debuglog.info("Grammar")
+        debuglog.info("")
+        for n,p in enumerate(grammar.Productions):
+            debuglog.info("Rule %-5d %s", n, p)
+
+    # Find unused non-terminals
+    unused_rules = grammar.unused_rules()
+    for prod in unused_rules:
+        errorlog.warning("%s:%d: Rule '%s' defined, but not used", prod.file, prod.line, prod.name)
+
+    if len(unused_terminals) == 1:
+        errorlog.warning("There is 1 unused token")
+    if len(unused_terminals) > 1:
+        errorlog.warning("There are %d unused tokens", len(unused_terminals))
+
+    if len(unused_rules) == 1:
+        errorlog.warning("There is 1 unused rule")
+    if len(unused_rules) > 1:
+        errorlog.warning("There are %d unused rules", len(unused_rules))
+
+    if debug:
+        debuglog.info("")
+        debuglog.info("Terminals, with rules where they appear")
+        debuglog.info("")
+        terms = list(grammar.Terminals)
+        terms.sort()
+        for term in terms:
+            debuglog.info("%-20s : %s", term, " ".join([str(s) for s in grammar.Terminals[term]]))
+        
+        debuglog.info("")
+        debuglog.info("Nonterminals, with rules where they appear")
+        debuglog.info("")
+        nonterms = list(grammar.Nonterminals)
+        nonterms.sort()
+        for nonterm in nonterms:
+            debuglog.info("%-20s : %s", nonterm, " ".join([str(s) for s in grammar.Nonterminals[nonterm]]))
+        debuglog.info("")
+
+    if check_recursion:
+        unreachable = grammar.find_unreachable()
+        for u in unreachable:
+            errorlog.warning("Symbol '%s' is unreachable",u)
+
+        infinite = grammar.infinite_cycles()
+        for inf in infinite:
+            errorlog.error("Infinite recursion detected for symbol '%s'", inf)
+            errors = 1
+        
+    unused_prec = grammar.unused_precedence()
+    for term, assoc in unused_prec:
+        errorlog.error("Precedence rule '%s' defined for unknown symbol '%s'", assoc, term)
+        errors = 1
+
+    if errors:
+        raise YaccError("Unable to build parser")
+    
+    # Run the LRGeneratedTable on the grammar
+    if debug:
+        errorlog.debug("Generating %s tables", method)
+            
+    lr = LRGeneratedTable(grammar,method,debuglog)
+
+    if debug:
+        num_sr = len(lr.sr_conflicts)
+
+        # Report shift/reduce and reduce/reduce conflicts
+        if num_sr == 1:
+            errorlog.warning("1 shift/reduce conflict")
+        elif num_sr > 1:
+            errorlog.warning("%d shift/reduce conflicts", num_sr)
+
+        num_rr = len(lr.rr_conflicts)
+        if num_rr == 1:
+            errorlog.warning("1 reduce/reduce conflict")
+        elif num_rr > 1:
+            errorlog.warning("%d reduce/reduce conflicts", num_rr)
+
+    # Write out conflicts to the output file
+    if debug and (lr.sr_conflicts or lr.rr_conflicts):
+        debuglog.warning("")
+        debuglog.warning("Conflicts:")
+        debuglog.warning("")
+
+        for state, tok, resolution in lr.sr_conflicts:
+            debuglog.warning("shift/reduce conflict for %s in state %d resolved as %s",  tok, state, resolution)
+        
+        already_reported = {}
+        for state, rule, rejected in lr.rr_conflicts:
+            if (state,id(rule),id(rejected)) in already_reported:
+                continue
+            debuglog.warning("reduce/reduce conflict in state %d resolved using rule (%s)", state, rule)
+            debuglog.warning("rejected rule (%s) in state %d", rejected,state)
+            errorlog.warning("reduce/reduce conflict in state %d resolved using rule (%s)", state, rule)
+            errorlog.warning("rejected rule (%s) in state %d", rejected, state)
+            already_reported[state,id(rule),id(rejected)] = 1
+        
+        warned_never = []
+        for state, rule, rejected in lr.rr_conflicts:
+            if not rejected.reduced and (rejected not in warned_never):
+                debuglog.warning("Rule (%s) is never reduced", rejected)
+                errorlog.warning("Rule (%s) is never reduced", rejected)
+                warned_never.append(rejected)
+
+    # Write the table file if requested
+    if write_tables:
+        lr.write_table(tabmodule,outputdir,signature)
+
+    # Write a pickled version of the tables
+    if picklefile:
+        lr.pickle_table(picklefile,signature)
+
+    # Build the parser
+    lr.bind_callables(pinfo.pdict)
+    parser = LRParser(lr,pinfo.error_func)
+
+    parse = parser.parse
+    return parser
diff --git a/lib/pysh/__init__.py b/lib/pysh/__init__.py
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/lib/pysh/__init__.py
diff --git a/lib/pysh/builtin.py b/lib/pysh/builtin.py
new file mode 100644
index 000000000..25ad22eb7
--- /dev/null
+++ b/lib/pysh/builtin.py
@@ -0,0 +1,710 @@
+# builtin.py - builtins and utilities definitions for pysh.
+#
+# Copyright 2007 Patrick Mezard
+#
+# This software may be used and distributed according to the terms
+# of the GNU General Public License, incorporated herein by reference.
+
+"""Builtin and internal utilities implementations.
+
+- Beware not to use python interpreter environment as if it were the shell
+environment. For instance, commands working directory must be explicitely handled
+through env['PWD'] instead of relying on python working directory.
+"""
+import errno
+import optparse
+import os
+import re
+import subprocess
+import sys
+import time
+
+def has_subprocess_bug():
+    return getattr(subprocess, 'list2cmdline') and \
+       (    subprocess.list2cmdline(['']) == '' or \
+            subprocess.list2cmdline(['foo|bar']) == 'foo|bar')
+            
+# Detect python bug 1634343: "subprocess swallows empty arguments under win32"
+# <http://sourceforge.net/tracker/index.php?func=detail&aid=1634343&group_id=5470&atid=105470>
+# Also detect: "[ 1710802 ] subprocess must escape redirection characters under win32"
+# <http://sourceforge.net/tracker/index.php?func=detail&aid=1710802&group_id=5470&atid=105470>
+if has_subprocess_bug():
+    import subprocess_fix
+    subprocess.list2cmdline = subprocess_fix.list2cmdline
+
+from sherrors import *
+
+class NonExitingParser(optparse.OptionParser):
+    """OptionParser default behaviour upon error is to print the error message and
+    exit. Raise a utility error instead.
+    """
+    def error(self, msg):
+        raise UtilityError(msg)
+
+#-------------------------------------------------------------------------------  
+# set special builtin
+#-------------------------------------------------------------------------------  
+OPT_SET = NonExitingParser(usage="set - set or unset options and positional parameters")
+OPT_SET.add_option( '-f', action='store_true', dest='has_f', default=False,
+    help='The shell shall disable pathname expansion.')
+OPT_SET.add_option('-e', action='store_true', dest='has_e', default=False,
+    help="""When this option is on, if a simple command fails for any of the \
+    reasons listed in Consequences of Shell Errors or returns an exit status \
+    value >0, and is not part of the compound list following a while, until, \
+    or if keyword, and is not a part of an AND or OR list, and is not a \
+    pipeline preceded by the ! reserved word, then the shell shall immediately \
+    exit.""")
+OPT_SET.add_option('-x', action='store_true', dest='has_x', default=False,
+    help="""The shell shall write to standard error a trace for each command \
+    after it expands the command and before it executes it. It is unspecified \
+    whether the command that turns tracing off is traced.""")
+
+def builtin_set(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+
+    option, args = OPT_SET.parse_args(args)
+    env = interp.get_env()
+    
+    if option.has_f:
+        env.set_opt('-f')
+    if option.has_e:
+        env.set_opt('-e')
+    if option.has_x:
+        env.set_opt('-x')
+    return 0
+    
+#-------------------------------------------------------------------------------  
+# shift special builtin
+#-------------------------------------------------------------------------------  
+def builtin_shift(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+        
+    params = interp.get_env().get_positional_args()
+    if args:
+        try:
+            n = int(args[0])
+            if n > len(params):
+                raise ValueError()
+        except ValueError:
+            return 1
+    else:
+        n = 1
+        
+    params[:n] = []
+    interp.get_env().set_positional_args(params)
+    return 0
+    
+#-------------------------------------------------------------------------------  
+# export special builtin
+#-------------------------------------------------------------------------------  
+OPT_EXPORT = NonExitingParser(usage="set - set or unset options and positional parameters")
+OPT_EXPORT.add_option('-p', action='store_true', dest='has_p', default=False)
+
+def builtin_export(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+        
+    option, args = OPT_EXPORT.parse_args(args)
+    if option.has_p:
+        raise NotImplementedError()
+    
+    for arg in args:
+        try:
+            name, value = arg.split('=', 1)
+        except ValueError:
+            name, value = arg, None
+        env = interp.get_env().export(name, value)
+    
+    return 0
+    
+#-------------------------------------------------------------------------------  
+# return special builtin
+#-------------------------------------------------------------------------------  
+def builtin_return(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+    res = 0
+    if args:
+        try:
+            res = int(args[0])
+        except ValueError:
+            res = 0
+        if not 0<=res<=255:
+            res = 0
+            
+    # BUG: should be last executed command exit code        
+    raise ReturnSignal(res)
+
+#-------------------------------------------------------------------------------  
+# trap special builtin
+#-------------------------------------------------------------------------------  
+def builtin_trap(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+    if len(args) < 2:
+        stderr.write('trap: usage: trap [[arg] signal_spec ...]\n')
+        return 2
+
+    action = args[0]
+    for sig in args[1:]:
+        try:
+            env.traps[sig] = action
+        except Exception, e:
+            stderr.write('trap: %s\n' % str(e))
+    return 0
+
+#-------------------------------------------------------------------------------  
+# unset special builtin
+#-------------------------------------------------------------------------------
+OPT_UNSET = NonExitingParser("unset - unset values and attributes of variables and functions")
+OPT_UNSET.add_option( '-f', action='store_true', dest='has_f', default=False)
+OPT_UNSET.add_option( '-v', action='store_true', dest='has_v', default=False)
+
+def builtin_unset(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+        
+    option, args = OPT_UNSET.parse_args(args)
+    
+    status = 0
+    env = interp.get_env()
+    for arg in args:    
+        try:
+            if option.has_f:
+                env.remove_function(arg)
+            else:
+                del env[arg]
+        except KeyError:
+            pass
+        except VarAssignmentError:
+            status = 1
+            
+    return status
+
+#-------------------------------------------------------------------------------  
+# wait special builtin
+#-------------------------------------------------------------------------------  
+def builtin_wait(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+
+    return interp.wait([int(arg) for arg in args])
+
+#-------------------------------------------------------------------------------  
+# cat utility
+#-------------------------------------------------------------------------------
+def utility_cat(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+
+    if not args:
+        args = ['-']
+
+    status = 0
+    for arg in args:
+        if arg == '-':
+            data = stdin.read()
+        else:
+            path = os.path.join(env['PWD'], arg)
+            try:
+                f = file(path, 'rb')
+                try:
+                    data = f.read()
+                finally:
+                    f.close()
+            except IOError, e:
+                if e.errno != errno.ENOENT:
+                    raise
+                status = 1
+                continue
+        stdout.write(data)
+        stdout.flush()
+    return status
+    
+#-------------------------------------------------------------------------------  
+# cd utility
+#-------------------------------------------------------------------------------  
+OPT_CD = NonExitingParser("cd - change the working directory")
+
+def utility_cd(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+
+    option, args = OPT_CD.parse_args(args)
+    env = interp.get_env()
+    
+    directory = None
+    printdir = False
+    if not args:
+        home = env.get('HOME')
+        if home:
+            # Unspecified, do nothing
+            return 0
+        else:
+            directory = home
+    elif len(args)==1:
+        directory = args[0]
+        if directory=='-':
+            if 'OLDPWD' not in env:
+                raise UtilityError("OLDPWD not set")
+            printdir = True
+            directory = env['OLDPWD']
+    else:
+        raise UtilityError("too many arguments")
+            
+    curpath = None
+    # Absolute directories will be handled correctly by the os.path.join call.
+    if not directory.startswith('.') and not directory.startswith('..'):
+        cdpaths = env.get('CDPATH', '.').split(';')
+        for cdpath in cdpaths:
+            p = os.path.join(cdpath, directory)
+            if os.path.isdir(p):
+                curpath = p
+                break
+    
+    if curpath is None:
+        curpath = directory
+    curpath = os.path.join(env['PWD'], directory)
+
+    env['OLDPWD'] = env['PWD']
+    env['PWD'] = curpath
+    if printdir:
+        stdout.write('%s\n' % curpath)
+    return 0
+
+#-------------------------------------------------------------------------------  
+# colon utility
+#-------------------------------------------------------------------------------  
+def utility_colon(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+    return 0
+    
+#-------------------------------------------------------------------------------  
+# echo utility
+#-------------------------------------------------------------------------------  
+def utility_echo(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+        
+    # Echo only takes arguments, no options. Use printf if you need fancy stuff.
+    output = ' '.join(args) + '\n'
+    stdout.write(output)
+    stdout.flush()
+    return 0
+    
+#-------------------------------------------------------------------------------  
+# egrep utility
+#-------------------------------------------------------------------------------
+# egrep is usually a shell script.
+# Unfortunately, pysh does not support shell scripts *with arguments* right now,
+# so the redirection is implemented here, assuming grep is available.
+def utility_egrep(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+        
+    return run_command('grep', ['-E'] + args, interp, env, stdin, stdout, 
+        stderr, debugflags)
+    
+#-------------------------------------------------------------------------------  
+# env utility
+#-------------------------------------------------------------------------------  
+def utility_env(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+    
+    if args and args[0]=='-i':
+        raise NotImplementedError('env: -i option is not implemented')
+    
+    i = 0
+    for arg in args:
+        if '=' not in arg:
+            break
+        # Update the current environment
+        name, value = arg.split('=', 1)
+        env[name] = value
+        i += 1
+        
+    if args[i:]:
+        # Find then execute the specified interpreter
+        utility = env.find_in_path(args[i])
+        if not utility:
+            return 127
+        args[i:i+1] = utility
+        name = args[i]
+        args = args[i+1:]
+        try:
+            return run_command(name, args, interp, env, stdin, stdout, stderr, 
+                debugflags)
+        except UtilityError:
+            stderr.write('env: failed to execute %s' % ' '.join([name]+args))
+            return 126            
+    else:
+        for pair in env.get_variables().iteritems():
+            stdout.write('%s=%s\n' % pair)
+    return 0
+    
+#-------------------------------------------------------------------------------  
+# exit utility
+#-------------------------------------------------------------------------------
+def utility_exit(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+        
+    res = None
+    if args:
+        try:
+            res = int(args[0])
+        except ValueError:
+            res = None
+        if not 0<=res<=255:
+            res = None
+            
+    if res is None:
+        # BUG: should be last executed command exit code
+        res = 0
+        
+    raise ExitSignal(res)
+
+#-------------------------------------------------------------------------------  
+# fgrep utility
+#-------------------------------------------------------------------------------
+# see egrep
+def utility_fgrep(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+        
+    return run_command('grep', ['-F'] + args, interp, env, stdin, stdout, 
+        stderr, debugflags)
+
+#-------------------------------------------------------------------------------  
+# gunzip utility
+#-------------------------------------------------------------------------------
+# see egrep
+def utility_gunzip(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+        
+    return run_command('gzip', ['-d'] + args, interp, env, stdin, stdout, 
+        stderr, debugflags)
+    
+#-------------------------------------------------------------------------------  
+# kill utility
+#-------------------------------------------------------------------------------
+def utility_kill(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+        
+    for arg in args:
+        pid = int(arg)
+        status = subprocess.call(['pskill', '/T', str(pid)],
+                                shell=True,
+                                stdout=subprocess.PIPE,
+                                stderr=subprocess.PIPE)
+        # pskill is asynchronous, hence the stupid polling loop
+        while 1:
+            p = subprocess.Popen(['pslist', str(pid)],
+                                shell=True,
+                                stdout=subprocess.PIPE,
+                                stderr=subprocess.STDOUT)
+            output = p.communicate()[0]
+            if ('process %d was not' % pid) in output:
+                break
+            time.sleep(1)
+    return status
+    
+#-------------------------------------------------------------------------------  
+# mkdir utility
+#-------------------------------------------------------------------------------
+OPT_MKDIR = NonExitingParser("mkdir - make directories.")
+OPT_MKDIR.add_option('-p', action='store_true', dest='has_p', default=False)
+
+def utility_mkdir(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+        
+    # TODO: implement umask
+    # TODO: implement proper utility error report
+    option, args = OPT_MKDIR.parse_args(args)
+    for arg in args:
+        path = os.path.join(env['PWD'], arg)
+        if option.has_p:
+            try:
+                os.makedirs(path)
+            except IOError, e:
+                if e.errno != errno.EEXIST:
+                    raise
+        else:               
+            os.mkdir(path)
+    return 0
+
+#-------------------------------------------------------------------------------  
+# netstat utility
+#-------------------------------------------------------------------------------
+def utility_netstat(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    # Do you really expect me to implement netstat ?
+    # This empty form is enough for Mercurial tests since it's
+    # supposed to generate nothing upon success. Faking this test
+    # is not a big deal either.
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+    return 0
+    
+#-------------------------------------------------------------------------------  
+# pwd utility
+#-------------------------------------------------------------------------------  
+OPT_PWD = NonExitingParser("pwd - return working directory name")
+OPT_PWD.add_option('-L', action='store_true', dest='has_L', default=True,
+    help="""If the PWD environment variable contains an absolute pathname of \
+    the current directory that does not contain the filenames dot or dot-dot, \
+    pwd shall write this pathname to standard output. Otherwise, the -L option \
+    shall behave as the -P option.""")
+OPT_PWD.add_option('-P', action='store_true', dest='has_L', default=False,
+    help="""The absolute pathname written shall not contain filenames that, in \
+    the context of the pathname, refer to files of type symbolic link.""")
+
+def utility_pwd(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+
+    option, args = OPT_PWD.parse_args(args)        
+    stdout.write('%s\n' % env['PWD'])
+    return 0
+    
+#-------------------------------------------------------------------------------  
+# printf utility
+#-------------------------------------------------------------------------------
+RE_UNESCAPE = re.compile(r'(\\x[a-zA-Z0-9]{2}|\\[0-7]{1,3}|\\.)')
+
+def utility_printf(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+        
+    def replace(m):
+        assert m.group()
+        g = m.group()[1:]
+        if g.startswith('x'):
+            return chr(int(g[1:], 16))
+        if len(g) <= 3 and len([c for c in g if c in '01234567']) == len(g):
+            # Yay, an octal number
+            return chr(int(g, 8))
+        return {
+            'a': '\a',
+            'b': '\b',
+            'f': '\f',
+            'n': '\n',
+            'r': '\r',
+            't': '\t',
+            'v': '\v',
+            '\\': '\\',
+        }.get(g)
+        
+    # Convert escape sequences
+    format = re.sub(RE_UNESCAPE, replace, args[0])
+    stdout.write(format % tuple(args[1:]))
+    return 0
+    
+#-------------------------------------------------------------------------------  
+# true utility
+#-------------------------------------------------------------------------------
+def utility_true(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+    return 0
+
+#-------------------------------------------------------------------------------  
+# sed utility
+#-------------------------------------------------------------------------------
+RE_SED = re.compile(r'^s(.).*\1[a-zA-Z]*$')
+
+# cygwin sed fails with some expressions when they do not end with a single space.
+# see unit tests for details. Interestingly, the same expressions works perfectly
+# in cygwin shell.
+def utility_sed(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+        
+    # Scan pattern arguments and append a space if necessary
+    for i in xrange(len(args)):
+        if not RE_SED.search(args[i]):
+            continue
+        args[i] = args[i] + ' '
+
+    return run_command(name, args, interp, env, stdin, stdout, 
+        stderr, debugflags)
+
+#-------------------------------------------------------------------------------  
+# sleep utility
+#-------------------------------------------------------------------------------
+def utility_sleep(name, args, interp, env, stdin, stdout, stderr, debugflags):
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+    time.sleep(int(args[0]))
+    return 0
+    
+#-------------------------------------------------------------------------------  
+# sort utility
+#-------------------------------------------------------------------------------
+OPT_SORT = NonExitingParser("sort - sort, merge, or sequence check text files")
+
+def utility_sort(name, args, interp, env, stdin, stdout, stderr, debugflags):
+
+    def sort(path):
+        if path == '-':
+            lines = stdin.readlines()
+        else:
+            try:
+                f = file(path)
+                try:
+                    lines = f.readlines()
+                finally:
+                    f.close()
+            except IOError, e:
+                stderr.write(str(e) + '\n')
+                return 1
+        
+        if lines and lines[-1][-1]!='\n':
+            lines[-1] = lines[-1] + '\n'
+        return lines
+    
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+        
+    option, args = OPT_SORT.parse_args(args)
+    alllines = []
+    
+    if len(args)<=0:
+        args += ['-']
+        
+    # Load all files lines
+    curdir = os.getcwd()
+    try:
+        os.chdir(env['PWD'])
+        for path in args:
+            alllines += sort(path)
+    finally:
+        os.chdir(curdir)
+            
+    alllines.sort()
+    for line in alllines:
+        stdout.write(line)
+    return 0
+    
+#-------------------------------------------------------------------------------
+# hg utility
+#-------------------------------------------------------------------------------
+
+hgcommands = [
+    'add',
+    'addremove',
+    'commit', 'ci',
+    'debugrename',
+    'debugwalk',
+    'falabala', # Dummy command used in a mercurial test
+    'incoming',
+    'locate',
+    'pull',
+    'push',
+    'qinit',
+    'remove', 'rm',
+    'rename', 'mv',
+    'revert',    
+    'showconfig',
+    'status', 'st',
+    'strip',
+    ]
+
+def rewriteslashes(name, args):
+    # Several hg commands output file paths, rewrite the separators
+    if len(args) > 1 and name.lower().endswith('python') \
+       and args[0].endswith('hg'):
+        for cmd in hgcommands:
+            if cmd in args[1:]:
+                return True
+            
+    # svn output contains many paths with OS specific separators.
+    # Normalize these to unix paths.
+    base = os.path.basename(name)
+    if base.startswith('svn'):
+        return True
+    
+    return False
+
+def rewritehg(output):
+    if not output:
+        return output
+    # Rewrite os specific messages
+    output = output.replace(': The system cannot find the file specified',
+                            ': No such file or directory')
+    output = re.sub(': Access is denied.*$', ': Permission denied', output)
+    output = output.replace(': No connection could be made because the target machine actively refused it',
+                            ': Connection refused')
+    return output
+                            
+
+def run_command(name, args, interp, env, stdin, stdout,
+                stderr, debugflags):
+    # Execute the command
+    if 'debug-utility' in debugflags:
+        print interp.log(' '.join([name, str(args), interp['PWD']]) + '\n')
+
+    hgbin = interp.options().hgbinary
+    ishg = hgbin and ('hg' in name or args and 'hg' in args[0])
+    unixoutput = 'cygwin' in name or ishg
+    
+    exec_env = env.get_variables()        
+    try:
+        # BUG: comparing file descriptor is clearly not a reliable way to tell
+        # whether they point on the same underlying object. But in pysh limited
+        # scope this is usually right, we do not expect complicated redirections
+        # besides usual 2>&1.
+        # Still there is one case we have but cannot deal with is when stdout
+        # and stderr are redirected *by pysh caller*. This the reason for the
+        # --redirect pysh() option.
+        # Now, we want to know they are the same because we sometimes need to 
+        # transform the command output, mostly remove CR-LF to ensure that
+        # command output is unix-like. Cygwin utilies are a special case because
+        # they explicitely set their output streams to binary mode, so we have
+        # nothing to do. For all others commands, we have to guess whether they
+        # are sending text data, in which case the transformation must be done.
+        # Again, the NUL character test is unreliable but should be enough for
+        # hg tests.
+        redirected = stdout.fileno()==stderr.fileno()
+        if not redirected:
+            p = subprocess.Popen([name] + args, cwd=env['PWD'], env=exec_env, 
+                    stdin=stdin, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+        else:
+            p = subprocess.Popen([name] + args, cwd=env['PWD'], env=exec_env, 
+                    stdin=stdin, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
+        out, err = p.communicate()
+    except WindowsError, e:
+        raise UtilityError(str(e))
+
+    if not unixoutput:
+        def encode(s):
+            if '\0' in s:
+                return s
+            return s.replace('\r\n', '\n')
+    else:
+        encode = lambda s: s
+
+    if rewriteslashes(name, args):
+        encode1_ = encode
+        def encode(s):
+            s = encode1_(s)
+            s = s.replace('\\\\', '\\')
+            s = s.replace('\\', '/')
+            return s
+
+    if ishg:
+        encode2_ = encode
+        def encode(s):
+            return rewritehg(encode2_(s))
+    
+    stdout.write(encode(out))
+    if not redirected:
+        stderr.write(encode(err))
+    return p.returncode
+            
diff --git a/lib/pysh/interp.py b/lib/pysh/interp.py
new file mode 100644
index 000000000..efe5181e1
--- /dev/null
+++ b/lib/pysh/interp.py
@@ -0,0 +1,1367 @@
+# interp.py - shell interpreter for pysh.
+#
+# Copyright 2007 Patrick Mezard
+#
+# This software may be used and distributed according to the terms
+# of the GNU General Public License, incorporated herein by reference.
+
+"""Implement the shell interpreter.
+
+Most references are made to "The Open Group Base Specifications Issue 6".
+<http://www.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html>
+"""
+# TODO: document the fact input streams must implement fileno() so Popen will work correctly.
+# it requires non-stdin stream to be implemented as files. Still to be tested...
+# DOC: pathsep is used in PATH instead of ':'. Clearly, there are path syntax issues here.
+# TODO: stop command execution upon error.
+# TODO: sort out the filename/io_number mess. It should be possible to use filenames only.
+# TODO: review subshell implementation
+# TODO: test environment cloning for non-special builtins
+# TODO: set -x should not rebuild commands from tokens, assignments/redirections are lost
+# TODO: unit test for variable assignment
+# TODO: test error management wrt error type/utility type
+# TODO: test for binary output everywhere
+# BUG: debug-parsing does not pass log file to PLY. Maybe a PLY upgrade is necessary.
+import base64
+import cPickle as pickle
+import errno
+import glob
+import os
+import re
+import subprocess
+import sys
+import tempfile
+
+try:
+    s = set()
+    del s
+except NameError:
+    from Set import Set as set
+
+import builtin
+from sherrors import *
+import pyshlex
+import pyshyacc
+
+def mappend(func, *args, **kargs):
+    """Like map but assume func returns a list. Returned lists are merged into
+    a single one.
+    """
+    return reduce(lambda a,b: a+b, map(func, *args, **kargs), [])
+
+class FileWrapper:
+    """File object wrapper to ease debugging.
+    
+    Allow mode checking and implement file duplication through a simple 
+    reference counting scheme. Not sure the latter is really useful since
+    only real file descriptors can be used.
+    """
+    def __init__(self, mode, file, close=True):
+        if mode not in ('r', 'w', 'a'):
+            raise IOError('invalid mode: %s' % mode)
+        self._mode = mode
+        self._close = close
+        if isinstance(file, FileWrapper):
+            if file._refcount[0] <= 0:
+                raise IOError(0, 'Error')
+            self._refcount = file._refcount
+            self._refcount[0] += 1
+            self._file = file._file
+        else:
+            self._refcount = [1]
+            self._file = file
+        
+    def dup(self):
+        return FileWrapper(self._mode, self, self._close)
+        
+    def fileno(self):
+        """fileno() should be only necessary for input streams."""
+        return self._file.fileno()
+        
+    def read(self, size=-1):
+        if self._mode!='r':
+            raise IOError(0, 'Error')
+        return self._file.read(size)
+        
+    def readlines(self, *args, **kwargs):
+        return self._file.readlines(*args, **kwargs)
+        
+    def write(self, s):
+        if self._mode not in ('w', 'a'):
+            raise IOError(0, 'Error')
+        return self._file.write(s)
+        
+    def flush(self):
+        self._file.flush()
+        
+    def close(self):        
+        if not self._refcount:
+            return
+        assert  self._refcount[0] > 0
+        
+        self._refcount[0] -= 1    
+        if self._refcount[0] == 0:
+            self._mode = 'c'
+            if self._close:
+                self._file.close()
+        self._refcount = None
+                
+    def mode(self):
+        return self._mode
+
+    def __getattr__(self, name):
+        if name == 'name':
+            self.name = getattr(self._file, name)
+            return self.name
+        else:
+            raise AttributeError(name)
+
+    def __del__(self):
+        self.close()
+               
+               
+def win32_open_devnull(mode):
+    return open('NUL', mode)
+    
+        
+class Redirections:
+    """Stores open files and their mapping to pseudo-sh file descriptor.
+    """
+    # BUG: redirections are not handled correctly: 1>&3 2>&3 3>&4 does 
+    # not make 1 to redirect to 4
+    def __init__(self, stdin=None, stdout=None, stderr=None):
+        self._descriptors = {}
+        if stdin is not None:
+            self._add_descriptor(0, stdin)
+        if stdout is not None:
+            self._add_descriptor(1, stdout)
+        if stderr is not None:
+            self._add_descriptor(2, stderr)
+            
+    def add_here_document(self, interp, name, content, io_number=None):
+        if io_number is None:
+            io_number = 0
+            
+        if name==pyshlex.unquote_wordtree(name):
+            content = interp.expand_here_document(('TOKEN', content))
+    
+        # Write document content in a temporary file
+        tmp = tempfile.TemporaryFile()
+        try:
+            tmp.write(content)
+            tmp.flush()
+            tmp.seek(0)
+            self._add_descriptor(io_number, FileWrapper('r', tmp))
+        except:
+            tmp.close()
+            raise                
+        
+    def add(self, interp, op, filename, io_number=None):
+        if op not in ('<', '>', '>|', '>>', '>&'):
+            # TODO: add descriptor duplication and here_documents      
+            raise RedirectionError('Unsupported redirection operator "%s"' % op)
+            
+        if io_number is not None:
+            io_number = int(io_number)
+            
+        if (op == '>&' and filename.isdigit()) or filename=='-':
+            # No expansion for file descriptors, quote them if you want a filename
+            fullname = filename
+        else:
+            if filename.startswith('/'):
+                # TODO: win32 kludge
+                if filename=='/dev/null':
+                    fullname = 'NUL'
+                else:
+                    # TODO: handle absolute pathnames, they are unlikely to exist on the
+                    # current platform (win32 for instance).
+                    raise NotImplementedError()
+            else:
+                fullname = interp.expand_redirection(('TOKEN', filename))
+                if not fullname:
+                    raise RedirectionError('%s: ambiguous redirect' % filename)
+                # Build absolute path based on PWD
+                fullname = os.path.join(interp.get_env()['PWD'], fullname)
+            
+        if op=='<':
+            return self._add_input_redirection(interp, fullname, io_number)
+        elif op in ('>', '>|'):
+            clobber = ('>|'==op)
+            return self._add_output_redirection(interp, fullname, io_number, clobber)
+        elif op=='>>':
+            return self._add_output_appending(interp, fullname, io_number)
+        elif op=='>&':
+            return self._dup_output_descriptor(fullname, io_number)
+        
+    def close(self):
+        if self._descriptors is not None:
+            for desc in self._descriptors.itervalues():
+                desc.flush()
+                desc.close()
+            self._descriptors = None
+            
+    def stdin(self):
+        return self._descriptors[0]
+          
+    def stdout(self):
+        return self._descriptors[1] 
+        
+    def stderr(self):
+        return self._descriptors[2] 
+            
+    def clone(self):
+        clone = Redirections()
+        for desc, fileobj in self._descriptors.iteritems():
+            clone._descriptors[desc] = fileobj.dup()
+        return clone
+           
+    def _add_output_redirection(self, interp, filename, io_number, clobber):    
+        if io_number is None:
+            # io_number default to standard output
+            io_number = 1
+        
+        if not clobber and interp.get_env().has_opt('-C') and os.path.isfile(filename):
+            # File already exist in no-clobber mode, bail out
+            raise RedirectionError('File "%s" already exists' % filename)
+            
+        # Open and register
+        self._add_file_descriptor(io_number, filename, 'w')
+        
+    def _add_output_appending(self, interp, filename, io_number):    
+        if io_number is None:
+            io_number = 1
+        self._add_file_descriptor(io_number, filename, 'a')
+            
+    def _add_input_redirection(self, interp, filename, io_number):
+        if io_number is None:
+            io_number = 0
+        self._add_file_descriptor(io_number, filename, 'r')
+        
+    def _add_file_descriptor(self, io_number, filename, mode):    
+        try:            
+            if filename.startswith('/'):
+                if filename=='/dev/null':
+                    f = win32_open_devnull(mode+'b')
+                else:
+                    # TODO: handle absolute pathnames, they are unlikely to exist on the
+                    # current platform (win32 for instance).
+                    raise NotImplementedError('cannot open absolute path %s' % repr(filename))
+            else:
+                f = file(filename, mode+'b')
+        except IOError, e:
+            raise RedirectionError(str(e))
+            
+        wrapper = None
+        try:
+            wrapper = FileWrapper(mode, f)
+            f = None
+            self._add_descriptor(io_number, wrapper)
+        except:
+            if f: f.close()
+            if wrapper: wrapper.close()
+            raise
+            
+    def _dup_output_descriptor(self, source_fd, dest_fd):
+        if source_fd is None:
+            source_fd = 1
+        self._dup_file_descriptor(source_fd, dest_fd, 'w')
+            
+    def _dup_file_descriptor(self, source_fd, dest_fd, mode):
+        source_fd = int(source_fd)
+        if source_fd not in self._descriptors:
+            raise RedirectionError('"%s" is not a valid file descriptor' % str(source_fd))
+        source = self._descriptors[source_fd]
+        
+        if source.mode()!=mode:
+            raise RedirectionError('Descriptor %s cannot be duplicated in mode "%s"' % (str(source), mode))
+        
+        if dest_fd=='-':
+            # Close the source descriptor
+            del self._descriptors[source_fd]
+            source.close()
+        else:
+            dest_fd = int(dest_fd)
+            if dest_fd not in self._descriptors:
+                raise RedirectionError('Cannot replace file descriptor %s' % str(dest_fd))
+                
+            dest = self._descriptors[dest_fd]
+            if dest.mode()!=mode:
+                raise RedirectionError('Descriptor %s cannot be cannot be redirected in mode "%s"' % (str(dest), mode))
+            
+            self._descriptors[dest_fd] = source.dup()
+            dest.close()        
+            
+    def _add_descriptor(self, io_number, file):
+        io_number = int(io_number)
+        
+        if io_number in self._descriptors:
+            # Close the current descriptor
+            d = self._descriptors[io_number]
+            del self._descriptors[io_number]
+            d.close()
+            
+        self._descriptors[io_number] = file
+
+    def __str__(self):
+        names = [('%d=%r' % (k, getattr(v, 'name', None))) for k,v
+                 in self._descriptors.iteritems()]
+        names = ','.join(names)
+        return 'Redirections(%s)' % names
+
+    def __del__(self):
+        self.close()
+    
+def cygwin_to_windows_path(path):
+    """Turn /cygdrive/c/foo into c:/foo, or return path if it
+    is not a cygwin path.
+    """
+    if not path.startswith('/cygdrive/'):
+        return path
+    path = path[len('/cygdrive/'):]
+    path = path[:1] + ':' + path[1:]
+    return path
+    
+def win32_to_unix_path(path):
+    if path is not None:
+        path = path.replace('\\', '/')
+    return path    
+    
+_RE_SHEBANG = re.compile(r'^\#!\s?([^\s]+)(?:\s([^\s]+))?')
+_SHEBANG_CMDS = {
+    '/usr/bin/env': 'env',
+    '/bin/sh': 'pysh',
+    'python': 'python',
+}
+    
+def resolve_shebang(path, ignoreshell=False):
+    """Return a list of arguments as shebang interpreter call or an empty list
+    if path does not refer to an executable script.
+    See <http://www.opengroup.org/austin/docs/austin_51r2.txt>.
+    
+    ignoreshell - set to True to ignore sh shebangs. Return an empty list instead.
+    """
+    try:
+        f = file(path)
+        try:
+            # At most 80 characters in the first line
+            header = f.read(80).splitlines()[0]
+        finally:
+            f.close()
+            
+        m = _RE_SHEBANG.search(header)
+        if not m:
+            return []
+        cmd, arg = m.group(1,2)
+        if os.path.isfile(cmd):
+            # Keep this one, the hg script for instance contains a weird windows
+            # shebang referencing the current python install.
+            cmdfile = os.path.basename(cmd).lower()
+            if cmdfile == 'python.exe':
+                cmd = 'python'
+            pass
+        elif cmd not in _SHEBANG_CMDS:
+            raise CommandNotFound('Unknown interpreter "%s" referenced in '\
+                'shebang' % header)
+        cmd = _SHEBANG_CMDS.get(cmd)
+        if cmd is None or (ignoreshell and cmd == 'pysh'):
+            return []
+        if arg is None:
+            return [cmd, win32_to_unix_path(path)]
+        return [cmd, arg, win32_to_unix_path(path)]
+    except IOError, e:
+        if  e.errno!=errno.ENOENT and \
+            (e.errno!=errno.EPERM and not os.path.isdir(path)): # Opening a directory raises EPERM
+            raise
+        return []
+        
+def win32_find_in_path(name, path):
+    if isinstance(path, str):
+        path = path.split(os.pathsep)
+        
+    exts = os.environ.get('PATHEXT', '').lower().split(os.pathsep)
+    for p in path:
+        p_name = os.path.join(p, name)
+        
+        prefix = resolve_shebang(p_name)
+        if prefix:
+            return prefix
+            
+        for ext in exts:    
+            p_name_ext = p_name + ext
+            if os.path.exists(p_name_ext):
+                return [win32_to_unix_path(p_name_ext)]
+    return []
+
+class Traps(dict):
+    def __setitem__(self, key, value):
+        if key not in ('EXIT',):
+            raise NotImplementedError()
+        super(Traps, self).__setitem__(key, value)
+
+# IFS white spaces character class
+_IFS_WHITESPACES = (' ', '\t', '\n')
+
+class Environment:
+    """Environment holds environment variables, export table, function 
+    definitions and whatever is defined in 2.12 "Shell Execution Environment",
+    redirection excepted.
+    """
+    def __init__(self, pwd):
+        self._opt = set()       #Shell options
+        
+        self._functions = {}        
+        self._env = {'?': '0', '#': '0'}
+        self._exported = set([
+            'HOME', 'IFS', 'PATH'
+        ])
+        
+        # Set environment vars with side-effects
+        self._ifs_ws = None     # Set of IFS whitespace characters
+        self._ifs_re = None     # Regular expression used to split between words using IFS classes
+        self['IFS'] = ''.join(_IFS_WHITESPACES) #Default environment values
+        self['PWD'] = pwd
+        self.traps = Traps()
+        
+    def clone(self, subshell=False):
+        env = Environment(self['PWD'])
+        env._opt = set(self._opt)
+        for k,v in self.get_variables().iteritems():
+            if k in self._exported:
+                env.export(k,v)
+            elif subshell:
+                env[k] = v
+                
+        if subshell:
+            env._functions = dict(self._functions)
+            
+        return env        
+        
+    def __getitem__(self, key):
+        if key in ('@', '*', '-', '$'):
+            raise NotImplementedError('%s is not implemented' % repr(key))
+        return self._env[key]
+        
+    def get(self, key, defval=None):
+        try:
+            return self[key]
+        except KeyError:
+            return defval
+        
+    def __setitem__(self, key, value):
+        if key=='IFS':
+            # Update the whitespace/non-whitespace classes
+            self._update_ifs(value)
+        elif key=='PWD':
+            pwd = os.path.abspath(value)
+            if not os.path.isdir(pwd):
+                raise VarAssignmentError('Invalid directory %s' % value)
+            value = pwd
+        elif key in ('?', '!'):
+            value = str(int(value))
+        self._env[key] = value
+        
+    def __delitem__(self, key):
+        if key in ('IFS', 'PWD', '?'):
+            raise VarAssignmentError('%s cannot be unset' % key)
+        del self._env[key]
+
+    def __contains__(self, item):
+        return item in self._env
+        
+    def set_positional_args(self, args):
+        """Set the content of 'args' as positional argument from 1 to len(args).
+        Return previous argument as a list of strings.
+        """
+        # Save and remove previous arguments
+        prevargs = []        
+        for i in xrange(int(self._env['#'])):
+            i = str(i+1)
+            prevargs.append(self._env[i])
+            del self._env[i]
+        self._env['#'] = '0'
+                
+        #Set new ones
+        for i,arg in enumerate(args):
+            self._env[str(i+1)] = str(arg)
+        self._env['#'] = str(len(args))
+        
+        return prevargs
+        
+    def get_positional_args(self):
+        return [self._env[str(i+1)] for i in xrange(int(self._env['#']))]
+        
+    def get_variables(self):
+        return dict(self._env)
+        
+    def export(self, key, value=None):
+        if value is not None:
+            self[key] = value
+        self._exported.add(key)
+        
+    def get_exported(self):
+        return [(k,self._env.get(k)) for k in self._exported]
+            
+    def split_fields(self, word):
+        if not self._ifs_ws or not word:
+            return [word]
+        return re.split(self._ifs_re, word)
+   
+    def _update_ifs(self, value):
+        """Update the split_fields related variables when IFS character set is
+        changed.
+        """
+        # TODO: handle NULL IFS
+        
+        # Separate characters in whitespace and non-whitespace
+        chars = set(value)
+        ws = [c for c in chars if c in _IFS_WHITESPACES]
+        nws = [c for c in chars if c not in _IFS_WHITESPACES]
+        
+        # Keep whitespaces in a string for left and right stripping
+        self._ifs_ws = ''.join(ws)
+        
+        # Build a regexp to split fields
+        trailing = '[' + ''.join([re.escape(c) for c in ws]) + ']'
+        if nws:
+            # First, the single non-whitespace occurence.
+            nws = '[' + ''.join([re.escape(c) for c in nws]) + ']'
+            nws = '(?:' + trailing + '*' + nws + trailing + '*' + '|' + trailing + '+)'
+        else:
+            # Then mix all parts with quantifiers
+            nws = trailing + '+'
+        self._ifs_re = re.compile(nws)
+       
+    def has_opt(self, opt, val=None):
+        return (opt, val) in self._opt
+        
+    def set_opt(self, opt, val=None):
+        self._opt.add((opt, val))
+        
+    def find_in_path(self, name, pwd=False):
+        path = self._env.get('PATH', '').split(os.pathsep)
+        if pwd:
+            path[:0] = [self['PWD']]
+        if os.name == 'nt':
+            return win32_find_in_path(name, self._env.get('PATH', ''))
+        else:
+            raise NotImplementedError()
+            
+    def define_function(self, name, body):
+        if not is_name(name):
+            raise ShellSyntaxError('%s is not a valid function name' % repr(name))
+        self._functions[name] = body
+        
+    def remove_function(self, name):
+        del self._functions[name]
+        
+    def is_function(self, name):
+        return name in self._functions
+        
+    def get_function(self, name):
+        return self._functions.get(name)
+        
+       
+name_charset = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_'
+name_charset = dict(zip(name_charset,name_charset))
+           
+def match_name(s):
+    """Return the length in characters of the longest prefix made of name
+    allowed characters in s.
+    """
+    for i,c in enumerate(s):
+        if c not in name_charset:
+            return s[:i]
+    return s
+    
+def is_name(s):
+    return len([c for c in s if c not in name_charset])<=0
+    
+def is_special_param(c):
+    return len(c)==1 and c in ('@','*','#','?','-','$','!','0')
+    
+def utility_not_implemented(name, *args, **kwargs):
+    raise NotImplementedError('%s utility is not implemented' % name)
+    
+
+class Utility:
+    """Define utilities properties:
+    func -- utility callable. See builtin module for utility samples.
+    is_special -- see XCU 2.8.
+    """
+    def __init__(self, func, is_special=0):
+        self.func = func
+        self.is_special = bool(is_special)
+
+
+def encodeargs(args):
+    def encodearg(s):
+        lines = base64.encodestring(s)
+        lines = [l.splitlines()[0] for l in lines]
+        return ''.join(lines)
+
+    s = pickle.dumps(args)
+    return encodearg(s)
+
+def decodeargs(s):
+    s = base64.decodestring(s)
+    return pickle.loads(s)
+    
+
+class GlobError(Exception):
+    pass
+
+class Options:
+    def __init__(self):
+        # True if Mercurial operates with binary streams
+        self.hgbinary = True
+
+class Interpreter:
+    # Implementation is very basic: the execute() method just makes a DFS on the
+    # AST and execute nodes one by one. Nodes are tuple (name,obj) where name
+    # is a string identifier and obj the AST element returned by the parser.
+    #
+    # Handler are named after the node identifiers.
+    # TODO: check node names and remove the switch in execute with some
+    # dynamic getattr() call to find node handlers.
+    """Shell interpreter.
+    
+    The following debugging flags can be passed:
+    debug-parsing - enable PLY debugging.
+    debug-tree - print the generated AST.
+    debug-cmd - trace command execution before word expansion, plus exit status.
+    debug-utility - trace utility execution.
+    """
+    
+    # List supported commands.
+    COMMANDS = {
+        'cat':       Utility(builtin.utility_cat,),
+        'cd':       Utility(builtin.utility_cd,),
+        ':':        Utility(builtin.utility_colon,),
+        'echo':     Utility(builtin.utility_echo),
+        'env':      Utility(builtin.utility_env),
+        'exit':     Utility(builtin.utility_exit),
+        'export':   Utility(builtin.builtin_export,     is_special=1),
+        'egrep':    Utility(builtin.utility_egrep),
+        'fgrep':    Utility(builtin.utility_fgrep),
+        'gunzip':   Utility(builtin.utility_gunzip),
+        'kill':     Utility(builtin.utility_kill),
+        'mkdir':    Utility(builtin.utility_mkdir),
+        'netstat':  Utility(builtin.utility_netstat),
+        'printf':   Utility(builtin.utility_printf),
+        'pwd':      Utility(builtin.utility_pwd),
+        'return':   Utility(builtin.builtin_return,     is_special=1),
+        'sed':      Utility(builtin.utility_sed,),
+        'set':      Utility(builtin.builtin_set,),
+        'shift':    Utility(builtin.builtin_shift,),
+        'sleep':    Utility(builtin.utility_sleep,),
+        'sort':     Utility(builtin.utility_sort,),
+        'trap':     Utility(builtin.builtin_trap,       is_special=1),
+        'true':     Utility(builtin.utility_true),
+        'unset':    Utility(builtin.builtin_unset,      is_special=1),
+        'wait':     Utility(builtin.builtin_wait,       is_special=1),
+    }
+    
+    def __init__(self, pwd, debugflags = [], env=None, redirs=None, stdin=None,
+                 stdout=None, stderr=None, opts=Options()):
+        self._env = env
+        if self._env is None:
+            self._env = Environment(pwd)
+        self._children = {}
+            
+        self._redirs = redirs
+        self._close_redirs = False
+        
+        if self._redirs is None:
+            if stdin is None:
+                stdin = sys.stdin
+            if stdout is None:
+                stdout = sys.stdout
+            if stderr is None:
+                stderr = sys.stderr
+            stdin = FileWrapper('r', stdin, False)
+            stdout = FileWrapper('w', stdout, False)
+            stderr = FileWrapper('w', stderr, False)
+            self._redirs = Redirections(stdin, stdout, stderr)
+            self._close_redirs = True
+            
+        self._debugflags = list(debugflags)
+        self._logfile = sys.stderr
+        self._options = opts
+        
+    def close(self):
+        """Must be called when the interpreter is no longer used."""
+        script = self._env.traps.get('EXIT')
+        if script:
+            try:
+                self.execute_script(script=script)
+            except:
+                pass
+
+        if self._redirs is not None and self._close_redirs:
+            self._redirs.close()
+            self._redirs = None
+            
+    def log(self, s):
+        self._logfile.write(s)
+        self._logfile.flush()
+            
+    def __getitem__(self, key):
+        return self._env[key]
+        
+    def __setitem__(self, key, value):
+        self._env[key] = value
+
+    def options(self):
+        return self._options
+
+    def redirect(self, redirs, ios):
+        def add_redir(io):
+            if isinstance(io, pyshyacc.IORedirect):
+                redirs.add(self, io.op, io.filename, io.io_number)
+            else:
+                redirs.add_here_document(self, io.name, io.content, io.io_number)
+                    
+        map(add_redir, ios)
+        return redirs
+            
+    def execute_script(self, script=None, ast=None, sourced=False,
+                       scriptpath=None):
+        """If script is not None, parse the input. Otherwise takes the supplied
+        AST. Then execute the AST.
+        Return the script exit status.
+        """
+        try:
+            if scriptpath is not None:
+                self._env['0'] = os.path.abspath(scriptpath)
+
+            if script is not None:
+                debug_parsing = ('debug-parsing' in self._debugflags)    
+                cmds, script = pyshyacc.parse(script, True, debug_parsing)
+                if 'debug-tree' in self._debugflags:
+                    pyshyacc.print_commands(cmds, self._logfile)
+                    self._logfile.flush()
+            else:
+                cmds, script = ast, ''                
+                
+            status = 0
+            for cmd in cmds:
+                try:
+                    status = self.execute(cmd)
+                except ExitSignal, e:
+                    if sourced:
+                        raise
+                    status = int(e.args[0])
+                    return status
+                except ShellError:
+                    self._env['?'] = 1
+                    raise
+                if 'debug-utility' in self._debugflags or 'debug-cmd' in self._debugflags:
+                    self.log('returncode ' + str(status)+ '\n')
+            return status
+        except CommandNotFound, e:
+            print >>self._redirs.stderr, str(e)
+            self._redirs.stderr.flush()
+            # Command not found by non-interactive shell
+            # return 127
+            raise
+        except RedirectionError, e:
+            # TODO: should be handled depending on the utility status
+            print >>self._redirs.stderr, str(e)
+            self._redirs.stderr.flush()
+            # Command not found by non-interactive shell
+            # return 127
+            raise
+
+    def dotcommand(self, env, args):
+        if len(args) < 1:
+            raise ShellError('. expects at least one argument')
+        path = args[0]
+        if '/' not in path:
+            found = env.find_in_path(args[0], True)
+            if found:
+                path = found[0]
+        script = file(path).read()
+        return self.execute_script(script=script, sourced=True)
+
+    def execute(self, token, redirs=None):
+        """Execute and AST subtree with supplied redirections overriding default
+        interpreter ones.
+        Return the exit status.
+        """
+        if not token:
+            return 0
+            
+        if redirs is None:
+            redirs = self._redirs
+            
+        if isinstance(token, list):
+            # Commands sequence
+            res = 0
+            for t in token:
+                res = self.execute(t, redirs)
+            return res
+
+        type, value = token
+        status = 0
+        if type=='simple_command':
+            redirs_copy = redirs.clone()
+            try:
+                # TODO: define and handle command return values
+                # TODO: implement set -e
+                status = self._execute_simple_command(value, redirs_copy)
+            finally:
+                redirs_copy.close()
+        elif type=='pipeline':
+            status = self._execute_pipeline(value, redirs)
+        elif type=='and_or':
+            status = self._execute_and_or(value, redirs)
+        elif type=='for_clause':
+            status = self._execute_for_clause(value, redirs)
+        elif type=='while_clause':
+            status = self._execute_while_clause(value, redirs)
+        elif type=='function_definition':
+            status = self._execute_function_definition(value, redirs)
+        elif type=='brace_group':
+            status = self._execute_brace_group(value, redirs)
+        elif type=='if_clause':
+            status = self._execute_if_clause(value, redirs)
+        elif type=='subshell':
+            status = self.subshell(ast=value.cmds, redirs=redirs)
+        elif type=='async':
+            status = self._asynclist(value)
+        elif type=='redirect_list':
+            redirs_copy = self.redirect(redirs.clone(), value.redirs)
+            try:
+                status = self.execute(value.cmd, redirs_copy)
+            finally:
+                redirs_copy.close()
+        else:
+            raise NotImplementedError('Unsupported token type ' + type)
+
+        if status < 0:
+            status = 255
+        return status
+            
+    def _execute_if_clause(self, if_clause, redirs):
+        cond_status = self.execute(if_clause.cond, redirs)
+        if cond_status==0:
+            return self.execute(if_clause.if_cmds, redirs)
+        else:
+            return self.execute(if_clause.else_cmds, redirs)
+      
+    def _execute_brace_group(self, group, redirs):
+        status = 0
+        for cmd in group.cmds:
+            status = self.execute(cmd, redirs)
+        return status
+            
+    def _execute_function_definition(self, fundef, redirs):
+        self._env.define_function(fundef.name, fundef.body)
+        return 0
+            
+    def _execute_while_clause(self, while_clause, redirs):
+        status = 0
+        while 1:
+            cond_status = 0
+            for cond in while_clause.condition:
+                cond_status = self.execute(cond, redirs)
+                
+            if cond_status:
+                break
+                
+            for cmd in while_clause.cmds:
+                status = self.execute(cmd, redirs)
+                
+        return status
+            
+    def _execute_for_clause(self, for_clause, redirs):
+        if not is_name(for_clause.name):
+            raise ShellSyntaxError('%s is not a valid name' % repr(for_clause.name))
+        items = mappend(self.expand_token, for_clause.items)
+        
+        status = 0    
+        for item in items:
+            self._env[for_clause.name] = item
+            for cmd in for_clause.cmds:
+                status = self.execute(cmd, redirs)
+        return status
+            
+    def _execute_and_or(self, or_and, redirs):
+        res = self.execute(or_and.left, redirs)        
+        if (or_and.op=='&&' and res==0) or (or_and.op!='&&' and res!=0):
+            res = self.execute(or_and.right, redirs)
+        return res
+            
+    def _execute_pipeline(self, pipeline, redirs):            
+        if len(pipeline.commands)==1:
+            status = self.execute(pipeline.commands[0], redirs)
+        else:
+            # Execute all commands one after the other
+            status = 0
+            inpath, outpath = None, None
+            try:
+                # Commands inputs and outputs cannot really be plugged as done
+                # by a real shell. Run commands sequentially and chain their
+                # input/output throught temporary files.
+                tmpfd, inpath = tempfile.mkstemp()
+                os.close(tmpfd)
+                tmpfd, outpath = tempfile.mkstemp()
+                os.close(tmpfd)
+                
+                inpath = win32_to_unix_path(inpath)
+                outpath = win32_to_unix_path(outpath)
+                
+                for i, cmd in enumerate(pipeline.commands):
+                    call_redirs = redirs.clone()
+                    try:
+                        if i!=0:
+                            call_redirs.add(self, '<', inpath)
+                        if i!=len(pipeline.commands)-1:
+                            call_redirs.add(self, '>', outpath)
+                        
+                        status = self.execute(cmd, call_redirs)
+                        
+                        # Chain inputs/outputs
+                        inpath, outpath = outpath, inpath
+                    finally:
+                        call_redirs.close()            
+            finally:
+                if inpath: os.remove(inpath)
+                if outpath: os.remove(outpath)
+        
+        if pipeline.reverse_status:
+            status = int(not status)
+        self._env['?'] = status
+        return status
+        
+    def _execute_function(self, name, args, interp, env, stdin, stdout, stderr, *others):
+        assert interp is self
+        
+        func = env.get_function(name)
+        #Set positional parameters
+        prevargs = None
+        try:
+            prevargs = env.set_positional_args(args)
+            try:
+                redirs = Redirections(stdin.dup(), stdout.dup(), stderr.dup())
+                try:
+                    status = self.execute(func, redirs)
+                finally:
+                    redirs.close()
+            except ReturnSignal, e:
+                status = int(e.args[0])
+                env['?'] = status
+            return status
+        finally:
+            #Reset positional parameters
+            if prevargs is not None:
+                env.set_positional_args(prevargs)
+                
+    def _execute_simple_command(self, token, redirs):
+        """Can raise ReturnSignal when return builtin is called, ExitSignal when
+        exit is called, and other shell exceptions upon builtin failures.
+        """
+        debug_command = 'debug-cmd' in self._debugflags
+        if debug_command:
+            self.log('word' + repr(token.words) + '\n')
+            self.log('assigns' + repr(token.assigns) + '\n')
+            self.log('redirs' + repr(token.redirs) + '\n')
+        
+        is_special = None
+        env = self._env
+        
+        try:
+            # Word expansion
+            args = []
+            for word in token.words:                
+                args += self.expand_token(word)
+                if is_special is None and args:
+                    is_special = env.is_function(args[0]) or \
+                        (args[0] in self.COMMANDS and self.COMMANDS[args[0]].is_special)
+                        
+            if debug_command:
+                self.log('_execute_simple_command' + str(args) + '\n')
+                
+            if not args:
+                # Redirections happen is a subshell
+                redirs = redirs.clone()
+            elif not is_special:
+                env = self._env.clone()
+            
+            # Redirections
+            self.redirect(redirs, token.redirs)
+                
+            # Variables assignments
+            res = 0
+            for type,(k,v) in token.assigns:
+                status, expanded = self.expand_variable((k,v))
+                if status is not None:
+                    res = status
+                if args:
+                    env.export(k, expanded)
+                else:
+                    env[k] = expanded
+                
+            if args and args[0] in ('.', 'source'):
+                res = self.dotcommand(env, args[1:])
+            elif args:
+                if args[0] in self.COMMANDS:
+                    command = self.COMMANDS[args[0]]
+                elif env.is_function(args[0]):
+                    command = Utility(self._execute_function, is_special=True)
+                else:
+                    if not '/' in args[0].replace('\\', '/'):
+                        cmd = env.find_in_path(args[0])
+                        if not cmd:
+                            # TODO: test error code on unknown command => 127
+                            raise CommandNotFound('Unknown command: "%s"' % args[0])
+                    else:
+                        # Handle commands like '/cygdrive/c/foo.bat'
+                        cmd = cygwin_to_windows_path(args[0])
+                        if not os.path.exists(cmd):
+                            raise CommandNotFound('%s: No such file or directory' % args[0])
+                        shebang = resolve_shebang(cmd)
+                        if shebang:
+                            cmd = shebang
+                        else:
+                            cmd = [cmd]
+                    args[0:1] = cmd
+                    command = Utility(builtin.run_command)
+                
+                # Command execution
+                if 'debug-cmd' in self._debugflags:
+                    self.log('redirections ' + str(redirs) + '\n')
+                    
+                res = command.func(args[0], args[1:], self, env,
+                                   redirs.stdin(), redirs.stdout(), 
+                                   redirs.stderr(), self._debugflags)
+            
+            if self._env.has_opt('-x'):
+                # Trace command execution in shell environment
+                # BUG: would be hard to reproduce a real shell behaviour since
+                # the AST is not annotated with source lines/tokens.
+                self._redirs.stdout().write(' '.join(args))
+                
+        except ReturnSignal:
+            raise
+        except ShellError, e:
+            if is_special or isinstance(e, (ExitSignal,
+                                            ShellSyntaxError, ExpansionError)):
+                raise e
+            self._redirs.stderr().write(str(e)+'\n')
+            return 1
+
+        return res
+
+    def expand_token(self, word):
+        """Expand a word as specified in [2.6 Word Expansions]. Return the list
+        of expanded words.
+        """
+        status, wtrees = self._expand_word(word)
+        return map(pyshlex.wordtree_as_string, wtrees)
+        
+    def expand_variable(self, word):
+        """Return a status code (or None if no command expansion occurred)
+        and a single word.
+        """
+        status, wtrees = self._expand_word(word, pathname=False, split=False)
+        words = map(pyshlex.wordtree_as_string, wtrees)
+        assert len(words)==1
+        return status, words[0]
+        
+    def expand_here_document(self, word):
+        """Return the expanded document as a single word. The here document is 
+        assumed to be unquoted.
+        """
+        status, wtrees = self._expand_word(word, pathname=False,
+                                           split=False, here_document=True)
+        words = map(pyshlex.wordtree_as_string, wtrees)
+        assert len(words)==1
+        return words[0]
+        
+    def expand_redirection(self, word):
+        """Return a single word."""
+        return self.expand_variable(word)[1]
+        
+    def get_env(self):
+        return self._env
+        
+    def _expand_word(self, token, pathname=True, split=True, here_document=False):
+        wtree = pyshlex.make_wordtree(token[1], here_document=here_document)
+        
+        # TODO: implement tilde expansion
+        def expand(wtree):
+            """Return a pseudo wordtree: the tree or its subelements can be empty
+            lists when no value result from the expansion.
+            """
+            status = None
+            for part in wtree:
+                if not isinstance(part, list):
+                    continue
+                if part[0]in ("'", '\\'):
+                    continue
+                elif part[0] in ('`', '$('):
+                    status, result = self._expand_command(part)
+                    part[:] = result
+                elif part[0] in ('$', '${'):
+                    part[:] = self._expand_parameter(part, wtree[0]=='"', split)
+                elif part[0] in ('', '"'):
+                    status, result = expand(part)
+                    part[:] = result
+                else:
+                    raise NotImplementedError('%s expansion is not implemented'
+                                              % part[0])
+            # [] is returned when an expansion result in no-field,
+            # like an empty $@
+            wtree = [p for p in wtree if p != []]
+            if len(wtree) < 3:
+                return status, []
+            return status, wtree
+        
+        status, wtree = expand(wtree)
+        if len(wtree) == 0:
+            return status, wtree
+        wtree = pyshlex.normalize_wordtree(wtree)
+        
+        if split:
+            wtrees = self._split_fields(wtree)
+        else:
+            wtrees = [wtree]
+        
+        if pathname:
+            wtrees = mappend(self._expand_pathname, wtrees)
+        
+        wtrees = map(self._remove_quotes, wtrees)
+        return status, wtrees
+        
+    def _expand_command(self, wtree):
+        # BUG: there is something to do with backslashes and quoted
+        # characters here
+        command = pyshlex.wordtree_as_string(wtree[1:-1])
+        status, output = self.subshell_output(command)
+        return status, ['', output, '']
+        
+    def _expand_parameter(self, wtree, quoted=False, split=False):
+        """Return a valid wtree or an empty list when no parameter results."""
+        # Get the parameter name
+        # TODO: implement weird expansion rules with ':'
+        name = pyshlex.wordtree_as_string(wtree[1:-1])
+        if not is_name(name) and not is_special_param(name):
+            raise ExpansionError('Bad substitution "%s"' % name)
+        # TODO: implement special parameters
+        if name in ('@', '*'):
+            args = self._env.get_positional_args()
+            if len(args) == 0:
+                return []
+            if len(args)<2:
+                return ['', ''.join(args), '']
+                
+            sep = self._env.get('IFS', '')[:1]
+            if split and quoted and name=='@':
+                # Introduce a new token to tell the caller that these parameters
+                # cause a split as specified in 2.5.2
+                return ['@'] + args + ['']
+            else:
+                return ['', sep.join(args), '']                
+        
+        return ['', self._env.get(name, ''), '']
+        
+    def _split_fields(self, wtree):
+        def is_empty(split):
+            return split==['', '', '']
+            
+        def split_positional(quoted):
+            # Return a list of wtree split according positional parameters rules.
+            # All remaining '@' groups are removed.
+            assert quoted[0]=='"'
+            
+            splits = [[]]
+            for part in quoted:
+                if not isinstance(part, list) or part[0]!='@':
+                    splits[-1].append(part)
+                else:
+                    # Empty or single argument list were dealt with already
+                    assert len(part)>3
+                    # First argument must join with the beginning part of the original word
+                    splits[-1].append(part[1])
+                    # Create double-quotes expressions for every argument after the first
+                    for arg in part[2:-1]:
+                        splits[-1].append('"')
+                        splits.append(['"', arg])
+            return splits
+        
+        # At this point, all expansions but pathnames have occured. Only quoted
+        # and positional sequences remain. Thus, all candidates for field splitting 
+        # are in the tree root, or are positional splits ('@') and lie in root
+        # children.
+        if not wtree or wtree[0] not in ('', '"'):
+            # The whole token is quoted or empty, nothing to split
+            return [wtree]
+            
+        if wtree[0]=='"':
+            wtree = ['', wtree, '']
+        
+        result = [['', '']]
+        for part in wtree[1:-1]:
+            if isinstance(part, list):
+                if part[0]=='"':
+                    splits = split_positional(part)
+                    if len(splits)<=1:
+                        result[-1] += [part, '']
+                    else:
+                        # Terminate the current split
+                        result[-1] += [splits[0], '']
+                        result += splits[1:-1]
+                        # Create a new split
+                        result += [['', splits[-1], '']]
+                else:
+                    result[-1] += [part, '']
+            else:
+                splits = self._env.split_fields(part)
+                if len(splits)<=1:
+                    # No split
+                    result[-1][-1] += part
+                else:
+                    # Terminate the current resulting part and create a new one
+                    result[-1][-1] += splits[0]
+                    result[-1].append('')
+                    result += [['', r, ''] for r in splits[1:-1]]
+                    result += [['', splits[-1]]]
+        result[-1].append('')
+        
+        # Leading and trailing empty groups come from leading/trailing blanks
+        if result and is_empty(result[-1]):
+            result[-1:] = []
+        if result and is_empty(result[0]):
+            result[:1] = []
+        return result
+        
+    def _expand_pathname(self, wtree):
+        """See [2.6.6 Pathname Expansion]."""
+        if self._env.has_opt('-f'):
+            return [wtree]
+        
+        # All expansions have been performed, only quoted sequences should remain
+        # in the tree. Generate the pattern by folding the tree, escaping special
+        # characters when appear quoted
+        special_chars = '*?[]'
+        
+        def make_pattern(wtree):
+            subpattern = []
+            for part in wtree[1:-1]:
+                if isinstance(part, list):
+                    part = make_pattern(part)
+                elif wtree[0]!='':
+                    for c in part:
+                        # Meta-characters cannot be quoted
+                        if c in special_chars:
+                            raise GlobError()
+                subpattern.append(part)
+            return ''.join(subpattern)
+            
+        def pwd_glob(pattern):
+            cwd = os.getcwd()
+            os.chdir(self._env['PWD'])
+            try:
+                return glob.glob(pattern) 
+            finally:
+                os.chdir(cwd)    
+            
+        #TODO: check working directory issues here wrt relative patterns
+        try:
+            pattern = make_pattern(wtree)
+            paths = pwd_glob(pattern)
+        except GlobError:
+            # BUG: Meta-characters were found in quoted sequences. The should 
+            # have been used literally but this is unsupported in current glob module.
+            # Instead we consider the whole tree must be used literally and
+            # therefore there is no point in globbing. This is wrong when meta
+            # characters are mixed with quoted meta in the same pattern like:
+            # < foo*"py*" >
+            paths = []
+            
+        if not paths:
+            return [wtree]
+        return [['', path, ''] for path in paths]
+        
+    def _remove_quotes(self, wtree):
+        """See [2.6.7 Quote Removal]."""
+        
+        def unquote(wtree):
+            unquoted = []
+            for part in wtree[1:-1]:
+                if isinstance(part, list):
+                    part = unquote(part)
+                unquoted.append(part)
+            return ''.join(unquoted)
+            
+        return ['', unquote(wtree), '']
+        
+    def subshell(self, script=None, ast=None, redirs=None):
+        """Execute the script or AST in a subshell, with inherited redirections
+        if redirs is not None.
+        """
+        if redirs:
+            sub_redirs = redirs
+        else:
+            sub_redirs = redirs.clone()
+        
+        subshell = None    
+        try:
+            subshell = Interpreter(None, self._debugflags, self._env.clone(True),
+                                   sub_redirs, opts=self._options)
+            return subshell.execute_script(script, ast)
+        finally:
+            if not redirs: sub_redirs.close()
+            if subshell: subshell.close()
+        
+    def subshell_output(self, script):
+        """Execute the script in a subshell and return the captured output."""        
+        # Create temporary file to capture subshell output
+        tmpfd, tmppath = tempfile.mkstemp()
+        try:
+            tmpfile = os.fdopen(tmpfd, 'wb')
+            stdout = FileWrapper('w', tmpfile)
+            
+            redirs = Redirections(self._redirs.stdin().dup(),
+                                  stdout,
+                                  self._redirs.stderr().dup())            
+            try:
+                status = self.subshell(script=script, redirs=redirs)
+            finally:
+                redirs.close()
+                redirs = None
+            
+            # Extract subshell standard output
+            tmpfile = open(tmppath, 'rb')
+            try:
+                output = tmpfile.read()
+                return status, output.rstrip('\n')
+            finally:
+                tmpfile.close()
+        finally:
+            os.remove(tmppath)
+
+    def _asynclist(self, cmd):
+        args = (self._env.get_variables(), cmd)
+        arg = encodeargs(args)
+        assert len(args) < 30*1024
+        cmd = ['pysh.bat', '--ast', '-c', arg]
+        p = subprocess.Popen(cmd, cwd=self._env['PWD'])
+        self._children[p.pid] = p
+        self._env['!'] = p.pid
+        return 0
+
+    def wait(self, pids=None):
+        if not pids:
+            pids = self._children.keys()
+
+        status = 127
+        for pid in pids:
+            if pid not in self._children:
+                continue
+            p = self._children.pop(pid)
+            status = p.wait()
+
+        return status
+
diff --git a/lib/pysh/lsprof.py b/lib/pysh/lsprof.py
new file mode 100644
index 000000000..b1831c22a
--- /dev/null
+++ b/lib/pysh/lsprof.py
@@ -0,0 +1,116 @@
+#! /usr/bin/env python
+
+import sys
+from _lsprof import Profiler, profiler_entry
+
+__all__ = ['profile', 'Stats']
+
+def profile(f, *args, **kwds):
+    """XXX docstring"""
+    p = Profiler()
+    p.enable(subcalls=True, builtins=True)
+    try:
+        f(*args, **kwds)
+    finally:
+        p.disable()
+    return Stats(p.getstats())
+
+
+class Stats(object):
+    """XXX docstring"""
+
+    def __init__(self, data):
+        self.data = data
+
+    def sort(self, crit="inlinetime"):
+        """XXX docstring"""
+        if crit not in profiler_entry.__dict__:
+            raise ValueError("Can't sort by %s" % crit)
+        self.data.sort(lambda b, a: cmp(getattr(a, crit),
+                                        getattr(b, crit)))
+        for e in self.data:
+            if e.calls:
+                e.calls.sort(lambda b, a: cmp(getattr(a, crit),
+                                              getattr(b, crit)))
+
+    def pprint(self, top=None, file=None, limit=None, climit=None):
+        """XXX docstring"""
+        if file is None:
+            file = sys.stdout
+        d = self.data
+        if top is not None:
+            d = d[:top]
+        cols = "% 12s %12s %11.4f %11.4f   %s\n"
+        hcols = "% 12s %12s %12s %12s %s\n"
+        cols2 = "+%12s %12s %11.4f %11.4f +  %s\n"
+        file.write(hcols % ("CallCount", "Recursive", "Total(ms)",
+                            "Inline(ms)", "module:lineno(function)"))
+        count = 0
+        for e in d:
+            file.write(cols % (e.callcount, e.reccallcount, e.totaltime,
+                               e.inlinetime, label(e.code)))
+            count += 1
+            if limit is not None and count == limit:
+                return
+            ccount = 0
+            if e.calls:
+                for se in e.calls:
+                    file.write(cols % ("+%s" % se.callcount, se.reccallcount,
+                                       se.totaltime, se.inlinetime,
+                                       "+%s" % label(se.code)))
+                    count += 1
+                    ccount += 1
+                    if limit is not None and count == limit:
+                        return
+                    if climit is not None and ccount == climit:
+                        break
+
+    def freeze(self):
+        """Replace all references to code objects with string
+        descriptions; this makes it possible to pickle the instance."""
+
+        # this code is probably rather ickier than it needs to be!
+        for i in range(len(self.data)):
+            e = self.data[i]
+            if not isinstance(e.code, str):
+                self.data[i] = type(e)((label(e.code),) + e[1:])
+            if e.calls:
+                for j in range(len(e.calls)):
+                    se = e.calls[j]
+                    if not isinstance(se.code, str):
+                        e.calls[j] = type(se)((label(se.code),) + se[1:])
+
+_fn2mod = {}
+
+def label(code):
+    if isinstance(code, str):
+        return code
+    try:
+        mname = _fn2mod[code.co_filename]
+    except KeyError:
+        for k, v in sys.modules.items():
+            if v is None:
+                continue
+            if not hasattr(v, '__file__'):
+                continue
+            if not isinstance(v.__file__, str):
+                continue
+            if v.__file__.startswith(code.co_filename):
+                mname = _fn2mod[code.co_filename] = k
+                break
+        else:
+            mname = _fn2mod[code.co_filename] = '<%s>'%code.co_filename
+
+    return '%s:%d(%s)' % (mname, code.co_firstlineno, code.co_name)
+
+
+if __name__ == '__main__':
+    import os
+    sys.argv = sys.argv[1:]
+    if not sys.argv:
+        print >> sys.stderr, "usage: lsprof.py <script> <arguments...>"
+        sys.exit(2)
+    sys.path.insert(0, os.path.abspath(os.path.dirname(sys.argv[0])))
+    stats = profile(execfile, sys.argv[0], globals(), locals())
+    stats.sort()
+    stats.pprint()
diff --git a/lib/pysh/pysh.py b/lib/pysh/pysh.py
new file mode 100644
index 000000000..b4e6145b5
--- /dev/null
+++ b/lib/pysh/pysh.py
@@ -0,0 +1,167 @@
+# pysh.py - command processing for pysh.
+#
+# Copyright 2007 Patrick Mezard
+#
+# This software may be used and distributed according to the terms
+# of the GNU General Public License, incorporated herein by reference.
+
+import optparse
+import os
+import sys
+
+import interp
+
+SH_OPT = optparse.OptionParser(prog='pysh', usage="%prog [OPTIONS]", version='0.1')
+SH_OPT.add_option('-c', action='store_true', dest='command_string', default=None, 
+    help='A string that shall be interpreted by the shell as one or more commands')
+SH_OPT.add_option('--redirect-to', dest='redirect_to', default=None, 
+    help='Redirect script commands stdout and stderr to the specified file')
+# See utility_command in builtin.py about the reason for this flag.
+SH_OPT.add_option('--redirected', dest='redirected', action='store_true', default=False, 
+    help='Tell the interpreter that stdout and stderr are actually the same objects, which is really stdout')
+SH_OPT.add_option('--debug-parsing', action='store_true', dest='debug_parsing', default=False, 
+    help='Trace PLY execution')
+SH_OPT.add_option('--debug-tree', action='store_true', dest='debug_tree', default=False, 
+    help='Display the generated syntax tree.')
+SH_OPT.add_option('--debug-cmd', action='store_true', dest='debug_cmd', default=False, 
+    help='Trace command execution before parameters expansion and exit status.')
+SH_OPT.add_option('--debug-utility', action='store_true', dest='debug_utility', default=False, 
+    help='Trace utility calls, after parameters expansions')
+SH_OPT.add_option('--ast', action='store_true', dest='ast', default=False,
+    help='Encoded commands to execute in a subprocess')
+SH_OPT.add_option('--profile', action='store_true', default=False,
+    help='Profile pysh run')
+    
+    
+def split_args(args):
+    # Separate shell arguments from command ones
+    # Just stop at the first argument not starting with a dash. I know, this is completely broken,
+    # it ignores files starting with a dash or may take option values for command file. This is not
+    # supposed to happen for now
+    command_index = len(args)
+    for i,arg in enumerate(args):
+        if not arg.startswith('-'):
+            command_index = i
+            break
+            
+    return args[:command_index], args[command_index:]
+
+
+def fixenv(env):
+    path = env.get('PATH')
+    if path is not None:
+        parts = path.split(os.pathsep)
+        # Remove Windows utilities from PATH, they are useless at best and
+        # some of them (find) may be confused with other utilities.
+        parts = [p for p in parts if 'system32' not in p.lower()]
+        env['PATH'] = os.pathsep.join(parts)
+    if env.get('HOME') is None:
+        # Several utilities, including cvsps, cannot work without
+        # a defined HOME directory.
+        env['HOME'] = os.path.expanduser('~')
+    return env
+
+def _sh(cwd, shargs, cmdargs, options, debugflags=None, env=None):
+    if os.environ.get('PYSH_TEXT') != '1':
+        import msvcrt
+        for fp in (sys.stdin, sys.stdout, sys.stderr):
+            msvcrt.setmode(fp.fileno(), os.O_BINARY)
+
+    hgbin = os.environ.get('PYSH_HGTEXT') != '1'
+    
+    if debugflags is None:
+        debugflags = []
+        if options.debug_parsing:    debugflags.append('debug-parsing')
+        if options.debug_utility:    debugflags.append('debug-utility')
+        if options.debug_cmd:        debugflags.append('debug-cmd')
+        if options.debug_tree:       debugflags.append('debug-tree')
+    
+    if env is None:
+        env = fixenv(dict(os.environ))
+    if cwd is None:
+        cwd = os.getcwd()
+
+    if not cmdargs:
+        # Nothing to do
+        return 0
+
+    ast = None
+    command_file = None
+    if options.command_string:
+        input = cmdargs[0]
+        if not options.ast:
+            input += '\n'
+        else:
+            args, input = interp.decodeargs(input), None
+            env, ast = args
+            cwd = env.get('PWD', cwd)
+    else:
+        command_file = cmdargs[0]
+        arguments = cmdargs[1:]
+
+        prefix = interp.resolve_shebang(command_file, ignoreshell=True)
+        if prefix:
+            input = ' '.join(prefix + [command_file] + arguments)
+        else:
+            # Read commands from file
+            f = file(command_file)
+            try:
+                # Trailing newline to help the parser
+                input = f.read() + '\n'
+            finally:
+                f.close()
+    
+    redirect = None
+    try:
+        if options.redirected:
+            stdout = sys.stdout
+            stderr = stdout
+        elif options.redirect_to:
+            redirect = open(options.redirect_to, 'wb')
+            stdout = redirect
+            stderr = redirect
+        else:
+            stdout = sys.stdout
+            stderr = sys.stderr
+            
+        # TODO: set arguments to environment variables
+        opts = interp.Options()
+        opts.hgbinary = hgbin
+        ip = interp.Interpreter(cwd, debugflags, stdout=stdout, stderr=stderr,
+                                opts=opts)
+        try:
+            # Export given environment in shell object
+            for k,v in env.iteritems():
+                ip.get_env().export(k,v)
+            return ip.execute_script(input, ast, scriptpath=command_file)
+        finally:
+            ip.close()
+    finally:
+        if redirect is not None:
+            redirect.close()
+
+def sh(cwd=None, args=None, debugflags=None, env=None):
+    if args is None:
+        args = sys.argv[1:]
+    shargs, cmdargs = split_args(args)
+    options, shargs = SH_OPT.parse_args(shargs)
+
+    if options.profile:
+        import lsprof
+        p = lsprof.Profiler()
+        p.enable(subcalls=True)
+        try:
+            return _sh(cwd, shargs, cmdargs, options, debugflags, env)
+        finally:
+            p.disable()
+            stats = lsprof.Stats(p.getstats())
+            stats.sort()
+            stats.pprint(top=10, file=sys.stderr, climit=5)
+    else:
+        return _sh(cwd, shargs, cmdargs, options, debugflags, env)
+            
+def main():
+    sys.exit(sh())
+
+if __name__=='__main__':
+    main()
diff --git a/lib/pysh/pyshlex.py b/lib/pysh/pyshlex.py
new file mode 100644
index 000000000..b977b5e86
--- /dev/null
+++ b/lib/pysh/pyshlex.py
@@ -0,0 +1,888 @@
+# pyshlex.py - PLY compatible lexer for pysh.
+#
+# Copyright 2007 Patrick Mezard
+#
+# This software may be used and distributed according to the terms
+# of the GNU General Public License, incorporated herein by reference.
+
+# TODO:
+# - review all "char in 'abc'" snippets: the empty string can be matched
+# - test line continuations within quoted/expansion strings
+# - eof is buggy wrt sublexers
+# - the lexer cannot really work in pull mode as it would be required to run
+# PLY in pull mode. It was designed to work incrementally and it would not be
+# that hard to enable pull mode.
+import re
+try:
+    s = set()
+    del s
+except NameError:
+    from Set import Set as set
+
+from ply import lex
+from sherrors import *
+
+class NeedMore(Exception):
+    pass
+
+def is_blank(c):
+    return c in (' ', '\t')
+    
+_RE_DIGITS = re.compile(r'^\d+$')
+
+def are_digits(s):
+    return _RE_DIGITS.search(s) is not None
+
+_OPERATORS = dict([
+    ('&&', 'AND_IF'),
+    ('||', 'OR_IF'),
+    (';;', 'DSEMI'),
+    ('<<', 'DLESS'),
+    ('>>', 'DGREAT'),
+    ('<&', 'LESSAND'),
+    ('>&', 'GREATAND'),
+    ('<>', 'LESSGREAT'),
+    ('<<-', 'DLESSDASH'),
+    ('>|', 'CLOBBER'),
+    ('&', 'AMP'),
+    (';', 'COMMA'),
+    ('<', 'LESS'),
+    ('>', 'GREATER'),
+    ('(', 'LPARENS'),
+    (')', 'RPARENS'),
+])
+
+#Make a function to silence pychecker "Local variable shadows global"
+def make_partial_ops():
+    partials = {}
+    for k in _OPERATORS:
+        for i in range(1, len(k)+1):
+            partials[k[:i]] = None
+    return partials  
+
+_PARTIAL_OPERATORS = make_partial_ops()    
+        
+def is_partial_op(s):
+    """Return True if s matches a non-empty subpart of an operator starting
+    at its first character.
+    """
+    return s in _PARTIAL_OPERATORS
+    
+def is_op(s):
+    """If s matches an operator, returns the operator identifier. Return None
+    otherwise.
+    """
+    return _OPERATORS.get(s)
+
+_RESERVEDS = dict([
+    ('if', 'If'),
+    ('then', 'Then'),
+    ('else', 'Else'),
+    ('elif', 'Elif'),
+    ('fi', 'Fi'),
+    ('do', 'Do'),
+    ('done', 'Done'),
+    ('case', 'Case'),
+    ('esac', 'Esac'),
+    ('while', 'While'),
+    ('until', 'Until'),
+    ('for', 'For'),
+    ('{', 'Lbrace'),
+    ('}', 'Rbrace'),
+    ('!', 'Bang'),
+    ('in', 'In'),
+    ('|', 'PIPE'),
+])
+    
+def get_reserved(s):
+    return _RESERVEDS.get(s)
+    
+_RE_NAME = re.compile(r'^[0-9a-zA-Z_]+$')
+
+def is_name(s):
+    return _RE_NAME.search(s) is not None
+
+def find_chars(seq, chars):
+    for i,v in enumerate(seq):
+        if v in chars:
+            return i,v
+    return -1, None
+
+class WordLexer:
+    """WordLexer parse quoted or expansion expressions and return an expression
+    tree. The input string can be any well formed sequence beginning with quoting
+    or expansion character. Embedded expressions are handled recursively. The
+    resulting tree is made of lists and strings. Lists represent quoted or
+    expansion expressions. Each list first element is the opening separator,
+    the last one the closing separator. In-between can be any number of strings
+    or lists for sub-expressions. Non quoted/expansion expression can written as
+    strings or as lists with empty strings as starting and ending delimiters.
+    """
+
+    NAME_CHARSET = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_'
+    NAME_CHARSET = dict(zip(NAME_CHARSET, NAME_CHARSET))
+    
+    SPECIAL_CHARSET = '@*#?-$!0'
+    
+    #Characters which can be escaped depends on the current delimiters
+    ESCAPABLE = {
+        '`': set(['$', '\\', '`']),
+        '"': set(['$', '\\', '`', '"']),
+        "'": set(),
+    }
+        
+    def __init__(self, heredoc = False):
+        # _buffer is the unprocessed input characters buffer
+        self._buffer = []
+        # _stack is empty or contains a quoted list being processed
+        # (this is the DFS path to the quoted expression being evaluated).
+        self._stack = []
+        self._escapable = None
+        # True when parsing unquoted here documents
+        self._heredoc = heredoc
+        
+    def add(self, data, eof=False):
+        """Feed the lexer with more data. If the quoted expression can be
+        delimited, return a tuple (expr, remaining) containing the expression
+        tree and the unconsumed data.
+        Otherwise, raise NeedMore.
+        """
+        self._buffer += list(data)
+        self._parse(eof)
+        
+        result = self._stack[0]
+        remaining = ''.join(self._buffer)
+        self._stack = []
+        self._buffer = []
+        return result, remaining
+        
+    def _is_escapable(self, c, delim=None):
+        if delim is None:
+            if self._heredoc:
+                # Backslashes works as if they were double quoted in unquoted
+                # here-documents
+                delim = '"'
+            else:
+                if len(self._stack)<=1:
+                    return True
+                delim = self._stack[-2][0]
+            
+        escapables = self.ESCAPABLE.get(delim, None)
+        return escapables is None or c in escapables
+        
+    def _parse_squote(self, buf, result, eof):
+        if not buf:
+            raise NeedMore()
+        try:
+            pos = buf.index("'")
+        except ValueError:
+            raise NeedMore()
+        result[-1] += ''.join(buf[:pos])
+        result += ["'"]
+        return pos+1, True
+        
+    def _parse_bquote(self, buf, result, eof):
+        if not buf:
+            raise NeedMore()
+            
+        if buf[0]=='\n':
+            #Remove line continuations
+            result[:] = ['', '', '']
+        elif self._is_escapable(buf[0]):
+            result[-1] += buf[0]
+            result += ['']
+        else:
+            #Keep as such
+            result[:] = ['', '\\'+buf[0], '']
+        
+        return 1, True
+        
+    def _parse_dquote(self, buf, result, eof):
+        if not buf:
+            raise NeedMore()
+        pos, sep = find_chars(buf, '$\\`"')
+        if pos==-1:
+            raise NeedMore()
+            
+        result[-1] += ''.join(buf[:pos])
+        if sep=='"':
+            result += ['"']
+            return pos+1, True
+        else:
+            #Keep everything until the separator and defer processing
+            return pos, False
+            
+    def _parse_command(self, buf, result, eof):
+        if not buf:
+            raise NeedMore()
+
+        chars = '$\\`"\''
+        if result[0] == '$(':
+            chars += ')'
+        pos, sep = find_chars(buf, chars)
+        if pos == -1:
+            raise NeedMore()
+            
+        result[-1] += ''.join(buf[:pos])
+        if (result[0]=='$(' and sep==')') or (result[0]=='`' and sep=='`'):
+            result += [sep]
+            return pos+1, True
+        else:
+            return pos, False
+            
+    def _parse_parameter(self, buf, result, eof):
+        if not buf:
+            raise NeedMore()
+            
+        pos, sep = find_chars(buf, '$\\`"\'}')
+        if pos==-1:
+            raise NeedMore()
+            
+        result[-1] += ''.join(buf[:pos])
+        if sep=='}':
+            result += [sep]
+            return pos+1, True
+        else:
+            return pos, False
+            
+    def _parse_dollar(self, buf, result, eof):
+        sep = result[0]
+        if sep=='$':            
+            if not buf:
+                #TODO: handle empty $
+                raise NeedMore()
+            if buf[0]=='(':
+                if len(buf)==1:
+                    raise NeedMore()
+                    
+                if buf[1]=='(':
+                    result[0] = '$(('
+                    buf[:2] = []
+                else:
+                    result[0] = '$('
+                    buf[:1] = []
+                
+            elif buf[0]=='{':
+                result[0] = '${'
+                buf[:1] = []
+            else:
+                if buf[0] in self.SPECIAL_CHARSET:
+                    result[-1] = buf[0]
+                    read = 1
+                else:
+                    for read,c in enumerate(buf):
+                        if c not in self.NAME_CHARSET:
+                            break
+                    else:
+                        if not eof:
+                            raise NeedMore()
+                        read += 1
+                        
+                    result[-1] += ''.join(buf[0:read])
+                    
+                if not result[-1]:
+                    result[:] = ['', result[0], '']
+                else:
+                    result += [''] 
+                return read,True
+        
+        sep = result[0]    
+        if sep=='$(':
+            parsefunc = self._parse_command
+        elif sep=='${':
+            parsefunc = self._parse_parameter
+        else:
+            raise NotImplementedError()
+            
+        pos, closed = parsefunc(buf, result, eof)
+        return pos, closed
+
+    def _parse(self, eof):
+        buf = self._buffer
+        stack = self._stack
+        recurse = False
+    
+        while 1:
+            if not stack or recurse:
+                if not buf:
+                    raise NeedMore()
+                if buf[0] not in ('"\\`$\''):
+                    raise ShellSyntaxError('Invalid quoted string sequence')
+                stack.append([buf[0], ''])
+                buf[:1] = []
+                recurse = False
+                
+            result = stack[-1]
+            if result[0]=="'":
+                parsefunc = self._parse_squote
+            elif result[0]=='\\':
+                parsefunc = self._parse_bquote
+            elif result[0]=='"':
+                parsefunc = self._parse_dquote
+            elif result[0]=='`':
+                parsefunc = self._parse_command
+            elif result[0][0]=='$':
+                parsefunc = self._parse_dollar
+            else:
+                raise NotImplementedError()
+                
+            read, closed = parsefunc(buf, result, eof)
+                
+            buf[:read] = []
+            if closed:
+                if len(stack)>1:
+                    #Merge in parent expression
+                    parsed = stack.pop()
+                    stack[-1] += [parsed]
+                    stack[-1] += ['']
+                else:
+                    break
+            else:
+                recurse = True
+
+def normalize_wordtree(wtree):
+    """Fold back every literal sequence (delimited with empty strings) into
+    parent sequence.
+    """
+    def normalize(wtree):
+        result = []
+        for part in wtree[1:-1]:
+            if isinstance(part, list):
+                part = normalize(part)
+                if part[0]=='':
+                    #Move the part content back at current level
+                    result += part[1:-1]
+                    continue
+            elif not part:
+                #Remove empty strings
+                continue
+            result.append(part)
+        if not result:
+            result = ['']    
+        return [wtree[0]] + result + [wtree[-1]]
+                
+    return normalize(wtree)
+    
+                
+def make_wordtree(token, here_document=False):
+    """Parse a delimited token and return a tree similar to the ones returned by
+    WordLexer. token may contain any combinations of expansion/quoted fields and
+    non-ones.
+    """    
+    tree = ['']
+    remaining = token
+    delimiters = '\\$`'
+    if not here_document:
+        delimiters += '\'"'
+    
+    while 1:
+        pos, sep = find_chars(remaining, delimiters)
+        if pos==-1:
+            tree += [remaining, '']
+            return normalize_wordtree(tree)
+        tree.append(remaining[:pos])
+        remaining = remaining[pos:]
+        
+        try:
+            result, remaining = WordLexer(heredoc = here_document).add(remaining, True)
+        except NeedMore:
+            raise ShellSyntaxError('Invalid token "%s"')
+        tree.append(result)
+        
+                
+def wordtree_as_string(wtree):
+    """Rewrite an expression tree generated by make_wordtree as string."""
+    def visit(node, output):
+        for child in node:
+            if isinstance(child, list):
+                visit(child, output)
+            else:
+                output.append(child)
+    
+    output = []
+    visit(wtree, output)
+    return ''.join(output)
+    
+    
+def unquote_wordtree(wtree):
+    """Fold the word tree while removing quotes everywhere. Other expansion
+    sequences are joined as such.
+    """
+    def unquote(wtree):
+        unquoted = []
+        if wtree[0] in ('', "'", '"', '\\'):
+            wtree = wtree[1:-1]
+            
+        for part in wtree:
+            if isinstance(part, list):
+                part = unquote(part)
+            unquoted.append(part)
+        return ''.join(unquoted)
+            
+    return unquote(wtree)
+    
+    
+class HereDocLexer:
+    """HereDocLexer delimits whatever comes from the here-document starting newline
+    not included to the closing delimiter line included.
+    """
+    def __init__(self, op, delim):
+        assert op in ('<<', '<<-')
+        if not delim:
+            raise ShellSyntaxError('invalid here document delimiter %s' % str(delim))
+            
+        self._op = op
+        self._delim = delim
+        self._buffer = []
+        self._token = []
+        
+    def add(self, data, eof):
+        """If the here-document was delimited, return a tuple (content, remaining).
+        Raise NeedMore() otherwise.
+        """
+        self._buffer += list(data)
+        self._parse(eof)
+        token = ''.join(self._token)
+        remaining = ''.join(self._buffer)
+        self._token, self._remaining = [], []
+        return token, remaining
+    
+    def _parse(self, eof):
+        while 1:
+            #Look for first unescaped newline. Quotes may be ignored
+            escaped = False
+            for i,c in enumerate(self._buffer):
+                if escaped:
+                    escaped = False
+                elif c=='\\':
+                    escaped = True
+                elif c=='\n':
+                    break
+            else:
+                i = -1
+                    
+            if i==-1 or self._buffer[i]!='\n':
+                if not eof:
+                    raise NeedMore()
+                #No more data, maybe the last line is closing delimiter
+                line = ''.join(self._buffer)
+                eol = ''
+                self._buffer[:] = []
+            else:
+                line = ''.join(self._buffer[:i])
+                eol = self._buffer[i]
+                self._buffer[:i+1] = []
+            
+            if self._op=='<<-':
+                line = line.lstrip('\t')
+                
+            if line==self._delim:
+                break
+                
+            self._token += [line, eol]
+            if i==-1:
+                break
+    
+class Token:
+    #TODO: check this is still in use
+    OPERATOR = 'OPERATOR'
+    WORD = 'WORD'
+    
+    def __init__(self):
+        self.value = ''
+        self.type = None
+        
+    def __getitem__(self, key):
+        #Behave like a two elements tuple
+        if key==0:
+            return self.type
+        if key==1:
+            return self.value
+        raise IndexError(key)
+               
+               
+class HereDoc:
+    def __init__(self, op, name=None):
+        self.op = op
+        self.name = name
+        self.pendings = []
+               
+TK_COMMA        = 'COMMA'
+TK_AMPERSAND    = 'AMP'
+TK_OP           = 'OP'
+TK_TOKEN        = 'TOKEN'
+TK_COMMENT      = 'COMMENT'
+TK_NEWLINE      = 'NEWLINE' 
+TK_IONUMBER     = 'IO_NUMBER'
+TK_ASSIGNMENT   = 'ASSIGNMENT_WORD'
+TK_HERENAME     = 'HERENAME'
+
+class Lexer:
+    """Main lexer.
+    
+    Call add() until the script AST is returned.
+    """
+    # Here-document handling makes the whole thing more complex because they basically
+    # force tokens to be reordered: here-content must come right after the operator
+    # and the here-document name, while some other tokens might be following the
+    # here-document expression on the same line.
+    #
+    # So, here-doc states are basically:
+    #   *self._state==ST_NORMAL
+    #       - self._heredoc.op is None: no here-document
+    #       - self._heredoc.op is not None but name is: here-document operator matched,
+    #           waiting for the document name/delimiter
+    #       - self._heredoc.op and name are not None: here-document is ready, following
+    #           tokens are being stored and will be pushed again when the document is
+    #           completely parsed.
+    #   *self._state==ST_HEREDOC
+    #       - The here-document is being delimited by self._herelexer. Once it is done
+    #           the content is pushed in front of the pending token list then all these
+    #           tokens are pushed once again.
+    ST_NORMAL       = 'ST_NORMAL'
+    ST_OP           = 'ST_OP'
+    ST_BACKSLASH    = 'ST_BACKSLASH'
+    ST_QUOTED       = 'ST_QUOTED'
+    ST_COMMENT      = 'ST_COMMENT'
+    ST_HEREDOC      = 'ST_HEREDOC'
+    
+    #Match end of backquote strings
+    RE_BACKQUOTE_END = re.compile(r'(?<!\\)(`)')
+
+    def __init__(self, parent_state = None):
+        self._input = []
+        self._pos = 0
+        
+        self._token = ''
+        self._type = TK_TOKEN
+        
+        self._state = self.ST_NORMAL
+        self._parent_state = parent_state
+        self._wordlexer = None
+        
+        self._heredoc = HereDoc(None)
+        self._herelexer = None
+        
+        ### Following attributes are not used for delimiting token and can safely
+        ### be changed after here-document detection (see _push_toke)
+        
+        # Count the number of tokens following a 'For' reserved word. Needed to
+        # return an 'In' reserved word if it comes in third place.
+        self._for_count = None
+        
+    def add(self, data, eof=False):
+        """Feed the lexer with data.
+        
+        When eof is set to True, returns unconsumed data or raise if the lexer
+        is in the middle of a delimiting operation.
+        Raise NeedMore otherwise.
+        """
+        self._input += list(data)
+        self._parse(eof)
+        self._input[:self._pos] = []
+        return ''.join(self._input)
+        
+    def _parse(self, eof):            
+        while self._state:
+            if self._pos>=len(self._input):
+                if not eof:
+                    raise NeedMore()
+                elif self._state not in (self.ST_OP, self.ST_QUOTED, self.ST_HEREDOC):
+                    #Delimit the current token and leave cleanly
+                    self._push_token('')
+                    break
+                else:
+                    #Let the sublexer handle the eof themselves
+                    pass
+                
+            if self._state==self.ST_NORMAL:
+                self._parse_normal()
+            elif self._state==self.ST_COMMENT:
+                self._parse_comment()
+            elif self._state==self.ST_OP:
+                self._parse_op(eof)
+            elif self._state==self.ST_QUOTED:
+                self._parse_quoted(eof)
+            elif self._state==self.ST_HEREDOC:
+                self._parse_heredoc(eof)
+            else:
+                assert False, "Unknown state " + str(self._state)
+                
+        if self._heredoc.op is not None:
+            raise ShellSyntaxError('missing here-document delimiter')
+                
+    def _parse_normal(self):
+        c = self._input[self._pos]
+        if c=='\n':
+            self._push_token(c)
+            self._token = c
+            self._type = TK_NEWLINE
+            self._push_token('')
+            self._pos += 1
+        elif c in ('\\', '\'', '"', '`', '$'):
+            self._state = self.ST_QUOTED
+        elif is_partial_op(c):
+            self._push_token(c)
+            
+            self._type = TK_OP
+            self._token += c
+            self._pos += 1
+            self._state = self.ST_OP
+        elif is_blank(c):
+            self._push_token(c)
+            
+            #Discard blanks
+            self._pos += 1
+        elif self._token:
+            self._token += c
+            self._pos += 1
+        elif c=='#':
+            self._state = self.ST_COMMENT
+            self._type = TK_COMMENT
+            self._pos += 1
+        else:
+            self._pos += 1
+            self._token += c          
+                
+    def _parse_op(self, eof):
+        assert self._token
+        
+        while 1:
+            if self._pos>=len(self._input):
+                if not eof:
+                    raise NeedMore()
+                c = ''
+            else:                
+                c = self._input[self._pos]
+                
+            op = self._token + c
+            if c and is_partial_op(op):
+                #Still parsing an operator
+                self._token = op
+                self._pos += 1
+            else:            
+                #End of operator
+                self._push_token(c)                    
+                self._state = self.ST_NORMAL
+                break
+                
+    def _parse_comment(self):
+        while 1:
+            if self._pos>=len(self._input):
+                raise NeedMore()
+                
+            c = self._input[self._pos]
+            if c=='\n':
+                #End of comment, do not consume the end of line
+                self._state = self.ST_NORMAL
+                break
+            else:
+                self._token += c
+                self._pos += 1
+                
+    def _parse_quoted(self, eof):
+        """Precondition: the starting backquote/dollar is still in the input queue."""
+        if not self._wordlexer:
+            self._wordlexer = WordLexer()
+        
+        if self._pos<len(self._input):
+             #Transfer input queue character into the subparser
+            input = self._input[self._pos:]
+            self._pos += len(input)
+            
+        wtree, remaining = self._wordlexer.add(input, eof)
+        self._wordlexer = None
+        self._token += wordtree_as_string(wtree)
+        
+        #Put unparsed character back in the input queue
+        if remaining:
+            self._input[self._pos:self._pos] = list(remaining)          
+        self._state = self.ST_NORMAL
+        
+    def _parse_heredoc(self, eof):
+        assert not self._token
+        
+        if self._herelexer is None:
+            self._herelexer = HereDocLexer(self._heredoc.op, self._heredoc.name)
+        
+        if self._pos<len(self._input):
+             #Transfer input queue character into the subparser
+            input = self._input[self._pos:]
+            self._pos += len(input)
+        
+        self._token, remaining = self._herelexer.add(input, eof)
+        
+        #Reset here-document state
+        self._herelexer = None
+        heredoc, self._heredoc = self._heredoc, HereDoc(None)
+        if remaining:
+            self._input[self._pos:self._pos] = list(remaining)
+        self._state = self.ST_NORMAL
+        
+        #Push pending tokens
+        heredoc.pendings[:0] = [(self._token, self._type, heredoc.name)]
+        for token, type, delim in heredoc.pendings:
+            self._token = token
+            self._type = type
+            self._push_token(delim)
+                     
+    def _push_token(self, delim):
+        if not self._token:
+            return 0
+            
+        if self._heredoc.op is not None:
+            if self._heredoc.name is None:
+                #Here-document name
+                if self._type!=TK_TOKEN:
+                    raise ShellSyntaxError("expecting here-document name, got '%s'" % self._token)
+                self._heredoc.name = unquote_wordtree(make_wordtree(self._token))
+                self._type = TK_HERENAME
+            else:
+                #Capture all tokens until the newline starting the here-document
+                if self._type==TK_NEWLINE:
+                    assert self._state==self.ST_NORMAL
+                    self._state = self.ST_HEREDOC    
+                
+                self._heredoc.pendings.append((self._token, self._type, delim))    
+                self._token = ''
+                self._type = TK_TOKEN
+                return 1
+                
+        # BEWARE: do not change parser state from here to the end of the function:
+        # when parsing between an here-document operator to the end of the line
+        # tokens are stored in self._heredoc.pendings. Therefore, they will not
+        # reach the section below.
+                    
+        #Check operators
+        if self._type==TK_OP:
+            #False positive because of partial op matching
+            op = is_op(self._token)
+            if not op:
+                self._type = TK_TOKEN
+            else:
+                #Map to the specific operator
+                self._type = op
+                if self._token in ('<<', '<<-'):
+                    #Done here rather than in _parse_op because there is no need
+                    #to change the parser state since we are still waiting for
+                    #the here-document name
+                    if self._heredoc.op is not None:
+                        raise ShellSyntaxError("syntax error near token '%s'" % self._token)
+                    assert self._heredoc.op is None
+                    self._heredoc.op = self._token
+                
+        if self._type==TK_TOKEN:            
+            if '=' in self._token and not delim:
+                if self._token.startswith('='):
+                    #Token is a WORD... a TOKEN that is.
+                    pass
+                else:
+                    prev = self._token[:self._token.find('=')]
+                    if is_name(prev):
+                        self._type = TK_ASSIGNMENT
+                    else:
+                        #Just a token (unspecified)
+                        pass
+            else:
+                reserved = get_reserved(self._token)
+                if reserved is not None:
+                    if reserved=='In' and self._for_count!=2:
+                        #Sorry, not a reserved word after all
+                        pass
+                    else:
+                        self._type = reserved
+                        if reserved in ('For', 'Case'):
+                            self._for_count = 0                    
+                elif are_digits(self._token) and delim in ('<', '>'):
+                    #Detect IO_NUMBER
+                    self._type = TK_IONUMBER
+                elif self._token==';':
+                    self._type = TK_COMMA
+                elif self._token=='&':
+                    self._type = TK_AMPERSAND
+        elif self._type==TK_COMMENT:
+            #Comments are not part of sh grammar, ignore them
+            self._token = ''
+            self._type = TK_TOKEN
+            return 0
+        
+        if self._for_count is not None:
+            #Track token count in 'For' expression to detect 'In' reserved words.
+            #Can only be in third position, no need to go beyond
+            self._for_count += 1
+            if self._for_count==3:
+                self._for_count = None
+                
+        self.on_token((self._token, self._type))
+        self._token = ''
+        self._type = TK_TOKEN
+        return 1
+                        
+    def on_token(self, token):
+        raise NotImplementedError
+                 
+
+tokens = [
+    TK_TOKEN,
+# To silence yacc unused token warnings
+#    TK_COMMENT,
+    TK_NEWLINE,
+    TK_IONUMBER,
+    TK_ASSIGNMENT,
+    TK_HERENAME,
+]            
+
+#Add specific operators
+tokens += _OPERATORS.values()
+#Add reserved words
+tokens += _RESERVEDS.values()
+            
+class PLYLexer(Lexer):
+    """Bridge Lexer and PLY lexer interface."""
+    def __init__(self):
+        Lexer.__init__(self)
+        self._tokens = []
+        self._current = 0
+        self.lineno = 0
+
+    def on_token(self, token):
+        value, type = token
+
+        self.lineno = 0
+        t = lex.LexToken()
+        t.value = value
+        t.type = type
+        t.lexer = self
+        t.lexpos = 0
+        t.lineno = 0
+        
+        self._tokens.append(t)
+        
+    def is_empty(self):
+        return not bool(self._tokens)
+        
+    #PLY compliant interface
+    def token(self):
+        if self._current>=len(self._tokens):
+            return None
+        t = self._tokens[self._current]
+        self._current += 1
+        return t      
+        
+        
+def get_tokens(s):
+    """Parse the input string and return a tuple (tokens, unprocessed) where
+    tokens is a list of parsed tokens and unprocessed is the part of the input
+    string left untouched by the lexer.
+    """
+    lexer = PLYLexer()
+    untouched = lexer.add(s, True) 
+    tokens = []
+    while 1:
+        token = lexer.token()
+        if token is None:
+            break
+        tokens.append(token)
+        
+    tokens = [(t.value, t.type) for t in tokens]
+    return tokens, untouched        
diff --git a/lib/pysh/pyshyacc.py b/lib/pysh/pyshyacc.py
new file mode 100644
index 000000000..3d9510c0c
--- /dev/null
+++ b/lib/pysh/pyshyacc.py
@@ -0,0 +1,772 @@
+# pyshyacc.py - PLY grammar definition for pysh
+#
+# Copyright 2007 Patrick Mezard
+#
+# This software may be used and distributed according to the terms
+# of the GNU General Public License, incorporated herein by reference.
+
+"""PLY grammar file.
+"""
+import sys
+
+import pyshlex
+tokens = pyshlex.tokens
+
+from ply import yacc
+import sherrors
+    
+class IORedirect:
+    def __init__(self, op, filename, io_number=None):
+        self.op = op
+        self.filename = filename
+        self.io_number = io_number
+        
+class HereDocument:
+    def __init__(self, op, name, content, io_number=None):
+        self.op = op
+        self.name = name
+        self.content = content
+        self.io_number = io_number
+
+def make_io_redirect(p):
+    """Make an IORedirect instance from the input 'io_redirect' production."""
+    name, io_number, io_target = p
+    assert name=='io_redirect'
+    
+    if io_target[0]=='io_file':
+        io_type, io_op, io_file = io_target
+        return IORedirect(io_op, io_file, io_number)
+    elif io_target[0]=='io_here':
+        io_type, io_op, io_name, io_content = io_target
+        return HereDocument(io_op, io_name, io_content, io_number)
+    else:
+        assert False, "Invalid IO redirection token %s" % repr(io_type)
+        
+class SimpleCommand:
+    """
+    assigns contains (name, value) pairs.
+    """
+    def __init__(self, words, redirs, assigns):
+        self.words = list(words)
+        self.redirs = list(redirs)
+        self.assigns = list(assigns)
+
+class Pipeline:
+    def __init__(self, commands, reverse_status=False):
+        self.commands = list(commands)
+        assert self.commands    #Grammar forbids this
+        self.reverse_status = reverse_status
+        
+class AndOr:
+    def __init__(self, op, left, right):
+        self.op = str(op)
+        self.left = left
+        self.right = right
+        
+class ForLoop:
+    def __init__(self, name, items, cmds):
+        self.name = str(name)
+        self.items = list(items)
+        self.cmds = list(cmds)
+        
+class WhileLoop:
+    def __init__(self, condition, cmds):
+        self.condition = list(condition)
+        self.cmds = list(cmds)
+        
+class UntilLoop:
+    def __init__(self, condition, cmds):
+        self.condition = list(condition)
+        self.cmds = list(cmds)
+
+class FunDef:
+    def __init__(self, name, body):
+        self.name = str(name)
+        self.body = body
+        
+class BraceGroup:
+    def __init__(self, cmds):
+        self.cmds = list(cmds)
+        
+class IfCond:
+    def __init__(self, cond, if_cmds, else_cmds):
+        self.cond = list(cond)
+        self.if_cmds = if_cmds
+        self.else_cmds = else_cmds
+
+class Case:
+    def __init__(self, name, items):
+        self.name = name
+        self.items = items
+        
+class SubShell:
+    def __init__(self, cmds):
+        self.cmds = cmds
+
+class RedirectList:
+    def __init__(self, cmd, redirs):
+        self.cmd = cmd
+        self.redirs = list(redirs)
+        
+def get_production(productions, ptype):
+    """productions must be a list of production tuples like (name, obj) where
+    name is the production string identifier.
+    Return the first production named 'ptype'. Raise KeyError if None can be
+    found.
+    """
+    for production in productions:
+        if production is not None and production[0]==ptype:
+            return production
+    raise KeyError(ptype)
+    
+#-------------------------------------------------------------------------------
+# PLY grammar definition
+#-------------------------------------------------------------------------------
+
+def p_multiple_commands(p):
+    """multiple_commands : newline_sequence
+                         | complete_command
+                         | multiple_commands complete_command"""
+    if len(p)==2:
+        if p[1] is not None:
+            p[0] = [p[1]]
+        else:
+            p[0] = []
+    else:
+        p[0] = p[1] + [p[2]]
+
+def p_complete_command(p):
+    """complete_command : list separator
+                        | list"""
+    if len(p)==3 and p[2] and p[2][1] == '&':
+        p[0] = ('async', p[1])
+    else:
+        p[0] = p[1]
+                 
+def p_list(p):
+    """list : list separator_op and_or
+            |                   and_or"""
+    if len(p)==2:
+        p[0] = [p[1]]
+    else:
+        #if p[2]!=';':
+        #    raise NotImplementedError('AND-OR list asynchronous execution is not implemented')
+        p[0] = p[1] + [p[3]]
+       
+def p_and_or(p):
+    """and_or : pipeline
+              | and_or AND_IF linebreak pipeline
+              | and_or OR_IF  linebreak pipeline"""
+    if len(p)==2:
+        p[0] = p[1]
+    else:
+        p[0] = ('and_or', AndOr(p[2], p[1], p[4]))
+        
+def p_maybe_bang_word(p):
+    """maybe_bang_word : Bang"""
+    p[0] = ('maybe_bang_word', p[1])
+            
+def p_pipeline(p):
+    """pipeline : pipe_sequence
+                | bang_word pipe_sequence"""
+    if len(p)==3:
+        p[0] = ('pipeline', Pipeline(p[2][1:], True))
+    else:
+        p[0] = ('pipeline', Pipeline(p[1][1:]))
+
+def p_pipe_sequence(p):
+    """pipe_sequence : command
+                     | pipe_sequence PIPE linebreak command"""
+    if len(p)==2:
+        p[0] = ['pipe_sequence', p[1]]
+    else:
+        p[0] = p[1] + [p[4]]
+
+def p_command(p):
+    """command : simple_command
+               | compound_command
+               | compound_command redirect_list
+               | function_definition"""
+        
+    if p[1][0] in ( 'simple_command', 
+                    'for_clause',
+                    'while_clause',
+                    'until_clause',
+                    'case_clause',
+                    'if_clause',
+                    'function_definition',
+                    'subshell',
+                    'brace_group',):
+        if len(p) == 2:
+            p[0] = p[1]
+        else:
+            p[0] = ('redirect_list', RedirectList(p[1], p[2][1:]))
+    else:
+        raise NotImplementedError('%s command is not implemented' % repr(p[1][0]))
+
+def p_compound_command(p):
+    """compound_command : brace_group
+                        | subshell
+                        | for_clause
+                        | case_clause
+                        | if_clause
+                        | while_clause
+                        | until_clause"""
+    p[0] = p[1]
+
+def p_subshell(p):
+    """subshell : LPARENS compound_list RPARENS"""
+    p[0] = ('subshell', SubShell(p[2][1:]))
+
+def p_compound_list(p):
+    """compound_list : term
+                     | newline_list term
+                     |              term separator
+                     | newline_list term separator"""
+    productions = p[1:]           
+    try:
+        sep = get_production(productions, 'separator')
+        if sep[1]!=';':
+            raise NotImplementedError()
+    except KeyError:
+        pass
+    term = get_production(productions, 'term')
+    p[0] = ['compound_list'] + term[1:]
+
+def p_term(p):
+    """term : term separator and_or
+            |                and_or"""
+    if len(p)==2:
+        p[0] = ['term', p[1]]
+    else:
+        if p[2] is not None and p[2][1] == '&':
+            p[0] = ['term', ('async', p[1][1:])] + [p[3]]
+        else:
+            p[0] = p[1] + [p[3]]
+            
+def p_maybe_for_word(p):
+    # Rearrange 'For' priority wrt TOKEN. See p_for_word
+    """maybe_for_word : For"""
+    p[0] = ('maybe_for_word', p[1])
+
+def p_for_clause(p):
+    """for_clause : for_word name linebreak                            do_group
+                  | for_word name linebreak in          sequential_sep do_group
+                  | for_word name linebreak in wordlist sequential_sep do_group"""
+    productions = p[1:]
+    do_group = get_production(productions, 'do_group')
+    try:
+        items = get_production(productions, 'in')[1:]
+    except KeyError:
+        raise NotImplementedError('"in" omission is not implemented')
+        
+    try:
+        items = get_production(productions, 'wordlist')[1:]
+    except KeyError:
+        items = []
+        
+    name = p[2]
+    p[0] = ('for_clause', ForLoop(name, items, do_group[1:]))
+
+def p_name(p):
+    """name : token""" #Was NAME instead of token
+    p[0] = p[1]
+
+def p_in(p):
+    """in : In"""
+    p[0] = ('in', p[1])
+
+def p_wordlist(p):
+    """wordlist : wordlist token
+                |          token"""
+    if len(p)==2:
+        p[0] = ['wordlist', ('TOKEN', p[1])]
+    else:
+        p[0] = p[1] + [('TOKEN', p[2])]
+
+def p_case_clause(p):
+    """case_clause : Case token linebreak in linebreak case_list    Esac
+                   | Case token linebreak in linebreak case_list_ns Esac
+                   | Case token linebreak in linebreak              Esac"""
+    if len(p) < 8:
+        items = []
+    else:
+        items = p[6][1:]
+    name = p[2]
+    p[0] = ('case_clause', Case(name, [c[1] for c in items]))
+       
+def p_case_list_ns(p):
+    """case_list_ns : case_list case_item_ns
+                    |           case_item_ns"""
+    p_case_list(p)
+      
+def p_case_list(p):
+    """case_list : case_list case_item
+                 |           case_item"""
+    if len(p)==2:
+        p[0] = ['case_list', p[1]]
+    else:
+        p[0] = p[1] + [p[2]]
+        
+def p_case_item_ns(p):
+    """case_item_ns :         pattern RPARENS               linebreak
+                    |         pattern RPARENS compound_list linebreak
+                    | LPARENS pattern RPARENS               linebreak
+                    | LPARENS pattern RPARENS compound_list linebreak"""
+    p_case_item(p)
+                 
+def p_case_item(p):
+    """case_item :         pattern RPARENS linebreak     DSEMI linebreak
+                 |         pattern RPARENS compound_list DSEMI linebreak
+                 | LPARENS pattern RPARENS linebreak     DSEMI linebreak
+                 | LPARENS pattern RPARENS compound_list DSEMI linebreak"""
+    if len(p) < 7:
+        name = p[1][1:]
+    else:
+        name = p[2][1:]
+
+    try:
+        cmds = get_production(p[1:], "compound_list")[1:]
+    except KeyError:
+        cmds = []
+
+    p[0] = ('case_item', (name, cmds))
+                 
+def p_pattern(p):
+    """pattern :              token
+               | pattern PIPE token"""
+    if len(p)==2:
+        p[0] = ['pattern', ('TOKEN', p[1])]
+    else:
+        p[0] = p[1] + [('TOKEN', p[2])]
+
+def p_maybe_if_word(p):
+    # Rearrange 'If' priority wrt TOKEN. See p_if_word
+    """maybe_if_word : If"""
+    p[0] = ('maybe_if_word', p[1])
+
+def p_maybe_then_word(p):
+    # Rearrange 'Then' priority wrt TOKEN. See p_then_word
+    """maybe_then_word : Then"""
+    p[0] = ('maybe_then_word', p[1])
+                 
+def p_if_clause(p):
+    """if_clause : if_word compound_list then_word compound_list else_part Fi
+                 | if_word compound_list then_word compound_list           Fi"""
+    else_part = []
+    if len(p)==7:
+        else_part = p[5]
+    p[0] = ('if_clause', IfCond(p[2][1:], p[4][1:], else_part))
+                 
+def p_else_part(p):
+    """else_part : Elif compound_list then_word compound_list else_part
+                 | Elif compound_list then_word compound_list
+                 | Else compound_list"""
+    if len(p)==3:
+        p[0] = p[2][1:]
+    else:
+        else_part = []
+        if len(p)==6:
+            else_part = p[5]
+        p[0] = ('elif', IfCond(p[2][1:], p[4][1:], else_part))
+                 
+def p_while_clause(p):
+    """while_clause : While compound_list do_group"""
+    p[0] = ('while_clause', WhileLoop(p[2][1:], p[3][1:]))
+    
+def p_maybe_until_word(p):
+    # Rearrange 'Until' priority wrt TOKEN. See p_until_word
+    """maybe_until_word : Until"""
+    p[0] = ('maybe_until_word', p[1])
+           
+def p_until_clause(p):
+    """until_clause : until_word compound_list do_group"""
+    p[0] = ('until_clause', UntilLoop(p[2][1:], p[3][1:]))
+                 
+def p_function_definition(p):
+    """function_definition : fname LPARENS RPARENS linebreak function_body"""
+    p[0] = ('function_definition', FunDef(p[1], p[5]))
+                 
+def p_function_body(p):
+    """function_body : compound_command
+                     | compound_command redirect_list"""
+    if len(p)!=2:
+        raise NotImplementedError('functions redirections lists are not implemented')    
+    p[0] = p[1]    
+
+def p_fname(p):
+    """fname : TOKEN""" #Was NAME instead of token
+    p[0] = p[1]
+
+def p_brace_group(p):
+    """brace_group : Lbrace compound_list Rbrace"""
+    p[0] = ('brace_group', BraceGroup(p[2][1:]))
+
+def p_maybe_done_word(p):
+    #See p_assignment_word for details.
+    """maybe_done_word : Done"""
+    p[0] = ('maybe_done_word', p[1])
+
+def p_maybe_do_word(p):
+    """maybe_do_word : Do"""
+    p[0] = ('maybe_do_word', p[1])
+
+def p_do_group(p):
+    """do_group : do_word compound_list done_word"""
+    #Do group contains a list of AndOr
+    p[0] = ['do_group'] + p[2][1:]
+
+def p_simple_command(p):
+    """simple_command : cmd_prefix cmd_word cmd_suffix
+                      | cmd_prefix cmd_word
+                      | cmd_prefix
+                      | cmd_name cmd_suffix
+                      | cmd_name"""
+    words, redirs, assigns = [], [], []
+    for e in p[1:]:
+        name = e[0]
+        if name in ('cmd_prefix', 'cmd_suffix'):
+            for sube in e[1:]:
+                subname = sube[0]
+                if subname=='io_redirect':
+                    redirs.append(make_io_redirect(sube))
+                elif subname=='ASSIGNMENT_WORD':
+                    assigns.append(sube)
+                else:
+                    words.append(sube)
+        elif name in ('cmd_word', 'cmd_name'):
+            words.append(e)
+            
+    cmd = SimpleCommand(words, redirs, assigns)
+    p[0] = ('simple_command', cmd)
+
+def p_cmd_name(p):
+    """cmd_name : TOKEN"""
+    p[0] = ('cmd_name', p[1])
+    
+def p_cmd_word(p):
+    """cmd_word : token"""
+    p[0] = ('cmd_word', p[1])
+
+def p_maybe_assignment_word(p):
+    #See p_assignment_word for details.
+    """maybe_assignment_word : ASSIGNMENT_WORD"""
+    p[0] = ('maybe_assignment_word', p[1])
+    
+def p_cmd_prefix(p):
+    """cmd_prefix :            io_redirect
+                  | cmd_prefix io_redirect
+                  |            assignment_word
+                  | cmd_prefix assignment_word"""
+    try:
+        prefix = get_production(p[1:], 'cmd_prefix')
+    except KeyError:
+        prefix = ['cmd_prefix']
+        
+    try:
+        value = get_production(p[1:], 'assignment_word')[1]
+        value = ('ASSIGNMENT_WORD', value.split('=', 1))
+    except KeyError:        
+        value = get_production(p[1:], 'io_redirect')
+    p[0] = prefix + [value]
+                                  
+def p_cmd_suffix(p):
+    """cmd_suffix   :            io_redirect
+                    | cmd_suffix io_redirect
+                    |            token
+                    | cmd_suffix token
+                    |            maybe_for_word
+                    | cmd_suffix maybe_for_word
+                    |            maybe_done_word
+                    | cmd_suffix maybe_done_word
+                    |            maybe_do_word
+                    | cmd_suffix maybe_do_word
+                    |            maybe_until_word
+                    | cmd_suffix maybe_until_word
+                    |            maybe_assignment_word
+                    | cmd_suffix maybe_assignment_word
+                    |            maybe_if_word
+                    | cmd_suffix maybe_if_word
+                    |            maybe_then_word
+                    | cmd_suffix maybe_then_word
+                    |            maybe_bang_word
+                    | cmd_suffix maybe_bang_word"""
+    try:
+        suffix = get_production(p[1:], 'cmd_suffix')
+        token = p[2]
+    except KeyError:
+        suffix = ['cmd_suffix']
+        token = p[1]
+        
+    if isinstance(token, tuple):
+        if token[0]=='io_redirect':
+            p[0] = suffix + [token]
+        else:
+            #Convert maybe_*  to TOKEN if necessary
+            p[0] = suffix + [('TOKEN', token[1])]
+    else:
+        p[0] = suffix + [('TOKEN', token)]
+                 
+def p_redirect_list(p):
+    """redirect_list : io_redirect
+                     | redirect_list io_redirect"""
+    if len(p) == 2:
+        p[0] = ['redirect_list', make_io_redirect(p[1])]
+    else:
+        p[0] = p[1] + [make_io_redirect(p[2])]
+    
+def p_io_redirect(p):
+    """io_redirect :           io_file
+                   | IO_NUMBER io_file
+                   |           io_here
+                   | IO_NUMBER io_here"""
+    if len(p)==3:
+        p[0] = ('io_redirect', p[1], p[2])
+    else:
+        p[0] = ('io_redirect', None, p[1])
+    
+def p_io_file(p):
+    #Return the tuple (operator, filename)
+    """io_file : LESS      filename
+               | LESSAND   filename
+               | GREATER   filename
+               | GREATAND  filename
+               | DGREAT    filename
+               | LESSGREAT filename
+               | CLOBBER   filename"""
+    #Extract the filename from the file
+    p[0] = ('io_file', p[1], p[2][1])
+
+def p_filename(p):
+    #Return the filename
+    """filename : TOKEN"""
+    p[0] = ('filename', p[1])
+        
+def p_io_here(p):
+    """io_here : DLESS here_end
+               | DLESSDASH here_end"""
+    p[0] = ('io_here', p[1], p[2][1], p[2][2])
+
+def p_here_end(p):
+    """here_end : HERENAME TOKEN"""
+    p[0] = ('here_document', p[1], p[2])
+    
+def p_newline_sequence(p):
+    # Nothing in the grammar can handle leading NEWLINE productions, so add
+    # this one with the lowest possible priority relatively to newline_list.
+    """newline_sequence : newline_list"""
+    p[0] = None
+    
+def p_newline_list(p):
+    """newline_list : NEWLINE
+                    | newline_list NEWLINE"""
+    p[0] = None
+                    
+def p_linebreak(p):
+    """linebreak : newline_list
+                 | empty"""
+    p[0] = None
+
+def p_separator_op(p):                 
+    """separator_op : COMMA
+                    | AMP"""
+    p[0] = p[1]
+
+def p_separator(p):
+    """separator : separator_op linebreak
+                 | newline_list"""
+    if len(p)==2:
+        #Ignore newlines
+        p[0] = None
+    else:
+        #Keep the separator operator
+        p[0] = ('separator', p[1])
+                 
+def p_sequential_sep(p):
+    """sequential_sep : COMMA linebreak
+                      | newline_list"""
+    p[0] = None
+
+# Low priority TOKEN => for_word conversion.
+# Let maybe_for_word be used as a token when necessary in higher priority
+# rules. 
+def p_for_word(p):
+    """for_word : maybe_for_word"""
+    p[0] = p[1]
+
+def p_if_word(p):
+    """if_word : maybe_if_word"""
+    p[0] = p[1]
+
+def p_then_word(p):
+    """then_word : maybe_then_word"""
+    p[0] = p[1]
+
+def p_done_word(p):
+    """done_word : maybe_done_word"""
+    p[0] = p[1]
+
+def p_do_word(p):
+    """do_word : maybe_do_word"""
+    p[0] = p[1]
+    
+def p_until_word(p):
+    """until_word : maybe_until_word"""
+    p[0] = p[1]
+    
+def p_assignment_word(p):
+    """assignment_word : maybe_assignment_word"""
+    p[0] = ('assignment_word', p[1][1])
+    
+def p_bang_word(p):
+    """bang_word : maybe_bang_word"""
+    p[0] = ('bang_word', p[1][1])
+
+def p_token(p):
+    """token : TOKEN
+             | Fi"""
+    p[0] = p[1]
+
+def p_empty(p):
+    'empty :'
+    p[0] = None
+    
+# Error rule for syntax errors
+def p_error(p):
+    msg = []
+    w = msg.append
+    w('%r\n' % p)
+    w('followed by:\n')
+    for i in range(5):
+        n = yacc.token()
+        if not n:
+            break
+        w('  %r\n' % n)
+    raise sherrors.ShellSyntaxError(''.join(msg))
+
+# Build the parser
+try:
+    import pyshtables
+except ImportError:
+    yacc.yacc(tabmodule = 'pyshtables')
+else:
+    yacc.yacc(tabmodule = 'pysh.pyshtables', write_tables = 0, debug = 0)
+
+
+def parse(input, eof=False, debug=False):
+    """Parse a whole script at once and return the generated AST and unconsumed
+    data in a tuple.
+    
+    NOTE: eof is probably meaningless for now, the parser being unable to work
+    in pull mode. It should be set to True.
+    """
+    lexer = pyshlex.PLYLexer()
+    remaining = lexer.add(input, eof)
+    if lexer.is_empty():
+        return [], remaining
+    if debug:
+        debug = 2
+    return yacc.parse(lexer=lexer, debug=debug), remaining
+
+#-------------------------------------------------------------------------------
+# AST rendering helpers
+#-------------------------------------------------------------------------------    
+
+def format_commands(v):
+    """Return a tree made of strings and lists. Make command trees easier to
+    display.
+    """
+    if isinstance(v, list):
+        return [format_commands(c) for c in v]
+    if isinstance(v, tuple):
+        if len(v)==2 and isinstance(v[0], str) and not isinstance(v[1], str):
+            if v[0] == 'async':
+                return ['AsyncList', map(format_commands, v[1])]
+            else:
+                #Avoid decomposing tuples like ('pipeline', Pipeline(...))
+                return format_commands(v[1])
+        return format_commands(list(v))
+    elif isinstance(v, IfCond):
+        name = ['IfCond']
+        name += ['if', map(format_commands, v.cond)]
+        name += ['then', map(format_commands, v.if_cmds)]
+        name += ['else', map(format_commands, v.else_cmds)]
+        return name
+    elif isinstance(v, ForLoop):
+        name = ['ForLoop']
+        name += [repr(v.name)+' in ', map(str, v.items)]
+        name += ['commands', map(format_commands, v.cmds)]
+        return name
+    elif isinstance(v, AndOr):
+        return [v.op, format_commands(v.left), format_commands(v.right)]
+    elif isinstance(v, Pipeline):
+        name = 'Pipeline'
+        if v.reverse_status:
+            name = '!' + name
+        return [name, format_commands(v.commands)]
+    elif isinstance(v, SimpleCommand):
+        name = ['SimpleCommand']
+        if v.words:                
+            name += ['words', map(str, v.words)]
+        if v.assigns:
+            assigns = [tuple(a[1]) for a in v.assigns]
+            name += ['assigns', map(str, assigns)]
+        if v.redirs:
+            name += ['redirs', map(format_commands, v.redirs)]
+        return name
+    elif isinstance(v, RedirectList):
+        name = ['RedirectList']
+        if v.redirs:
+            name += ['redirs', map(format_commands, v.redirs)]
+        name += ['command', format_commands(v.cmd)]
+        return name
+    elif isinstance(v, IORedirect):
+        return ' '.join(map(str, (v.io_number, v.op, v.filename)))
+    elif isinstance(v, HereDocument):
+        return ' '.join(map(str, (v.io_number, v.op, repr(v.name), repr(v.content))))
+    elif isinstance(v, SubShell):
+        return ['SubShell', map(format_commands, v.cmds)]
+    else:
+        return repr(v)
+             
+def print_commands(cmds, output=sys.stdout):
+    """Pretty print a command tree."""
+    def print_tree(cmd, spaces, output):
+        if isinstance(cmd, list):
+            for c in cmd:
+                print_tree(c, spaces + 3, output)              
+        else:
+            print >>output, ' '*spaces + str(cmd)
+    
+    formatted = format_commands(cmds)
+    print_tree(formatted, 0, output)
+    
+    
+def stringify_commands(cmds): 
+    """Serialize a command tree as a string.
+    
+    Returned string is not pretty and is currently used for unit tests only.
+    """   
+    def stringify(value):
+        output = []
+        if isinstance(value, list):
+            formatted = []
+            for v in value:
+                formatted.append(stringify(v))
+            formatted = ' '.join(formatted)
+            output.append(''.join(['<', formatted, '>']))
+        else:
+            output.append(value)
+        return ' '.join(output)
+            
+    return stringify(format_commands(cmds))
+    
+        
+def visit_commands(cmds, callable):
+    """Visit the command tree and execute callable on every Pipeline and 
+    SimpleCommand instances.
+    """
+    if isinstance(cmds, (tuple, list)):
+        map(lambda c: visit_commands(c,callable), cmds)
+    elif isinstance(cmds, (Pipeline, SimpleCommand)):
+        callable(cmds)
diff --git a/lib/pysh/sherrors.py b/lib/pysh/sherrors.py
new file mode 100644
index 000000000..1d5bd53b3
--- /dev/null
+++ b/lib/pysh/sherrors.py
@@ -0,0 +1,41 @@
+# sherrors.py - shell errors and signals
+#
+# Copyright 2007 Patrick Mezard
+#
+# This software may be used and distributed according to the terms
+# of the GNU General Public License, incorporated herein by reference.
+
+"""Define shell exceptions and error codes.
+"""
+
+class ShellError(Exception):
+    pass
+
+class ShellSyntaxError(ShellError):
+    pass
+    
+class UtilityError(ShellError):
+    """Raised upon utility syntax error (option or operand error)."""
+    pass
+   
+class ExpansionError(ShellError):
+    pass
+     
+class CommandNotFound(ShellError):
+    """Specified command was not found."""
+    pass
+    
+class RedirectionError(ShellError):
+    pass
+    
+class VarAssignmentError(ShellError):
+    """Variable assignment error."""
+    pass
+    
+class ExitSignal(ShellError):
+    """Exit signal."""
+    pass
+    
+class ReturnSignal(ShellError):
+    """Exit signal."""
+    pass
\ No newline at end of file
diff --git a/lib/pysh/subprocess_fix.py b/lib/pysh/subprocess_fix.py
new file mode 100644
index 000000000..46eca2280
--- /dev/null
+++ b/lib/pysh/subprocess_fix.py
@@ -0,0 +1,77 @@
+# subprocess - Subprocesses with accessible I/O streams
+#
+# For more information about this module, see PEP 324.
+#
+# This module should remain compatible with Python 2.2, see PEP 291.
+#
+# Copyright (c) 2003-2005 by Peter Astrand <astrand@lysator.liu.se>
+#
+# Licensed to PSF under a Contributor Agreement.
+# See http://www.python.org/2.4/license for licensing details.
+
+def list2cmdline(seq):
+    """
+    Translate a sequence of arguments into a command line
+    string, using the same rules as the MS C runtime:
+
+    1) Arguments are delimited by white space, which is either a
+       space or a tab.
+
+    2) A string surrounded by double quotation marks is
+       interpreted as a single argument, regardless of white space
+       contained within.  A quoted string can be embedded in an
+       argument.
+
+    3) A double quotation mark preceded by a backslash is
+       interpreted as a literal double quotation mark.
+
+    4) Backslashes are interpreted literally, unless they
+       immediately precede a double quotation mark.
+
+    5) If backslashes immediately precede a double quotation mark,
+       every pair of backslashes is interpreted as a literal
+       backslash.  If the number of backslashes is odd, the last
+       backslash escapes the next double quotation mark as
+       described in rule 3.
+    """
+
+    # See
+    # http://msdn.microsoft.com/library/en-us/vccelng/htm/progs_12.asp
+    result = []
+    needquote = False
+    for arg in seq:
+        bs_buf = []
+
+        # Add a space to separate this argument from the others
+        if result:
+            result.append(' ')
+
+        needquote = (" " in arg) or ("\t" in arg) or ("|" in arg) or arg == ""
+        if needquote:
+            result.append('"')
+
+        for c in arg:
+            if c == '\\':
+                # Don't know if we need to double yet.
+                bs_buf.append(c)
+            elif c == '"':
+                # Double backspaces.
+                result.append('\\' * len(bs_buf)*2)
+                bs_buf = []
+                result.append('\\"')
+            else:
+                # Normal char
+                if bs_buf:
+                    result.extend(bs_buf)
+                    bs_buf = []
+                result.append(c)
+
+        # Add remaining backspaces, if any.
+        if bs_buf:
+            result.extend(bs_buf)
+
+        if needquote:
+            result.extend(bs_buf)
+            result.append('"')
+            
+    return ''.join(result)