mogrify yapps2 into exyapps

git-svn-id: http://svn.stsci.edu/svn/ssb/etal/exyapps/trunk@361 d34015c8-bcbb-4646-8ac8-8ba5febf221d

5 files changed, 1465 insertions, 0 deletions

diff --git a/exyapps/__init__.py b/exyapps/__init__.py
new file mode 100644
index 0000000..1bb8bf6
--- /dev/null
+++ b/exyapps/__init__.py
@@ -0,0 +1 @@
+# empty
diff --git a/exyapps/grammar.py b/exyapps/grammar.py
new file mode 100644
index 0000000..258c464
--- /dev/null
+++ b/exyapps/grammar.py
@@ -0,0 +1,213 @@
+# THIS FILE WAS AUTOMATICALLY GENERATED
+# grammar.py, part of Yapps 2 - yet another python parser system
+# Copyright 1999-2003 by Amit J. Patel <amitp@cs.stanford.edu>
+# Enhancements copyright 2003-2004 by Matthias Urlichs <smurf@debian.org>
+#
+# This version of the Yapps 2 grammar can be distributed under the
+# terms of the MIT open source license, either found in the LICENSE
+# file included with the Yapps distribution
+# <http://theory.stanford.edu/~amitp/yapps/> or at
+# <http://www.opensource.org/licenses/mit-license.php>
+#
+
+"""Parser for Yapps grammars.
+
+This file defines the grammar of Yapps grammars.  Naturally, it is
+implemented in Yapps.  The grammar.py module needed by Yapps is built
+by running Yapps on yapps_grammar.g.  (Holy circularity, Batman!)
+
+"""
+
+import sys, re
+from exyapps import parsetree
+
+######################################################################
+def cleanup_choice(rule, lst):
+    if len(lst) == 0: return Sequence(rule, [])
+    if len(lst) == 1: return lst[0]
+    return parsetree.Choice(rule, *tuple(lst))
+
+def cleanup_sequence(rule, lst):
+    if len(lst) == 1: return lst[0]
+    return parsetree.Sequence(rule, *tuple(lst))
+
+def resolve_name(rule, tokens, id, args):
+    if id in [x[0] for x in tokens]:
+	# It's a token
+	if args:
+	    print 'Warning: ignoring parameters on TOKEN %s<<%s>>' % (id, args)
+        return parsetree.Terminal(rule, id)
+    else:
+        # It's a name, so assume it's a nonterminal
+        return parsetree.NonTerminal(rule, id, args)
+
+
+# Begin -- grammar generated by Yapps
+import sys, re
+from exyapps import runtime
+
+class ParserDescriptionScanner(runtime.Scanner):
+    patterns = [
+        ('"rule"', re.compile('rule')),
+        ('"ignore"', re.compile('ignore')),
+        ('"token"', re.compile('token')),
+        ('"option"', re.compile('option')),
+        ('":"', re.compile(':')),
+        ('"parser"', re.compile('parser')),
+        ('[ \t\r\n]+', re.compile('[ \t\r\n]+')),
+        ('#.*?\r?\n', re.compile('#.*?\r?\n')),
+        ('EOF', re.compile('$')),
+        ('ATTR', re.compile('<<.+?>>')),
+        ('STMT', re.compile('{{.+?}}')),
+        ('ID', re.compile('[a-zA-Z_][a-zA-Z_0-9]*')),
+        ('STR', re.compile('[rR]?\'([^\\n\'\\\\]|\\\\.)*\'|[rR]?"([^\\n"\\\\]|\\\\.)*"')),
+        ('LP', re.compile('\\(')),
+        ('RP', re.compile('\\)')),
+        ('LB', re.compile('\\[')),
+        ('RB', re.compile('\\]')),
+        ('OR', re.compile('[|]')),
+        ('STAR', re.compile('[*]')),
+        ('PLUS', re.compile('[+]')),
+        ('QUEST', re.compile('[?]')),
+        ('COLON', re.compile(':')),
+    ]
+    def __init__(self, str,*args,**kw):
+        runtime.Scanner.__init__(self,None,{'[ \t\r\n]+':None,'#.*?\r?\n':None,},str,*args,**kw)
+
+class ParserDescription(runtime.Parser):
+    Context = runtime.Context
+    def Parser(self, _parent=None):
+        _context = self.Context(_parent, self._scanner, 'Parser', [])
+        self._scan('"parser"', context=_context)
+        ID = self._scan('ID', context=_context)
+        self._scan('":"', context=_context)
+        Options = self.Options(_context)
+        Tokens = self.Tokens(_context)
+        Rules = self.Rules(Tokens, _context)
+        EOF = self._scan('EOF', context=_context)
+        return parsetree.Generator(ID,Options,Tokens,Rules)
+
+    def Options(self, _parent=None):
+        _context = self.Context(_parent, self._scanner, 'Options', [])
+        opt = {}
+        while self._peek('"option"', '"token"', '"ignore"', 'EOF', '"rule"', context=_context) == '"option"':
+            self._scan('"option"', context=_context)
+            self._scan('":"', context=_context)
+            Str = self.Str(_context)
+            opt[Str] = 1
+        return opt
+
+    def Tokens(self, _parent=None):
+        _context = self.Context(_parent, self._scanner, 'Tokens', [])
+        tok = []
+        while self._peek('"token"', '"ignore"', 'EOF', '"rule"', context=_context) in ['"token"', '"ignore"']:
+            _token = self._peek('"token"', '"ignore"', context=_context)
+            if _token == '"token"':
+                self._scan('"token"', context=_context)
+                ID = self._scan('ID', context=_context)
+                self._scan('":"', context=_context)
+                Str = self.Str(_context)
+                tok.append( (ID,Str) )
+            else: # == '"ignore"'
+                self._scan('"ignore"', context=_context)
+                self._scan('":"', context=_context)
+                Str = self.Str(_context)
+                ign = ('#ignore',Str)
+                if self._peek('STMT', '"token"', '"ignore"', 'EOF', '"rule"', context=_context) == 'STMT':
+                    STMT = self._scan('STMT', context=_context)
+                    ign = ign + (STMT[2:-2],)
+                tok.append( ign )
+        return tok
+
+    def Rules(self, tokens, _parent=None):
+        _context = self.Context(_parent, self._scanner, 'Rules', [tokens])
+        rul = []
+        while self._peek('"rule"', 'EOF', context=_context) == '"rule"':
+            self._scan('"rule"', context=_context)
+            ID = self._scan('ID', context=_context)
+            OptParam = self.OptParam(_context)
+            self._scan('":"', context=_context)
+            ClauseA = self.ClauseA(ID, tokens, _context)
+            rul.append( (ID, OptParam, ClauseA) )
+        return rul
+
+    def ClauseA(self, rule, tokens, _parent=None):
+        _context = self.Context(_parent, self._scanner, 'ClauseA', [rule, tokens])
+        ClauseB = self.ClauseB(rule,tokens, _context)
+        v = [ClauseB]
+        while self._peek('OR', 'RP', 'RB', '"rule"', 'EOF', context=_context) == 'OR':
+            OR = self._scan('OR', context=_context)
+            ClauseB = self.ClauseB(rule,tokens, _context)
+            v.append(ClauseB)
+        return cleanup_choice(rule,v)
+
+    def ClauseB(self, rule,tokens, _parent=None):
+        _context = self.Context(_parent, self._scanner, 'ClauseB', [rule,tokens])
+        v = []
+        while self._peek('STR', 'ID', 'LP', 'LB', 'STMT', 'OR', 'RP', 'RB', '"rule"', 'EOF', context=_context) in ['STR', 'ID', 'LP', 'LB', 'STMT']:
+            ClauseC = self.ClauseC(rule,tokens, _context)
+            v.append(ClauseC)
+        return cleanup_sequence(rule, v)
+
+    def ClauseC(self, rule,tokens, _parent=None):
+        _context = self.Context(_parent, self._scanner, 'ClauseC', [rule,tokens])
+        ClauseD = self.ClauseD(rule,tokens, _context)
+        _token = self._peek('PLUS', 'STAR', 'QUEST', 'STR', 'ID', 'LP', 'LB', 'STMT', 'OR', 'RP', 'RB', '"rule"', 'EOF', context=_context)
+        if _token == 'PLUS':
+            PLUS = self._scan('PLUS', context=_context)
+            return parsetree.Plus(rule, ClauseD)
+        elif _token == 'STAR':
+            STAR = self._scan('STAR', context=_context)
+            return parsetree.Star(rule, ClauseD)
+        elif _token == 'QUEST':
+            QUEST = self._scan('QUEST', context=_context)
+            return parsetree.Option(rule, ClauseD)
+        else:
+            return ClauseD
+
+    def ClauseD(self, rule,tokens, _parent=None):
+        _context = self.Context(_parent, self._scanner, 'ClauseD', [rule,tokens])
+        _token = self._peek('STR', 'ID', 'LP', 'LB', 'STMT', context=_context)
+        if _token == 'STR':
+            STR = self._scan('STR', context=_context)
+            t = (STR, eval(STR,{},{}))
+            if t not in tokens: tokens.insert( 0, t )
+            return parsetree.Terminal(rule, STR)
+        elif _token == 'ID':
+            ID = self._scan('ID', context=_context)
+            OptParam = self.OptParam(_context)
+            return resolve_name(rule,tokens, ID, OptParam)
+        elif _token == 'LP':
+            LP = self._scan('LP', context=_context)
+            ClauseA = self.ClauseA(rule,tokens, _context)
+            RP = self._scan('RP', context=_context)
+            return ClauseA
+        elif _token == 'LB':
+            LB = self._scan('LB', context=_context)
+            ClauseA = self.ClauseA(rule,tokens, _context)
+            RB = self._scan('RB', context=_context)
+            return parsetree.Option(rule, ClauseA)
+        else: # == 'STMT'
+            STMT = self._scan('STMT', context=_context)
+            return parsetree.Eval(rule, STMT[2:-2])
+
+    def OptParam(self, _parent=None):
+        _context = self.Context(_parent, self._scanner, 'OptParam', [])
+        if self._peek('ATTR', '":"', 'PLUS', 'STAR', 'QUEST', 'STR', 'ID', 'LP', 'LB', 'STMT', 'OR', 'RP', 'RB', '"rule"', 'EOF', context=_context) == 'ATTR':
+            ATTR = self._scan('ATTR', context=_context)
+            return ATTR[2:-2]
+        return ''
+
+    def Str(self, _parent=None):
+        _context = self.Context(_parent, self._scanner, 'Str', [])
+        STR = self._scan('STR', context=_context)
+        return eval(STR,{},{})
+
+
+def parse(rule, text):
+    P = ParserDescription(ParserDescriptionScanner(text))
+    return runtime.wrap_error_reporter(P, rule)
+
+# End -- grammar generated by Yapps
+
+
diff --git a/exyapps/main.py b/exyapps/main.py
new file mode 100755
index 0000000..881c3cc
--- /dev/null
+++ b/exyapps/main.py
@@ -0,0 +1,135 @@
+#!/usr/bin/python
+
+#
+# Yapps 2 - yet another python parser system
+# Copyright 1999-2003 by Amit J. Patel <amitp@cs.stanford.edu>
+#
+# This version of Yapps 2 can be distributed under the
+# terms of the MIT open source license, either found in the LICENSE file
+# included with the Yapps distribution
+# <http://theory.stanford.edu/~amitp/yapps/> or at
+# <http://www.opensource.org/licenses/mit-license.php>
+#
+
+import sys, re
+
+import exyapps.runtime as runtime
+import exyapps.parsetree as parsetree
+
+def generate(inputfilename, outputfilename=None, dump=0, **flags):
+    """Generate a grammar, given an input filename (X.g)
+    and an output filename (defaulting to X.py)."""
+
+    if not outputfilename:
+        # recognize *.g because that is what the old yapps used
+        if inputfilename.endswith('.g'):
+            outputfilename = inputfilename[:-2] + '.py'
+
+        # recognize *.exy for the new grammar
+        elif inputfilename.endswith('.exy'):
+            outputfilename = inputfilename[:-3] + '.py'
+
+        # cannot automatically generate the output file name if we don't recognize extension
+        else:
+            raise Exception('Must specify output filename if input filename is not *.exy or *.g')
+        
+    DIVIDER = '\n%%\n' # This pattern separates the pre/post parsers
+    preparser, postparser = None, None # Code before and after the parser desc
+
+    # Read the entire file
+    s = open(inputfilename,'r').read()
+
+    # See if there's a separation between the pre-parser and parser
+    f = s.find(DIVIDER)
+    if f >= 0: 
+        preparser, s = s[:f]+'\n\n', s[f+len(DIVIDER):]
+
+    # See if there's a separation between the parser and post-parser
+    f = s.find(DIVIDER)
+    if f >= 0: 
+        s, postparser = s[:f], '\n\n'+s[f+len(DIVIDER):]
+
+    # Create the parser and scanner and parse the text
+    scanner = grammar.ParserDescriptionScanner(s, filename=inputfilename)
+    if preparser:   
+        scanner.del_line += preparser.count('\n')
+
+    parser = grammar.ParserDescription(scanner)
+    t = runtime.wrap_error_reporter(parser, 'Parser')
+    if t is None: 
+        return 1 # Failure
+    if preparser is not None: 
+        t.preparser = preparser
+    if postparser is not None: 
+        t.postparser = postparser
+
+    # Check the options
+    for f in t.options.keys():
+        for opt,_,_ in yapps_options:
+            if f == opt: 
+                break
+        else:
+            print >>sys.stderr, 'Warning: unrecognized option', f
+
+    # Add command line options to the set
+    for f in flags.keys(): 
+        t.options[f] = flags[f]
+            
+    # Generate the output
+    if dump:
+        t.dump_information()
+    else:
+        t.output = open(outputfilename, 'w')
+        t.generate_output()
+    return 0
+
+def main() :
+    import doctest
+    doctest.testmod(sys.modules['__main__'])
+    doctest.testmod(parsetree)
+
+    # Someday I will use optparse, but Python 2.3 is too new at the moment.
+    yapps_options = [
+        ('context-insensitive-scanner',
+         'context-insensitive-scanner',
+         'Scan all tokens (see docs)'),
+        ]
+
+    import getopt
+    optlist, args = getopt.getopt(sys.argv[1:], 'f:', ['help', 'dump', 'use-devel-grammar'])
+    if not args or len(args) > 2:
+        print >>sys.stderr, 'Usage:'
+        print >>sys.stderr, '  python', sys.argv[0], '[flags] input.g [output.py]'
+        print >>sys.stderr, 'Flags:'
+        print >>sys.stderr, ('  --dump' + ' '*40)[:35] + 'Dump out grammar information'
+        print >>sys.stderr, ('  --use-devel-grammar' + ' '*40)[:35] + 'Use the devel grammar parser from yapps_grammar.py instead of the stable grammar from grammar.py'
+        for flag, _, doc in yapps_options:
+            print >>sys.stderr, ('  -f' + flag + ' '*40)[:35] + doc
+        return 1
+    else:
+        # Read in the options and create a list of flags
+        flags = {}
+        use_devel_grammar = 0
+        for opt in optlist:
+            for flag, name, _ in yapps_options:
+                if opt == ('-f', flag):
+                    flags[name] = 1
+                    break
+            else:
+                if opt == ('--dump', ''):
+                    flags['dump'] = 1
+                elif opt == ('--use-devel-grammar', ''):
+                    use_devel_grammar = 1
+                else:
+                    print >>sys.stderr, 'Warning: unrecognized option', opt[0], opt[1]
+
+        if use_devel_grammar:
+            import yapps_grammar as g2
+        else:
+            import exyapps.grammar as g2
+
+        global grammar
+        grammar = g2
+            
+        return generate(*tuple(args), **flags)
+
diff --git a/exyapps/parsetree.py b/exyapps/parsetree.py
new file mode 100644
index 0000000..8831609
--- /dev/null
+++ b/exyapps/parsetree.py
@@ -0,0 +1,674 @@
+# parsetree.py, part of Yapps 2 - yet another python parser system
+# Copyright 1999-2003 by Amit J. Patel <amitp@cs.stanford.edu>
+#
+# This version of the Yapps 2 Runtime can be distributed under the
+# terms of the MIT open source license, either found in the LICENSE file
+# included with the Yapps distribution
+# <http://theory.stanford.edu/~amitp/yapps/> or at
+# <http://www.opensource.org/licenses/mit-license.php>
+#
+
+"""Classes used to represent parse trees and generate output.
+
+This module defines the Generator class, which drives the generation
+of Python output from a grammar parse tree.  It also defines nodes
+used to represent the parse tree; they are derived from class Node.
+
+The main logic of Yapps is in this module.
+"""
+
+import sys, re
+
+######################################################################
+INDENT = ' '*4
+class Generator:
+
+    # TODO: many of the methods here should be class methods, not instance methods
+    
+    def __init__(self, name, options, tokens, rules):
+        self.change_count = 0
+        self.name = name
+        self.options = options
+        self.preparser = ''
+        self.postparser = None
+        
+        self.tokens = {} # Map from tokens to regexps
+        self.ignore = {} # List of token names to ignore in parsing, map to statements
+        self.terminals = [] # List of token names (to maintain ordering)
+        for t in tokens:
+            if len(t) == 3:
+                n,t,s = t
+            else:
+                n,t = t
+                s = None
+
+            if n == '#ignore':
+                n = t
+                self.ignore[n] = s
+            if n in self.tokens.keys() and self.tokens[n] != t:
+                print >>sys.stderr, 'Warning: token %s defined more than once.' % n
+            self.tokens[n] = t
+            self.terminals.append(n)
+            
+        self.rules = {} # Map from rule names to parser nodes
+        self.params = {} # Map from rule names to parameters
+        self.goals = [] # List of rule names (to maintain ordering)
+        for n,p,r in rules:
+            self.params[n] = p
+            self.rules[n] = r
+            self.goals.append(n)
+            
+        self.output = sys.stdout
+
+    def has_option(self, name):
+        return self.options.get(name, 0)
+    
+    def non_ignored_tokens(self):
+        return [x for x in self.terminals if x not in self.ignore]
+    
+    def changed(self):
+        """Increments the change count.
+
+        >>> t = Generator('', [], [], [])
+        >>> old_count = t.change_count
+        >>> t.changed()
+        >>> assert t.change_count == old_count + 1
+        """
+        self.change_count = 1+self.change_count
+
+    def set_subtract(self, a, b):
+        """Returns the elements of a that are not in b.
+
+        >>> t = Generator('', [], [], [])
+        >>> t.set_subtract([], [])
+        []
+        >>> t.set_subtract([1, 2], [1, 2])
+        []
+        >>> t.set_subtract([1, 2, 3], [2])
+        [1, 3]
+        >>> t.set_subtract([1], [2, 3, 4])
+        [1]
+        """
+        result = []
+        for x in a:
+            if x not in b:
+                result.append(x)
+        return result
+    
+    def subset(self, a, b):
+        """True iff all elements of sequence a are inside sequence b
+
+        >>> t = Generator('', [], [], [])
+        >>> t.subset([], [1, 2, 3])
+        1
+        >>> t.subset([1, 2, 3], [])
+        0
+        >>> t.subset([1], [1, 2, 3])
+        1
+        >>> t.subset([3, 2, 1], [1, 2, 3])
+        1
+        >>> t.subset([1, 1, 1], [1, 2, 3])
+        1
+        >>> t.subset([1, 2, 3], [1, 1, 1])
+        0
+        """
+        for x in a:
+            if x not in b:
+                return 0
+        return 1
+
+    def equal_set(self, a, b):
+        """True iff subset(a, b) and subset(b, a)
+
+        >>> t = Generator('', [], [], [])
+        >>> a_set = [1, 2, 3]
+        >>> t.equal_set(a_set, a_set)
+        1
+        >>> t.equal_set(a_set, a_set[:])
+        1
+        >>> t.equal_set([], a_set)
+        0
+        >>> t.equal_set([1, 2, 3], [3, 2, 1])
+        1
+        """
+        if len(a) != len(b): return 0
+        if a == b: return 1
+        return self.subset(a, b) and self.subset(b, a)
+    
+    def add_to(self, parent, additions):
+        "Modify _parent_ to include all elements in _additions_"
+        for x in additions:
+            if x not in parent:
+                parent.append(x)
+                self.changed()
+
+    def equate(self, a, b):
+        """Extend (a) and (b) so that they contain each others' elements.
+
+        >>> t = Generator('', [], [], [])
+        >>> a = [1, 2]
+        >>> b = [2, 3]
+        >>> t.equate(a, b)
+        >>> a
+        [1, 2, 3]
+        >>> b
+        [2, 3, 1]
+        """
+        self.add_to(a, b)
+        self.add_to(b, a)
+
+    def write(self, *args):
+        for a in args:
+            self.output.write(a)
+
+    def in_test(self, expr, full, set):
+        """Generate a test of (expr) being in (set), where (set) is a subset of (full)
+
+        expr is a string (Python expression)
+        set is a list of values (which will be converted with repr)
+        full is the list of all values expr could possibly evaluate to
+        
+        >>> t = Generator('', [], [], [])
+        >>> t.in_test('x', [1,2,3,4], [])
+        '0'
+        >>> t.in_test('x', [1,2,3,4], [1,2,3,4])
+        '1'
+        >>> t.in_test('x', [1,2,3,4], [1])
+        'x == 1'
+        >>> t.in_test('a+b', [1,2,3,4], [1,2])
+        'a+b in [1, 2]'
+        >>> t.in_test('x', [1,2,3,4,5], [1,2,3])
+        'x not in [4, 5]'
+        >>> t.in_test('x', [1,2,3,4,5], [1,2,3,4])
+        'x != 5'
+        """
+        
+        if not set: return '0'
+        if len(set) == 1: return '%s == %s' % (expr, repr(set[0]))
+        if full and len(set) > len(full)/2:
+            # Reverse the sense of the test.
+            not_set = [x for x in full if x not in set]
+            return self.not_in_test(expr, full, not_set)
+        return '%s in %s' % (expr, repr(set))
+    
+    def not_in_test(self, expr, full, set):
+        """Like in_test, but the reverse test."""
+        if not set: return '1'
+        if len(set) == 1: return '%s != %s' % (expr, repr(set[0]))
+        return '%s not in %s' % (expr, repr(set))
+
+    def peek_call(self, a):
+        """Generate a call to scan for a token in the set 'a'"""
+        assert type(a) == type([])
+        a_set = (repr(a)[1:-1])
+        if self.equal_set(a, self.non_ignored_tokens()): a_set = ''
+        if self.has_option('context-insensitive-scanner'): a_set = ''
+        if a_set: a_set += ","
+        
+        return 'self._peek(%s context=_context)' % a_set
+    
+    def peek_test(self, a, b):
+        """Generate a call to test whether the next token (which could be any of
+        the elements in a) is in the set b."""
+        if self.subset(a, b): return '1'
+        if self.has_option('context-insensitive-scanner'): a = self.non_ignored_tokens()
+        return self.in_test(self.peek_call(a), a, b)
+
+    def not_peek_test(self, a, b):
+        """Like peek_test, but the opposite sense."""
+        if self.subset(a, b): return '0'
+        return self.not_in_test(self.peek_call(a), a, b)
+
+    def calculate(self):
+        """The main loop to compute the epsilon, first, follow sets.
+        The loop continues until the sets converge.  This works because
+        each set can only get larger, so when they stop getting larger,
+        we're done."""
+        # First we determine whether a rule accepts epsilon (the empty sequence)
+        while 1:
+            for r in self.goals:
+                self.rules[r].setup(self)
+            if self.change_count == 0: break
+            self.change_count = 0
+
+        # Now we compute the first/follow sets
+        while 1:
+            for r in self.goals:
+                self.rules[r].update(self)
+            if self.change_count == 0: break
+            self.change_count = 0
+
+    def dump_information(self):
+        """Display the grammar in somewhat human-readable form."""
+        self.calculate()
+        for r in self.goals:
+            print '    _____' + '_'*len(r)
+            print ('___/Rule '+r+'\\' + '_'*80)[:79]
+            queue = [self.rules[r]]
+            while queue:
+                top = queue[0]
+                del queue[0]
+
+                print 'Rule', repr(top), 'of class', top.__class__.__name__
+                top.first.sort()
+                top.follow.sort()
+                eps = []
+                if top.accepts_epsilon: eps = ['(null)']
+                print '     FIRST:', ', '.join(top.first+eps)
+                print '    FOLLOW:', ', '.join(top.follow)
+                for x in top.get_children(): queue.append(x)
+                
+    def repr_ignore(self):
+        out="{"
+        for t,s in self.ignore.iteritems():
+            if s is None: s=repr(s)
+            out += "%s:%s," % (repr(t),s)
+        out += "}"
+        return out
+        
+    def generate_output(self):
+        self.write("# THIS FILE WAS AUTOMATICALLY GENERATED\n")
+        self.calculate()
+        self.write(self.preparser)
+        self.write("# Begin -- grammar generated by Yapps\n")
+        self.write("import sys, re\n")
+        self.write("from exyapps import runtime\n")
+        self.write("\n")
+        self.write("class ", self.name, "Scanner(runtime.Scanner):\n")
+        self.write("    patterns = [\n")
+        for p in self.terminals:
+            self.write("        (%s, re.compile(%s)),\n" % (
+                repr(p), repr(self.tokens[p])))
+        self.write("    ]\n")
+        self.write("    def __init__(self, str,*args,**kw):\n")
+        self.write("        runtime.Scanner.__init__(self,None,%s,str,*args,**kw)\n" %
+                   self.repr_ignore())
+        self.write("\n")
+        
+        self.write("class ", self.name, "(runtime.Parser):\n")
+        self.write(INDENT, "Context = runtime.Context\n")
+        for r in self.goals:
+            self.write(INDENT, "def ", r, "(self")
+            if self.params[r]: self.write(", ", self.params[r])
+            self.write(", _parent=None):\n")
+            self.write(INDENT+INDENT, "_context = self.Context(_parent, self._scanner, %s, [%s])\n" %
+                       (repr(r), self.params.get(r, '')))
+            self.rules[r].output(self, INDENT+INDENT)
+            self.write("\n")
+
+        self.write("\n")
+        self.write("def parse(rule, text):\n")
+        self.write("    P = ", self.name, "(", self.name, "Scanner(text))\n")
+        self.write("    return runtime.wrap_error_reporter(P, rule)\n")
+        self.write("\n")
+        if self.postparser is not None:
+            self.write("# End -- grammar generated by Yapps\n")
+            self.write(self.postparser)
+        else:
+            self.write("if __name__ == '__main__':\n")
+            self.write(INDENT, "from sys import argv, stdin\n")
+            self.write(INDENT, "if len(argv) >= 2:\n")
+            self.write(INDENT*2, "if len(argv) >= 3:\n")
+            self.write(INDENT*3, "f = open(argv[2],'r')\n")
+            self.write(INDENT*2, "else:\n")
+            self.write(INDENT*3, "f = stdin\n")
+            self.write(INDENT*2, "print parse(argv[1], f.read())\n")
+            self.write(INDENT, "else: print >>sys.stderr, 'Args:  <rule> [<filename>]'\n")
+            self.write("# End -- grammar generated by Yapps\n")
+
+######################################################################
+class Node:
+    """This is the base class for all components of a grammar."""
+    def __init__(self, rule):
+        self.rule = rule # name of the rule containing this node
+        self.first = []
+        self.follow = []
+        self.accepts_epsilon = 0
+        
+    def setup(self, gen):
+        # Setup will change accepts_epsilon,
+        # sometimes from 0 to 1 but never 1 to 0.
+        # It will take a finite number of steps to set things up
+        pass
+    
+    def used(self, vars):
+        "Return two lists: one of vars used, and the other of vars assigned"
+        return vars, []
+
+    def get_children(self):
+        "Return a list of sub-nodes"
+        return []
+    
+    def __repr__(self):
+        return str(self)
+    
+    def update(self, gen):
+        if self.accepts_epsilon:
+            gen.add_to(self.first, self.follow)
+
+    def output(self, gen, indent):
+        "Write out code to _gen_ with _indent_:string indentation"
+        gen.write(indent, "assert 0 # Invalid parser node\n")
+    
+class Terminal(Node):
+    """This class stores terminal nodes, which are tokens."""
+    def __init__(self, rule, token):
+        Node.__init__(self, rule)
+        self.token = token
+        self.accepts_epsilon = 0
+
+    def __str__(self):
+        return self.token
+
+    def update(self, gen):
+        Node.update(self, gen)
+        if self.first != [self.token]:
+            self.first = [self.token]
+            gen.changed()
+
+    def output(self, gen, indent):
+        gen.write(indent)
+        if re.match('[a-zA-Z_][a-zA-Z_0-9]*$', self.token):
+            gen.write(self.token, " = ")
+        gen.write("self._scan(%s, context=_context)\n" % repr(self.token))
+        
+class Eval(Node):
+    """This class stores evaluation nodes, from {{ ... }} clauses."""
+    def __init__(self, rule, expr):
+        Node.__init__(self, rule)
+        self.expr = expr
+
+    def setup(self, gen):
+        Node.setup(self, gen)
+        if not self.accepts_epsilon:
+            self.accepts_epsilon = 1
+            gen.changed()
+
+    def __str__(self):
+        return '{{ %s }}' % self.expr.strip()
+
+    def output(self, gen, indent):
+        gen.write(indent, self.expr.strip(), '\n')
+        
+class NonTerminal(Node):
+    """This class stores nonterminal nodes, which are rules with arguments."""
+    def __init__(self, rule, name, args):
+        Node.__init__(self, rule)
+        self.name = name
+        self.args = args
+
+    def setup(self, gen):
+        Node.setup(self, gen)
+        try:
+            self.target = gen.rules[self.name]
+            if self.accepts_epsilon != self.target.accepts_epsilon:
+                self.accepts_epsilon = self.target.accepts_epsilon
+                gen.changed()
+        except KeyError: # Oops, it's nonexistent
+            print >>sys.stderr, 'Error: no rule <%s>' % self.name
+            self.target = self
+            
+    def __str__(self):
+        return '%s' % self.name
+
+    def update(self, gen):
+        Node.update(self, gen)
+        gen.equate(self.first, self.target.first)
+        gen.equate(self.follow, self.target.follow)
+
+    def output(self, gen, indent):
+        gen.write(indent)
+        gen.write(self.name, " = ")
+        args = self.args
+        if args: args += ', '
+        args += '_context'
+        gen.write("self.", self.name, "(", args, ")\n")
+        
+class Sequence(Node):
+    """This class stores a sequence of nodes (A B C ...)"""
+    def __init__(self, rule, *children):
+        Node.__init__(self, rule)
+        self.children = children
+
+    def setup(self, gen):
+        Node.setup(self, gen)
+        for c in self.children: c.setup(gen)
+        
+        if not self.accepts_epsilon:
+            # If it's not already accepting epsilon, it might now do so.
+            for c in self.children:
+                # any non-epsilon means all is non-epsilon
+                if not c.accepts_epsilon: break
+            else:
+                self.accepts_epsilon = 1
+                gen.changed()
+
+    def get_children(self):
+        return self.children
+    
+    def __str__(self):
+        return '( %s )' % ' '.join(map(str, self.children))
+
+    def update(self, gen):
+        Node.update(self, gen)
+        for g in self.children:
+            g.update(gen)
+
+        empty = 1
+        for g_i in range(len(self.children)):
+            g = self.children[g_i]
+
+            if empty: gen.add_to(self.first, g.first)
+            if not g.accepts_epsilon: empty = 0
+            
+            if g_i == len(self.children)-1:
+                next = self.follow
+            else:
+                next = self.children[1+g_i].first
+            gen.add_to(g.follow, next)
+
+        if self.children:
+            gen.add_to(self.follow, self.children[-1].follow)
+
+    def output(self, gen, indent):
+        if self.children:
+            for c in self.children:
+                c.output(gen, indent)
+        else:
+            # Placeholder for empty sequences, just in case
+            gen.write(indent, 'pass\n')
+            
+class Choice(Node):
+    """This class stores a choice between nodes (A | B | C | ...)"""
+    def __init__(self, rule, *children):
+        Node.__init__(self, rule)
+        self.children = children
+
+    def setup(self, gen):
+        Node.setup(self, gen)
+        for c in self.children: c.setup(gen)
+            
+        if not self.accepts_epsilon:
+            for c in self.children:
+                if c.accepts_epsilon:
+                    self.accepts_epsilon = 1
+                    gen.changed()
+
+    def get_children(self):
+        return self.children
+    
+    def __str__(self):
+        return '( %s )' % ' | '.join(map(str, self.children))
+
+    def update(self, gen):
+        Node.update(self, gen)
+        for g in self.children:
+            g.update(gen)
+
+        for g in self.children:
+            gen.add_to(self.first, g.first)
+            gen.add_to(self.follow, g.follow)
+        for g in self.children:
+            gen.add_to(g.follow, self.follow)
+        if self.accepts_epsilon:
+            gen.add_to(self.first, self.follow)
+
+    def output(self, gen, indent):
+        test = "if"
+        gen.write(indent, "_token = ", gen.peek_call(self.first), "\n")
+        tokens_seen = []
+        tokens_unseen = self.first[:]
+        if gen.has_option('context-insensitive-scanner'):
+            # Context insensitive scanners can return ANY token,
+            # not only the ones in first.
+            tokens_unseen = gen.non_ignored_tokens()
+        for c in self.children:
+            testset = c.first[:]
+            removed = []
+            for x in testset:
+                if x in tokens_seen:
+                    testset.remove(x)
+                    removed.append(x)
+                if x in tokens_unseen: tokens_unseen.remove(x)
+            tokens_seen = tokens_seen + testset
+            if removed:
+                if not testset:
+                    print >>sys.stderr, 'Error in rule', self.rule+':'
+                else:
+                    print >>sys.stderr, 'Warning in rule', self.rule+':'
+                print >>sys.stderr, ' *', self
+                print >>sys.stderr, ' * These tokens could be matched by more than one clause:'
+                print >>sys.stderr, ' *', ' '.join(removed)
+                
+            if testset:
+                if not tokens_unseen: # context sensitive scanners only!
+                    if test == 'if':
+                        # if it's the first AND last test, then
+                        # we can simply put the code without an if/else
+                        c.output(gen, indent)
+                    else:
+                        gen.write(indent, "else:")
+                        t = gen.in_test('', [], testset)
+                        if len(t) < 70-len(indent):
+                            gen.write(' #', t)
+                        gen.write("\n")
+                        c.output(gen, indent+INDENT)
+                else:
+                    gen.write(indent, test, " ",
+                              gen.in_test('_token', tokens_unseen, testset),
+                              ":\n")
+                    c.output(gen, indent+INDENT)
+                test = "elif"
+
+        if tokens_unseen:
+            gen.write(indent, "else:\n")
+            gen.write(indent, INDENT, "raise runtime.SyntaxError(_token[0], ")
+            gen.write("'Could not match ", self.rule, "')\n")
+        
+class Wrapper(Node):
+    """This is a base class for nodes that modify a single child."""
+    def __init__(self, rule, child):
+        Node.__init__(self, rule)
+        self.child = child
+
+    def setup(self, gen):
+        Node.setup(self, gen)
+        self.child.setup(gen)
+
+    def get_children(self):
+        return [self.child]
+    
+    def update(self, gen):
+        Node.update(self, gen)
+        self.child.update(gen)
+        gen.add_to(self.first, self.child.first)
+        gen.equate(self.follow, self.child.follow)
+
+class Option(Wrapper):
+    """This class represents an optional clause of the form [A]"""
+    def setup(self, gen):
+        Wrapper.setup(self, gen)
+        if not self.accepts_epsilon:
+            self.accepts_epsilon = 1
+            gen.changed()
+
+    def __str__(self):
+        return '[ %s ]' % str(self.child)
+
+    def output(self, gen, indent):
+        if self.child.accepts_epsilon:
+            print >>sys.stderr, 'Warning in rule', self.rule+': contents may be empty.'
+        gen.write(indent, "if %s:\n" %
+                  gen.peek_test(self.first, self.child.first))
+        self.child.output(gen, indent+INDENT)
+
+        if gen.has_option('context-insensitive-scanner'):
+            gen.write(indent, "if %s:\n" %
+                    gen.not_peek_test(gen.non_ignored_tokens(), self.follow))
+            gen.write(indent+INDENT, "raise runtime.SyntaxError(pos=self._scanner.get_pos(), context=_context, msg='Need one of ' + ', '.join(%s))\n" %
+                    repr(self.first))
+
+        
+class Plus(Wrapper):
+    """This class represents a 1-or-more repetition clause of the form A+"""
+    def setup(self, gen):
+        Wrapper.setup(self, gen)
+        if self.accepts_epsilon != self.child.accepts_epsilon:
+            self.accepts_epsilon = self.child.accepts_epsilon
+            gen.changed()
+
+    def __str__(self):
+        return '%s+' % str(self.child)
+
+    def update(self, gen):
+        Wrapper.update(self, gen)
+        gen.add_to(self.child.follow, self.child.first)
+        
+    def output(self, gen, indent):
+        if self.child.accepts_epsilon:
+            print >>sys.stderr, 'Warning in rule', self.rule+':'
+            print >>sys.stderr, ' * The repeated pattern could be empty.  The resulting parser may not work properly.'
+        gen.write(indent, "while 1:\n")
+        self.child.output(gen, indent+INDENT)
+        union = self.first[:]
+        gen.add_to(union, self.follow)
+        gen.write(indent+INDENT, "if %s: break\n" %
+                  gen.not_peek_test(union, self.child.first))
+
+        if gen.has_option('context-insensitive-scanner'):
+            gen.write(indent, "if %s:\n" %
+                    gen.not_peek_test(gen.non_ignored_tokens(), self.follow))
+            gen.write(indent+INDENT, "raise runtime.SyntaxError(pos=self._scanner.get_pos(), context=_context, msg='Need one of ' + ', '.join(%s))\n" %
+                    repr(self.first))
+
+
+class Star(Wrapper):
+    """This class represents a 0-or-more repetition clause of the form A*"""
+    def setup(self, gen):
+        Wrapper.setup(self, gen)
+        if not self.accepts_epsilon:
+            self.accepts_epsilon = 1
+            gen.changed()
+
+    def __str__(self):
+        return '%s*' % str(self.child)
+
+    def update(self, gen):
+        Wrapper.update(self, gen)
+        gen.add_to(self.child.follow, self.child.first)
+        
+    def output(self, gen, indent):
+        if self.child.accepts_epsilon:
+            print >>sys.stderr, 'Warning in rule', self.rule+':'
+            print >>sys.stderr, ' * The repeated pattern could be empty.  The resulting parser probably will not work properly.'
+        gen.write(indent, "while %s:\n" %
+                  gen.peek_test(self.follow, self.child.first))
+        self.child.output(gen, indent+INDENT)
+
+        # TODO: need to generate tests like this in lots of rules
+        if gen.has_option('context-insensitive-scanner'):
+            gen.write(indent, "if %s:\n" %
+                    gen.not_peek_test(gen.non_ignored_tokens(), self.follow))
+            gen.write(indent+INDENT, "raise runtime.SyntaxError(pos=self._scanner.get_pos(), context=_context, msg='Need one of ' + ', '.join(%s))\n" %
+                    repr(self.first))
+
diff --git a/exyapps/runtime.py b/exyapps/runtime.py
new file mode 100644
index 0000000..5d9d1d6
--- /dev/null
+++ b/exyapps/runtime.py
@@ -0,0 +1,442 @@
+# Yapps 2 Runtime, part of Yapps 2 - yet another python parser system
+# Copyright 1999-2003 by Amit J. Patel <amitp@cs.stanford.edu>
+# Enhancements copyright 2003-2004 by Matthias Urlichs <smurf@debian.org>
+#
+# This version of the Yapps 2 Runtime can be distributed under the
+# terms of the MIT open source license, either found in the LICENSE file
+# included with the Yapps distribution
+# <http://theory.stanford.edu/~amitp/yapps/> or at
+# <http://www.opensource.org/licenses/mit-license.php>
+#
+
+"""Run time libraries needed to run parsers generated by Yapps.
+
+This module defines parse-time exception classes, a scanner class, a
+base class for parsers produced by Yapps, and a context class that
+keeps track of the parse stack.
+
+"""
+
+import sys, re
+
+MIN_WINDOW=4096
+# File lookup window
+
+class SyntaxError(Exception):
+	"""When we run into an unexpected token, this is the exception to use"""
+	def __init__(self, pos=None, msg="Bad Token", context=None):
+		Exception.__init__(self)
+		self.pos = pos
+		self.msg = msg
+		self.context = context
+		
+	def __str__(self):
+		if not self.pos: return 'SyntaxError'
+		else: return 'SyntaxError@%s(%s)' % (repr(self.pos), self.msg)
+
+class NoMoreTokens(Exception):
+	"""Another exception object, for when we run out of tokens"""
+	pass
+
+class Token(object):
+	"""Yapps token.
+
+	This is a container for a scanned token.
+	"""
+
+	def __init__(self, type,value, pos=None):
+		"""Initialize a token."""
+		self.type = type
+		self.value = value
+		self.pos = pos
+
+	def __repr__(self):
+		output = '<%s: %s' % (self.type, repr(self.value))
+		if self.pos:
+			output += " @ "
+			if self.pos[0]:
+				output += "%s:" % self.pos[0]
+			if self.pos[1]:
+				output += "%d" % self.pos[1]
+			if self.pos[2] is not None:
+				output += ".%d" % self.pos[2]
+		output += ">"
+		return output
+
+in_name=0
+class Scanner(object):
+	"""Yapps scanner.
+
+	The Yapps scanner can work in context sensitive or context
+	insensitive modes.  The token(i) method is used to retrieve the
+	i-th token.  It takes a restrict set that limits the set of tokens
+	it is allowed to return.  In context sensitive mode, this restrict
+	set guides the scanner.  In context insensitive mode, there is no
+	restriction (the set is always the full set of tokens).
+	
+	"""
+	
+	def __init__(self, patterns, ignore, input="",
+			file=None,filename=None,stacked=False):
+		"""Initialize the scanner.
+
+		Parameters:
+		  patterns : [(terminal, uncompiled regex), ...] or None
+		  ignore : {terminal:None, ...}
+		  input : string
+
+		If patterns is None, we assume that the subclass has
+		defined self.patterns : [(terminal, compiled regex), ...].
+		Note that the patterns parameter expects uncompiled regexes,
+		whereas the self.patterns field expects compiled regexes.
+
+		The 'ignore' value is either None or a callable, which is called
+		with the scanner and the to-be-ignored match object; this can
+		be used for include file or comment handling.
+		"""
+
+		if not filename:
+			global in_name
+			filename="<f.%d>" % in_name
+			in_name += 1
+
+		self.input = input
+		self.ignore = ignore
+		self.file = file
+		self.filename = filename
+		self.pos = 0
+		self.del_pos = 0 # skipped
+		self.line = 1
+		self.del_line = 0 # skipped
+		self.col = 0
+		self.tokens = []
+		self.stack = None
+		self.stacked = stacked
+		
+		self.last_read_token = None
+		self.last_token = None
+		self.last_types = None
+
+		if patterns is not None:
+			# Compile the regex strings into regex objects
+			self.patterns = []
+			for terminal, regex in patterns:
+				self.patterns.append( (terminal, re.compile(regex)) )
+
+	def stack_input(self, input="", file=None, filename=None):
+		"""Temporarily parse from a second file."""
+
+		# Already reading from somewhere else: Go on top of that, please.
+		if self.stack:
+			# autogenerate a recursion-level-identifying filename
+			if not filename:
+				filename = 1
+			else:
+				try:
+					filename += 1
+				except TypeError:
+					pass
+				# now pass off to the include file
+			self.stack.stack_input(input,file,filename)
+		else:
+
+			try:
+				filename += 0
+			except TypeError:
+				pass
+			else:
+				filename = "<str_%d>" % filename
+
+#			self.stack = object.__new__(self.__class__)
+#			Scanner.__init__(self.stack,self.patterns,self.ignore,input,file,filename, stacked=True)
+
+			# Note that the pattern+ignore are added by the generated
+			# scanner code
+			self.stack = self.__class__(input,file,filename, stacked=True)
+
+	def get_pos(self):
+		"""Return a file/line/char tuple."""
+		if self.stack: return self.stack.get_pos()
+
+		return (self.filename, self.line+self.del_line, self.col)
+
+#	def __repr__(self):
+#		"""Print the last few tokens that have been scanned in"""
+#		output = ''
+#		for t in self.tokens:
+#			output += '%s\n' % (repr(t),)
+#		return output
+	
+	def print_line_with_pointer(self, pos, length=0, out=sys.stderr):
+		"""Print the line of 'text' that includes position 'p',
+		along with a second line with a single caret (^) at position p"""
+
+		file,line,p = pos
+		if file != self.filename:
+			if self.stack: return self.stack.print_line_with_pointer(pos,length=length,out=out)
+			print >>out, "(%s: not in input buffer)" % file
+			return
+
+		text = self.input
+		p += length-1 # starts at pos 1
+
+		origline=line
+		line -= self.del_line
+		spos=0
+		if line > 0:
+			while 1:
+				line = line - 1
+				try:
+					cr = text.index("\n",spos)
+				except ValueError:
+					if line:
+						text = ""
+					break
+				if line == 0:
+					text = text[spos:cr]
+					break
+				spos = cr+1
+		else:
+			print >>out, "(%s:%d not in input buffer)" % (file,origline)
+			return
+
+		# Now try printing part of the line
+		text = text[max(p-80, 0):p+80]
+		p = p - max(p-80, 0)
+
+		# Strip to the left
+		i = text[:p].rfind('\n')
+		j = text[:p].rfind('\r')
+		if i < 0 or (0 <= j < i): i = j
+		if 0 <= i < p:
+			p = p - i - 1
+			text = text[i+1:]
+
+		# Strip to the right
+		i = text.find('\n', p)
+		j = text.find('\r', p)
+		if i < 0 or (0 <= j < i): i = j
+		if i >= 0:
+			text = text[:i]
+
+		# Now shorten the text
+		while len(text) > 70 and p > 60:
+			# Cut off 10 chars
+			text = "..." + text[10:]
+			p = p - 7
+
+		# Now print the string, along with an indicator
+		print >>out, '> ',text
+		print >>out, '> ',' '*p + '^'
+	
+	def grab_input(self):
+		"""Get more input if possible."""
+		if not self.file: return
+		if len(self.input) - self.pos >= MIN_WINDOW: return
+
+		data = self.file.read(MIN_WINDOW)
+		if data is None or data == "":
+			self.file = None
+
+		# Drop bytes from the start, if necessary.
+		if self.pos > 2*MIN_WINDOW:
+			self.del_pos += MIN_WINDOW
+			self.del_line += self.input[:MIN_WINDOW].count("\n")
+			self.pos -= MIN_WINDOW
+			self.input = self.input[MIN_WINDOW:] + data
+		else:
+			self.input = self.input + data
+
+	def getchar(self):
+		"""Return the next character."""
+		self.grab_input()
+
+		c = self.input[self.pos]
+		self.pos += 1
+		return c
+
+	def token(self, restrict, context=None):
+		"""Scan for another token."""
+
+		while 1:
+			if self.stack:
+				try:
+					return self.stack.token(restrict, context)
+				except StopIteration:
+					self.stack = None
+
+		# Keep looking for a token, ignoring any in self.ignore
+			self.grab_input()
+
+			# special handling for end-of-file
+			if self.stacked and self.pos==len(self.input):
+				raise StopIteration
+
+			# Search the patterns for the longest match, with earlier
+			# tokens in the list having preference
+			best_match = -1
+			best_pat = '(error)'
+			best_m = None
+			for p, regexp in self.patterns:
+				# First check to see if we're ignoring this token
+				if restrict and p not in restrict and p not in self.ignore:
+					continue
+				m = regexp.match(self.input, self.pos)
+				if m and m.end()-m.start() > best_match:
+					# We got a match that's better than the previous one
+					best_pat = p
+					best_match = m.end()-m.start()
+					best_m = m
+					
+			# If we didn't find anything, raise an error
+			if best_pat == '(error)' and best_match < 0:
+				msg = 'Bad Token'
+				if restrict:
+					msg = 'Trying to find one of '+', '.join(restrict)
+				raise SyntaxError(self.get_pos(), msg, context=context)
+
+			ignore = best_pat in self.ignore
+			value = self.input[self.pos:self.pos+best_match]
+			if not ignore:
+				tok=Token(type=best_pat, value=value, pos=self.get_pos())
+
+			self.pos += best_match
+
+			npos = value.rfind("\n")
+			if npos > -1:
+				self.col = best_match-npos
+				self.line += value.count("\n")
+			else:
+				self.col += best_match
+
+			# If we found something that isn't to be ignored, return it
+			if not ignore:
+				if len(self.tokens) >= 10:
+					del self.tokens[0]
+				self.tokens.append(tok)
+				self.last_read_token = tok
+				# print repr(tok)
+				return tok
+			else:
+				ignore = self.ignore[best_pat]
+				if ignore:
+					ignore(self, best_m)
+
+	def peek(self, *types, **kw):
+		"""Returns the token type for lookahead; if there are any args
+		then the list of args is the set of token types to allow"""
+		context = kw.get("context",None)
+		if self.last_token is None:
+			self.last_types = types
+			self.last_token = self.token(types,context)
+		elif self.last_types:
+			for t in types:
+				if t not in self.last_types:
+					raise NotImplementedError("Unimplemented: restriction set changed")
+		return self.last_token.type
+		
+	def scan(self, type, **kw):
+		"""Returns the matched text, and moves to the next token"""
+		context = kw.get("context",None)
+
+		if self.last_token is None:
+			tok = self.token([type],context)
+		else:
+			if self.last_types and type not in self.last_types:
+				raise NotImplementedError("Unimplemented: restriction set changed")
+
+			tok = self.last_token
+			self.last_token = None
+		if tok.type != type:
+			if not self.last_types: self.last_types=[]
+			raise SyntaxError(tok.pos, 'Trying to find '+type+': '+ ', '.join(self.last_types)+", got "+tok.type, context=context)
+		return tok.value
+
+class Parser(object):
+	"""Base class for Yapps-generated parsers.
+
+	"""
+	
+	def __init__(self, scanner):
+		self._scanner = scanner
+		
+	def _stack(self, input="",file=None,filename=None):
+		"""Temporarily read from someplace else"""
+		self._scanner.stack_input(input,file,filename)
+		self._tok = None
+
+	def _peek(self, *types, **kw):
+		"""Returns the token type for lookahead; if there are any args
+		then the list of args is the set of token types to allow"""
+		return self._scanner.peek(*types, **kw)
+		
+	def _scan(self, type, **kw):
+		"""Returns the matched text, and moves to the next token"""
+		return self._scanner.scan(type, **kw)
+
+class Context(object):
+	"""Class to represent the parser's call stack.
+
+	Every rule creates a Context that links to its parent rule.  The
+	contexts can be used for debugging.
+
+	"""
+	
+	def __init__(self, parent, scanner, rule, args=()):
+		"""Create a new context.
+
+		Args:
+		parent: Context object or None
+		scanner: Scanner object
+		rule: string (name of the rule)
+		args: tuple listing parameters to the rule
+
+		"""
+		self.parent = parent
+		self.scanner = scanner
+		self.rule = rule
+		self.args = args
+		while scanner.stack: scanner = scanner.stack
+		self.token = scanner.last_read_token
+
+	def __str__(self):
+		output = ''
+		if self.parent: output = str(self.parent) + ' > '
+		output += self.rule
+		return output
+	
+def print_error(err, scanner, max_ctx=None):
+	"""Print error messages, the parser stack, and the input text -- for human-readable error messages."""
+	# NOTE: this function assumes 80 columns :-(
+	# Figure out the line number
+	pos = err.pos
+	if not pos:
+		pos = scanner.get_pos()
+
+	file_name, line_number, column_number = pos
+	print >>sys.stderr, '%s:%d:%d: %s' % (file_name, line_number, column_number, err.msg)
+
+	scanner.print_line_with_pointer(pos)
+		
+	context = err.context
+	token = None
+	while context:
+		print >>sys.stderr, 'while parsing %s%s:' % (context.rule, tuple(context.args))
+		if context.token:
+			token = context.token
+		if token:
+			scanner.print_line_with_pointer(token.pos, length=len(token.value))
+		context = context.parent
+		if max_ctx:
+			max_ctx = max_ctx-1
+			if not max_ctx:
+				break
+
+def wrap_error_reporter(parser, rule, *args,**kw):
+	try:
+		return getattr(parser, rule)(*args,**kw)
+	except SyntaxError, e:
+		print_error(e, parser._scanner)
+	except NoMoreTokens:
+		print >>sys.stderr, 'Could not complete parsing; stopped around here:'
+		print >>sys.stderr, parser._scanner