yapps2-2.1.1.orig/0000775000000000000000000000000010051117330013617 5ustar rootroot00000000000000yapps2-2.1.1.orig/ChangeLog0000644000000000000000000000730507723227430015413 0ustar rootroot000000000000002003-08-27 Amit Patel * *: (VERSION) Release 2.1.1 * *: Added a test/ directory for test cases; I had previously put tests in the examples/ directory, which is a bad place to put them. Examples are useful for learning how Yapps works. Tests are for testing specific features of Yapps. * parsetree.py (Plus.update): Fixed a long-standing bug in which the FOLLOW set of 'a'+ would include 'a'. In theory this makes no practical difference because the 'a'+ rule eats up all the 'a' tokens anyway. However, it makes error messages a little bit more confusing because they imply that an 'a' can follow. * yappsrt.py (print_error): Incorporated the context object into the printing of error messages. 2003-08-12 Amit Patel * *: (VERSION) Release 2.1.0 * parsetree.py: Improved error message generation. Instead of relying on the scanner to produce errors, the parser now checks things explicitly and produces errors directly. The parser has better knowledge of the context, so its error messages are more precise and helpful. * yapps_grammar.g: Instead of setting self.rule in the setup() method, pass it in the constructor. To make it available at construction time, pass it along as another attribute in the attribute grammar. 2003-08-11 Amit Patel * parsetree.py: Generated parsers now include a context object that describes the parse rule stack. For example, while parsing rule A, called from rule B, called from rule D, the context object will let you reconstruct the path D > B > A. [Thanks David Morley] * *: Removed all output when things are working properly; all warnings/errors now go to stderr. * yapps_grammar.g: Added support for A? meaning an optional A. This is equivalent to [A]. * yapps2.py: Design - refactored yapps2.py into yapps2.py + grammar.py + parsetree.py. grammar.py is automatically generated from grammar.g. Added lots of docstrings. 2003-08-09 Amit Patel * yapps2.py: Documentation - added doctest tests to some of the set algorithms in class Generator. * yapps2.py: Style - removed "import *" everywhere. * yapps2.py: Style - moved to Python 2 -- string methods, list comprehensions, inline syntax for apply 2003-07-28 Amit Patel * *: (VERSION) Release 2.0.4 * yappsrt.py: Style - replaced raising string exceptions with raising class exceptions. [Thanks Alex Verstak] * yappsrt.py: (SyntaxError) Bug fix - SyntaxError.__init__ should call Exception.__init__ * yapps2.py: Bug fix - identifiers in grammar rules that had digits in them were not accessible in the {{python code}} sections of the grammar. * yapps2.py: Style - changed "b >= a and b < c" to "a <= b < c" * yapps2.py: Style - change "`expr`" to "repr(expr)" 2002-08-00 Amit Patel * *: (VERSION) Release 2.0.3 * yapps2.py: Bug fix - inline tokens using the r"" syntax weren't treated properly. 2002-04-00 Amit Patel * *: (VERSION) Release 2.0.2 * yapps2.py: Bug fix - when generating the "else" clause, if the comment was too long, Yapps was not emitting a newline. [Thanks Steven Engelhardt] 2001-10-00 Amit Patel * *: (VERSION) Release 2.0.1 * yappsrt.py: (SyntaxError) Style - the exception classes now inherit from Exception. [Thanks Rich Salz] * yappsrt.py: (Scanner) Performance - instead of passing the set of tokens into the scanner at initialization time, we build the list at compile time. You can still override the default list per instance of the scanner, but in the common case, we don't have to rebuild the token list. [Thanks Amaury Forgeot d'Arc] yapps2-2.1.1.orig/LICENSE0000644000000000000000000000211107715752507014645 0ustar rootroot00000000000000 Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. yapps2-2.1.1.orig/NOTES0000644000000000000000000000571307716216375014465 0ustar rootroot00000000000000[Last updated August 11, 2003] Notes for myself: Document the LINENO trick Add a way to have a self-contained mode that doesn't require yappsrt? Add a debugging mode that helps you understand how the grammar is constructed and how things are being parsed Optimize (remove) unused variables Yapps produces a bunch of inline list literals. We should be able to instead create these lists as class variables (but this makes it harder to read the code). Also, 'A in X' could be written 'X.has_key(A)' if we can convert the lists into dictionaries ahead of time. Add a convenience to automatically gather up the values returned from subpatterns, put them into a list, and return them "Gather" mode that simply outputs the return values for certain nodes. For example, if you just want all expressions, you could ask yapps to gather the results of the 'expr' rule into a list. This would ignore all the higher level structure. Improve the documentation Write some larger examples (probably XML/HTML) EOF needs to be dealt with. It's probably a token that can match anywhere. Get rid of old-style regex support Use SRE's lex support to speed up lexing (this may be hard given that yapps allows for context-sensitive lexers) Look over Dan Connoly's experience with Yapps (bugs, frustrations, etc.) and see what improvements could be made Add something to pretty-print the grammar (without the actions) Maybe conditionals? Follow this rule only if holds. But this would be useful mainly when multiple rules match, and we want the first matching rule. The conditional would mean we skip to the next rule. Maybe this is part of the attribute grammar system, where rule X<0> can be specified separately from X. Convenience functions that could build return values for all rules without specifying the code for each rule individually Patterns (abstractions over rules) -- for example, comma separated values have a certain rule pattern that gets replicated all over the place These are rules that take other rules as parameters. rule list: {{ result = [] }} [ element {{ result.append(element) }} ( separator element {{ result.append(element) }} )* ] {{ return result }} Inheritance of parser and scanner classes. The base class (Parser) may define common tokens like ID, STR, NUM, space, comments, EOF, etc., and common rules/patterns like optional, sequence, delimiter-separated sequence. Why do A? and (A | ) produce different code? It seems that they should produce the very same code. Look at everyone's Yapps grammars, and come up with larger examples http://www.w3.org/2000/10/swap/SemEnglish.g http://www.w3.org/2000/10/swap/kifExpr.g http://www.w3.org/2000/10/swap/rdfn3.g Construct lots of erroneous grammars and see what Yapps does with them (improve error reporting) yapps2-2.1.1.orig/yapps2.py0000755000000000000000000000774707716230463015450 0ustar rootroot00000000000000#!/usr/bin/python2 # # Yapps 2 - yet another python parser system # Copyright 1999-2003 by Amit J. Patel # # 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 # or at # # import sys, re import yappsrt, parsetree def generate(inputfilename, outputfilename='', dump=0, **flags): """Generate a grammar, given an input filename (X.g) and an output filename (defaulting to X.py).""" if not outputfilename: if inputfilename.endswith('.g'): outputfilename = inputfilename[:-2] + '.py' else: raise Exception('Must specify output filename if input filename is not *.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) if preparser: scanner.first_line_number = 1 + preparser.count('\n') parser = grammar.ParserDescription(scanner) t = yappsrt.wrap_error_reporter(parser, 'Parser') if t is None: return # 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() if __name__ == '__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 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 grammar else: import grammar generate(*tuple(args), **flags) yapps2-2.1.1.orig/examples/0000775000000000000000000000000010051117330015435 5ustar rootroot00000000000000yapps2-2.1.1.orig/examples/calc.g0000644000000000000000000000466707715756645016561 0ustar rootroot00000000000000globalvars = {} # We will store the calculator's variables here def lookup(map, name): for x,v in map: if x == name: return v if not globalvars.has_key(name): print 'Undefined (defaulting to 0):', name return globalvars.get(name, 0) %% parser Calculator: ignore: "[ \r\t\n]+" token END: "$" token NUM: "[0-9]+" token VAR: "[a-zA-Z_]+" # Each line can either be an expression or an assignment statement rule goal: expr<<[]>> END {{ print '=', expr }} {{ return expr }} | "set" VAR expr<<[]>> END {{ globalvars[VAR] = expr }} {{ print VAR, '=', expr }} {{ return expr }} # An expression is the sum and difference of factors rule expr<>: factor<> {{ n = factor }} ( "[+]" factor<> {{ n = n+factor }} | "-" factor<> {{ n = n-factor }} )* {{ return n }} # A factor is the product and division of terms rule factor<>: term<> {{ v = term }} ( "[*]" term<> {{ v = v*term }} | "/" term<> {{ v = v/term }} )* {{ return v }} # A term is a number, variable, or an expression surrounded by parentheses rule term<>: NUM {{ return atoi(NUM) }} | VAR {{ return lookup(V, VAR) }} | "\\(" expr "\\)" {{ return expr }} | "let" VAR "=" expr<> {{ V = [(VAR, expr)] + V }} "in" expr<> {{ return expr }} %% if __name__=='__main__': print 'Welcome to the calculator sample for Yapps 2.' print ' Enter either "" or "set ",' print ' or just press return to exit. An expression can have' print ' local variables: let x = expr in expr' # We could have put this loop into the parser, by making the # `goal' rule use (expr | set var expr)*, but by putting the # loop into Python code, we can make it interactive (i.e., enter # one expression, get the result, enter another expression, etc.) while 1: try: s = raw_input('>>> ') except EOFError: break if not strip(s): break parse('goal', s) print 'Bye.' yapps2-2.1.1.orig/examples/expr.g0000644000000000000000000000162107714625576016615 0ustar rootroot00000000000000parser Calculator: token END: "$" token NUM: "[0-9]+" rule goal: expr END {{ return expr }} # An expression is the sum and difference of factors rule expr: factor {{ v = factor }} ( "[+]" factor {{ v = v+factor }} | "-" factor {{ v = v-factor }} )* {{ return v }} # A factor is the product and division of terms rule factor: term {{ v = term }} ( "[*]" term {{ v = v*term }} | "/" term {{ v = v/term }} )* {{ return v }} # A term is either a number or an expression surrounded by parentheses rule term: NUM {{ return atoi(NUM) }} | "\\(" expr "\\)" {{ return expr }} yapps2-2.1.1.orig/examples/lisp.g0000644000000000000000000000110607715756752016606 0ustar rootroot00000000000000parser Lisp: ignore: r'\s+' token NUM: r'[0-9]+' token ID: r'[-+*/!@$%^&=.a-zA-Z0-9_]+' token STR: r'"([^\\"]+|\\.)*"' rule expr: ID {{ return ('id',ID) }} | STR {{ return ('str',eval(STR)) }} | NUM {{ return ('num',int(NUM)) }} | r"\(" {{ e = [] }} # initialize the list ( expr {{ e.append(expr) }} ) * # put each expr into the list r"\)" {{ return e }} # return the list yapps2-2.1.1.orig/examples/xml.g0000644000000000000000000000465307723177063016440 0ustar rootroot00000000000000#!/usr/bin/python2 # xml.g # # Amit J. Patel, August 2003 # # Simple (non-conforming, non-validating) parsing of XML documents, # based on Robert D. Cameron's "REX" shallow parser. It doesn't # handle CDATA and lots of other stuff; it's meant to demonstrate # Yapps, not replace a proper XML parser. %% parser xml: token nodetext: r'[^<>]+' token attrtext_singlequote: "[^']*" token attrtext_doublequote: '[^"]*' token SP: r'\s' token id: r'[a-zA-Z_:][a-zA-Z0-9_:.-]*' rule node: r'' {{ return ['!--comment'] }} | r'' {{ return ['![CDATA['] }} | r']*>' {{ return ['!doctype'] }} | '<' SP* id SP* attributes SP* {{ startid = id }} ( '>' nodes '' {{ assert startid == id, 'Mismatched tags <%s> ... ' % (startid, id) }} {{ return [id, attributes] + nodes }} | '/\s*>' {{ return [id, attributes] }} ) | nodetext {{ return nodetext }} rule nodes: {{ result = [] }} ( node {{ result.append(node) }} ) * {{ return result }} rule attribute: id SP* '=' SP* ( '"' attrtext_doublequote '"' {{ return (id, attrtext_doublequote) }} | "'" attrtext_singlequote "'" {{ return (id, attrtext_singlequote) }} ) rule attributes: {{ result = {} }} ( attribute SP* {{ result[attribute[0]] = attribute[1] }} ) * {{ return result }} %% if __name__ == '__main__': tests = ['', 'some text', '< bad xml', '
', '< spacey a = "foo" / >', 'text ... ', ' middle ', ' foo bar ', ] print print '____Running tests_______________________________________' for test in tests: print try: parser = xml(xmlScanner(test)) output = '%s ==> %s' % (repr(test), repr(parser.node())) except (yappsrt.SyntaxError, AssertionError), e: output = '%s ==> FAILED ==> %s' % (repr(test), e) print output yapps2-2.1.1.orig/test/0000775000000000000000000000000010051117330014576 5ustar rootroot00000000000000yapps2-2.1.1.orig/test/empty_clauses.g0000644000000000000000000000040007723223433017631 0ustar rootroot00000000000000# This parser tests the use of OR clauses with one of them being empty # # The output of --dump should indicate the FOLLOW set for (A | ) is 'c'. parser Test: rule TestPlus: ( A | ) 'c' rule A: 'a'+ rule TestStar: ( B | ) 'c' rule B: 'b'*yapps2-2.1.1.orig/test/line_numbers.g0000644000000000000000000000031507723227500017442 0ustar rootroot00000000000000# # The error messages produced by Yapps have a line number. # The line number should take the Python code section into account. # The line number should be 10. %% parser error_1: this_is_an_error; yapps2-2.1.1.orig/test/option.g0000644000000000000000000000040507715761712016301 0ustar rootroot00000000000000 %% parser test_option: ignore: r'\s+' token a: 'a' token b: 'b' token EOF: r'$' rule test_brackets: a [b] EOF rule test_question_mark: a b? EOF %% # The generated code for test_brackets and test_question_mark should # be the same. yapps2-2.1.1.orig/changelog0000644000000000000000000004504110051117330015473 0ustar rootroot00000000000000 BitKeeper/etc/logging_ok 1.1 04/05/14 11:33:13 smurf@smurf.noris.de +1 -0 ChangeSet 1.4.1.1 04/05/14 11:33:13 smurf@linux.smurf.noris.de +2 -0 Added tex documentation from yapps-2.0.4. BitKeeper/etc/logging_ok 1.0 04/05/14 11:33:13 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/BitKeeper/etc/logging_ok yapps2.tex 1.1 04/05/14 11:33:10 smurf@smurf.noris.de +1225 -0 yapps2.tex 1.0 04/05/14 11:33:10 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/yapps2.tex ChangeSet 1.21 04/05/14 11:31:18 smurf@linux.smurf.noris.de +7 -0 Renamed the package to "yapps2". setup.py 1.2 04/05/14 11:31:17 smurf@smurf.noris.de +17 -2 Fixed name Updated long description debian/rules 1.2 04/05/14 11:31:17 smurf@smurf.noris.de +8 -8 rename: python-yapps => yapps2 debian/overrides.lintian 1.2 04/05/14 11:31:17 smurf@smurf.noris.de +1 -1 rename: python-yapps => yapps2 debian/dirs 1.2 04/05/14 11:31:17 smurf@smurf.noris.de +1 -1 rename: python-yapps => yapps2 debian/copyright 1.2 04/05/14 11:31:16 smurf@smurf.noris.de +11 -3 Added pointer to original source debian/control 1.4 04/05/14 11:31:16 smurf@smurf.noris.de +18 -10 rename: python-yapps => yapps2 debian/changelog 1.9 04/05/14 11:31:16 smurf@smurf.noris.de +13 -13 Cleanup ChangeSet 1.20 03/12/31 14:00:42 smurf@linux.smurf.noris.de +2 -0 require python-dev because of distutils debian/changelog 1.8 03/12/31 14:00:42 smurf@linux.smurf.noris.de +6 -0 Version 2.1.1-8 debian/control 1.3 03/12/31 14:00:40 smurf@smurf.noris.de +1 -1 require python-dev because of distutils ChangeSet 1.19 03/12/31 13:57:38 smurf@linux.smurf.noris.de +2 -0 Change yapps.py t exit 1 on failure to parse debian/changelog 1.7 03/12/31 13:57:38 smurf@linux.smurf.noris.de +6 -0 Version 2.1.1-7 yapps2.py 1.6 03/12/31 13:57:37 smurf@smurf.noris.de +3 -2 exit 1 on error ChangeSet 1.18 03/12/30 15:36:56 smurf@linux.smurf.noris.de +2 -0 Update to 3.6.1, use build-depends-indep. debian/changelog 1.6 03/12/30 15:36:56 smurf@linux.smurf.noris.de +6 -0 Version 2.1.1-6 debian/control 1.2 03/12/30 15:36:55 smurf@smurf.noris.de +2 -2 Update to 3.6.1, use build-depends-indep. ChangeSet 1.17 03/12/30 15:33:19 smurf@linux.smurf.noris.de +2 -0 Add some notes. debian/changelog 1.5 03/12/30 15:33:19 smurf@linux.smurf.noris.de +6 -0 Version 2.1.1-5 examples/notes 1.1 03/12/30 15:33:18 smurf@smurf.noris.de +44 -0 examples/notes 1.0 03/12/30 15:33:17 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/examples/notes ChangeSet 1.16 03/12/30 15:30:05 smurf@linux.smurf.noris.de +2 -0 Correctly report syntax errors without line number debian/changelog 1.4 03/12/30 15:30:05 smurf@linux.smurf.noris.de +6 -0 Version 2.1.1-4 yapps/runtime.py 1.11 03/12/30 15:30:04 smurf@smurf.noris.de +6 -2 Report syntax errors with no line number ChangeSet 1.15 03/12/30 14:02:37 smurf@linux.smurf.noris.de +2 -0 Repair ignored-pattern upcall. debian/changelog 1.3 03/12/30 14:02:37 smurf@linux.smurf.noris.de +6 -0 Version 2.1.1-3 yapps/runtime.py 1.10 03/12/30 14:02:36 smurf@smurf.noris.de +4 -2 Repair ignore upcall. ChangeSet 1.14 03/12/30 13:30:14 smurf@linux.smurf.noris.de +2 -0 runtime: fix error reporting debian/changelog 1.2 03/12/30 13:30:14 smurf@linux.smurf.noris.de +6 -0 Version 2.1.1-2 yapps/runtime.py 1.9 03/12/30 13:30:12 smurf@smurf.noris.de +9 -9 Fix error reporting ChangeSet 1.13 03/12/30 12:25:29 smurf@linux.smurf.noris.de +2 -0 replace runtime grammar yapps_grammar.g: delete shebang line, fix imports yapps_grammar.g 1.4 03/12/30 12:25:28 smurf@smurf.noris.de +1 -3 fix import delete shebang line yapps/grammar.py 1.11 03/12/30 12:25:28 smurf@smurf.noris.de +49 -66 replace runtime grammar ChangeSet 1.12 03/12/30 11:51:26 smurf@linux.smurf.noris.de +19 -0 D setup.py 1.1 03/12/30 11:51:25 smurf@smurf.noris.de +27 -0 debian/yapps.1 1.1 03/12/30 11:51:25 smurf@smurf.noris.de +58 -0 debian/rules 1.1 03/12/30 11:51:25 smurf@smurf.noris.de +91 -0 debian/overrides.lintian 1.1 03/12/30 11:51:25 smurf@smurf.noris.de +1 -0 setup.py 1.0 03/12/30 11:51:25 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/setup.py debian/yapps.1 1.0 03/12/30 11:51:25 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/debian/yapps.1 debian/rules 1.0 03/12/30 11:51:25 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/debian/rules debian/overrides.lintian 1.0 03/12/30 11:51:25 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/debian/overrides.lintian debian/overrides.linda 1.1 03/12/30 11:51:24 smurf@smurf.noris.de +3 -0 debian/exporter 1.1 03/12/30 11:51:24 smurf@smurf.noris.de +10 -0 debian/docs 1.1 03/12/30 11:51:24 smurf@smurf.noris.de +3 -0 debian/dirs 1.1 03/12/30 11:51:24 smurf@smurf.noris.de +5 -0 debian/copyright 1.1 03/12/30 11:51:24 smurf@smurf.noris.de +15 -0 debian/control 1.1 03/12/30 11:51:24 smurf@smurf.noris.de +19 -0 debian/compat 1.1 03/12/30 11:51:24 smurf@smurf.noris.de +1 -0 debian/README 1.1 03/12/30 11:51:24 smurf@smurf.noris.de +6 -0 yapps_grammar.g 1.3 03/12/30 11:51:24 smurf@smurf.noris.de +0 -1 Make the scanner context-sensitive. Works better. yapps2.py 1.5 03/12/30 11:51:24 smurf@smurf.noris.de +1 -1 Fix path yapps/runtime.py 1.8 03/12/30 11:51:24 smurf@smurf.noris.de +0 -1 Regularize header yapps/parsetree.py 1.7 03/12/30 11:51:24 smurf@smurf.noris.de +0 -2 Drop shebang line, this is not a program. yapps/grammar.py 1.10 03/12/30 11:51:24 smurf@smurf.noris.de +0 -2 Drop shebang line, this is not a program. debian/overrides.linda 1.0 03/12/30 11:51:24 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/debian/overrides.linda debian/exporter 1.0 03/12/30 11:51:24 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/debian/exporter debian/docs 1.0 03/12/30 11:51:24 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/debian/docs debian/dirs 1.0 03/12/30 11:51:24 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/debian/dirs debian/copyright 1.0 03/12/30 11:51:24 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/debian/copyright debian/control 1.0 03/12/30 11:51:24 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/debian/control debian/compat 1.0 03/12/30 11:51:24 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/debian/compat debian/README 1.0 03/12/30 11:51:24 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/debian/README debian/changelog 1.1 03/12/30 11:41:14 smurf@smurf.noris.de +15 -0 debian/changelog 1.0 03/12/30 11:41:14 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/debian/changelog BitKeeper/etc/ignore 1.12 03/12/30 11:40:56 smurf@smurf.noris.de +1 -0 added changelog ChangeSet 1.11 03/12/30 11:23:09 smurf@linux.smurf.noris.de +5 -0 Rewrote imports et al. to create+use a real "yapps" module yapps/__init__.py 1.1 03/12/30 11:23:08 smurf@smurf.noris.de +0 -0 yapps2.py 1.4 03/12/30 11:23:08 smurf@smurf.noris.de +3 -3 Refactor to use reasonable "yapps" module yapps/runtime.py 1.7 03/12/30 11:23:08 smurf@smurf.noris.de +0 -0 Rename: yappsrt.py -> yapps/runtime.py yapps/parsetree.py 1.6 03/12/30 11:23:08 smurf@smurf.noris.de +10 -10 Refactor to use reasonable "yapps" module Rename: parsetree.py -> yapps/parsetree.py yapps/__init__.py 1.0 03/12/30 11:23:08 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/yapps/__init__.py yapps/grammar.py 1.9 03/12/30 11:23:07 smurf@smurf.noris.de +16 -16 Refactor to use reasonable "yapps" module Rename: grammar.py -> yapps/grammar.py BitKeeper/etc/ignore 1.11 03/12/30 11:22:15 smurf@smurf.noris.de +4 -0 added build/* debian/python-yapps/* debian/*.debhelper debian/*.substvars ChangeSet 1.10 03/12/29 22:10:59 smurf@linux.smurf.noris.de +1 -0 Added context-insensitive-scanner end test to a couple of composite grammar statements. It's probably overkill to do that with all statements..? parsetree.py 1.5 03/12/29 22:10:58 smurf@smurf.noris.de +19 -5 Added context-insensitive-scanner end test to a couple of composite statements. It's probably overkill to do that with all statements..? ChangeSet 1.9 03/12/29 22:05:00 smurf@linux.smurf.noris.de +1 -0 yappsrt.py: Bugfix: stored token type yappsrt.py 1.6 03/12/29 22:04:59 smurf@smurf.noris.de +1 -1 Bugfix: stored token type ChangeSet 1.8 03/12/29 21:42:41 smurf@linux.smurf.noris.de +4 -0 Pass init arguments to the scanner Simplify stuff a bit yappsrt.py 1.5 03/12/29 21:42:40 smurf@smurf.noris.de +16 -8 Fix line counting simplify pattern length determination yapps2.py 1.3 03/12/29 21:42:40 smurf@smurf.noris.de +3 -2 Pass filename to scanner parsetree.py 1.4 03/12/29 21:42:40 smurf@smurf.noris.de +2 -2 Pass init arguments to the scanner grammar.py 1.8 03/12/29 21:42:40 smurf@smurf.noris.de +3 -2 Update for changed yapps2.py ChangeSet 1.7 03/12/29 20:37:55 smurf@linux.smurf.noris.de +6 -0 Cleanup ignored-symbol commands Fix including and error reporting yappsrt.py 1.4 03/12/29 20:37:54 smurf@smurf.noris.de +88 -52 cleanup ignored symbol handling refactor _scan and _peek: move to Scanner generate pseudo filenames for inline documents accept context for error handling yapps_grammar.g 1.2 03/12/29 20:37:54 smurf@smurf.noris.de +4 -1 Cleanup statements for ignored symbols yapps2.py 1.2 03/12/29 20:37:54 smurf@smurf.noris.de +1 -1 Setup line numbers correctly parsetree.py 1.3 03/12/29 20:37:54 smurf@smurf.noris.de +22 -6 Ignored-symbol handling extended Pass context to scanners grammar.py 1.7 03/12/29 20:37:54 smurf@smurf.noris.de +1 -1 Use a hash for ignored stuff examples/calc.g 1.3 03/12/29 20:37:54 smurf@smurf.noris.de +7 -4 Cleanup include handling: use an ignored token ChangeSet 1.6 03/12/29 18:16:19 smurf@linux.smurf.noris.de +6 -0 Reproduce current grammar file One problem with attribute remains. yapps_grammar.g 1.1 03/12/29 18:16:18 smurf@smurf.noris.de +120 -0 yappsrt.py 1.3 03/12/29 18:16:18 smurf@smurf.noris.de +5 -5 charpos => pos yapps_grammar.g 1.0 03/12/29 18:16:18 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/yapps_grammar.g BitKeeper/etc/ignore 1.10 03/12/29 18:15:23 smurf@smurf.noris.de +1 -0 added *.swp BitKeeper/etc/ignore 1.9 03/12/29 18:15:02 smurf@smurf.noris.de +1 -0 added yapps_grammar.py BitKeeper/deleted/.del-yapps_grammar.py~276aa227aa238250 1.4 03/12/29 18:14:35 smurf@smurf.noris.de +0 -0 Delete: yapps_grammar.py grammar.py 1.6 03/12/29 18:14:17 smurf@smurf.noris.de +0 -0 Rename: BitKeeper/deleted/.del-grammar.py~46b22024b3b85127 -> grammar.py BitKeeper/deleted/.del-grammar.py~46b22024b3b85127 1.5 03/12/29 18:13:11 smurf@smurf.noris.de +0 -0 Delete: grammar.py yapps_grammar.py 1.3 03/12/29 18:13:04 smurf@smurf.noris.de +0 -0 Rename: BitKeeper/deleted/.del-yapps_grammar.py~276aa227aa238250 -> yapps_grammar.py grammar.py 1.4 03/12/29 18:12:51 smurf@smurf.noris.de +0 -0 Rename: BitKeeper/deleted/.del-grammar.py~46b22024b3b85127 -> grammar.py BitKeeper/deleted/.del-grammar.py~46b22024b3b85127 1.3 03/12/29 18:12:30 smurf@smurf.noris.de +19 -20 Delete: grammar.py BitKeeper/etc/ignore 1.8 03/12/29 17:15:10 smurf@smurf.noris.de +3 -0 added *-stamp debian/files debian/tmp/* BitKeeper/etc/ignore 1.7 03/12/29 17:15:08 smurf@smurf.noris.de +3 -0 added *-stamp debian/files debian/tmp/* BitKeeper/etc/ignore 1.6 03/12/29 17:14:00 smurf@smurf.noris.de +3 -0 added *-stamp debian/files debian/tmp/* BitKeeper/triggers/post-commit.changelog 1.1 03/12/29 17:13:58 smurf@smurf.noris.de +3 -0 BitKeeper/triggers/post-commit.changelog 1.0 03/12/29 17:13:58 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/BitKeeper/triggers/post-commit.changelog BitKeeper/etc/logging_ok 1.1 03/12/29 17:13:41 smurf@smurf.noris.de +1 -0 ChangeSet 1.5 03/12/29 17:13:41 smurf@linux.smurf.noris.de +7 -0 Major enhancements: - Use a Token object - Allow incremental reading from a file - Allow stacking of inputs (#include, whatever) - Remember line numbers - Refactor print_line_with_error into the Scanner object BitKeeper/etc/logging_ok 1.0 03/12/29 17:13:41 smurf@smurf.noris.de +0 -0 BitKeeper file /usr/local/src/misc/yapps/BitKeeper/etc/logging_ok yappsrt.py 1.2 03/12/29 17:13:38 smurf@smurf.noris.de +219 -141 Major enhancements: - Use a Token object - Allow incremental reading from a file - Allow stacking of inputs (#include, whatever) - Remember line numbers - Refactor print_line_with_error into the Scanner object parsetree.py 1.2 03/12/29 17:13:38 smurf@smurf.noris.de +2 -2 don't pass pos explicitly grammar.py 1.2 03/12/29 17:13:38 smurf@smurf.noris.de +15 -19 Cleanup generated from non-available file! examples/calc.g 1.2 03/12/29 17:13:38 smurf@smurf.noris.de +5 -2 cleanup (strip, atoi) allow reading in of expressions via stacking (TEST) BitKeeper/etc/ignore 1.5 03/12/29 17:10:56 smurf@smurf.noris.de +1 -0 added *.pyc BitKeeper/etc/ignore 1.4 03/12/29 17:10:51 smurf@smurf.noris.de +1 -0 added test/*.py BitKeeper/etc/ignore 1.3 03/12/29 17:10:46 smurf@smurf.noris.de +1 -0 added examples/*.py BitKeeper/deleted/.del-yapps_grammar.py~276aa227aa238250 1.2 03/12/29 13:58:49 smurf@smurf.noris.de +0 -0 Delete: yapps_grammar.py ChangeSet 1.4 03/08/28 00:22:57 ?@smurf.noris.de +15 -0 Version 2.1.1 ChangeSet 1.3 03/08/28 00:22:57 ?@smurf.noris.de +1 -0 CVS-Ignore ChangeSet 1.2 03/12/29 12:56:52 smurf@smurf.noris.de +1 -0 Versionsnummern-Updateskript BitKeeper/etc/ignore 1.2 03/08/28 00:22:57 ?@smurf.noris.de +3 -0 added CVS .cvsignore CVSROOT ChangeSet 1.1 03/12/29 12:56:52 smurf@smurf.noris.de +2 -0 Initial repository create BitKeeper/triggers/pre-commit.upversion 1.1 03/12/29 12:56:52 smurf@smurf.noris.de +3 -0 BitKeeper/etc/ignore 1.1 03/12/29 12:56:52 smurf@smurf.noris.de +2 -0 BitKeeper/etc/config 1.1 03/12/29 12:56:52 smurf@smurf.noris.de +13 -0 ChangeSet 1.0 03/12/29 12:56:52 smurf@smurf.noris.de +0 -0 BitKeeper file /tmp/b.s.20059/ChangeSet BitKeeper/triggers/pre-commit.upversion 1.0 03/12/29 12:56:52 smurf@smurf.noris.de +0 -0 BitKeeper file /tmp/b.s.20059/BitKeeper/triggers/pre-commit.upversion BitKeeper/etc/ignore 1.0 03/12/29 12:56:52 smurf@smurf.noris.de +0 -0 BitKeeper file /tmp/b.s.20059/BitKeeper/etc/ignore BitKeeper/etc/config 1.0 03/12/29 12:56:52 smurf@smurf.noris.de +0 -0 BitKeeper file /tmp/b.s.20059/BitKeeper/etc/config yappsrt.py 1.1 03/08/27 23:12:19 ?@smurf.noris.de +296 -0 New:Version 2.1.1 yapps_grammar.py 1.1 03/08/28 00:22:32 ?@smurf.noris.de +234 -0 New:Version 2.1.1 yapps2.py 1.1 03/08/12 20:25:55 ?@smurf.noris.de +111 -0 New:Version 2.1.1 test/option.g 1.1 03/08/11 20:43:22 ?@smurf.noris.de +17 -0 New:Version 2.1.1 test/line_numbers.g 1.1 03/08/28 00:22:56 ?@smurf.noris.de +10 -0 New:Version 2.1.1 test/empty_clauses.g 1.1 03/08/27 23:48:11 ?@smurf.noris.de +10 -0 New:Version 2.1.1 parsetree.py 1.1 03/08/28 00:18:14 ?@smurf.noris.de +645 -0 New:Version 2.1.1 grammar.py 1.1 03/08/28 00:16:28 ?@smurf.noris.de +234 -0 New:Version 2.1.1 examples/xml.g 1.1 03/08/27 20:53:39 ?@smurf.noris.de +66 -0 New:Version 2.1.1 examples/lisp.g 1.1 03/08/11 20:18:18 ?@smurf.noris.de +13 -0 New:Version 2.1.1 examples/expr.g 1.1 03/08/08 06:47:58 ?@smurf.noris.de +21 -0 New:Version 2.1.1 examples/calc.g 1.1 03/08/11 20:17:09 ?@smurf.noris.de +58 -0 New:Version 2.1.1 NOTES 1.1 03/08/12 18:59:41 ?@smurf.noris.de +78 -0 New:Version 2.1.1 LICENSE 1.1 03/08/11 19:41:27 ?@smurf.noris.de +20 -0 New:Version 2.1.1 ChangeLog 1.1 03/08/28 00:22:16 ?@smurf.noris.de +108 -0 New:Version 2.1.1 yappsrt.py 1.0 03/08/27 23:12:19 ?@smurf.noris.de +0 -0 BitKeeper file /home/smurf/neu/yapps-2.1.1/yapps3/yappsrt.py yapps_grammar.py 1.0 03/08/28 00:22:32 ?@smurf.noris.de +0 -0 BitKeeper file /home/smurf/neu/yapps-2.1.1/yapps3/yapps_grammar.py yapps2.py 1.0 03/08/12 20:25:55 ?@smurf.noris.de +0 -0 BitKeeper file /home/smurf/neu/yapps-2.1.1/yapps3/yapps2.py test/option.g 1.0 03/08/11 20:43:22 ?@smurf.noris.de +0 -0 BitKeeper file /home/smurf/neu/yapps-2.1.1/yapps3/test/option.g test/line_numbers.g 1.0 03/08/28 00:22:56 ?@smurf.noris.de +0 -0 BitKeeper file /home/smurf/neu/yapps-2.1.1/yapps3/test/line_numbers.g test/empty_clauses.g 1.0 03/08/27 23:48:11 ?@smurf.noris.de +0 -0 BitKeeper file /home/smurf/neu/yapps-2.1.1/yapps3/test/empty_clauses.g parsetree.py 1.0 03/08/28 00:18:14 ?@smurf.noris.de +0 -0 BitKeeper file /home/smurf/neu/yapps-2.1.1/yapps3/parsetree.py grammar.py 1.0 03/08/28 00:16:28 ?@smurf.noris.de +0 -0 BitKeeper file /home/smurf/neu/yapps-2.1.1/yapps3/grammar.py examples/xml.g 1.0 03/08/27 20:53:39 ?@smurf.noris.de +0 -0 BitKeeper file /home/smurf/neu/yapps-2.1.1/yapps3/examples/xml.g examples/lisp.g 1.0 03/08/11 20:18:18 ?@smurf.noris.de +0 -0 BitKeeper file /home/smurf/neu/yapps-2.1.1/yapps3/examples/lisp.g examples/expr.g 1.0 03/08/08 06:47:58 ?@smurf.noris.de +0 -0 BitKeeper file /home/smurf/neu/yapps-2.1.1/yapps3/examples/expr.g examples/calc.g 1.0 03/08/11 20:17:09 ?@smurf.noris.de +0 -0 BitKeeper file /home/smurf/neu/yapps-2.1.1/yapps3/examples/calc.g NOTES 1.0 03/08/12 18:59:41 ?@smurf.noris.de +0 -0 BitKeeper file /home/smurf/neu/yapps-2.1.1/yapps3/NOTES LICENSE 1.0 03/08/11 19:41:27 ?@smurf.noris.de +0 -0 BitKeeper file /home/smurf/neu/yapps-2.1.1/yapps3/LICENSE ChangeLog 1.0 03/08/28 00:22:16 ?@smurf.noris.de +0 -0 BitKeeper file /home/smurf/neu/yapps-2.1.1/yapps3/ChangeLog yapps2-2.1.1.orig/doc/0000755000000000000000000000000010051117330014362 5ustar rootroot00000000000000yapps2-2.1.1.orig/doc/yapps2.tex0000644000000000000000000014403210051111126016323 0ustar rootroot00000000000000\documentclass[10pt]{article} \usepackage{palatino} \usepackage{html} \usepackage{color} \setlength{\headsep}{0in} \setlength{\headheight}{0in} \setlength{\textheight}{8.5in} \setlength{\textwidth}{5.9in} \setlength{\oddsidemargin}{0.25in} \definecolor{darkblue}{rgb}{0,0,0.6} \definecolor{darkerblue}{rgb}{0,0,0.3} %% \newcommand{\mysection}[1]{\section{\textcolor{darkblue}{#1}}} %% \newcommand{\mysubsection}[1]{\subsection{\textcolor{darkerblue}{#1}}} \newcommand{\mysection}[1]{\section{#1}} \newcommand{\mysubsection}[1]{\subsection{#1}} \bodytext{bgcolor=white text=black link=#004080 vlink=#006020} \newcommand{\first}{\textsc{first}} \newcommand{\follow}{\textsc{follow}} \begin{document} \begin{center} \hfill \begin{tabular}{c} {\Large The \emph{Yapps} Parser Generator System}\\ \verb|http://theory.stanford.edu/~amitp/Yapps/|\\ Version 2\\ \\ Amit J. Patel\\ \htmladdnormallink{http://www-cs-students.stanford.edu/~amitp/} {http://www-cs-students.stanford.edu/~amitp/} \end{tabular} \hfill \rule{0in}{0in} \end{center} \mysection{Introduction} \emph{Yapps} (\underline{Y}et \underline{A}nother \underline{P}ython \underline{P}arser \underline{S}ystem) is an easy to use parser generator that is written in Python and generates Python code. There are several parser generator systems already available for Python, including \texttt{PyLR, kjParsing, PyBison,} and \texttt{mcf.pars,} but I had different goals for my parser. Yapps is simple, is easy to use, and produces human-readable parsers. It is not the fastest or most powerful parser. Yapps is designed to be used when regular expressions are not enough and other parser systems are too much: situations where you may write your own recursive descent parser. Some unusual features of Yapps that may be of interest are: \begin{enumerate} \item Yapps produces recursive descent parsers that are readable by humans, as opposed to table-driven parsers that are difficult to read. A Yapps parser for a simple calculator looks similar to the one that Mark Lutz wrote by hand for \emph{Programming Python.} \item Yapps also allows for rules that accept parameters and pass arguments to be used while parsing subexpressions. Grammars that allow for arguments to be passed to subrules and for values to be passed back are often called \emph{attribute grammars.} In many cases parameterized rules can be used to perform actions at ``parse time'' that are usually delayed until later. For example, information about variable declarations can be passed into the rules that parse a procedure body, so that undefined variables can be detected at parse time. The types of defined variables can be used in parsing as well---for example, if the type of {\tt X} is known, we can determine whether {\tt X(1)} is an array reference or a function call. \item Yapps grammars are fairly easy to write, although there are some inconveniences having to do with ELL(1) parsing that have to be worked around. For example, rules have to be left factored and rules may not be left recursive. However, neither limitation seems to be a problem in practice. Yapps grammars look similar to the notation used in the Python reference manual, with operators like \verb:*:, \verb:+:, \verb:|:, \verb:[]:, and \verb:(): for patterns, names ({\tt tim}) for rules, regular expressions (\verb:"[a-z]+":) for tokens, and \verb:#: for comments. \item The Yapps parser generator is written as a single Python module with no C extensions. Yapps produces parsers that are written entirely in Python, and require only the Yapps run-time module (5k) for support. \item Yapps's scanner is context-sensitive, picking tokens based on the types of the tokens accepted by the parser. This can be helpful when implementing certain kinds of parsers, such as for a preprocessor. \end{enumerate} There are several disadvantages of using Yapps over another parser system: \begin{enumerate} \item Yapps parsers are \texttt{ELL(1)} (Extended LL(1)), which is less powerful than \texttt{LALR} (used by \texttt{PyLR}) or \texttt{SLR} (used by \texttt{kjParsing}), so Yapps would not be a good choice for parsing complex languages. For example, allowing both \texttt{x := 5;} and \texttt{x;} as statements is difficult because we must distinguish based on only one token of lookahead. Seeing only \texttt{x}, we cannot decide whether we have an assignment statement or an expression statement. (Note however that this kind of grammar can be matched with backtracking; see section \ref{sec:future}.) \item The scanner that Yapps provides can only read from strings, not files, so an entire file has to be read in before scanning can begin. It is possible to build a custom scanner, though, so in cases where stream input is needed (from the console, a network, or a large file are examples), the Yapps parser can be given a custom scanner that reads from a stream instead of a string. \item Yapps is not designed with efficiency in mind. \end{enumerate} Yapps provides an easy to use parser generator that produces parsers similar to what you might write by hand. It is not meant to be a solution for all parsing problems, but instead an aid for those times you would write a parser by hand rather than using one of the more powerful parsing packages available. Yapps 2.0 is easier to use than Yapps 1.0. New features include a less restrictive input syntax, which allows mixing of sequences, choices, terminals, and nonterminals; optional matching; the ability to insert single-line statements into the generated parser; and looping constructs \verb|*| and \verb|+| similar to the repetitive matching constructs in regular expressions. Unfortunately, the addition of these constructs has made Yapps 2.0 incompatible with Yapps 1.0, so grammars will have to be rewritten. See section \ref{sec:Upgrading} for tips on changing Yapps 1.0 grammars for use with Yapps 2.0. \mysection{Examples} In this section are several examples that show the use of Yapps. First, an introduction shows how to construct grammars and write them in Yapps form. This example can be skipped by someone familiar with grammars and parsing. Next is a Lisp expression grammar that produces a parse tree as output. This example demonstrates the use of tokens and rules, as well as returning values from rules. The third example is a expression evaluation grammar that evaluates during parsing (instead of producing a parse tree). \mysubsection{Introduction to Grammars} A \emph{grammar} for a natural language specifies how words can be put together to form large structures, such as phrases and sentences. A grammar for a computer language is similar in that it specifies how small components (called \emph{tokens}) can be put together to form larger structures. In this section we will write a grammar for a tiny subset of English. Simple English sentences can be described as being a noun phrase followed by a verb followed by a noun phrase. For example, in the sentence, ``Jack sank the blue ship,'' the word ``Jack'' is the first noun phrase, ``sank'' is the verb, and ``the blue ship'' is the second noun phrase. In addition we should say what a noun phrase is; for this example we shall say that a noun phrase is an optional article (a, an, the) followed by any number of adjectives followed by a noun. The tokens in our language are the articles, nouns, verbs, and adjectives. The \emph{rules} in our language will tell us how to combine the tokens together to form lists of adjectives, noun phrases, and sentences: \begin{itemize} \item \texttt{sentence: noun\_phrase verb noun\_phrase} \item \texttt{noun\_phrase: [article] adjective* noun} \end{itemize} Notice that some things that we said easily in English, such as ``optional article,'' are expressed using special syntax, such as brackets. When we said, ``any number of adjectives,'' we wrote \texttt{adjective*}, where the \texttt{*} means ``zero or more of the preceding pattern''. The grammar given above is close to a Yapps grammar. We also have to specify what the tokens are, and what to do when a pattern is matched. For this example, we will do nothing when patterns are matched; the next example will explain how to perform match actions. \begin{verbatim} parser TinyEnglish: ignore: "\\W+" token noun: "(Jack|spam|ship)" token verb: "(sank|threw)" token article: "(a|an|the)" token adjective: "(blue|red|green)" rule sentence: noun_phrase verb noun_phrase rule noun_phrase: [article] adjective* noun \end{verbatim} The tokens are specified as Python \emph{regular expressions}. Since Yapps produces Python code, you can write any regular expression that would be accepted by Python. (\emph{Note:} These are Python 1.5 regular expressions from the \texttt{re} module, not Python 1.4 regular expressions from the \texttt{regex} module.) In addition to tokens that you want to see (which are given names), you can also specify tokens to ignore, marked by the \texttt{ignore} keyword. In this parser we want to ignore whitespace. The TinyEnglish grammar shows how you define tokens and rules, but it does not specify what should happen once we've matched the rules. In the next example, we will take a grammar and produce a \emph{parse tree} from it. \mysubsection{Lisp Expressions} Lisp syntax, although hated by many, has a redeeming quality: it is simple to parse. In this section we will construct a Yapps grammar to parse Lisp expressions and produce a parse tree as output. \subsubsection*{Defining the Grammar} The syntax of Lisp is simple. It has expressions, which are identifiers, strings, numbers, and lists. A list is a left parenthesis followed by some number of expressions (separated by spaces) followed by a right parenthesis. For example, \verb|5|, \verb|"ni"|, and \verb|(print "1+2 = " (+ 1 2))| are Lisp expressions. Written as a grammar, \begin{verbatim} expr: ID | STR | NUM | list list: ( expr* ) \end{verbatim} In addition to having a grammar, we need to specify what to do every time something is matched. For the tokens, which are strings, we just want to get the ``value'' of the token, attach its type (identifier, string, or number) in some way, and return it. For the lists, we want to construct and return a Python list. Once some pattern is matched, we enclose a return statement enclosed in \verb|{{...}}|. The braces allow us to insert any one-line statement into the parser. Within this statement, we can refer to the values returned by matching each part of the rule. After matching a token such as \texttt{ID}, ``ID'' will be bound to the text of the matched token. Let's take a look at the rule: \begin{verbatim} rule expr: ID {{ return ('id', ID) }} ... \end{verbatim} In a rule, tokens return the text that was matched. For identifiers, we just return the identifier, along with a ``tag'' telling us that this is an identifier and not a string or some other value. Sometimes we may need to convert this text to a different form. For example, if a string is matched, we want to remove quotes and handle special forms like \verb|\n|. If a number is matched, we want to convert it into a number. Let's look at the return values for the other tokens: \begin{verbatim} ... | STR {{ return ('str', eval(STR)) }} | NUM {{ return ('num', atoi(NUM)) }} ... \end{verbatim} If we get a string, we want to remove the quotes and process any special backslash codes, so we run \texttt{eval} on the quoted string. If we get a number, we convert it to an integer with \texttt{atoi} and then return the number along with its type tag. For matching a list, we need to do something slightly more complicated. If we match a Lisp list of expressions, we want to create a Python list with those values. \begin{verbatim} rule list: "\\(" # Match the opening parenthesis {{ result = [] }} # Create a Python list ( expr # When we match an expression, {{ result.append(expr) }} # add it to the list )* # * means repeat this if needed "\\)" # Match the closing parenthesis {{ return result }} # Return the Python list \end{verbatim} In this rule we first match the opening parenthesis, then go into a loop. In this loop we match expressions and add them to the list. When there are no more expressions to match, we match the closing parenthesis and return the resulting. Note that \verb:#: is used for comments, just as in Python. The complete grammar is specified as follows: \begin{verbatim} parser Lisp: ignore: '\\s+' token NUM: '[0-9]+' token ID: '[-+*/!@%^&=.a-zA-Z0-9_]+' token STR: '"([^\\"]+|\\\\.)*"' rule expr: ID {{ return ('id', ID) }} | STR {{ return ('str', eval(STR)) }} | NUM {{ return ('num', atoi(NUM)) }} | list {{ return list }} rule list: "\\(" {{ result = [] }} ( expr {{ result.append(expr) }} )* "\\)" {{ return result }} \end{verbatim} One thing you may have noticed is that \verb|"\\("| and \verb|"\\)"| appear in the \texttt{list} rule. These are \emph{inline tokens}: they appear in the rules without being given a name with the \texttt{token} keyword. Inline tokens are more convenient to use, but since they do not have a name, the text that is matched cannot be used in the return value. They are best used for short simple patterns (usually punctuation or keywords). Another thing to notice is that the number and identifier tokens overlap. For example, ``487'' matches both NUM and ID. In Yapps, the scanner only tries to match tokens that are acceptable to the parser. This rule doesn't help here, since both NUM and ID can appear in the same place in the grammar. There are two rules used to pick tokens if more than one matches. One is that the \emph{longest} match is preferred. For example, ``487x'' will match as an ID (487x) rather than as a NUM (487) followed by an ID (x). The second rule is that if the two matches are the same length, the \emph{first} one listed in the grammar is preferred. For example, ``487'' will match as an NUM rather than an ID because NUM is listed first in the grammar. Inline tokens have preference over any tokens you have listed. Now that our grammar is defined, we can run Yapps to produce a parser, and then run the parser to produce a parse tree. \subsubsection*{Running Yapps} In the Yapps module is a function \texttt{generate} that takes an input filename and writes a parser to another file. We can use this function to generate the Lisp parser, which is assumed to be in \texttt{lisp.g}. \begin{verbatim} % python Python 1.5.1 (#1, Sep 3 1998, 22:51:17) [GCC 2.7.2.3] on linux-i386 Copyright 1991-1995 Stichting Mathematisch Centrum, Amsterdam >>> import yapps >>> yapps.generate('lisp.g') \end{verbatim} At this point, Yapps has written a file \texttt{lisp.py} that contains the parser. In that file are two classes (one scanner and one parser) and a function (called \texttt{parse}) that puts things together for you. Alternatively, we can run Yapps from the command line to generate the parser file: \begin{verbatim} % python yapps.py lisp.g \end{verbatim} After running Yapps either from within Python or from the command line, we can use the Lisp parser by calling the \texttt{parse} function. The first parameter should be the rule we want to match, and the second parameter should be the string to parse. \begin{verbatim} >>> import lisp >>> lisp.parse('expr', '(+ 3 4)') [('id', '+'), ('num', 3), ('num', 4)] >>> lisp.parse('expr', '(print "3 = " (+ 1 2))') [('id', 'print'), ('str', '3 = '), [('id', '+'), ('num', 1), ('num', 2)]] \end{verbatim} The \texttt{parse} function is not the only way to use the parser; section \ref{sec:Parser-Objects} describes how to access parser objects directly. We've now gone through the steps in creating a grammar, writing a grammar file for Yapps, producing a parser, and using the parser. In the next example we'll see how rules can take parameters and also how to do computations instead of just returning a parse tree. \mysubsection{Calculator} A common example parser given in many textbooks is that for simple expressions, with numbers, addition, subtraction, multiplication, division, and parenthesization of subexpressions. We'll write this example in Yapps, evaluating the expression as we parse. Unlike \texttt{yacc}, Yapps does not have any way to specify precedence rules, so we have to do it ourselves. We say that an expression is the sum of terms, and that a term is the product of factors, and that a factor is a number or a parenthesized expression: \begin{verbatim} expr: factor ( ("+"|"-") factor )* factor: term ( ("*"|"/") term )* term: NUM | "(" expr ")" \end{verbatim} In order to evaluate the expression as we go, we should keep along an accumulator while evaluating the lists of terms or factors. Just as we kept a ``result'' variable to build a parse tree for Lisp expressions, we will use a variable to evaluate numerical expressions. The full grammar is given below: \begin{verbatim} parser Calculator: token END: "$" # $ means end of string token NUM: "[0-9]+" rule goal: expr END {{ return expr }} # An expression is the sum and difference of factors rule expr: factor {{ v = factor }} ( "[+]" factor {{ v = v+factor }} | "-" factor {{ v = v-factor }} )* {{ return v }} # A factor is the product and division of terms rule factor: term {{ v = term }} ( "[*]" term {{ v = v*term }} | "/" term {{ v = v/term }} )* {{ return v }} # A term is either a number or an expression surrounded by parentheses rule term: NUM {{ return atoi(NUM) }} | "\\(" expr "\\)" {{ return expr }} \end{verbatim} The top-level rule is \emph{goal}, which says that we are looking for an expression followed by the end of the string. The \texttt{END} token is needed because without it, it isn't clear when to stop parsing. For example, the string ``1+3'' could be parsed either as the expression ``1'' followed by the string ``+3'' or it could be parsed as the expression ``1+3''. By requiring expressions to end with \texttt{END}, the parser is forced to take ``1+3''. In the two rules with repetition, the accumulator is named \texttt{v}. After reading in one expression, we initialize the accumulator. Each time through the loop, we modify the accumulator by adding, subtracting, multiplying by, or dividing the previous accumulator by the expression that has been parsed. At the end of the rule, we return the accumulator. The calculator example shows how to process lists of elements using loops, as well as how to handle precedence of operators. \emph{Note:} It's often important to put the \texttt{END} token in, so put it in unless you are sure that your grammar has some other non-ambiguous token marking the end of the program. \mysubsection{Calculator with Memory} In the previous example we learned how to write a calculator that evaluates simple numerical expressions. In this section we will extend the example to support both local and global variables. To support global variables, we will add assignment statements to the ``goal'' rule. \begin{verbatim} rule goal: expr END {{ return expr }} | 'set' ID expr END {{ global_vars[ID] = expr }} {{ return expr }} \end{verbatim} To use these variables, we need a new kind of terminal: \begin{verbatim} rule term: ... | ID {{ return global_vars[ID] }} \end{verbatim} So far, these changes are straightforward. We simply have a global dictionary \texttt{global\_vars} that stores the variables and values, we modify it when there is an assignment statement, and we look up variables in it when we see a variable name. To support local variables, we will add variable declarations to the set of allowed expressions. \begin{verbatim} rule term: ... | 'let' VAR '=' expr 'in' expr ... \end{verbatim} This is where it becomes tricky. Local variables should be stored in a local dictionary, not in the global one. One trick would be to save a copy of the global dictionary, modify it, and then restore it later. In this example we will instead use \emph{attributes} to create local information and pass it to subrules. A rule can optionally take parameters. When we invoke the rule, we must pass in arguments. For local variables, let's use a single parameter, \texttt{local\_vars}: \begin{verbatim} rule expr<>: ... rule factor<>: ... rule term<>: ... \end{verbatim} Each time we want to match \texttt{expr}, \texttt{factor}, or \texttt{term}, we will pass the local variables in the current rule to the subrule. One interesting case is when we pass as an argument something \emph{other} than \texttt{local\_vars}: \begin{verbatim} rule term<>: ... | 'let' VAR '=' expr<> {{ local_vars = [(VAR, expr)] + local_vars }} 'in' expr<> {{ return expr }} \end{verbatim} Note that the assignment to the local variables list does not modify the original list. This is important to keep local variables from being seen outside the ``let''. The other interesting case is when we find a variable: \begin{verbatim} global_vars = {} def lookup(map, name): for x,v in map: if x==name: return v return global_vars[name] %% ... rule term<: ... | VAR {{ return lookup(local_vars, VAR) }} \end{verbatim} The lookup function will search through the local variable list, and if it cannot find the name there, it will look it up in the global variable dictionary. A complete grammar for this example, including a read-eval-print loop for interacting with the calculator, can be found in the examples subdirectory included with Yapps. In this section we saw how to insert code before the parser. We also saw how to use attributes to transmit local information from one rule to its subrules. \mysection{Grammars} Each Yapps grammar has a name, a list of tokens, and a set of production rules. A grammar named \texttt{X} will be used to produce a parser named \texttt{X} and a scanner anmed \texttt{XScanner}. As in Python, names are case sensitive, start with a letter, and contain letters, numbers, and underscores (\_). There are three kinds of tokens in Yapps: named, inline, and ignored. As their name implies, named tokens are given a name, using the token construct: \texttt{token \emph{name} : \emph{regexp}}. In a rule, the token can be matched by using the name. Inline tokens are regular expressions that are used in rules without being declared. Ignored tokens are declared using the ignore construct: \texttt{ignore: \emph{regexp}}. These tokens are ignored by the scanner, and are not seen by the parser. Often whitespace is an ignored token. The regular expressions used to define tokens should use the syntax defined in the \texttt{re} module, so some symbols may have to be backslashed. Production rules in Yapps have a name and a pattern to match. If the rule is parameterized, the name should be followed by a list of parameter names in \verb|<<...>>|. A pattern can be a simple pattern or a compound pattern. Simple patterns are the name of a named token, a regular expression in quotes (inline token), the name of a production rule (followed by arguments in \verb|<<...>>|, if the rule has parameters), and single line Python statements (\verb|{{...}}|). Compound patterns are sequences (\verb|A B C ...|), choices ( \verb:A | B | C | ...:), options (\verb|[...]|), zero-or-more repetitions (\verb|...*|), and one-or-more repetitions (\verb|...+|). Like regular expressions, repetition operators have a higher precedence than sequences, and sequences have a higher precedence than choices. Whenever \verb|{{...}}| is used, a legal one-line Python statement should be put inside the braces. The token \verb|}}| should not appear within the \verb|{{...}}| section, even within a string, since Yapps does not attempt to parse the Python statement. A workaround for strings is to put two strings together (\verb|"}" "}"|), or to use backslashes (\verb|"}\}"|). At the end of a rule you should use a \verb|{{ return X }}| statement to return a value. However, you should \emph{not} use any control statements (\texttt{return}, \texttt{continue}, \texttt{break}) in the middle of a rule. Yapps needs to make assumptions about the control flow to generate a parser, and any changes to the control flow will confuse Yapps. The \verb|<<...>>| form can occur in two places: to define parameters to a rule and to give arguments when matching a rule. Parameters use the syntax used for Python functions, so they can include default arguments and the special forms (\verb|*args| and \verb|**kwargs|). Arguments use the syntax for Python function call arguments, so they can include normal arguments and keyword arguments. The token \verb|>>| should not appear within the \verb|<<...>>| section. In both the statements and rule arguments, you can use names defined by the parser to refer to matched patterns. You can refer to the text matched by a named token by using the token name. You can use the value returned by a production rule by using the name of that rule. If a name \texttt{X} is matched more than once (such as in loops), you will have to save the earlier value(s) in a temporary variable, and then use that temporary variable in the return value. The next section has an example of a name that occurs more than once. \mysubsection{Left Factoring} \label{sec:Left-Factoring} Yapps produces ELL(1) parsers, which determine which clause to match based on the first token available. Sometimes the leftmost tokens of several clauses may be the same. The classic example is the \emph{if/then/else} construct in Pascal: \begin{verbatim} rule stmt: "if" expr "then" stmt {{ then_part = stmt }} "else" stmt {{ return ('If',expr,then_part,stmt) }} | "if" expr "then" stmt {{ return ('If',expr,stmt,[]) }} \end{verbatim} (Note that we have to save the first \texttt{stmt} into a variable because there is another \texttt{stmt} that will be matched.) The left portions of the two clauses are the same, which presents a problem for the parser. The solution is \emph{left-factoring}: the common parts are put together, and \emph{then} a choice is made about the remaining part: \begin{verbatim} rule stmt: "if" expr "then" stmt {{ then_part = stmt }} {{ else_part = [] }} [ "else" stmt {{ else_part = stmt }} ] {{ return ('If', expr, then_part, else_part) }} \end{verbatim} Unfortunately, the classic \emph{if/then/else} situation is \emph{still} ambiguous when you left-factor. Yapps can deal with this situation, but will report a warning; see section \ref{sec:Ambiguous-Grammars} for details. In general, replace rules of the form: \begin{verbatim} rule A: a b1 {{ return E1 }} | a b2 {{ return E2 }} | c3 {{ return E3 }} | c4 {{ return E4 }} \end{verbatim} with rules of the form: \begin{verbatim} rule A: a ( b1 {{ return E1 }} | b2 {{ return E2 }} ) | c3 {{ return E3 }} | c4 {{ return E4 }} \end{verbatim} \mysubsection{Left Recursion} A common construct in grammars is for matching a list of patterns, sometimes separated with delimiters such as commas or semicolons. In LR-based parser systems, we can parse a list with something like this: \begin{verbatim} rule sum: NUM {{ return NUM }} | sum "+" NUM {{ return (sum, NUM) }} \end{verbatim} Parsing \texttt{1+2+3+4} would produce the output \texttt{(((1,2),3),4)}, which is what we want from a left-associative addition operator. Unfortunately, this grammar is \emph{left recursive,} because the \texttt{sum} rule contains a clause that begins with \texttt{sum}. (The recursion occurs at the left side of the clause.) We must restructure this grammar to be \emph{right recursive} instead: \begin{verbatim} rule sum: NUM {{ return NUM }} | NUM "+" sum {{ return (NUM, sum) }} \end{verbatim} Unfortunately, using this grammar, \texttt{1+2+3+4} would be parsed as \texttt{(1,(2,(3,4)))}, which no longer follows left associativity. The rule also needs to be left-factored. Instead, we write the pattern as a loop instead: \begin{verbatim} rule sum: NUM {{ v = NUM }} ( "[+]" NUM {{ v = (v,NUM) }} )* {{ return v }} \end{verbatim} In general, replace rules of the form: \begin{verbatim} rule A: A a1 -> << E1 >> | A a2 -> << E2 >> | b3 -> << E3 >> | b4 -> << E4 >> \end{verbatim} with rules of the form: \begin{verbatim} rule A: ( b3 {{ A = E3 }} | b4 {{ A = E4 }} ) ( a1 {{ A = E1 }} | a2 {{ A = E2 }} )* {{ return A }} \end{verbatim} We have taken a rule that proved problematic for with recursion and turned it into a rule that works well with looping constructs. \mysubsection{Ambiguous Grammars} \label{sec:Ambiguous-Grammars} In section \ref{sec:Left-Factoring} we saw the classic if/then/else ambiguity, which occurs because the ``else \ldots'' portion of an ``if \ldots then \ldots else \ldots'' construct is optional. Programs with nested if/then/else constructs can be ambiguous when one of the else clauses is missing: \begin{verbatim} if 1 then if 1 then if 5 then if 5 then x := 1; x := 1; else else y := 9; y := 9; \end{verbatim} The indentation shows that the program can be parsed in two different ways. (Of course, if we all would adopt Python's indentation-based structuring, this would never happen!) Usually we want the parsing on the left: the ``else'' should be associated with the closest ``if'' statement. In section \ref{sec:Left-Factoring} we ``solved'' the problem by using the following grammar: \begin{verbatim} rule stmt: "if" expr "then" stmt {{ then_part = stmt }} {{ else_part = [] }} [ "else" stmt {{ else_part = stmt }} ] {{ return ('If', expr, then_part, else_part) }} \end{verbatim} Here, we have an optional match of ``else'' followed by a statement. The ambiguity is that if an ``else'' is present, it is not clear whether you want it parsed immediately or if you want it to be parsed by the outer ``if''. Yapps will deal with the situation by matching when the else pattern when it can. The parser will work in this case because it prefers the \emph{first} matching clause, which tells Yapps to parse the ``else''. That is exactly what we want! For ambiguity cases with choices, Yapps will choose the \emph{first} matching choice. However, remember that Yapps only looks at the first token to determine its decision, so {\tt (a b | a c)} will result in Yapps choosing {\tt a b} even when the input is {\tt a c}. It only looks at the first token, {\tt a}, to make its decision. \mysection{Customization} Both the parsers and the scanners can be customized. The parser is usually extended by subclassing, and the scanner can either be subclassed or completely replaced. \mysubsection{Customizing Parsers} If additional fields and methods are needed in order for a parser to work, Python subclassing can be used. (This is unlike parser classes written in static languages, in which these fields and methods must be defined in the generated parser class.) We simply subclass the generated parser, and add any fields or methods required. Expressions in the grammar can call methods of the subclass to perform any actions that cannot be expressed as a simple expression. For example, consider this simple grammar: \begin{verbatim} parser X: rule goal: "something" {{ self.printmsg() }} \end{verbatim} The \texttt{printmsg} function need not be implemented in the parser class \texttt{X}; it can be implemented in a subclass: \begin{verbatim} import Xparser class MyX(Xparser.X): def printmsg(self): print "Hello!" \end{verbatim} \mysubsection{Customizing Scanners} The generated parser class is not dependent on the generated scanner class. A scanner object is passed to the parser object's constructor in the \texttt{parse} function. To use a different scanner, write your own function to construct parser objects, with an instance of a different scanner. Scanner objects must have a \texttt{token} method that accepts an integer \texttt{N} as well as a list of allowed token types, and returns the Nth token, as a tuple. The default scanner raises \texttt{NoMoreTokens} if no tokens are available, and \texttt{SyntaxError} if no token could be matched. However, the parser does not rely on these exceptions; only the \texttt{parse} convenience function (which calls \texttt{wrap\_error\_reporter}) and the \texttt{print\_error} error display function use those exceptions. The tuples representing tokens have four elements. The first two are the beginning and ending indices of the matched text in the input string. The third element is the type tag, matching either the name of a named token or the quoted regexp of an inline or ignored token. The fourth element of the token tuple is the matched text. If the input string is \texttt{s}, and the token tuple is \texttt{(b,e,type,val)}, then \texttt{val} should be equal to \texttt{s[b:e]}. The generated parsers do not the beginning or ending index. They use only the token type and value. However, the default error reporter uses the beginning and ending index to show the user where the error is. \mysection{Parser Mechanics} The base parser class (Parser) defines two methods, \texttt{\_scan} and \texttt{\_peek}, and two fields, \texttt{\_pos} and \texttt{\_scanner}. The generated parser inherits from the base parser, and contains one method for each rule in the grammar. To avoid name clashes, do not use names that begin with an underscore (\texttt{\_}). \mysubsection{Parser Objects} \label{sec:Parser-Objects} Yapps produces as output two exception classes, a scanner class, a parser class, and a function \texttt{parse} that puts everything together. The \texttt{parse} function does not have to be used; instead, one can create a parser and scanner object and use them together for parsing. \begin{verbatim} def parse(rule, text): P = X(XScanner(text)) return wrap_error_reporter(P, rule) \end{verbatim} The \texttt{parse} function takes a name of a rule and an input string as input. It creates a scanner and parser object, then calls \texttt{wrap\_error\_reporter} to execute the method in the parser object named \texttt{rule}. The wrapper function will call the appropriate parser rule and report any parsing errors to standard output. There are several situations in which the \texttt{parse} function would not be useful. If a different parser or scanner is being used, or exceptions are to be handled differently, a new \texttt{parse} function would be required. The supplied \texttt{parse} function can be used as a template for writing a function for your own needs. An example of a custom parse function is the \texttt{generate} function in \texttt{Yapps.py}. \mysubsection{Context Sensitive Scanner} Unlike most scanners, the scanner produced by Yapps can take into account the context in which tokens are needed, and try to match only good tokens. For example, in the grammar: \begin{verbatim} parser IniFile: token ID: "[a-zA-Z_0-9]+" token VAL: ".*" rule pair: ID "[ \t]*=[ \t]*" VAL "\n" \end{verbatim} we would like to scan lines of text and pick out a name/value pair. In a conventional scanner, the input string \texttt{shell=progman.exe} would be turned into a single token of type \texttt{VAL}. The Yapps scanner, however, knows that at the beginning of the line, an \texttt{ID} is expected, so it will return \texttt{"shell"} as a token of type \texttt{ID}. Later, it will return \texttt{"progman.exe"} as a token of type \texttt{VAL}. Context sensitivity decreases the separation between scanner and parser, but it is useful in parsers like \texttt{IniFile}, where the tokens themselves are not unambiguous, but \emph{are} unambiguous given a particular stage in the parsing process. Unfortunately, context sensitivity can make it more difficult to detect errors in the input. For example, in parsing a Pascal-like language with ``begin'' and ``end'' as keywords, a context sensitive scanner would only match ``end'' as the END token if the parser is in a place that will accept the END token. If not, then the scanner would match ``end'' as an identifier. To disable the context sensitive scanner in Yapps, add the \texttt{context-insensitive-scanner} option to the grammar: \begin{verbatim} Parser X: option: "context-insensitive-scanner" \end{verbatim} Context-insensitive scanning makes the parser look cleaner as well. \mysubsection{Internal Variables} There are two internal fields that may be of use. The parser object has two fields, \texttt{\_pos}, which is the index of the current token being matched, and \texttt{\_scanner}, which is the scanner object. The token itself can be retrieved by accessing the scanner object and calling the \texttt{token} method with the token index. However, if you call \texttt{token} before the token has been requested by the parser, it may mess up a context-sensitive scanner.\footnote{When using a context-sensitive scanner, the parser tells the scanner what the valid token types are at each point. If you call \texttt{token} before the parser can tell the scanner the valid token types, the scanner will attempt to match without considering the context.} A potentially useful combination of these fields is to extract the portion of the input matched by the current rule. To do this, just save the scanner state (\texttt{\_scanner.pos}) before the text is matched and then again after the text is matched: \begin{verbatim} rule R: {{ start = self._scanner.pos }} a b c {{ end = self._scanner.pos }} {{ print 'Text is', self._scanner.input[start:end] }} \end{verbatim} \mysubsection{Pre- and Post-Parser Code} Sometimes the parser code needs to rely on helper variables, functions, and classes. A Yapps grammar can optionally be surrounded by double percent signs, to separate the grammar from Python code. \begin{verbatim} ... Python code ... %% ... Yapps grammar ... %% ... Python code ... \end{verbatim} The second \verb|%%| can be omitted if there is no Python code at the end, and the first \verb|%%| can be omitted if there is no extra Python code at all. (To have code only at the end, both separators are required.) If the second \verb|%%| is omitted, Yapps will insert testing code that allows you to use the generated parser to parse a file. The extended calculator example in the Yapps examples subdirectory includes both pre-parser and post-parser code. \mysubsection{Representation of Grammars} For each kind of pattern there is a class derived from Pattern. Yapps has classes for Terminal, NonTerminal, Sequence, Choice, Option, Plus, Star, and Eval. Each of these classes has the following interface: \begin{itemize} \item[setup(\emph{gen})] Set accepts-$\epsilon$, and call \emph{gen.changed()} if it changed. This function can change the flag from false to true but \emph{not} from true to false. \item[update(\emph(gen))] Set \first and \follow, and call \emph{gen.changed()} if either changed. This function can add to the sets but \emph{not} remove from them. \item[output(\emph{gen}, \emph{indent})] Generate code for matching this rule, using \emph{indent} as the current indentation level. Writes are performed using \emph{gen.write}. \item[used(\emph{vars})] Given a list of variables \emph{vars}, return two lists: one containing the variables that are used, and one containing the variables that are assigned. This function is used for optimizing the resulting code. \end{itemize} Both \emph{setup} and \emph{update} monotonically increase the variables they modify. Since the variables can only increase a finite number of times, we can repeatedly call the function until the variable stabilized. The \emph{used} function is not currently implemented. With each pattern in the grammar Yapps associates three pieces of information: the \first set, the \follow set, and the accepts-$\epsilon$ flag. The \first set contains the tokens that can appear as we start matching the pattern. The \follow set contains the tokens that can appear immediately after we match the pattern. The accepts-$\epsilon$ flag is true if the pattern can match no tokens. In this case, \first will contain all the elements in \follow. The \follow set is not needed when accepts-$\epsilon$ is false, and may not be accurate in those cases. Yapps does not compute these sets precisely. Its approximation can miss certain cases, such as this one: \begin{verbatim} rule C: ( A* | B ) rule B: C [A] \end{verbatim} Yapps will calculate {\tt C}'s \follow set to include {\tt A}. However, {\tt C} will always match all the {\tt A}'s, so {\tt A} will never follow it. Yapps 2.0 does not properly handle this construct, but if it seems important, I may add support for it in a future version. Yapps also cannot handle constructs that depend on the calling sequence. For example: \begin{verbatim} rule R: U | 'b' rule S: | 'c' rule T: S 'b' rule U: S 'a' \end{verbatim} The \follow set for {\tt S} includes {\tt a} and {\tt b}. Since {\tt S} can be empty, the \first set for {\tt S} should include {\tt a}, {\tt b}, and {\tt c}. However, when parsing {\tt R}, if the lookahead is {\tt b} we should \emph{not} parse {\tt U}. That's because in {\tt U}, {\tt S} is followed by {\tt a} and not {\tt b}. Therefore in {\tt R}, we should choose rule {\tt U} only if there is an {\tt a} or {\tt c}, but not if there is a {\tt b}. Yapps and many other LL(1) systems do not distinguish {\tt S b} and {\tt S a}, making {\tt S}'s \follow set {\tt a, b}, and making {\tt R} always try to match {\tt U}. In this case we can solve the problem by changing {\tt R} to \verb:'b' | U: but it may not always be possible to solve all such problems in this way. \appendix \mysection{Grammar for Parsers} This is the grammar for parsers, without any Python code mixed in. The complete grammar can be found in \texttt{parsedesc.g} in the Yapps distribution. \begin{verbatim} parser ParserDescription: ignore: "\\s+" ignore: "#.*?\r?\n" token END: "$" # $ means end of string token ATTR: "<<.+?>>" token STMT: "{{.+?}}" token ID: '[a-zA-Z_][a-zA-Z_0-9]*' token STR: '[rR]?\'([^\\n\'\\\\]|\\\\.)*\'|[rR]?"([^\\n"\\\\]|\\\\.)*"' rule Parser: "parser" ID ":" Options Tokens Rules END rule Options: ( "option" ":" STR )* rule Tokens: ( "token" ID ":" STR | "ignore" ":" STR )* rule Rules: ( "rule" ID OptParam ":" ClauseA )* rule ClauseA: ClauseB ( '[|]' ClauseB )* rule ClauseB: ClauseC* rule ClauseC: ClauseD [ '[+]' | '[*]' ] rule ClauseD: STR | ID [ATTR] | STMT | '\\(' ClauseA '\\) | '\\[' ClauseA '\\]' \end{verbatim} \mysection{Upgrading} Yapps 2.0 is not backwards compatible with Yapps 1.0. In this section are some tips for upgrading: \begin{enumerate} \item Yapps 1.0 was distributed as a single file. Yapps 2.0 is instead distributed as two Python files: a \emph{parser generator} (26k) and a \emph{parser runtime} (5k). You need both files to create parsers, but you need only the runtime (\texttt{yappsrt.py}) to use the parsers. \item Yapps 1.0 supported Python 1.4 regular expressions from the \texttt{regex} module. Yapps 2.0 uses Python 1.5 regular expressions from the \texttt{re} module. \emph{The new syntax for regular expressions is not compatible with the old syntax.} Andrew Kuchling has a \htmladdnormallink{guide to converting regular expressions}{http://www.python.org/doc/howto/regex-to-re/} on his web page. \item Yapps 1.0 wants a pattern and then a return value in \verb|->| \verb|<<...>>|. Yapps 2.0 allows patterns and Python statements to be mixed. To convert a rule like this: \begin{verbatim} rule R: A B C -> << E1 >> | X Y Z -> << E2 >> \end{verbatim} to Yapps 2.0 form, replace the return value specifiers with return statements: \begin{verbatim} rule R: A B C {{ return E1 }} | X Y Z {{ return E2 }} \end{verbatim} \item Yapps 2.0 does not perform tail recursion elimination. This means any recursive rules you write will be turned into recursive methods in the parser. The parser will work, but may be slower. It can be made faster by rewriting recursive rules, using instead the looping operators \verb|*| and \verb|+| provided in Yapps 2.0. \end{enumerate} \mysection{Troubleshooting} \begin{itemize} \item A common error is to write a grammar that doesn't have an END token. End tokens are needed when it is not clear when to stop parsing. For example, when parsing the expression {\tt 3+5}, it is not clear after reading {\tt 3} whether to treat it as a complete expression or whether the parser should continue reading. Therefore the grammar for numeric expressions should include an end token. Another example is the grammar for Lisp expressions. In Lisp, it is always clear when you should stop parsing, so you do \emph{not} need an end token. In fact, it may be more useful not to have an end token, so that you can read in several Lisp expressions. \item If there is a chance of ambiguity, make sure to put the choices in the order you want them checked. Usually the most specific choice should be first. Empty sequences should usually be last. \item The context sensitive scanner is not appropriate for all grammars. You might try using the insensitive scanner with the {\tt context-insensitive-scanner} option in the grammar. \item If performance turns out to be a problem, try writing a custom scanner. The Yapps scanner is rather slow (but flexible and easy to understand). \end{itemize} \mysection{History} Yapps 1 had several limitations that bothered me while writing parsers: \begin{enumerate} \item It was not possible to insert statements into the generated parser. A common workaround was to write an auxilliary function that executed those statements, and to call that function as part of the return value calculation. For example, several of my parsers had an ``append(x,y)'' function that existed solely to call ``x.append(y)''. \item The way in which grammars were specified was rather restrictive: a rule was a choice of clauses. Each clause was a sequence of tokens and rule names, followed by a return value. \item Optional matching had to be put into a separate rule because choices were only made at the beginning of a rule. \item Repetition had to be specified in terms of recursion. Not only was this awkward (sometimes requiring additional rules), I had to add a tail recursion optimization to Yapps to transform the recursion back into a loop. \end{enumerate} Yapps 2 addresses each of these limitations. \begin{enumerate} \item Statements can occur anywhere within a rule. (However, only one-line statements are allowed; multiline blocks marked by indentation are not.) \item Grammars can be specified using any mix of sequences, choices, tokens, and rule names. To allow for complex structures, parentheses can be used for grouping. \item Given choices and parenthesization, optional matching can be expressed as a choice between some pattern and nothing. In addition, Yapps 2 has the convenience syntax \verb|[A B ...]| for matching \verb|A B ...| optionally. \item Repetition operators \verb|*| for zero or more and \verb|+| for one or more make it easy to specify repeating patterns. \end{enumerate} It is my hope that Yapps 2 will be flexible enough to meet my needs for another year, yet simple enough that I do not hesitate to use it. \mysection{Future Extensions} \label{sec:future} I am still investigating the possibility of LL(2) and higher lookahead. However, it looks like the resulting parsers will be somewhat ugly. It would be nice to control choices with user-defined predicates. The most likely future extension is backtracking. A grammar pattern like \verb|(VAR ':=' expr)? {{ return Assign(VAR,expr) }} : expr {{ return expr }}| would turn into code that attempted to match \verb|VAR ':=' expr|. If it succeeded, it would run \verb|{{ return ... }}|. If it failed, it would match \verb|expr {{ return expr }}|. Backtracking may make it less necessary to write LL(2) grammars. \mysection{References} \begin{enumerate} \item The \htmladdnormallink{Python-Parser SIG}{http://www.python.org/sigs/parser-sig/} is the first place to look for a list of parser systems for Python. \item ANTLR/PCCTS, by Terrence Parr, is available at \htmladdnormallink{The ANTLR Home Page}{http://www.antlr.org/}. \item PyLR, by Scott Cotton, is at \htmladdnormallink{his Starship page}{http://starship.skyport.net/crew/scott/PyLR.html}. \item John Aycock's \htmladdnormallink{Compiling Little Languages Framework}{http://www.foretec.com/python/workshops/1998-11/proceedings/papers/aycock-little/aycock-little.html}. \item PyBison, by Scott Hassan, can be found at \htmladdnormallink{his Python Projects page}{http://coho.stanford.edu/\~{}hassan/Python/}. \item mcf.pars, by Mike C. Fletcher, is available at \htmladdnormallink{his web page}{http://members.rogers.com/mcfletch/programming/simpleparse/simpleparse.html}. \item kwParsing, by Aaron Watters, is available at \htmladdnormallink{his Starship page}{http://starship.skyport.net/crew/aaron_watters/kwParsing/}. \end{enumerate} \end{document} yapps2-2.1.1.orig/yapps/0000755000000000000000000000000010051117330014751 5ustar rootroot00000000000000yapps2-2.1.1.orig/yapps/runtime.py0000644000000000000000000002502407723217263017033 0ustar rootroot00000000000000# # Yapps 2 Runtime, part of Yapps 2 - yet another python parser system # Copyright 1999-2003 by Amit J. Patel # # 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 # or at # # """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 class SyntaxError(Exception): """When we run into an unexpected token, this is the exception to use""" def __init__(self, charpos=-1, msg="Bad Token", context=None): Exception.__init__(self) self.charpos = charpos self.msg = msg self.context = context def __str__(self): if self.charpos < 0: return 'SyntaxError' else: return 'SyntaxError@char%s(%s)' % (repr(self.charpos), self.msg) class NoMoreTokens(Exception): """Another exception object, for when we run out of tokens""" pass class Scanner: """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): """Initialize the scanner. Parameters: patterns : [(terminal, uncompiled regex), ...] or None ignore : [terminal,...] 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. """ self.tokens = [] # [(begin char pos, end char pos, token name, matched text), ...] self.restrictions = [] self.input = input self.pos = 0 self.ignore = ignore self.first_line_number = 1 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 get_token_pos(self): """Get the current token position in the input text.""" return len(self.tokens) def get_char_pos(self): """Get the current char position in the input text.""" return self.pos def get_prev_char_pos(self, i=None): """Get the previous position (one token back) in the input text.""" if self.pos == 0: return 0 if i is None: i = -1 return self.tokens[i][0] def get_line_number(self): """Get the line number of the current position in the input text.""" # TODO: make this work at any token/char position return self.first_line_number + self.get_input_scanned().count('\n') def get_column_number(self): """Get the column number of the current position in the input text.""" s = self.get_input_scanned() i = s.rfind('\n') # may be -1, but that's okay in this case return len(s) - (i+1) def get_input_scanned(self): """Get the portion of the input that has been tokenized.""" return self.input[:self.pos] def get_input_unscanned(self): """Get the portion of the input that has not yet been tokenized.""" return self.input[self.pos:] def token(self, i, restrict=None): """Get the i'th token in the input. If i is one past the end, then scan for another token. Args: restrict : [token, ...] or None; if restrict is None, then any token is allowed. You may call token(i) more than once. However, the restrict set may never be larger than what was passed in on the first call to token(i). """ if i == len(self.tokens): self.scan(restrict) if i < len(self.tokens): # Make sure the restriction is more restricted. This # invariant is needed to avoid ruining tokenization at # position i+1 and higher. if restrict and self.restrictions[i]: for r in restrict: if r not in self.restrictions[i]: raise NotImplementedError("Unimplemented: restriction set changed") return self.tokens[i] raise NoMoreTokens() def __repr__(self): """Print the last 10 tokens that have been scanned in""" output = '' for t in self.tokens[-10:]: output = '%s\n (@%s) %s = %s' % (output,t[0],t[2],repr(t[3])) return output def scan(self, restrict): """Should scan another token and add it to the list, self.tokens, and add the restriction to self.restrictions""" # Keep looking for a token, ignoring any in self.ignore while 1: # Search the patterns for the longest match, with earlier # tokens in the list having preference best_match = -1 best_pat = '(error)' 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 len(m.group(0)) > best_match: # We got a match that's better than the previous one best_pat = p best_match = len(m.group(0)) # 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.pos, msg) # If we found something that isn't to be ignored, return it if best_pat not in self.ignore: # Create a token with this data token = (self.pos, self.pos+best_match, best_pat, self.input[self.pos:self.pos+best_match]) self.pos = self.pos + best_match # Only add this token if it's not in the list # (to prevent looping) if not self.tokens or token != self.tokens[-1]: self.tokens.append(token) self.restrictions.append(restrict) return else: # This token should be ignored .. self.pos = self.pos + best_match class Parser: """Base class for Yapps-generated parsers. """ def __init__(self, scanner): self._scanner = scanner self._pos = 0 def _peek(self, *types): """Returns the token type for lookahead; if there are any args then the list of args is the set of token types to allow""" tok = self._scanner.token(self._pos, types) return tok[2] def _scan(self, type): """Returns the matched text, and moves to the next token""" tok = self._scanner.token(self._pos, [type]) if tok[2] != type: raise SyntaxError(tok[0], 'Trying to find '+type+' :'+ ' ,'.join(self._scanner.restrictions[self._pos])) self._pos = 1 + self._pos return tok[3] class Context: """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, tokenpos, rule, args=()): """Create a new context. Args: parent: Context object or None scanner: Scanner object pos: integer (scanner token position) rule: string (name of the rule) args: tuple listing parameters to the rule """ self.parent = parent self.scanner = scanner self.tokenpos = tokenpos self.rule = rule self.args = args def __str__(self): output = '' if self.parent: output = str(self.parent) + ' > ' output += self.rule return output def print_line_with_pointer(text, p): """Print the line of 'text' that includes position 'p', along with a second line with a single caret (^) at position p""" # 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 >>sys.stderr, '> ',text print >>sys.stderr, '> ',' '*p + '^' def print_error(input, err, scanner): """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 line_number = scanner.get_line_number() column_number = scanner.get_column_number() print >>sys.stderr, '%d:%d: %s' % (line_number, column_number, err.msg) context = err.context if not context: print_line_with_pointer(input, err.charpos) while context: # TODO: add line number print >>sys.stderr, 'while parsing %s%s:' % (context.rule, tuple(context.args)) print_line_with_pointer(input, context.scanner.get_prev_char_pos(context.tokenpos)) context = context.parent def wrap_error_reporter(parser, rule): try: return getattr(parser, rule)() except SyntaxError, e: input = parser._scanner.input print_error(input, e, parser._scanner) except NoMoreTokens: print >>sys.stderr, 'Could not complete parsing; stopped around here:' print >>sys.stderr, parser._scanner yapps2-2.1.1.orig/yapps/parsetree.py0000644000000000000000000005432407723227046017347 0ustar rootroot00000000000000#!/usr/bin/python2 # # parsetree.py, part of Yapps 2 - yet another python parser system # Copyright 1999-2003 by Amit J. Patel # # 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 # or at # # """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 self.terminals = [] # List of token names (to maintain ordering) for n, t in tokens: if n == '#ignore': n = t self.ignore.append(n) 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 = '' return 'self._peek(%s)' % 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 generate_output(self): self.calculate() self.write(self.preparser) self.write("# Begin -- grammar generated by Yapps\n") self.write("import sys, re\n") self.write("import yappsrt\n") self.write("\n") self.write("class ", self.name, "Scanner(yappsrt.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):\n") self.write(" yappsrt.Scanner.__init__(self,None,%s,str)\n" % repr(self.ignore)) self.write("\n") self.write("class ", self.name, "(yappsrt.Parser):\n") self.write(INDENT, "Context = yappsrt.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, self._pos, %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 yappsrt.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: []'\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)\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 yappsrt.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) 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)) 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 # TODO: do we need to do this only when it's a context-insensitive scanner? gen.write(indent, "if %s:\n" % gen.not_peek_test(gen.non_ignored_tokens(), self.follow)) gen.write(indent+INDENT, "raise yappsrt.SyntaxError(charpos=self._scanner.get_prev_char_pos(), context=_context, msg='Need one of ' + ', '.join(%s))\n" % repr(self.first)) yapps2-2.1.1.orig/yapps/grammar.py0000644000000000000000000002266007723226674017007 0ustar rootroot00000000000000#!/usr/bin/python2 # # grammar.py, part of Yapps 2 - yet another python parser system # Copyright 1999-2003 by Amit J. Patel # # 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 # or at # # """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 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 import yappsrt class ParserDescriptionScanner(yappsrt.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): yappsrt.Scanner.__init__(self,None,['[ \t\r\n]+', '#.*?\r?\n'],str) class ParserDescription(yappsrt.Parser): Context = yappsrt.Context def LINENO(self, _parent=None): _context = self.Context(_parent, self._scanner, self._pos, 'LINENO', []) return 1 + self._scanner.get_input_scanned().count('\n') def Parser(self, _parent=None): _context = self.Context(_parent, self._scanner, self._pos, 'Parser', []) self._scan('"parser"') ID = self._scan('ID') self._scan('":"') Options = self.Options(_context) Tokens = self.Tokens(_context) Rules = self.Rules(Tokens, _context) EOF = self._scan('EOF') return parsetree.Generator(ID,Options,Tokens,Rules) def Options(self, _parent=None): _context = self.Context(_parent, self._scanner, self._pos, 'Options', []) opt = {} while self._peek() == '"option"': self._scan('"option"') self._scan('":"') Str = self.Str(_context) opt[Str] = 1 if self._peek() not in ['"option"', '"token"', '"ignore"', 'EOF', '"rule"']: raise yappsrt.SyntaxError(charpos=self._scanner.get_prev_char_pos(), context=_context, msg='Need one of ' + ', '.join(['"option"', '"token"', '"ignore"', 'EOF', '"rule"'])) return opt def Tokens(self, _parent=None): _context = self.Context(_parent, self._scanner, self._pos, 'Tokens', []) tok = [] while self._peek() in ['"token"', '"ignore"']: _token = self._peek() if _token == '"token"': self._scan('"token"') ID = self._scan('ID') self._scan('":"') Str = self.Str(_context) tok.append( (ID,Str) ) elif _token == '"ignore"': self._scan('"ignore"') self._scan('":"') Str = self.Str(_context) tok.append( ('#ignore',Str) ) else: raise yappsrt.SyntaxError(_token[0], 'Could not match Tokens') if self._peek() not in ['"token"', '"ignore"', 'EOF', '"rule"']: raise yappsrt.SyntaxError(charpos=self._scanner.get_prev_char_pos(), context=_context, msg='Need one of ' + ', '.join(['"token"', '"ignore"', 'EOF', '"rule"'])) return tok def Rules(self, tokens, _parent=None): _context = self.Context(_parent, self._scanner, self._pos, 'Rules', [tokens]) rul = [] while self._peek() == '"rule"': LINENO = self.LINENO(_context) self._scan('"rule"') ID = self._scan('ID') OptParam = self.OptParam(_context) self._scan('":"') ClauseA = self.ClauseA(ID, tokens, _context) rul.append( (ID, OptParam, ClauseA) ) if self._peek() not in ['"rule"', 'EOF']: raise yappsrt.SyntaxError(charpos=self._scanner.get_prev_char_pos(), context=_context, msg='Need one of ' + ', '.join(['"rule"', 'EOF'])) return rul def ClauseA(self, rule, tokens, _parent=None): _context = self.Context(_parent, self._scanner, self._pos, 'ClauseA', [rule, tokens]) ClauseB = self.ClauseB(rule, tokens, _context) v = [ClauseB] while self._peek() == 'OR': OR = self._scan('OR') ClauseB = self.ClauseB(rule, tokens, _context) v.append(ClauseB) if self._peek() not in ['OR', 'RP', 'RB', '"rule"', 'EOF']: raise yappsrt.SyntaxError(charpos=self._scanner.get_prev_char_pos(), context=_context, msg='Need one of ' + ', '.join(['OR', 'RP', 'RB', '"rule"', 'EOF'])) return cleanup_choice(rule, v) def ClauseB(self, rule, tokens, _parent=None): _context = self.Context(_parent, self._scanner, self._pos, 'ClauseB', [rule, tokens]) v = [] while self._peek() in ['STR', 'ID', 'LP', 'LB', 'STMT']: ClauseC = self.ClauseC(rule, tokens, _context) v.append(ClauseC) if self._peek() not in ['STR', 'ID', 'LP', 'LB', 'STMT', 'OR', 'RP', 'RB', '"rule"', 'EOF']: raise yappsrt.SyntaxError(charpos=self._scanner.get_prev_char_pos(), context=_context, msg='Need one of ' + ', '.join(['STR', 'ID', 'LP', 'LB', 'STMT', 'OR', 'RP', 'RB', '"rule"', 'EOF'])) return cleanup_sequence(rule, v) def ClauseC(self, rule, tokens, _parent=None): _context = self.Context(_parent, self._scanner, self._pos, 'ClauseC', [rule, tokens]) ClauseD = self.ClauseD(rule, tokens, _context) _token = self._peek() if _token == 'PLUS': PLUS = self._scan('PLUS') return parsetree.Plus(rule, ClauseD) elif _token == 'STAR': STAR = self._scan('STAR') return parsetree.Star(rule, ClauseD) elif _token == 'QUEST': QUEST = self._scan('QUEST') return parsetree.Option(rule, ClauseD) elif _token not in ['"ignore"', '"token"', '"option"', '":"', '"parser"', 'ATTR', 'COLON']: return ClauseD else: raise yappsrt.SyntaxError(_token[0], 'Could not match ClauseC') def ClauseD(self, rule, tokens, _parent=None): _context = self.Context(_parent, self._scanner, self._pos, 'ClauseD', [rule, tokens]) _token = self._peek() if _token == 'STR': STR = self._scan('STR') 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') OptParam = self.OptParam(_context) return resolve_name(rule, tokens, ID, OptParam) elif _token == 'LP': LP = self._scan('LP') ClauseA = self.ClauseA(rule, tokens, _context) RP = self._scan('RP') return ClauseA elif _token == 'LB': LB = self._scan('LB') ClauseA = self.ClauseA(rule, tokens, _context) RB = self._scan('RB') return parsetree.Option(rule, ClauseA) elif _token == 'STMT': STMT = self._scan('STMT') return parsetree.Eval(rule, STMT[2:-2]) else: raise yappsrt.SyntaxError(_token[0], 'Could not match ClauseD') def OptParam(self, _parent=None): _context = self.Context(_parent, self._scanner, self._pos, 'OptParam', []) _token = self._peek() if _token == 'ATTR': ATTR = self._scan('ATTR') return ATTR[2:-2] elif _token not in ['"ignore"', '"token"', '"option"', '"parser"', 'COLON']: return '' else: raise yappsrt.SyntaxError(_token[0], 'Could not match OptParam') def Str(self, _parent=None): _context = self.Context(_parent, self._scanner, self._pos, 'Str', []) STR = self._scan('STR') return eval(STR,{},{}) def parse(rule, text): P = ParserDescription(ParserDescriptionScanner(text)) return yappsrt.wrap_error_reporter(P, rule) # End -- grammar generated by Yapps