| #----------------------------------------------------------------------------- |
| # ply: yacc.py |
| # |
| # Author(s): David M. Beazley (dave@dabeaz.com) |
| # |
| # Copyright (C) 2001-2006, David M. Beazley |
| # |
| # This library is free software; you can redistribute it and/or |
| # modify it under the terms of the GNU Lesser General Public |
| # License as published by the Free Software Foundation; either |
| # version 2.1 of the License, or (at your option) any later version. |
| # |
| # This library is distributed in the hope that it will be useful, |
| # but WITHOUT ANY WARRANTY; without even the implied warranty of |
| # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| # Lesser General Public License for more details. |
| # |
| # You should have received a copy of the GNU Lesser General Public |
| # License along with this library; if not, write to the Free Software |
| # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA |
| # |
| # See the file COPYING for a complete copy of the LGPL. |
| # |
| # |
| # This implements an LR parser that is constructed from grammar rules defined |
| # as Python functions. The grammer is specified by supplying the BNF inside |
| # Python documentation strings. The inspiration for this technique was borrowed |
| # from John Aycock's Spark parsing system. PLY might be viewed as cross between |
| # Spark and the GNU bison utility. |
| # |
| # The current implementation is only somewhat object-oriented. The |
| # LR parser itself is defined in terms of an object (which allows multiple |
| # parsers to co-exist). However, most of the variables used during table |
| # construction are defined in terms of global variables. Users shouldn't |
| # notice unless they are trying to define multiple parsers at the same |
| # time using threads (in which case they should have their head examined). |
| # |
| # This implementation supports both SLR and LALR(1) parsing. LALR(1) |
| # support was originally implemented by Elias Ioup (ezioup@alumni.uchicago.edu), |
| # using the algorithm found in Aho, Sethi, and Ullman "Compilers: Principles, |
| # Techniques, and Tools" (The Dragon Book). LALR(1) has since been replaced |
| # by the more efficient DeRemer and Pennello algorithm. |
| # |
| # :::::::: WARNING ::::::: |
| # |
| # Construction of LR parsing tables is fairly complicated and expensive. |
| # To make this module run fast, a *LOT* of work has been put into |
| # optimization---often at the expensive of readability and what might |
| # consider to be good Python "coding style." Modify the code at your |
| # own risk! |
| # ---------------------------------------------------------------------------- |
| |
| __version__ = "2.2" |
| |
| #----------------------------------------------------------------------------- |
| # === User configurable parameters === |
| # |
| # Change these to modify the default behavior of yacc (if you wish) |
| #----------------------------------------------------------------------------- |
| |
| yaccdebug = 1 # Debugging mode. If set, yacc generates a |
| # a 'parser.out' file in the current directory |
| |
| debug_file = 'parser.out' # Default name of the debugging file |
| tab_module = 'parsetab' # Default name of the table module |
| default_lr = 'LALR' # Default LR table generation method |
| |
| error_count = 3 # Number of symbols that must be shifted to leave recovery mode |
| |
| import re, types, sys, hashlib, os.path |
| try: |
| from cStringIO import StringIO |
| except ImportError: |
| from io import StringIO |
| |
| from . import util |
| |
| # Exception raised for yacc-related errors |
| class YaccError(Exception): pass |
| |
| #----------------------------------------------------------------------------- |
| # === LR Parsing Engine === |
| # |
| # The following classes are used for the LR parser itself. These are not |
| # used during table construction and are independent of the actual LR |
| # table generation algorithm |
| #----------------------------------------------------------------------------- |
| |
| # This class is used to hold non-terminal grammar symbols during parsing. |
| # It normally has the following attributes set: |
| # .type = Grammar symbol type |
| # .value = Symbol value |
| # .lineno = Starting line number |
| # .endlineno = Ending line number (optional, set automatically) |
| # .lexpos = Starting lex position |
| # .endlexpos = Ending lex position (optional, set automatically) |
| |
| class YaccSymbol: |
| def __str__(self): return self.type |
| def __repr__(self): return str(self) |
| |
| # This class is a wrapper around the objects actually passed to each |
| # grammar rule. Index lookup and assignment actually assign the |
| # .value attribute of the underlying YaccSymbol object. |
| # The lineno() method returns the line number of a given |
| # item (or 0 if not defined). The linespan() method returns |
| # a tuple of (startline,endline) representing the range of lines |
| # for a symbol. The lexspan() method returns a tuple (lexpos,endlexpos) |
| # representing the range of positional information for a symbol. |
| |
| class YaccProduction: |
| def __init__(self,s,stack=None): |
| self.slice = s |
| self.pbstack = [] |
| self.stack = stack |
| |
| def __getitem__(self,n): |
| if type(n) == int: |
| if n >= 0: return self.slice[n].value |
| else: return self.stack[n].value |
| else: |
| return [s.value for s in self.slice[n.start:n.stop:n.step]] |
| |
| def __setitem__(self,n,v): |
| self.slice[n].value = v |
| |
| def __len__(self): |
| return len(self.slice) |
| |
| def lineno(self,n): |
| return getattr(self.slice[n],"lineno",0) |
| |
| def linespan(self,n): |
| startline = getattr(self.slice[n],"lineno",0) |
| endline = getattr(self.slice[n],"endlineno",startline) |
| return startline,endline |
| |
| def lexpos(self,n): |
| return getattr(self.slice[n],"lexpos",0) |
| |
| def lexspan(self,n): |
| startpos = getattr(self.slice[n],"lexpos",0) |
| endpos = getattr(self.slice[n],"endlexpos",startpos) |
| return startpos,endpos |
| |
| def pushback(self,n): |
| if n <= 0: |
| raise ValueError("Expected a positive value") |
| if n > (len(self.slice)-1): |
| raise ValueError("Can't push %d tokens. Only %d are available." % (n,len(self.slice)-1)) |
| for i in range(0,n): |
| self.pbstack.append(self.slice[-i-1]) |
| |
| # The LR Parsing engine. This is defined as a class so that multiple parsers |
| # can exist in the same process. A user never instantiates this directly. |
| # Instead, the global yacc() function should be used to create a suitable Parser |
| # object. |
| |
| class Parser: |
| def __init__(self,magic=None): |
| |
| # This is a hack to keep users from trying to instantiate a Parser |
| # object directly. |
| |
| if magic != "xyzzy": |
| raise YaccError("Can't instantiate Parser. Use yacc() instead.") |
| |
| # Reset internal state |
| self.productions = None # List of productions |
| self.errorfunc = None # Error handling function |
| self.action = { } # LR Action table |
| self.goto = { } # LR goto table |
| self.require = { } # Attribute require table |
| self.method = "Unknown LR" # Table construction method used |
| |
| def errok(self): |
| self.errorcount = 0 |
| |
| def restart(self): |
| del self.statestack[:] |
| del self.symstack[:] |
| sym = YaccSymbol() |
| sym.type = '$end' |
| self.symstack.append(sym) |
| self.statestack.append(0) |
| |
| def parse(self,input=None,lexer=None,debug=0): |
| lookahead = None # Current lookahead symbol |
| lookaheadstack = [ ] # Stack of lookahead symbols |
| actions = self.action # Local reference to action table |
| goto = self.goto # Local reference to goto table |
| prod = self.productions # Local reference to production list |
| pslice = YaccProduction(None) # Production object passed to grammar rules |
| pslice.parser = self # Parser object |
| self.errorcount = 0 # Used during error recovery |
| |
| # If no lexer was given, we will try to use the lex module |
| if not lexer: |
| from . import lex |
| lexer = lex.lexer |
| |
| pslice.lexer = lexer |
| |
| # If input was supplied, pass to lexer |
| if input: |
| lexer.input(input) |
| |
| # Tokenize function |
| get_token = lexer.token |
| |
| statestack = [ ] # Stack of parsing states |
| self.statestack = statestack |
| symstack = [ ] # Stack of grammar symbols |
| self.symstack = symstack |
| |
| pslice.stack = symstack # Put in the production |
| errtoken = None # Err token |
| |
| # The start state is assumed to be (0,$end) |
| statestack.append(0) |
| sym = YaccSymbol() |
| sym.type = '$end' |
| symstack.append(sym) |
| |
| while 1: |
| # Get the next symbol on the input. If a lookahead symbol |
| # is already set, we just use that. Otherwise, we'll pull |
| # the next token off of the lookaheadstack or from the lexer |
| if debug > 1: |
| print('state', statestack[-1]) |
| if not lookahead: |
| if not lookaheadstack: |
| lookahead = get_token() # Get the next token |
| else: |
| lookahead = lookaheadstack.pop() |
| if not lookahead: |
| lookahead = YaccSymbol() |
| lookahead.type = '$end' |
| if debug: |
| errorlead = ("%s . %s" % (" ".join([xx.type for xx in symstack][1:]), str(lookahead))).lstrip() |
| |
| # Check the action table |
| s = statestack[-1] |
| ltype = lookahead.type |
| t = actions.get((s,ltype),None) |
| |
| if debug > 1: |
| print('action', t) |
| if t is not None: |
| if t > 0: |
| # shift a symbol on the stack |
| if ltype == '$end': |
| # Error, end of input |
| sys.stderr.write("yacc: Parse error. EOF\n") |
| return |
| statestack.append(t) |
| if debug > 1: |
| sys.stderr.write("%-60s shift state %s\n" % (errorlead, t)) |
| symstack.append(lookahead) |
| lookahead = None |
| |
| # Decrease error count on successful shift |
| if self.errorcount > 0: |
| self.errorcount -= 1 |
| |
| continue |
| |
| if t < 0: |
| # reduce a symbol on the stack, emit a production |
| p = prod[-t] |
| pname = p.name |
| plen = p.len |
| |
| # Get production function |
| sym = YaccSymbol() |
| sym.type = pname # Production name |
| sym.value = None |
| if debug > 1: |
| sys.stderr.write("%-60s reduce %d\n" % (errorlead, -t)) |
| |
| if plen: |
| targ = symstack[-plen-1:] |
| targ[0] = sym |
| try: |
| sym.lineno = targ[1].lineno |
| sym.endlineno = getattr(targ[-1],"endlineno",targ[-1].lineno) |
| sym.lexpos = targ[1].lexpos |
| sym.endlexpos = getattr(targ[-1],"endlexpos",targ[-1].lexpos) |
| except AttributeError: |
| sym.lineno = 0 |
| del symstack[-plen:] |
| del statestack[-plen:] |
| else: |
| sym.lineno = 0 |
| targ = [ sym ] |
| pslice.slice = targ |
| pslice.pbstack = [] |
| # Call the grammar rule with our special slice object |
| p.func(pslice) |
| |
| # If there was a pushback, put that on the stack |
| if pslice.pbstack: |
| lookaheadstack.append(lookahead) |
| for _t in pslice.pbstack: |
| lookaheadstack.append(_t) |
| lookahead = None |
| |
| symstack.append(sym) |
| statestack.append(goto[statestack[-1],pname]) |
| continue |
| |
| if t == 0: |
| n = symstack[-1] |
| return getattr(n,"value",None) |
| sys.stderr.write(errorlead, "\n") |
| |
| if t == None: |
| if debug: |
| sys.stderr.write(errorlead + "\n") |
| # We have some kind of parsing error here. To handle |
| # this, we are going to push the current token onto |
| # the tokenstack and replace it with an 'error' token. |
| # If there are any synchronization rules, they may |
| # catch it. |
| # |
| # In addition to pushing the error token, we call call |
| # the user defined p_error() function if this is the |
| # first syntax error. This function is only called if |
| # errorcount == 0. |
| if not self.errorcount: |
| self.errorcount = error_count |
| errtoken = lookahead |
| if errtoken.type == '$end': |
| errtoken = None # End of file! |
| if self.errorfunc: |
| global errok,token,restart |
| errok = self.errok # Set some special functions available in error recovery |
| token = get_token |
| restart = self.restart |
| tok = self.errorfunc(errtoken) |
| del errok, token, restart # Delete special functions |
| |
| if not self.errorcount: |
| # User must have done some kind of panic |
| # mode recovery on their own. The |
| # returned token is the next lookahead |
| lookahead = tok |
| errtoken = None |
| continue |
| else: |
| if errtoken: |
| if hasattr(errtoken,"lineno"): lineno = lookahead.lineno |
| else: lineno = 0 |
| if lineno: |
| sys.stderr.write("yacc: Syntax error at line %d, token=%s\n" % (lineno, errtoken.type)) |
| else: |
| sys.stderr.write("yacc: Syntax error, token=%s" % errtoken.type) |
| else: |
| sys.stderr.write("yacc: Parse error in input. EOF\n") |
| return |
| |
| else: |
| self.errorcount = error_count |
| |
| # case 1: the statestack only has 1 entry on it. If we're in this state, the |
| # entire parse has been rolled back and we're completely hosed. The token is |
| # discarded and we just keep going. |
| |
| if len(statestack) <= 1 and lookahead.type != '$end': |
| lookahead = None |
| errtoken = None |
| # Nuke the pushback stack |
| del lookaheadstack[:] |
| continue |
| |
| # case 2: the statestack has a couple of entries on it, but we're |
| # at the end of the file. nuke the top entry and generate an error token |
| |
| # Start nuking entries on the stack |
| if lookahead.type == '$end': |
| # Whoa. We're really hosed here. Bail out |
| return |
| |
| if lookahead.type != 'error': |
| sym = symstack[-1] |
| if sym.type == 'error': |
| # Hmmm. Error is on top of stack, we'll just nuke input |
| # symbol and continue |
| lookahead = None |
| continue |
| t = YaccSymbol() |
| t.type = 'error' |
| if hasattr(lookahead,"lineno"): |
| t.lineno = lookahead.lineno |
| t.value = lookahead |
| lookaheadstack.append(lookahead) |
| lookahead = t |
| else: |
| symstack.pop() |
| statestack.pop() |
| |
| continue |
| |
| # Call an error function here |
| raise RuntimeError("yacc: internal parser error!!!\n") |
| |
| # ----------------------------------------------------------------------------- |
| # === Parser Construction === |
| # |
| # The following functions and variables are used to implement the yacc() function |
| # itself. This is pretty hairy stuff involving lots of error checking, |
| # construction of LR items, kernels, and so forth. Although a lot of |
| # this work is done using global variables, the resulting Parser object |
| # is completely self contained--meaning that it is safe to repeatedly |
| # call yacc() with different grammars in the same application. |
| # ----------------------------------------------------------------------------- |
| |
| # ----------------------------------------------------------------------------- |
| # validate_file() |
| # |
| # This function checks to see if there are duplicated p_rulename() functions |
| # in the parser module file. Without this function, it is really easy for |
| # users to make mistakes by cutting and pasting code fragments (and it's a real |
| # bugger to try and figure out why the resulting parser doesn't work). Therefore, |
| # we just do a little regular expression pattern matching of def statements |
| # to try and detect duplicates. |
| # ----------------------------------------------------------------------------- |
| |
| def validate_file(filename): |
| base,ext = os.path.splitext(filename) |
| if ext != '.py': return 1 # No idea. Assume it's okay. |
| |
| try: |
| f = open(filename) |
| lines = f.readlines() |
| f.close() |
| except IOError: |
| return 1 # Oh well |
| |
| # Match def p_funcname( |
| fre = re.compile(r'\s*def\s+(p_[a-zA-Z_0-9]*)\(') |
| counthash = { } |
| linen = 1 |
| noerror = 1 |
| for l in lines: |
| m = fre.match(l) |
| if m: |
| name = m.group(1) |
| prev = counthash.get(name) |
| if not prev: |
| counthash[name] = linen |
| else: |
| sys.stderr.write("%s:%d: Function %s redefined. Previously defined on line %d\n" % (filename,linen,name,prev)) |
| noerror = 0 |
| linen += 1 |
| return noerror |
| |
| # This function looks for functions that might be grammar rules, but which don't have the proper p_suffix. |
| def validate_dict(d): |
| for n,v in d.items(): |
| if n[0:2] == 'p_' and type(v) in (types.FunctionType, types.MethodType): continue |
| if n[0:2] == 't_': continue |
| |
| if n[0:2] == 'p_': |
| sys.stderr.write("yacc: Warning. '%s' not defined as a function\n" % n) |
| if 1 and isinstance(v,types.FunctionType) and v.__code__.co_argcount == 1: |
| try: |
| doc = v.__doc__.split(" ") |
| if doc[1] == ':': |
| sys.stderr.write("%s:%d: Warning. Possible grammar rule '%s' defined without p_ prefix.\n" % (v.__code__.co_filename, v.__code__.co_firstlineno,n)) |
| except Exception: |
| pass |
| |
| # ----------------------------------------------------------------------------- |
| # === GRAMMAR FUNCTIONS === |
| # |
| # The following global variables and functions are used to store, manipulate, |
| # and verify the grammar rules specified by the user. |
| # ----------------------------------------------------------------------------- |
| |
| # Initialize all of the global variables used during grammar construction |
| def initialize_vars(): |
| global Productions, Prodnames, Prodmap, Terminals |
| global Nonterminals, First, Follow, Precedence, LRitems |
| global Errorfunc, Signature, Requires |
| |
| Productions = [None] # A list of all of the productions. The first |
| # entry is always reserved for the purpose of |
| # building an augmented grammar |
| |
| Prodnames = { } # A dictionary mapping the names of nonterminals to a list of all |
| # productions of that nonterminal. |
| |
| Prodmap = { } # A dictionary that is only used to detect duplicate |
| # productions. |
| |
| Terminals = { } # A dictionary mapping the names of terminal symbols to a |
| # list of the rules where they are used. |
| |
| Nonterminals = { } # A dictionary mapping names of nonterminals to a list |
| # of rule numbers where they are used. |
| |
| First = { } # A dictionary of precomputed FIRST(x) symbols |
| |
| Follow = { } # A dictionary of precomputed FOLLOW(x) symbols |
| |
| Precedence = { } # Precedence rules for each terminal. Contains tuples of the |
| # form ('right',level) or ('nonassoc', level) or ('left',level) |
| |
| LRitems = [ ] # A list of all LR items for the grammar. These are the |
| # productions with the "dot" like E -> E . PLUS E |
| |
| Errorfunc = None # User defined error handler |
| |
| Signature = hashlib.sha256() # Digital signature of the grammar rules, precedence |
| # and other information. Used to determined when a |
| # parsing table needs to be regenerated. |
| |
| Requires = { } # Requires list |
| |
| # File objects used when creating the parser.out debugging file |
| global _vf, _vfc |
| _vf = StringIO() |
| _vfc = StringIO() |
| |
| # ----------------------------------------------------------------------------- |
| # class Production: |
| # |
| # This class stores the raw information about a single production or grammar rule. |
| # It has a few required attributes: |
| # |
| # name - Name of the production (nonterminal) |
| # prod - A list of symbols making up its production |
| # number - Production number. |
| # |
| # In addition, a few additional attributes are used to help with debugging or |
| # optimization of table generation. |
| # |
| # file - File where production action is defined. |
| # lineno - Line number where action is defined |
| # func - Action function |
| # prec - Precedence level |
| # lr_next - Next LR item. Example, if we are ' E -> E . PLUS E' |
| # then lr_next refers to 'E -> E PLUS . E' |
| # lr_index - LR item index (location of the ".") in the prod list. |
| # lookaheads - LALR lookahead symbols for this item |
| # len - Length of the production (number of symbols on right hand side) |
| # ----------------------------------------------------------------------------- |
| |
| class Production: |
| def __init__(self,**kw): |
| for k,v in kw.items(): |
| setattr(self,k,v) |
| self.lr_index = -1 |
| self.lr0_added = 0 # Flag indicating whether or not added to LR0 closure |
| self.lr1_added = 0 # Flag indicating whether or not added to LR1 |
| self.usyms = [ ] |
| self.lookaheads = { } |
| self.lk_added = { } |
| self.setnumbers = [ ] |
| |
| def __str__(self): |
| if self.prod: |
| s = "%s -> %s" % (self.name," ".join(self.prod)) |
| else: |
| s = "%s -> <empty>" % self.name |
| return s |
| |
| def __repr__(self): |
| return str(self) |
| |
| # Compute lr_items from the production |
| def lr_item(self,n): |
| if n > len(self.prod): return None |
| p = Production() |
| p.name = self.name |
| p.prod = list(self.prod) |
| p.number = self.number |
| p.lr_index = n |
| p.lookaheads = { } |
| p.setnumbers = self.setnumbers |
| p.prod.insert(n,".") |
| p.prod = tuple(p.prod) |
| p.len = len(p.prod) |
| p.usyms = self.usyms |
| |
| # Precompute list of productions immediately following |
| try: |
| p.lrafter = Prodnames[p.prod[n+1]] |
| except (IndexError,KeyError) as e: |
| p.lrafter = [] |
| try: |
| p.lrbefore = p.prod[n-1] |
| except IndexError: |
| p.lrbefore = None |
| |
| return p |
| |
| class MiniProduction: |
| pass |
| |
| # regex matching identifiers |
| _is_identifier = re.compile(r'^[a-zA-Z0-9_-~]+$') |
| |
| # ----------------------------------------------------------------------------- |
| # add_production() |
| # |
| # Given an action function, this function assembles a production rule. |
| # The production rule is assumed to be found in the function's docstring. |
| # This rule has the general syntax: |
| # |
| # name1 ::= production1 |
| # | production2 |
| # | production3 |
| # ... |
| # | productionn |
| # name2 ::= production1 |
| # | production2 |
| # ... |
| # ----------------------------------------------------------------------------- |
| |
| def add_production(f,file,line,prodname,syms): |
| |
| if prodname in Terminals: |
| sys.stderr.write("%s:%d: Illegal rule name '%s'. Already defined as a token.\n" % (file,line,prodname)) |
| return -1 |
| if prodname == 'error': |
| sys.stderr.write("%s:%d: Illegal rule name '%s'. error is a reserved word.\n" % (file,line,prodname)) |
| return -1 |
| |
| if not _is_identifier.match(prodname): |
| sys.stderr.write("%s:%d: Illegal rule name '%s'\n" % (file,line,prodname)) |
| return -1 |
| |
| for x in range(len(syms)): |
| s = syms[x] |
| if s[0] in "'\"": |
| try: |
| c = eval(s) |
| if (len(c) > 1): |
| sys.stderr.write("%s:%d: Literal token %s in rule '%s' may only be a single character\n" % (file,line,s, prodname)) |
| return -1 |
| if c not in Terminals: |
| Terminals[c] = [] |
| syms[x] = c |
| continue |
| except SyntaxError: |
| pass |
| if not _is_identifier.match(s) and s != '%prec': |
| sys.stderr.write("%s:%d: Illegal name '%s' in rule '%s'\n" % (file,line,s, prodname)) |
| return -1 |
| |
| # See if the rule is already in the rulemap |
| map = "%s -> %s" % (prodname,syms) |
| if map in Prodmap: |
| m = Prodmap[map] |
| sys.stderr.write("%s:%d: Duplicate rule %s.\n" % (file,line, m)) |
| sys.stderr.write("%s:%d: Previous definition at %s:%d\n" % (file,line, m.file, m.line)) |
| return -1 |
| |
| p = Production() |
| p.name = prodname |
| p.prod = syms |
| p.file = file |
| p.line = line |
| p.func = f |
| p.number = len(Productions) |
| |
| |
| Productions.append(p) |
| Prodmap[map] = p |
| if prodname not in Nonterminals: |
| Nonterminals[prodname] = [ ] |
| |
| # Add all terminals to Terminals |
| i = 0 |
| while i < len(p.prod): |
| t = p.prod[i] |
| if t == '%prec': |
| try: |
| precname = p.prod[i+1] |
| except IndexError: |
| sys.stderr.write("%s:%d: Syntax error. Nothing follows %%prec.\n" % (p.file,p.line)) |
| return -1 |
| |
| prec = Precedence.get(precname,None) |
| if not prec: |
| sys.stderr.write("%s:%d: Nothing known about the precedence of '%s'\n" % (p.file,p.line,precname)) |
| return -1 |
| else: |
| p.prec = prec |
| del p.prod[i] |
| del p.prod[i] |
| continue |
| |
| if t in Terminals: |
| Terminals[t].append(p.number) |
| # Is a terminal. We'll assign a precedence to p based on this |
| if not hasattr(p,"prec"): |
| p.prec = Precedence.get(t,('right',0)) |
| else: |
| if t not in Nonterminals: |
| Nonterminals[t] = [ ] |
| Nonterminals[t].append(p.number) |
| i += 1 |
| |
| if not hasattr(p,"prec"): |
| p.prec = ('right',0) |
| |
| # Set final length of productions |
| p.len = len(p.prod) |
| p.prod = tuple(p.prod) |
| |
| # Calculate unique syms in the production |
| p.usyms = [ ] |
| for s in p.prod: |
| if s not in p.usyms: |
| p.usyms.append(s) |
| |
| # Add to the global productions list |
| try: |
| Prodnames[p.name].append(p) |
| except KeyError: |
| Prodnames[p.name] = [ p ] |
| return 0 |
| |
| # Given a raw rule function, this function rips out its doc string |
| # and adds rules to the grammar |
| |
| def add_function(f): |
| line = f.__code__.co_firstlineno |
| file = f.__code__.co_filename |
| error = 0 |
| |
| if isinstance(f,types.MethodType): |
| reqdargs = 2 |
| else: |
| reqdargs = 1 |
| |
| if f.__code__.co_argcount > reqdargs: |
| sys.stderr.write("%s:%d: Rule '%s' has too many arguments.\n" % (file,line,f.__name__)) |
| return -1 |
| |
| if f.__code__.co_argcount < reqdargs: |
| sys.stderr.write("%s:%d: Rule '%s' requires an argument.\n" % (file,line,f.__name__)) |
| return -1 |
| |
| if f.__doc__: |
| # Split the doc string into lines |
| pstrings = f.__doc__.splitlines() |
| lastp = None |
| dline = line |
| for ps in pstrings: |
| dline += 1 |
| p = ps.split() |
| if not p: continue |
| try: |
| if p[0] == '|': |
| # This is a continuation of a previous rule |
| if not lastp: |
| sys.stderr.write("%s:%d: Misplaced '|'.\n" % (file,dline)) |
| return -1 |
| prodname = lastp |
| if len(p) > 1: |
| syms = p[1:] |
| else: |
| syms = [ ] |
| else: |
| prodname = p[0] |
| lastp = prodname |
| assign = p[1] |
| if len(p) > 2: |
| syms = p[2:] |
| else: |
| syms = [ ] |
| if assign != ':' and assign != '::=': |
| sys.stderr.write("%s:%d: Syntax error. Expected ':'\n" % (file,dline)) |
| return -1 |
| |
| |
| e = add_production(f,file,dline,prodname,syms) |
| error += e |
| |
| |
| except Exception: |
| sys.stderr.write("%s:%d: Syntax error in rule '%s'\n" % (file,dline,ps)) |
| error -= 1 |
| else: |
| sys.stderr.write("%s:%d: No documentation string specified in function '%s'\n" % (file,line,f.__name__)) |
| return error |
| |
| |
| # Cycle checking code (Michael Dyck) |
| |
| def compute_reachable(): |
| ''' |
| Find each symbol that can be reached from the start symbol. |
| Print a warning for any nonterminals that can't be reached. |
| (Unused terminals have already had their warning.) |
| ''' |
| Reachable = { } |
| for s in list(Terminals.keys()) + list(Nonterminals.keys()): |
| Reachable[s] = 0 |
| |
| mark_reachable_from( Productions[0].prod[0], Reachable ) |
| |
| for s in Nonterminals.keys(): |
| if not Reachable[s]: |
| sys.stderr.write("yacc: Symbol '%s' is unreachable.\n" % s) |
| |
| def mark_reachable_from(s, Reachable): |
| ''' |
| Mark all symbols that are reachable from symbol s. |
| ''' |
| if Reachable[s]: |
| # We've already reached symbol s. |
| return |
| Reachable[s] = 1 |
| for p in Prodnames.get(s,[]): |
| for r in p.prod: |
| mark_reachable_from(r, Reachable) |
| |
| # ----------------------------------------------------------------------------- |
| # compute_terminates() |
| # |
| # This function looks at the various parsing rules and tries to detect |
| # infinite recursion cycles (grammar rules where there is no possible way |
| # to derive a string of only terminals). |
| # ----------------------------------------------------------------------------- |
| def compute_terminates(): |
| ''' |
| Raise an error for any symbols that don't terminate. |
| ''' |
| Terminates = {} |
| |
| # Terminals: |
| for t in Terminals.keys(): |
| Terminates[t] = 1 |
| |
| Terminates['$end'] = 1 |
| |
| # Nonterminals: |
| |
| # Initialize to false: |
| for n in Nonterminals.keys(): |
| Terminates[n] = 0 |
| |
| # Then propagate termination until no change: |
| while 1: |
| some_change = 0 |
| for (n,pl) in Prodnames.items(): |
| # Nonterminal n terminates iff any of its productions terminates. |
| for p in pl: |
| # Production p terminates iff all of its rhs symbols terminate. |
| for s in p.prod: |
| if not Terminates[s]: |
| # The symbol s does not terminate, |
| # so production p does not terminate. |
| p_terminates = 0 |
| break |
| else: |
| # didn't break from the loop, |
| # so every symbol s terminates |
| # so production p terminates. |
| p_terminates = 1 |
| |
| if p_terminates: |
| # symbol n terminates! |
| if not Terminates[n]: |
| Terminates[n] = 1 |
| some_change = 1 |
| # Don't need to consider any more productions for this n. |
| break |
| |
| if not some_change: |
| break |
| |
| some_error = 0 |
| for (s,terminates) in Terminates.items(): |
| if not terminates: |
| if s not in Prodnames and s not in Terminals and s != 'error': |
| # s is used-but-not-defined, and we've already warned of that, |
| # so it would be overkill to say that it's also non-terminating. |
| pass |
| else: |
| sys.stderr.write("yacc: Infinite recursion detected for symbol '%s'.\n" % s) |
| some_error = 1 |
| |
| return some_error |
| |
| # ----------------------------------------------------------------------------- |
| # verify_productions() |
| # |
| # This function examines all of the supplied rules to see if they seem valid. |
| # ----------------------------------------------------------------------------- |
| def verify_productions(cycle_check=1): |
| error = 0 |
| for p in Productions: |
| if not p: continue |
| |
| for s in p.prod: |
| if s not in Prodnames and s not in Terminals and s != 'error': |
| sys.stderr.write("%s:%d: Symbol '%s' used, but not defined as a token or a rule.\n" % (p.file,p.line,s)) |
| error = 1 |
| continue |
| |
| unused_tok = 0 |
| # Now verify all of the tokens |
| if yaccdebug: |
| _vf.write("Unused terminals:\n\n") |
| for s,v in Terminals.items(): |
| if s != 'error' and not v: |
| sys.stderr.write("yacc: Warning. Token '%s' defined, but not used.\n" % s) |
| if yaccdebug: _vf.write(" %s\n"% s) |
| unused_tok += 1 |
| |
| # Print out all of the productions |
| if yaccdebug: |
| _vf.write("\nGrammar\n\n") |
| for i in range(1,len(Productions)): |
| _vf.write("Rule %-5d %s\n" % (i, Productions[i])) |
| |
| unused_prod = 0 |
| # Verify the use of all productions |
| for s,v in Nonterminals.items(): |
| if not v: |
| p = Prodnames[s][0] |
| sys.stderr.write("%s:%d: Warning. Rule '%s' defined, but not used.\n" % (p.file,p.line, s)) |
| unused_prod += 1 |
| |
| |
| if unused_tok == 1: |
| sys.stderr.write("yacc: Warning. There is 1 unused token.\n") |
| if unused_tok > 1: |
| sys.stderr.write("yacc: Warning. There are %d unused tokens.\n" % unused_tok) |
| |
| if unused_prod == 1: |
| sys.stderr.write("yacc: Warning. There is 1 unused rule.\n") |
| if unused_prod > 1: |
| sys.stderr.write("yacc: Warning. There are %d unused rules.\n" % unused_prod) |
| |
| if yaccdebug: |
| _vf.write("\nTerminals, with rules where they appear\n\n") |
| ks = list(Terminals.keys()) |
| ks.sort() |
| for k in ks: |
| _vf.write("%-20s : %s\n" % (k, " ".join([str(s) for s in Terminals[k]]))) |
| _vf.write("\nNonterminals, with rules where they appear\n\n") |
| ks = list(Nonterminals.keys()) |
| ks.sort() |
| for k in ks: |
| _vf.write("%-20s : %s\n" % (k, " ".join([str(s) for s in Nonterminals[k]]))) |
| |
| if (cycle_check): |
| compute_reachable() |
| error += compute_terminates() |
| # error += check_cycles() |
| return error |
| |
| # ----------------------------------------------------------------------------- |
| # build_lritems() |
| # |
| # This function walks the list of productions and builds a complete set of the |
| # LR items. The LR items are stored in two ways: First, they are uniquely |
| # numbered and placed in the list _lritems. Second, a linked list of LR items |
| # is built for each production. For example: |
| # |
| # E -> E PLUS E |
| # |
| # Creates the list |
| # |
| # [E -> . E PLUS E, E -> E . PLUS E, E -> E PLUS . E, E -> E PLUS E . ] |
| # ----------------------------------------------------------------------------- |
| |
| def build_lritems(): |
| for p in Productions: |
| lastlri = p |
| lri = p.lr_item(0) |
| i = 0 |
| while 1: |
| lri = p.lr_item(i) |
| lastlri.lr_next = lri |
| if not lri: break |
| lri.lr_num = len(LRitems) |
| LRitems.append(lri) |
| lastlri = lri |
| i += 1 |
| |
| # In order for the rest of the parser generator to work, we need to |
| # guarantee that no more lritems are generated. Therefore, we nuke |
| # the p.lr_item method. (Only used in debugging) |
| # Production.lr_item = None |
| |
| # ----------------------------------------------------------------------------- |
| # add_precedence() |
| # |
| # Given a list of precedence rules, add to the precedence table. |
| # ----------------------------------------------------------------------------- |
| |
| def add_precedence(plist): |
| plevel = 0 |
| error = 0 |
| for p in plist: |
| plevel += 1 |
| try: |
| prec = p[0] |
| terms = p[1:] |
| if prec != 'left' and prec != 'right' and prec != 'nonassoc': |
| sys.stderr.write("yacc: Invalid precedence '%s'\n" % prec) |
| return -1 |
| for t in terms: |
| if t in Precedence: |
| sys.stderr.write("yacc: Precedence already specified for terminal '%s'\n" % t) |
| error += 1 |
| continue |
| Precedence[t] = (prec,plevel) |
| except: |
| sys.stderr.write("yacc: Invalid precedence table.\n") |
| error += 1 |
| |
| return error |
| |
| # ----------------------------------------------------------------------------- |
| # augment_grammar() |
| # |
| # Compute the augmented grammar. This is just a rule S' -> start where start |
| # is the starting symbol. |
| # ----------------------------------------------------------------------------- |
| |
| def augment_grammar(start=None): |
| if not start: |
| start = Productions[1].name |
| Productions[0] = Production(name="S'",prod=[start],number=0,len=1,prec=('right',0),func=None) |
| Productions[0].usyms = [ start ] |
| Nonterminals[start].append(0) |
| |
| |
| # ------------------------------------------------------------------------- |
| # first() |
| # |
| # Compute the value of FIRST1(beta) where beta is a tuple of symbols. |
| # |
| # During execution of compute_first1, the result may be incomplete. |
| # Afterward (e.g., when called from compute_follow()), it will be complete. |
| # ------------------------------------------------------------------------- |
| def first(beta): |
| |
| # We are computing First(x1,x2,x3,...,xn) |
| result = [ ] |
| for x in beta: |
| x_produces_empty = 0 |
| |
| # Add all the non-<empty> symbols of First[x] to the result. |
| for f in First[x]: |
| if f == '<empty>': |
| x_produces_empty = 1 |
| else: |
| if f not in result: result.append(f) |
| |
| if x_produces_empty: |
| # We have to consider the next x in beta, |
| # i.e. stay in the loop. |
| pass |
| else: |
| # We don't have to consider any further symbols in beta. |
| break |
| else: |
| # There was no 'break' from the loop, |
| # so x_produces_empty was true for all x in beta, |
| # so beta produces empty as well. |
| result.append('<empty>') |
| |
| return result |
| |
| |
| # FOLLOW(x) |
| # Given a non-terminal. This function computes the set of all symbols |
| # that might follow it. Dragon book, p. 189. |
| |
| def compute_follow(start=None): |
| # Add '$end' to the follow list of the start symbol |
| for k in Nonterminals.keys(): |
| Follow[k] = [ ] |
| |
| if not start: |
| start = Productions[1].name |
| |
| Follow[start] = [ '$end' ] |
| |
| while 1: |
| didadd = 0 |
| for p in Productions[1:]: |
| # Here is the production set |
| for i in range(len(p.prod)): |
| B = p.prod[i] |
| if B in Nonterminals: |
| # Okay. We got a non-terminal in a production |
| fst = first(p.prod[i+1:]) |
| hasempty = 0 |
| for f in fst: |
| if f != '<empty>' and f not in Follow[B]: |
| Follow[B].append(f) |
| didadd = 1 |
| if f == '<empty>': |
| hasempty = 1 |
| if hasempty or i == (len(p.prod)-1): |
| # Add elements of follow(a) to follow(b) |
| for f in Follow[p.name]: |
| if f not in Follow[B]: |
| Follow[B].append(f) |
| didadd = 1 |
| if not didadd: break |
| |
| if 0 and yaccdebug: |
| _vf.write('\nFollow:\n') |
| for k in Nonterminals.keys(): |
| _vf.write("%-20s : %s\n" % (k, " ".join([str(s) for s in Follow[k]]))) |
| |
| # ------------------------------------------------------------------------- |
| # compute_first1() |
| # |
| # Compute the value of FIRST1(X) for all symbols |
| # ------------------------------------------------------------------------- |
| def compute_first1(): |
| |
| # Terminals: |
| for t in Terminals.keys(): |
| First[t] = [t] |
| |
| First['$end'] = ['$end'] |
| First['#'] = ['#'] # what's this for? |
| |
| # Nonterminals: |
| |
| # Initialize to the empty set: |
| for n in Nonterminals.keys(): |
| First[n] = [] |
| |
| # Then propagate symbols until no change: |
| while 1: |
| some_change = 0 |
| for n in Nonterminals.keys(): |
| for p in Prodnames[n]: |
| for f in first(p.prod): |
| if f not in First[n]: |
| First[n].append( f ) |
| some_change = 1 |
| if not some_change: |
| break |
| |
| if 0 and yaccdebug: |
| _vf.write('\nFirst:\n') |
| for k in Nonterminals.keys(): |
| _vf.write("%-20s : %s\n" % |
| (k, " ".join([str(s) for s in First[k]]))) |
| |
| # ----------------------------------------------------------------------------- |
| # === SLR Generation === |
| # |
| # The following functions are used to construct SLR (Simple LR) parsing tables |
| # as described on p.221-229 of the dragon book. |
| # ----------------------------------------------------------------------------- |
| |
| # Global variables for the LR parsing engine |
| def lr_init_vars(): |
| global _lr_action, _lr_goto, _lr_method |
| global _lr_goto_cache, _lr0_cidhash |
| |
| _lr_action = { } # Action table |
| _lr_goto = { } # Goto table |
| _lr_method = "Unknown" # LR method used |
| _lr_goto_cache = { } |
| _lr0_cidhash = { } |
| |
| |
| # Compute the LR(0) closure operation on I, where I is a set of LR(0) items. |
| # prodlist is a list of productions. |
| |
| _add_count = 0 # Counter used to detect cycles |
| |
| def lr0_closure(I): |
| global _add_count |
| |
| _add_count += 1 |
| prodlist = Productions |
| |
| # Add everything in I to J |
| J = I[:] |
| didadd = 1 |
| while didadd: |
| didadd = 0 |
| for j in J: |
| for x in j.lrafter: |
| if x.lr0_added == _add_count: continue |
| # Add B --> .G to J |
| J.append(x.lr_next) |
| x.lr0_added = _add_count |
| didadd = 1 |
| |
| return J |
| |
| # Compute the LR(0) goto function goto(I,X) where I is a set |
| # of LR(0) items and X is a grammar symbol. This function is written |
| # in a way that guarantees uniqueness of the generated goto sets |
| # (i.e. the same goto set will never be returned as two different Python |
| # objects). With uniqueness, we can later do fast set comparisons using |
| # id(obj) instead of element-wise comparison. |
| |
| def lr0_goto(I,x): |
| # First we look for a previously cached entry |
| g = _lr_goto_cache.get((id(I),x),None) |
| if g: return g |
| |
| # Now we generate the goto set in a way that guarantees uniqueness |
| # of the result |
| |
| s = _lr_goto_cache.get(x,None) |
| if not s: |
| s = { } |
| _lr_goto_cache[x] = s |
| |
| gs = [ ] |
| for p in I: |
| n = p.lr_next |
| if n and n.lrbefore == x: |
| s1 = s.get(id(n),None) |
| if not s1: |
| s1 = { } |
| s[id(n)] = s1 |
| gs.append(n) |
| s = s1 |
| g = s.get('$end',None) |
| if not g: |
| if gs: |
| g = lr0_closure(gs) |
| s['$end'] = g |
| else: |
| s['$end'] = gs |
| _lr_goto_cache[(id(I),x)] = g |
| return g |
| |
| _lr0_cidhash = { } |
| |
| # Compute the LR(0) sets of item function |
| def lr0_items(): |
| |
| C = [ lr0_closure([Productions[0].lr_next]) ] |
| i = 0 |
| for I in C: |
| _lr0_cidhash[id(I)] = i |
| i += 1 |
| |
| # Loop over the items in C and each grammar symbols |
| i = 0 |
| while i < len(C): |
| I = C[i] |
| i += 1 |
| |
| # Collect all of the symbols that could possibly be in the goto(I,X) sets |
| asyms = { } |
| for ii in I: |
| for s in ii.usyms: |
| asyms[s] = None |
| |
| for x in asyms.keys(): |
| g = lr0_goto(I,x) |
| if not g: continue |
| if id(g) in _lr0_cidhash: continue |
| _lr0_cidhash[id(g)] = len(C) |
| C.append(g) |
| |
| return C |
| |
| # ----------------------------------------------------------------------------- |
| # ==== LALR(1) Parsing ==== |
| # |
| # LALR(1) parsing is almost exactly the same as SLR except that instead of |
| # relying upon Follow() sets when performing reductions, a more selective |
| # lookahead set that incorporates the state of the LR(0) machine is utilized. |
| # Thus, we mainly just have to focus on calculating the lookahead sets. |
| # |
| # The method used here is due to DeRemer and Pennelo (1982). |
| # |
| # DeRemer, F. L., and T. J. Pennelo: "Efficient Computation of LALR(1) |
| # Lookahead Sets", ACM Transactions on Programming Languages and Systems, |
| # Vol. 4, No. 4, Oct. 1982, pp. 615-649 |
| # |
| # Further details can also be found in: |
| # |
| # J. Tremblay and P. Sorenson, "The Theory and Practice of Compiler Writing", |
| # McGraw-Hill Book Company, (1985). |
| # |
| # Note: This implementation is a complete replacement of the LALR(1) |
| # implementation in PLY-1.x releases. That version was based on |
| # a less efficient algorithm and it had bugs in its implementation. |
| # ----------------------------------------------------------------------------- |
| |
| # ----------------------------------------------------------------------------- |
| # compute_nullable_nonterminals() |
| # |
| # Creates a dictionary containing all of the non-terminals that might produce |
| # an empty production. |
| # ----------------------------------------------------------------------------- |
| |
| def compute_nullable_nonterminals(): |
| nullable = {} |
| num_nullable = 0 |
| while 1: |
| for p in Productions[1:]: |
| if p.len == 0: |
| nullable[p.name] = 1 |
| continue |
| for t in p.prod: |
| if t not in nullable: break |
| else: |
| nullable[p.name] = 1 |
| if len(nullable) == num_nullable: break |
| num_nullable = len(nullable) |
| return nullable |
| |
| # ----------------------------------------------------------------------------- |
| # find_nonterminal_trans(C) |
| # |
| # Given a set of LR(0) items, this functions finds all of the non-terminal |
| # transitions. These are transitions in which a dot appears immediately before |
| # a non-terminal. Returns a list of tuples of the form (state,N) where state |
| # is the state number and N is the nonterminal symbol. |
| # |
| # The input C is the set of LR(0) items. |
| # ----------------------------------------------------------------------------- |
| |
| def find_nonterminal_transitions(C): |
| trans = [] |
| for state in range(len(C)): |
| for p in C[state]: |
| if p.lr_index < p.len - 1: |
| t = (state,p.prod[p.lr_index+1]) |
| if t[1] in Nonterminals: |
| if t not in trans: trans.append(t) |
| state = state + 1 |
| return trans |
| |
| # ----------------------------------------------------------------------------- |
| # dr_relation() |
| # |
| # Computes the DR(p,A) relationships for non-terminal transitions. The input |
| # is a tuple (state,N) where state is a number and N is a nonterminal symbol. |
| # |
| # Returns a list of terminals. |
| # ----------------------------------------------------------------------------- |
| |
| def dr_relation(C,trans,nullable): |
| dr_set = { } |
| state,N = trans |
| terms = [] |
| |
| g = lr0_goto(C[state],N) |
| for p in g: |
| if p.lr_index < p.len - 1: |
| a = p.prod[p.lr_index+1] |
| if a in Terminals: |
| if a not in terms: terms.append(a) |
| |
| # This extra bit is to handle the start state |
| if state == 0 and N == Productions[0].prod[0]: |
| terms.append('$end') |
| |
| return terms |
| |
| # ----------------------------------------------------------------------------- |
| # reads_relation() |
| # |
| # Computes the READS() relation (p,A) READS (t,C). |
| # ----------------------------------------------------------------------------- |
| |
| def reads_relation(C, trans, empty): |
| # Look for empty transitions |
| rel = [] |
| state, N = trans |
| |
| g = lr0_goto(C[state],N) |
| j = _lr0_cidhash.get(id(g),-1) |
| for p in g: |
| if p.lr_index < p.len - 1: |
| a = p.prod[p.lr_index + 1] |
| if a in empty: |
| rel.append((j,a)) |
| |
| return rel |
| |
| # ----------------------------------------------------------------------------- |
| # compute_lookback_includes() |
| # |
| # Determines the lookback and includes relations |
| # |
| # LOOKBACK: |
| # |
| # This relation is determined by running the LR(0) state machine forward. |
| # For example, starting with a production "N : . A B C", we run it forward |
| # to obtain "N : A B C ." We then build a relationship between this final |
| # state and the starting state. These relationships are stored in a dictionary |
| # lookdict. |
| # |
| # INCLUDES: |
| # |
| # Computes the INCLUDE() relation (p,A) INCLUDES (p',B). |
| # |
| # This relation is used to determine non-terminal transitions that occur |
| # inside of other non-terminal transition states. (p,A) INCLUDES (p', B) |
| # if the following holds: |
| # |
| # B -> LAT, where T -> epsilon and p' -L-> p |
| # |
| # L is essentially a prefix (which may be empty), T is a suffix that must be |
| # able to derive an empty string. State p' must lead to state p with the string L. |
| # |
| # ----------------------------------------------------------------------------- |
| |
| def compute_lookback_includes(C,trans,nullable): |
| |
| lookdict = {} # Dictionary of lookback relations |
| includedict = {} # Dictionary of include relations |
| |
| # Make a dictionary of non-terminal transitions |
| dtrans = {} |
| for t in trans: |
| dtrans[t] = 1 |
| |
| # Loop over all transitions and compute lookbacks and includes |
| for state,N in trans: |
| lookb = [] |
| includes = [] |
| for p in C[state]: |
| if p.name != N: continue |
| |
| # Okay, we have a name match. We now follow the production all the way |
| # through the state machine until we get the . on the right hand side |
| |
| lr_index = p.lr_index |
| j = state |
| while lr_index < p.len - 1: |
| lr_index = lr_index + 1 |
| t = p.prod[lr_index] |
| |
| # Check to see if this symbol and state are a non-terminal transition |
| if (j,t) in dtrans: |
| # Yes. Okay, there is some chance that this is an includes relation |
| # the only way to know for certain is whether the rest of the |
| # production derives empty |
| |
| li = lr_index + 1 |
| while li < p.len: |
| if p.prod[li] in Terminals: break # No forget it |
| if p.prod[li] not in nullable: break |
| li = li + 1 |
| else: |
| # Appears to be a relation between (j,t) and (state,N) |
| includes.append((j,t)) |
| |
| g = lr0_goto(C[j],t) # Go to next set |
| j = _lr0_cidhash.get(id(g),-1) # Go to next state |
| |
| # When we get here, j is the final state, now we have to locate the production |
| for r in C[j]: |
| if r.name != p.name: continue |
| if r.len != p.len: continue |
| i = 0 |
| # This look is comparing a production ". A B C" with "A B C ." |
| while i < r.lr_index: |
| if r.prod[i] != p.prod[i+1]: break |
| i = i + 1 |
| else: |
| lookb.append((j,r)) |
| for i in includes: |
| if i not in includedict: includedict[i] = [] |
| includedict[i].append((state,N)) |
| lookdict[(state,N)] = lookb |
| |
| return lookdict,includedict |
| |
| # ----------------------------------------------------------------------------- |
| # digraph() |
| # traverse() |
| # |
| # The following two functions are used to compute set valued functions |
| # of the form: |
| # |
| # F(x) = F'(x) U U{F(y) | x R y} |
| # |
| # This is used to compute the values of Read() sets as well as FOLLOW sets |
| # in LALR(1) generation. |
| # |
| # Inputs: X - An input set |
| # R - A relation |
| # FP - Set-valued function |
| # ------------------------------------------------------------------------------ |
| |
| def digraph(X,R,FP): |
| N = { } |
| for x in X: |
| N[x] = 0 |
| stack = [] |
| F = { } |
| for x in X: |
| if N[x] == 0: traverse(x,N,stack,F,X,R,FP) |
| return F |
| |
| def traverse(x,N,stack,F,X,R,FP): |
| stack.append(x) |
| d = len(stack) |
| N[x] = d |
| F[x] = FP(x) # F(X) <- F'(x) |
| |
| rel = R(x) # Get y's related to x |
| for y in rel: |
| if N[y] == 0: |
| traverse(y,N,stack,F,X,R,FP) |
| N[x] = min(N[x],N[y]) |
| for a in F.get(y,[]): |
| if a not in F[x]: F[x].append(a) |
| if N[x] == d: |
| N[stack[-1]] = sys.maxsize |
| F[stack[-1]] = F[x] |
| element = stack.pop() |
| while element != x: |
| N[stack[-1]] = sys.maxsize |
| F[stack[-1]] = F[x] |
| element = stack.pop() |
| |
| # ----------------------------------------------------------------------------- |
| # compute_read_sets() |
| # |
| # Given a set of LR(0) items, this function computes the read sets. |
| # |
| # Inputs: C = Set of LR(0) items |
| # ntrans = Set of nonterminal transitions |
| # nullable = Set of empty transitions |
| # |
| # Returns a set containing the read sets |
| # ----------------------------------------------------------------------------- |
| |
| def compute_read_sets(C, ntrans, nullable): |
| FP = lambda x: dr_relation(C,x,nullable) |
| R = lambda x: reads_relation(C,x,nullable) |
| F = digraph(ntrans,R,FP) |
| return F |
| |
| # ----------------------------------------------------------------------------- |
| # compute_follow_sets() |
| # |
| # Given a set of LR(0) items, a set of non-terminal transitions, a readset, |
| # and an include set, this function computes the follow sets |
| # |
| # Follow(p,A) = Read(p,A) U U {Follow(p',B) | (p,A) INCLUDES (p',B)} |
| # |
| # Inputs: |
| # ntrans = Set of nonterminal transitions |
| # readsets = Readset (previously computed) |
| # inclsets = Include sets (previously computed) |
| # |
| # Returns a set containing the follow sets |
| # ----------------------------------------------------------------------------- |
| |
| def compute_follow_sets(ntrans,readsets,inclsets): |
| FP = lambda x: readsets[x] |
| R = lambda x: inclsets.get(x,[]) |
| F = digraph(ntrans,R,FP) |
| return F |
| |
| # ----------------------------------------------------------------------------- |
| # add_lookaheads() |
| # |
| # Attaches the lookahead symbols to grammar rules. |
| # |
| # Inputs: lookbacks - Set of lookback relations |
| # followset - Computed follow set |
| # |
| # This function directly attaches the lookaheads to productions contained |
| # in the lookbacks set |
| # ----------------------------------------------------------------------------- |
| |
| def add_lookaheads(lookbacks,followset): |
| for trans,lb in lookbacks.items(): |
| # Loop over productions in lookback |
| for state,p in lb: |
| if state not in p.lookaheads: |
| p.lookaheads[state] = [] |
| f = followset.get(trans,[]) |
| for a in f: |
| if a not in p.lookaheads[state]: p.lookaheads[state].append(a) |
| |
| # ----------------------------------------------------------------------------- |
| # add_lalr_lookaheads() |
| # |
| # This function does all of the work of adding lookahead information for use |
| # with LALR parsing |
| # ----------------------------------------------------------------------------- |
| |
| def add_lalr_lookaheads(C): |
| # Determine all of the nullable nonterminals |
| nullable = compute_nullable_nonterminals() |
| |
| # Find all non-terminal transitions |
| trans = find_nonterminal_transitions(C) |
| |
| # Compute read sets |
| readsets = compute_read_sets(C,trans,nullable) |
| |
| # Compute lookback/includes relations |
| lookd, included = compute_lookback_includes(C,trans,nullable) |
| |
| # Compute LALR FOLLOW sets |
| followsets = compute_follow_sets(trans,readsets,included) |
| |
| # Add all of the lookaheads |
| add_lookaheads(lookd,followsets) |
| |
| # ----------------------------------------------------------------------------- |
| # lr_parse_table() |
| # |
| # This function constructs the parse tables for SLR or LALR |
| # ----------------------------------------------------------------------------- |
| def lr_parse_table(method): |
| global _lr_method |
| goto = _lr_goto # Goto array |
| action = _lr_action # Action array |
| actionp = { } # Action production array (temporary) |
| |
| _lr_method = method |
| |
| n_srconflict = 0 |
| n_rrconflict = 0 |
| |
| if yaccdebug: |
| sys.stderr.write("yacc: Generating %s parsing table...\n" % method) |
| _vf.write("\n\nParsing method: %s\n\n" % method) |
| |
| # Step 1: Construct C = { I0, I1, ... IN}, collection of LR(0) items |
| # This determines the number of states |
| |
| C = lr0_items() |
| |
| if method == 'LALR': |
| add_lalr_lookaheads(C) |
| |
| # Build the parser table, state by state |
| st = 0 |
| for I in C: |
| # Loop over each production in I |
| actlist = [ ] # List of actions |
| |
| if yaccdebug: |
| _vf.write("\nstate %d\n\n" % st) |
| for p in I: |
| _vf.write(" (%d) %s\n" % (p.number, str(p))) |
| _vf.write("\n") |
| |
| for p in I: |
| try: |
| if p.prod[-1] == ".": |
| if p.name == "S'": |
| # Start symbol. Accept! |
| action[st,"$end"] = 0 |
| actionp[st,"$end"] = p |
| else: |
| # We are at the end of a production. Reduce! |
| if method == 'LALR': |
| laheads = p.lookaheads[st] |
| else: |
| laheads = Follow[p.name] |
| for a in laheads: |
| actlist.append((a,p,"reduce using rule %d (%s)" % (p.number,p))) |
| r = action.get((st,a),None) |
| if r is not None: |
| # Whoa. Have a shift/reduce or reduce/reduce conflict |
| if r > 0: |
| # Need to decide on shift or reduce here |
| # By default we favor shifting. Need to add |
| # some precedence rules here. |
| sprec,slevel = Productions[actionp[st,a].number].prec |
| rprec,rlevel = Precedence.get(a,('right',0)) |
| if (slevel < rlevel) or ((slevel == rlevel) and (rprec == 'left')): |
| # We really need to reduce here. |
| action[st,a] = -p.number |
| actionp[st,a] = p |
| if not slevel and not rlevel: |
| _vfc.write("shift/reduce conflict in state %d resolved as reduce.\n" % st) |
| _vf.write(" ! shift/reduce conflict for %s resolved as reduce.\n" % a) |
| n_srconflict += 1 |
| elif (slevel == rlevel) and (rprec == 'nonassoc'): |
| action[st,a] = None |
| else: |
| # Hmmm. Guess we'll keep the shift |
| if not rlevel: |
| _vfc.write("shift/reduce conflict in state %d resolved as shift.\n" % st) |
| _vf.write(" ! shift/reduce conflict for %s resolved as shift.\n" % a) |
| n_srconflict +=1 |
| elif r < 0: |
| # Reduce/reduce conflict. In this case, we favor the rule |
| # that was defined first in the grammar file |
| oldp = Productions[-r] |
| pp = Productions[p.number] |
| if oldp.line > pp.line: |
| action[st,a] = -p.number |
| actionp[st,a] = p |
| # sys.stderr.write("Reduce/reduce conflict in state %d\n" % st) |
| n_rrconflict += 1 |
| _vfc.write("reduce/reduce conflict in state %d resolved using rule %d (%s).\n" % (st, actionp[st,a].number, actionp[st,a])) |
| _vf.write(" ! reduce/reduce conflict for %s resolved using rule %d (%s).\n" % (a,actionp[st,a].number, actionp[st,a])) |
| else: |
| sys.stderr.write("Unknown conflict in state %d\n" % st) |
| else: |
| action[st,a] = -p.number |
| actionp[st,a] = p |
| else: |
| i = p.lr_index |
| a = p.prod[i+1] # Get symbol right after the "." |
| if a in Terminals: |
| g = lr0_goto(I,a) |
| j = _lr0_cidhash.get(id(g),-1) |
| if j >= 0: |
| # We are in a shift state |
| actlist.append((a,p,"shift and go to state %d" % j)) |
| r = action.get((st,a),None) |
| if r is not None: |
| # Whoa have a shift/reduce or shift/shift conflict |
| if r > 0: |
| if r != j: |
| sys.stderr.write("Shift/shift conflict in state %d\n" % st) |
| elif r < 0: |
| # Do a precedence check. |
| # - if precedence of reduce rule is higher, we reduce. |
| # - if precedence of reduce is same and left assoc, we reduce. |
| # - otherwise we shift |
| rprec,rlevel = Productions[actionp[st,a].number].prec |
| sprec,slevel = Precedence.get(a,('right',0)) |
| if (slevel > rlevel) or ((slevel == rlevel) and (rprec != 'left')): |
| # We decide to shift here... highest precedence to shift |
| action[st,a] = j |
| actionp[st,a] = p |
| if not rlevel: |
| n_srconflict += 1 |
| _vfc.write("shift/reduce conflict in state %d resolved as shift.\n" % st) |
| _vf.write(" ! shift/reduce conflict for %s resolved as shift.\n" % a) |
| elif (slevel == rlevel) and (rprec == 'nonassoc'): |
| action[st,a] = None |
| else: |
| # Hmmm. Guess we'll keep the reduce |
| if not slevel and not rlevel: |
| n_srconflict +=1 |
| _vfc.write("shift/reduce conflict in state %d resolved as reduce.\n" % st) |
| _vf.write(" ! shift/reduce conflict for %s resolved as reduce.\n" % a) |
| |
| else: |
| sys.stderr.write("Unknown conflict in state %d\n" % st) |
| else: |
| action[st,a] = j |
| actionp[st,a] = p |
| |
| except Exception as e: |
| raise YaccError("Hosed in lr_parse_table").with_traceback(e) |
| |
| # Print the actions associated with each terminal |
| if yaccdebug: |
| _actprint = { } |
| for a,p,m in actlist: |
| if (st,a) in action: |
| if p is actionp[st,a]: |
| _vf.write(" %-15s %s\n" % (a,m)) |
| _actprint[(a,m)] = 1 |
| _vf.write("\n") |
| for a,p,m in actlist: |
| if (st,a) in action: |
| if p is not actionp[st,a]: |
| if (a,m) not in _actprint: |
| _vf.write(" ! %-15s [ %s ]\n" % (a,m)) |
| _actprint[(a,m)] = 1 |
| |
| # Construct the goto table for this state |
| if yaccdebug: |
| _vf.write("\n") |
| nkeys = { } |
| for ii in I: |
| for s in ii.usyms: |
| if s in Nonterminals: |
| nkeys[s] = None |
| for n in nkeys.keys(): |
| g = lr0_goto(I,n) |
| j = _lr0_cidhash.get(id(g),-1) |
| if j >= 0: |
| goto[st,n] = j |
| if yaccdebug: |
| _vf.write(" %-30s shift and go to state %d\n" % (n,j)) |
| |
| st += 1 |
| |
| if yaccdebug: |
| if n_srconflict == 1: |
| sys.stderr.write("yacc: %d shift/reduce conflict\n" % n_srconflict) |
| if n_srconflict > 1: |
| sys.stderr.write("yacc: %d shift/reduce conflicts\n" % n_srconflict) |
| if n_rrconflict == 1: |
| sys.stderr.write("yacc: %d reduce/reduce conflict\n" % n_rrconflict) |
| if n_rrconflict > 1: |
| sys.stderr.write("yacc: %d reduce/reduce conflicts\n" % n_rrconflict) |
| |
| # ----------------------------------------------------------------------------- |
| # ==== LR Utility functions ==== |
| # ----------------------------------------------------------------------------- |
| |
| # ----------------------------------------------------------------------------- |
| # _lr_write_tables() |
| # |
| # This function writes the LR parsing tables to a file |
| # ----------------------------------------------------------------------------- |
| |
| def lr_write_tables(modulename=tab_module,outputdir=''): |
| filename = os.path.join(outputdir,modulename) + ".py" |
| try: |
| f = open(filename,"w") |
| |
| f.write(""" |
| # %s |
| # This file is automatically generated. Do not edit. |
| |
| _lr_method = %s |
| |
| _lr_signature = %s |
| """ % (filename, repr(_lr_method), repr(Signature.digest()))) |
| |
| # Change smaller to 0 to go back to original tables |
| smaller = 1 |
| |
| # Factor out names to try and make smaller |
| if smaller: |
| items = { } |
| |
| for k,v in _lr_action.items(): |
| i = items.get(k[1]) |
| if not i: |
| i = ([],[]) |
| items[k[1]] = i |
| i[0].append(k[0]) |
| i[1].append(v) |
| |
| f.write("\n_lr_action_items = {") |
| for k,v in items.items(): |
| f.write("%r:([" % k) |
| for i in v[0]: |
| f.write("%r," % i) |
| f.write("],[") |
| for i in v[1]: |
| f.write("%r," % i) |
| |
| f.write("]),") |
| f.write("}\n") |
| |
| f.write(""" |
| _lr_action = { } |
| for _k, _v in _lr_action_items.items(): |
| for _x,_y in zip(_v[0],_v[1]): |
| _lr_action[(_x,_k)] = _y |
| del _lr_action_items |
| """) |
| |
| else: |
| f.write("\n_lr_action = { "); |
| for k,v in _lr_action.items(): |
| f.write("(%r,%r):%r," % (k[0],k[1],v)) |
| f.write("}\n"); |
| |
| if smaller: |
| # Factor out names to try and make smaller |
| items = { } |
| |
| for k,v in _lr_goto.items(): |
| i = items.get(k[1]) |
| if not i: |
| i = ([],[]) |
| items[k[1]] = i |
| i[0].append(k[0]) |
| i[1].append(v) |
| |
| f.write("\n_lr_goto_items = {") |
| for k,v in items.items(): |
| f.write("%r:([" % k) |
| for i in v[0]: |
| f.write("%r," % i) |
| f.write("],[") |
| for i in v[1]: |
| f.write("%r," % i) |
| |
| f.write("]),") |
| f.write("}\n") |
| |
| f.write(""" |
| _lr_goto = { } |
| for _k, _v in _lr_goto_items.items(): |
| for _x,_y in zip(_v[0],_v[1]): |
| _lr_goto[(_x,_k)] = _y |
| del _lr_goto_items |
| """) |
| else: |
| f.write("\n_lr_goto = { "); |
| for k,v in _lr_goto.items(): |
| f.write("(%r,%r):%r," % (k[0],k[1],v)) |
| f.write("}\n"); |
| |
| # Write production table |
| f.write("_lr_productions = [\n") |
| for p in Productions: |
| if p: |
| if (p.func): |
| f.write(" (%r,%d,%r,%r,%d),\n" % (p.name, p.len, p.func.__name__,p.file,p.line)) |
| else: |
| f.write(" (%r,%d,None,None,None),\n" % (p.name, p.len)) |
| else: |
| f.write(" None,\n") |
| f.write("]\n") |
| |
| f.close() |
| |
| except IOError as e: |
| print("Unable to create '%s'" % filename) |
| print(e) |
| |
| def lr_read_tables(module=tab_module,optimize=0): |
| global _lr_action, _lr_goto, _lr_productions, _lr_method |
| try: |
| exec("import %s as parsetab" % module) |
| |
| if (optimize) or (Signature.digest() == parsetab._lr_signature): |
| _lr_action = parsetab._lr_action |
| _lr_goto = parsetab._lr_goto |
| _lr_productions = parsetab._lr_productions |
| _lr_method = parsetab._lr_method |
| return 1 |
| else: |
| return 0 |
| |
| except (ImportError,AttributeError): |
| return 0 |
| |
| |
| # Available instance types. This is used when parsers are defined by a class. |
| # In Python3 the InstanceType and ObjectType are no more, they've passed, ceased |
| # to be, they are ex-classes along with old-style classes |
| |
| try: |
| _INSTANCETYPE = (types.InstanceType, types.ObjectType) |
| except AttributeError: |
| _INSTANCETYPE = object |
| |
| # ----------------------------------------------------------------------------- |
| # yacc(module) |
| # |
| # Build the parser module |
| # ----------------------------------------------------------------------------- |
| |
| def yacc(method=default_lr, debug=yaccdebug, module=None, tabmodule=tab_module, start=None, check_recursion=1, optimize=0,write_tables=1,debugfile=debug_file,outputdir=''): |
| global yaccdebug |
| yaccdebug = debug |
| |
| initialize_vars() |
| files = { } |
| error = 0 |
| |
| |
| # Add parsing method to signature |
| Signature.update(util.encode_input(method)) |
| |
| # If a "module" parameter was supplied, extract its dictionary. |
| # Note: a module may in fact be an instance as well. |
| |
| if module: |
| # User supplied a module object. |
| if isinstance(module, types.ModuleType): |
| ldict = module.__dict__ |
| elif isinstance(module, _INSTANCETYPE): |
| _items = [(k,getattr(module,k)) for k in dir(module)] |
| ldict = { } |
| for i in _items: |
| ldict[i[0]] = i[1] |
| else: |
| raise ValueError("Expected a module") |
| |
| else: |
| # No module given. We might be able to get information from the caller. |
| # Throw an exception and unwind the traceback to get the globals |
| |
| try: |
| raise RuntimeError |
| except RuntimeError: |
| e,b,t = sys.exc_info() |
| f = t.tb_frame |
| f = f.f_back # Walk out to our calling function |
| ldict = f.f_globals # Grab its globals dictionary |
| |
| # Add starting symbol to signature |
| if not start: |
| start = ldict.get("start",None) |
| if start: |
| Signature.update(util.encode_input(start)) |
| |
| # If running in optimized mode. We're going to |
| |
| if (optimize and lr_read_tables(tabmodule,1)): |
| # Read parse table |
| del Productions[:] |
| for p in _lr_productions: |
| if not p: |
| Productions.append(None) |
| else: |
| m = MiniProduction() |
| m.name = p[0] |
| m.len = p[1] |
| m.file = p[3] |
| m.line = p[4] |
| if p[2]: |
| m.func = ldict[p[2]] |
| Productions.append(m) |
| |
| else: |
| # Get the tokens map |
| if (module and isinstance(module,_INSTANCETYPE)): |
| tokens = getattr(module,"tokens",None) |
| else: |
| tokens = ldict.get("tokens",None) |
| |
| if not tokens: |
| raise YaccError("module does not define a list 'tokens'") |
| if not (isinstance(tokens,list) or isinstance(tokens,tuple)): |
| raise YaccError("tokens must be a list or tuple.") |
| |
| # Check to see if a requires dictionary is defined. |
| requires = ldict.get("require",None) |
| if requires: |
| if not (isinstance(requires,dict)): |
| raise YaccError("require must be a dictionary.") |
| |
| for r,v in requires.items(): |
| try: |
| if not (isinstance(v,list)): |
| raise TypeError |
| v1 = [x.split(".") for x in v] |
| Requires[r] = v1 |
| except Exception: |
| print("Invalid specification for rule '%s' in require. Expected a list of strings" % r) |
| |
| |
| # Build the dictionary of terminals. We a record a 0 in the |
| # dictionary to track whether or not a terminal is actually |
| # used in the grammar |
| |
| if 'error' in tokens: |
| print("yacc: Illegal token 'error'. Is a reserved word.") |
| raise YaccError("Illegal token name") |
| |
| for n in tokens: |
| if n in Terminals: |
| print("yacc: Warning. Token '%s' multiply defined." % n) |
| Terminals[n] = [ ] |
| |
| Terminals['error'] = [ ] |
| |
| # Get the precedence map (if any) |
| prec = ldict.get("precedence",None) |
| if prec: |
| if not (isinstance(prec,list) or isinstance(prec,tuple)): |
| raise YaccError("precedence must be a list or tuple.") |
| add_precedence(prec) |
| Signature.update(util.encode_input(repr(prec))) |
| |
| for n in tokens: |
| if n not in Precedence: |
| Precedence[n] = ('right',0) # Default, right associative, 0 precedence |
| |
| # Look for error handler |
| ef = ldict.get('p_error',None) |
| if ef: |
| if isinstance(ef,types.FunctionType): |
| ismethod = 0 |
| elif isinstance(ef, types.MethodType): |
| ismethod = 1 |
| else: |
| raise YaccError("'p_error' defined, but is not a function or method.") |
| eline = ef.__code__.co_firstlineno |
| efile = ef.__code__.co_filename |
| files[efile] = None |
| |
| if (ef.__code__.co_argcount != 1+ismethod): |
| raise YaccError("%s:%d: p_error() requires 1 argument." % (efile,eline)) |
| global Errorfunc |
| Errorfunc = ef |
| else: |
| print("yacc: Warning. no p_error() function is defined.") |
| |
| # Get the list of built-in functions with p_ prefix |
| symbols = [ldict[f] for f in ldict.keys() |
| if (type(ldict[f]) in (types.FunctionType, types.MethodType) and ldict[f].__name__[:2] == 'p_' |
| and ldict[f].__name__ != 'p_error')] |
| |
| # Check for non-empty symbols |
| if len(symbols) == 0: |
| raise YaccError("no rules of the form p_rulename are defined.") |
| |
| # Sort the symbols by line number |
| symbols.sort(key=lambda x: x.__code__.co_firstlineno) |
| |
| # Add all of the symbols to the grammar |
| for f in symbols: |
| if (add_function(f)) < 0: |
| error += 1 |
| else: |
| files[f.__code__.co_filename] = None |
| |
| # Make a signature of the docstrings |
| for f in symbols: |
| if f.__doc__: |
| Signature.update(util.encode_input(f.__doc__)) |
| |
| lr_init_vars() |
| |
| if error: |
| raise YaccError("Unable to construct parser.") |
| |
| if not lr_read_tables(tabmodule): |
| |
| # Validate files |
| for filename in files.keys(): |
| if not validate_file(filename): |
| error = 1 |
| |
| # Validate dictionary |
| validate_dict(ldict) |
| |
| if start and start not in Prodnames: |
| raise YaccError("Bad starting symbol '%s'" % start) |
| |
| augment_grammar(start) |
| error = verify_productions(cycle_check=check_recursion) |
| otherfunc = [ldict[f] for f in ldict.keys() |
| if (type(f) in (types.FunctionType,types.MethodType) and ldict[f].__name__[:2] != 'p_')] |
| |
| if error: |
| raise YaccError("Unable to construct parser.") |
| |
| build_lritems() |
| compute_first1() |
| compute_follow(start) |
| |
| if method in ['SLR','LALR']: |
| lr_parse_table(method) |
| else: |
| raise YaccError("Unknown parsing method '%s'" % method) |
| |
| if write_tables: |
| lr_write_tables(tabmodule,outputdir) |
| |
| if yaccdebug: |
| try: |
| f = open(os.path.join(outputdir,debugfile),"w") |
| f.write(_vfc.getvalue()) |
| f.write("\n\n") |
| f.write(_vf.getvalue()) |
| f.close() |
| except IOError as e: |
| print("yacc: can't create '%s'" % debugfile,e) |
| |
| # Made it here. Create a parser object and set up its internal state. |
| # Set global parse() method to bound method of parser object. |
| |
| p = Parser("xyzzy") |
| p.productions = Productions |
| p.errorfunc = Errorfunc |
| p.action = _lr_action |
| p.goto = _lr_goto |
| p.method = _lr_method |
| p.require = Requires |
| |
| global parse |
| parse = p.parse |
| |
| global parser |
| parser = p |
| |
| # Clean up all of the globals we created |
| if (not optimize): |
| yacc_cleanup() |
| return p |
| |
| # yacc_cleanup function. Delete all of the global variables |
| # used during table construction |
| |
| def yacc_cleanup(): |
| global _lr_action, _lr_goto, _lr_method, _lr_goto_cache |
| del _lr_action, _lr_goto, _lr_method, _lr_goto_cache |
| |
| global Productions, Prodnames, Prodmap, Terminals |
| global Nonterminals, First, Follow, Precedence, LRitems |
| global Errorfunc, Signature, Requires |
| |
| del Productions, Prodnames, Prodmap, Terminals |
| del Nonterminals, First, Follow, Precedence, LRitems |
| del Errorfunc, Signature, Requires |
| |
| global _vf, _vfc |
| del _vf, _vfc |
| |
| |
| # Stub that raises an error if parsing is attempted without first calling yacc() |
| def parse(*args,**kwargs): |
| raise YaccError("yacc: No parser built with yacc()") |
| |
