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\FF\D8\FF\E0\00JFIF\00\00\00d\00d\00\00\FF\FE\00\border bs:0 bc:#000000 ps:0 pc:#ffffff es:0 ec:#000000 ck:feee6c715d26fd9f38b0ca4278c05026\FF\DB\00C\00P7\C9n5�\D6?\BD�\9Ds\EBp\9F[`8m\B7)o\B5\E8\E6I\99\FE3]]A2\BA\8Cw\D6E\93\\DEv\C8\009\F2\F1NI?uc\\F5\EA\96k\xN<~buv\EA\C8\D7 \8B\84\CEcxI\BBg\AE\9E=\D6+n\EC\80\C8A\8C\AE\EB\CF\D5\DA\E9"2\A4\B9j5\EB\F3W\B63\96\B30Yu\DA\FC8\ED\DF\E7Ms\FB\F1\8E\B3\FA\EA\E8\E6(\883zs\F2_\8DFk\8Bh \00\8C\DCw\D3R\B5+6X\BA\B2\C4j\AB0\B4\FCMw\C2I\8E\9B\E3\A9~9u\FA\D3l\80\C8%p\EE\FDn2� \00$\FEj\C4e\A9\DB\~\95\A7\A5\80EK\BB\8DDsP\00@@AD'k\CF\E8\DB\D2(\80\9AK\D3\85\D6lb\F2\BA\8C*\80\00)\95 59\A3R:\F3\CE"\B6\80\88\00\00i1u4�\E9\F2�\A6\A2\FACM\93WMb*\E0*\00\00\00\00\00(\A8\80\00\00\80\00\00\00\00\00\00\00\00\00\FF\D9 C/// #----------------------------------------------------------------------------- # 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 -> " % 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- symbols of First[x] to the result. for f in First[x]: if f == '': 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('') 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 != '' and f not in Follow[B]: Follow[B].append(f) didadd = 1 if f == '': 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'