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#----------------------------------------------------------------------------- # 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()")