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Edit File: yacc.py

# ----------------------------------------------------------------------------- # ply: yacc.py # # Copyright (C) 2001-2011, # David M. Beazley (Dabeaz LLC) # All rights reserved. # # Redistribution and use in source and binary forms, with or without # modification, are permitted provided that the following conditions are # met: # # * Redistributions of source code must retain the above copyright notice, # this list of conditions and the following disclaimer. # * Redistributions in binary form must reproduce the above copyright notice, # this list of conditions and the following disclaimer in the documentation # and/or other materials provided with the distribution. # * Neither the name of the David Beazley or Dabeaz LLC may be used to # endorse or promote products derived from this software without # specific prior written permission. # # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT # OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. # ----------------------------------------------------------------------------- # # 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__ = "3.4" __tabversion__ = "3.2" # Table version #----------------------------------------------------------------------------- # === 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 yaccdevel = 0 # Set to True if developing yacc. This turns off optimized # implementations of certain functions. resultlimit = 40 # Size limit of results when running in debug mode. pickle_protocol = 0 # Protocol to use when writing pickle files import re, types, sys, os.path # Compatibility function for python 2.6/3.0 if sys.version_info[0] < 3: def func_code(f): return f.func_code else: def func_code(f): return f.__code__ # Compatibility try: MAXINT = sys.maxint except AttributeError: MAXINT = sys.maxsize # Python 2.x/3.0 compatibility. def load_ply_lex(): if sys.version_info[0] < 3: import lex else: import ply.lex as lex return lex # This object is a stand-in for a logging object created by the # logging module. PLY will use this by default to create things # such as the parser.out file. If a user wants more detailed # information, they can create their own logging object and pass # it into PLY. class PlyLogger(object): def __init__(self,f): self.f = f def debug(self,msg,*args,**kwargs): self.f.write((msg % args) + "\n") info = debug def warning(self,msg,*args,**kwargs): self.f.write("WARNING: "+ (msg % args) + "\n") def error(self,msg,*args,**kwargs): self.f.write("ERROR: " + (msg % args) + "\n") critical = debug # Null logger is used when no output is generated. Does nothing. class NullLogger(object): def __getattribute__(self,name): return self def __call__(self,*args,**kwargs): return self # Exception raised for yacc-related errors class YaccError(Exception): pass # Format the result message that the parser produces when running in debug mode. def format_result(r): repr_str = repr(r) if '\n' in repr_str: repr_str = repr(repr_str) if len(repr_str) > resultlimit: repr_str = repr_str[:resultlimit]+" ..." result = "<%s @ 0x%x> (%s)" % (type(r).__name__,id(r),repr_str) return result # Format stack entries when the parser is running in debug mode def format_stack_entry(r): repr_str = repr(r) if '\n' in repr_str: repr_str = repr(repr_str) if len(repr_str) < 16: return repr_str else: return "<%s @ 0x%x>" % (type(r).__name__,id(r)) #----------------------------------------------------------------------------- # === 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.stack = stack self.lexer = None self.parser= None def __getitem__(self,n): if n >= 0: return self.slice[n].value else: return self.stack[n].value def __setitem__(self,n,v): self.slice[n].value = v def __getslice__(self,i,j): return [s.value for s in self.slice[i:j]] def __len__(self): return len(self.slice) def lineno(self,n): return getattr(self.slice[n],"lineno",0) def set_lineno(self,n,lineno): self.slice[n].lineno = lineno 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 error(self): raise SyntaxError # ----------------------------------------------------------------------------- # == LRParser == # # The LR Parsing engine. # ----------------------------------------------------------------------------- class LRParser: def __init__(self,lrtab,errorf): self.productions = lrtab.lr_productions self.action = lrtab.lr_action self.goto = lrtab.lr_goto self.errorfunc = errorf def errok(self): self.errorok = 1 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,tracking=0,tokenfunc=None): if debug or yaccdevel: if isinstance(debug,int): debug = PlyLogger(sys.stderr) return self.parsedebug(input,lexer,debug,tracking,tokenfunc) elif tracking: return self.parseopt(input,lexer,debug,tracking,tokenfunc) else: return self.parseopt_notrack(input,lexer,debug,tracking,tokenfunc) # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! # parsedebug(). # # This is the debugging enabled version of parse(). All changes made to the # parsing engine should be made here. For the non-debugging version, # copy this code to a method parseopt() and delete all of the sections # enclosed in: # # #--! DEBUG # statements # #--! DEBUG # # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! def parsedebug(self,input=None,lexer=None,debug=None,tracking=0,tokenfunc=None): lookahead = None # Current lookahead symbol lookaheadstack = [ ] # Stack of lookahead symbols actions = self.action # Local reference to action table (to avoid lookup on self.) goto = self.goto # Local reference to goto table (to avoid lookup on self.) prod = self.productions # Local reference to production list (to avoid lookup on self.) pslice = YaccProduction(None) # Production object passed to grammar rules errorcount = 0 # Used during error recovery # --! DEBUG debug.info("PLY: PARSE DEBUG START") # --! DEBUG # If no lexer was given, we will try to use the lex module if not lexer: lex = load_ply_lex() lexer = lex.lexer # Set up the lexer and parser objects on pslice pslice.lexer = lexer pslice.parser = self # If input was supplied, pass to lexer if input is not None: lexer.input(input) if tokenfunc is None: # Tokenize function get_token = lexer.token else: get_token = tokenfunc # Set up the state and symbol stacks 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 = "$end" symstack.append(sym) state = 0 while 1: # Get the next symbol on the input. If a lookahead symbol # is already set, we just use that. Otherwise, we'll pull # the next token off of the lookaheadstack or from the lexer # --! DEBUG debug.debug('') debug.debug('State : %s', state) # --! DEBUG if not lookahead: if not lookaheadstack: lookahead = get_token() # Get the next token else: lookahead = lookaheadstack.pop() if not lookahead: lookahead = YaccSymbol() lookahead.type = "$end" # --! DEBUG debug.debug('Stack : %s', ("%s . %s" % (" ".join([xx.type for xx in symstack][1:]), str(lookahead))).lstrip()) # --! DEBUG # Check the action table ltype = lookahead.type t = actions[state].get(ltype) if t is not None: if t > 0: # shift a symbol on the stack statestack.append(t) state = t # --! DEBUG debug.debug("Action : Shift and goto state %s", t) # --! DEBUG symstack.append(lookahead) lookahead = None # Decrease error count on successful shift if errorcount: 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 # --! DEBUG if plen: debug.info("Action : Reduce rule [%s] with %s and goto state %d", p.str, "["+",".join([format_stack_entry(_v.value) for _v in symstack[-plen:]])+"]",-t) else: debug.info("Action : Reduce rule [%s] with %s and goto state %d", p.str, [],-t) # --! DEBUG if plen: targ = symstack[-plen-1:] targ[0] = sym # --! TRACKING if tracking: t1 = targ[1] sym.lineno = t1.lineno sym.lexpos = t1.lexpos t1 = targ[-1] sym.endlineno = getattr(t1,"endlineno",t1.lineno) sym.endlexpos = getattr(t1,"endlexpos",t1.lexpos) # --! TRACKING # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! # The code enclosed in this section is duplicated # below as a performance optimization. Make sure # changes get made in both locations. pslice.slice = targ try: # Call the grammar rule with our special slice object del symstack[-plen:] del statestack[-plen:] p.callable(pslice) # --! DEBUG debug.info("Result : %s", format_result(pslice[0])) # --! DEBUG symstack.append(sym) state = goto[statestack[-1]][pname] statestack.append(state) except SyntaxError: # If an error was set. Enter error recovery state lookaheadstack.append(lookahead) symstack.pop() statestack.pop() state = statestack[-1] sym.type = 'error' lookahead = sym errorcount = error_count self.errorok = 0 continue # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! else: # --! TRACKING if tracking: sym.lineno = lexer.lineno sym.lexpos = lexer.lexpos # --! TRACKING targ = [ sym ] # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! # The code enclosed in this section is duplicated # above as a performance optimization. Make sure # changes get made in both locations. pslice.slice = targ try: # Call the grammar rule with our special slice object p.callable(pslice) # --! DEBUG debug.info("Result : %s", format_result(pslice[0])) # --! DEBUG symstack.append(sym) state = goto[statestack[-1]][pname] statestack.append(state) except SyntaxError: # If an error was set. Enter error recovery state lookaheadstack.append(lookahead) symstack.pop() statestack.pop() state = statestack[-1] sym.type = 'error' lookahead = sym errorcount = error_count self.errorok = 0 continue # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! if t == 0: n = symstack[-1] result = getattr(n,"value",None) # --! DEBUG debug.info("Done : Returning %s", format_result(result)) debug.info("PLY: PARSE DEBUG END") # --! DEBUG return result if t == None: # --! DEBUG debug.error('Error : %s', ("%s . %s" % (" ".join([xx.type for xx in symstack][1:]), str(lookahead))).lstrip()) # --! DEBUG # 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 errorcount == 0 or self.errorok: errorcount = error_count self.errorok = 0 errtoken = lookahead if errtoken.type == "$end": errtoken = None # End of file! if self.errorfunc: global errok,token,restart errok = self.errok # Set some special functions available in error recovery token = get_token restart = self.restart if errtoken and not hasattr(errtoken,'lexer'): errtoken.lexer = lexer tok = self.errorfunc(errtoken) del errok, token, restart # Delete special functions if self.errorok: # User must have done some kind of panic # mode recovery on their own. The # returned token is the next lookahead lookahead = tok errtoken = None continue else: if errtoken: if hasattr(errtoken,"lineno"): lineno = lookahead.lineno else: lineno = 0 if lineno: sys.stderr.write("yacc: Syntax error at line %d, token=%s\n" % (lineno, errtoken.type)) else: sys.stderr.write("yacc: Syntax error, token=%s" % errtoken.type) else: sys.stderr.write("yacc: Parse error in input. EOF\n") return else: errorcount = error_count # case 1: the statestack only has 1 entry on it. If we're in this state, the # entire parse has been rolled back and we're completely hosed. The token is # discarded and we just keep going. if len(statestack) <= 1 and lookahead.type != "$end": lookahead = None errtoken = None state = 0 # 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() state = statestack[-1] # Potential bug fix continue # Call an error function here raise RuntimeError("yacc: internal parser error!!!\n") # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! # parseopt(). # # Optimized version of parse() method. DO NOT EDIT THIS CODE DIRECTLY. # Edit the debug version above, then copy any modifications to the method # below while removing #--! DEBUG sections. # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! def parseopt(self,input=None,lexer=None,debug=0,tracking=0,tokenfunc=None): lookahead = None # Current lookahead symbol lookaheadstack = [ ] # Stack of lookahead symbols actions = self.action # Local reference to action table (to avoid lookup on self.) goto = self.goto # Local reference to goto table (to avoid lookup on self.) prod = self.productions # Local reference to production list (to avoid lookup on self.) pslice = YaccProduction(None) # Production object passed to grammar rules errorcount = 0 # Used during error recovery # If no lexer was given, we will try to use the lex module if not lexer: lex = load_ply_lex() lexer = lex.lexer # Set up the lexer and parser objects on pslice pslice.lexer = lexer pslice.parser = self # If input was supplied, pass to lexer if input is not None: lexer.input(input) if tokenfunc is None: # Tokenize function get_token = lexer.token else: get_token = tokenfunc # Set up the state and symbol stacks 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 = '$end' symstack.append(sym) state = 0 while 1: # Get the next symbol on the input. If a lookahead symbol # is already set, we just use that. Otherwise, we'll pull # the next token off of the lookaheadstack or from the lexer if not lookahead: if not lookaheadstack: lookahead = get_token() # Get the next token else: lookahead = lookaheadstack.pop() if not lookahead: lookahead = YaccSymbol() lookahead.type = '$end' # Check the action table ltype = lookahead.type t = actions[state].get(ltype) if t is not None: if t > 0: # shift a symbol on the stack statestack.append(t) state = t symstack.append(lookahead) lookahead = None # Decrease error count on successful shift if errorcount: 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 plen: targ = symstack[-plen-1:] targ[0] = sym # --! TRACKING if tracking: t1 = targ[1] sym.lineno = t1.lineno sym.lexpos = t1.lexpos t1 = targ[-1] sym.endlineno = getattr(t1,"endlineno",t1.lineno) sym.endlexpos = getattr(t1,"endlexpos",t1.lexpos) # --! TRACKING # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! # The code enclosed in this section is duplicated # below as a performance optimization. Make sure # changes get made in both locations. pslice.slice = targ try: # Call the grammar rule with our special slice object del symstack[-plen:] del statestack[-plen:] p.callable(pslice) symstack.append(sym) state = goto[statestack[-1]][pname] statestack.append(state) except SyntaxError: # If an error was set. Enter error recovery state lookaheadstack.append(lookahead) symstack.pop() statestack.pop() state = statestack[-1] sym.type = 'error' lookahead = sym errorcount = error_count self.errorok = 0 continue # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! else: # --! TRACKING if tracking: sym.lineno = lexer.lineno sym.lexpos = lexer.lexpos # --! TRACKING targ = [ sym ] # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! # The code enclosed in this section is duplicated # above as a performance optimization. Make sure # changes get made in both locations. pslice.slice = targ try: # Call the grammar rule with our special slice object p.callable(pslice) symstack.append(sym) state = goto[statestack[-1]][pname] statestack.append(state) except SyntaxError: # If an error was set. Enter error recovery state lookaheadstack.append(lookahead) symstack.pop() statestack.pop() state = statestack[-1] sym.type = 'error' lookahead = sym errorcount = error_count self.errorok = 0 continue # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! if t == 0: n = symstack[-1] return getattr(n,"value",None) if t == None: # 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 errorcount == 0 or self.errorok: errorcount = error_count self.errorok = 0 errtoken = lookahead if errtoken.type == '$end': errtoken = None # End of file! if self.errorfunc: global errok,token,restart errok = self.errok # Set some special functions available in error recovery token = get_token restart = self.restart if errtoken and not hasattr(errtoken,'lexer'): errtoken.lexer = lexer tok = self.errorfunc(errtoken) del errok, token, restart # Delete special functions if self.errorok: # User must have done some kind of panic # mode recovery on their own. The # returned token is the next lookahead lookahead = tok errtoken = None continue else: if errtoken: if hasattr(errtoken,"lineno"): lineno = lookahead.lineno else: lineno = 0 if lineno: sys.stderr.write("yacc: Syntax error at line %d, token=%s\n" % (lineno, errtoken.type)) else: sys.stderr.write("yacc: Syntax error, token=%s" % errtoken.type) else: sys.stderr.write("yacc: Parse error in input. EOF\n") return else: errorcount = error_count # case 1: the statestack only has 1 entry on it. If we're in this state, the # entire parse has been rolled back and we're completely hosed. The token is # discarded and we just keep going. if len(statestack) <= 1 and lookahead.type != '$end': lookahead = None errtoken = None state = 0 # 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() state = statestack[-1] # Potential bug fix continue # Call an error function here raise RuntimeError("yacc: internal parser error!!!\n") # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! # parseopt_notrack(). # # Optimized version of parseopt() with line number tracking removed. # DO NOT EDIT THIS CODE DIRECTLY. Copy the optimized version and remove # code in the #--! TRACKING sections # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! def parseopt_notrack(self,input=None,lexer=None,debug=0,tracking=0,tokenfunc=None): lookahead = None # Current lookahead symbol lookaheadstack = [ ] # Stack of lookahead symbols actions = self.action # Local reference to action table (to avoid lookup on self.) goto = self.goto # Local reference to goto table (to avoid lookup on self.) prod = self.productions # Local reference to production list (to avoid lookup on self.) pslice = YaccProduction(None) # Production object passed to grammar rules errorcount = 0 # Used during error recovery # If no lexer was given, we will try to use the lex module if not lexer: lex = load_ply_lex() lexer = lex.lexer # Set up the lexer and parser objects on pslice pslice.lexer = lexer pslice.parser = self # If input was supplied, pass to lexer if input is not None: lexer.input(input) if tokenfunc is None: # Tokenize function get_token = lexer.token else: get_token = tokenfunc # Set up the state and symbol stacks 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 = '$end' symstack.append(sym) state = 0 while 1: # Get the next symbol on the input. If a lookahead symbol # is already set, we just use that. Otherwise, we'll pull # the next token off of the lookaheadstack or from the lexer if not lookahead: if not lookaheadstack: lookahead = get_token() # Get the next token else: lookahead = lookaheadstack.pop() if not lookahead: lookahead = YaccSymbol() lookahead.type = '$end' # Check the action table ltype = lookahead.type t = actions[state].get(ltype) if t is not None: if t > 0: # shift a symbol on the stack statestack.append(t) state = t symstack.append(lookahead) lookahead = None # Decrease error count on successful shift if errorcount: 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 plen: targ = symstack[-plen-1:] targ[0] = sym # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! # The code enclosed in this section is duplicated # below as a performance optimization. Make sure # changes get made in both locations. pslice.slice = targ try: # Call the grammar rule with our special slice object del symstack[-plen:] del statestack[-plen:] p.callable(pslice) symstack.append(sym) state = goto[statestack[-1]][pname] statestack.append(state) except SyntaxError: # If an error was set. Enter error recovery state lookaheadstack.append(lookahead) symstack.pop() statestack.pop() state = statestack[-1] sym.type = 'error' lookahead = sym errorcount = error_count self.errorok = 0 continue # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! else: targ = [ sym ] # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! # The code enclosed in this section is duplicated # above as a performance optimization. Make sure # changes get made in both locations. pslice.slice = targ try: # Call the grammar rule with our special slice object p.callable(pslice) symstack.append(sym) state = goto[statestack[-1]][pname] statestack.append(state) except SyntaxError: # If an error was set. Enter error recovery state lookaheadstack.append(lookahead) symstack.pop() statestack.pop() state = statestack[-1] sym.type = 'error' lookahead = sym errorcount = error_count self.errorok = 0 continue # !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! if t == 0: n = symstack[-1] return getattr(n,"value",None) if t == None: # 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 errorcount == 0 or self.errorok: errorcount = error_count self.errorok = 0 errtoken = lookahead if errtoken.type == '$end': errtoken = None # End of file! if self.errorfunc: global errok,token,restart errok = self.errok # Set some special functions available in error recovery token = get_token restart = self.restart if errtoken and not hasattr(errtoken,'lexer'): errtoken.lexer = lexer tok = self.errorfunc(errtoken) del errok, token, restart # Delete special functions if self.errorok: # User must have done some kind of panic # mode recovery on their own. The # returned token is the next lookahead lookahead = tok errtoken = None continue else: if errtoken: if hasattr(errtoken,"lineno"): lineno = lookahead.lineno else: lineno = 0 if lineno: sys.stderr.write("yacc: Syntax error at line %d, token=%s\n" % (lineno, errtoken.type)) else: sys.stderr.write("yacc: Syntax error, token=%s" % errtoken.type) else: sys.stderr.write("yacc: Parse error in input. EOF\n") return else: errorcount = error_count # case 1: the statestack only has 1 entry on it. If we're in this state, the # entire parse has been rolled back and we're completely hosed. The token is # discarded and we just keep going. if len(statestack) <= 1 and lookahead.type != '$end': lookahead = None errtoken = None state = 0 # 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 == '$end': # Whoa. We're really hosed here. Bail out return if lookahead.type != 'error': sym = symstack[-1] if sym.type == 'error': # Hmmm. Error is on top of stack, we'll just nuke input # symbol and continue lookahead = None continue t = YaccSymbol() t.type = 'error' if hasattr(lookahead,"lineno"): t.lineno = lookahead.lineno t.value = lookahead lookaheadstack.append(lookahead) lookahead = t else: symstack.pop() statestack.pop() state = statestack[-1] # Potential bug fix continue # Call an error function here raise RuntimeError("yacc: internal parser error!!!\n") # ----------------------------------------------------------------------------- # === Grammar Representation === # # The following functions, classes, and variables are used to represent and # manipulate the rules that make up a grammar. # ----------------------------------------------------------------------------- import re # regex matching identifiers _is_identifier = re.compile(r'^[a-zA-Z0-9_-]+$') # ----------------------------------------------------------------------------- # class Production: # # This class stores the raw information about a single production or grammar rule. # A grammar rule refers to a specification such as this: # # expr : expr PLUS term # # Here are the basic attributes defined on all productions # # name - Name of the production. For example 'expr' # prod - A list of symbols on the right side ['expr','PLUS','term'] # prec - Production precedence level # number - Production number. # func - Function that executes on reduce # file - File where production function is defined # lineno - Line number where production function is defined # # The following attributes are defined or optional. # # len - Length of the production (number of symbols on right hand side) # usyms - Set of unique symbols found in the production # ----------------------------------------------------------------------------- class Production(object): reduced = 0 def __init__(self,number,name,prod,precedence=('right',0),func=None,file='',line=0): self.name = name self.prod = tuple(prod) self.number = number self.func = func self.callable = None self.file = file self.line = line self.prec = precedence # Internal settings used during table construction self.len = len(self.prod) # Length of the production # Create a list of unique production symbols used in the production self.usyms = [ ] for s in self.prod: if s not in self.usyms: self.usyms.append(s) # List of all LR items for the production self.lr_items = [] self.lr_next = None # Create a string representation if self.prod: self.str = "%s -> %s" % (self.name," ".join(self.prod)) else: self.str = "%s -> <empty>" % self.name def __str__(self): return self.str def __repr__(self): return "Production("+str(self)+")" def __len__(self): return len(self.prod) def __nonzero__(self): return 1 def __getitem__(self,index): return self.prod[index] # Return the nth lr_item from the production (or None if at the end) def lr_item(self,n): if n > len(self.prod): return None p = LRItem(self,n) # Precompute the list of productions immediately following. Hack. Remove later try: p.lr_after = Prodnames[p.prod[n+1]] except (IndexError,KeyError): p.lr_after = [] try: p.lr_before = p.prod[n-1] except IndexError: p.lr_before = None return p # Bind the production function name to a callable def bind(self,pdict): if self.func: self.callable = pdict[self.func] # This class serves as a minimal standin for Production objects when # reading table data from files. It only contains information # actually used by the LR parsing engine, plus some additional # debugging information. class MiniProduction(object): def __init__(self,str,name,len,func,file,line): self.name = name self.len = len self.func = func self.callable = None self.file = file self.line = line self.str = str def __str__(self): return self.str def __repr__(self): return "MiniProduction(%s)" % self.str # Bind the production function name to a callable def bind(self,pdict): if self.func: self.callable = pdict[self.func] # ----------------------------------------------------------------------------- # class LRItem # # This class represents a specific stage of parsing a production rule. For # example: # # expr : expr . PLUS term # # In the above, the "." represents the current location of the parse. Here # basic attributes: # # name - Name of the production. For example 'expr' # prod - A list of symbols on the right side ['expr','.', 'PLUS','term'] # number - Production number. # # lr_next Next LR item. Example, if we are ' expr -> expr . PLUS term' # then lr_next refers to 'expr -> expr PLUS . term' # 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) # lr_after - List of all productions that immediately follow # lr_before - Grammar symbol immediately before # ----------------------------------------------------------------------------- class LRItem(object): def __init__(self,p,n): self.name = p.name self.prod = list(p.prod) self.number = p.number self.lr_index = n self.lookaheads = { } self.prod.insert(n,".") self.prod = tuple(self.prod) self.len = len(self.prod) self.usyms = p.usyms 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 "LRItem("+str(self)+")" # ----------------------------------------------------------------------------- # rightmost_terminal() # # Return the rightmost terminal from a list of symbols. Used in add_production() # ----------------------------------------------------------------------------- def rightmost_terminal(symbols, terminals): i = len(symbols) - 1 while i >= 0: if symbols[i] in terminals: return symbols[i] i -= 1 return None # ----------------------------------------------------------------------------- # === GRAMMAR CLASS === # # The following class represents the contents of the specified grammar along # with various computed properties such as first sets, follow sets, LR items, etc. # This data is used for critical parts of the table generation process later. # ----------------------------------------------------------------------------- class GrammarError(YaccError): pass class Grammar(object): def __init__(self,terminals): self.Productions = [None] # A list of all of the productions. The first # entry is always reserved for the purpose of # building an augmented grammar self.Prodnames = { } # A dictionary mapping the names of nonterminals to a list of all # productions of that nonterminal. self.Prodmap = { } # A dictionary that is only used to detect duplicate # productions. self.Terminals = { } # A dictionary mapping the names of terminal symbols to a # list of the rules where they are used. for term in terminals: self.Terminals[term] = [] self.Terminals['error'] = [] self.Nonterminals = { } # A dictionary mapping names of nonterminals to a list # of rule numbers where they are used. self.First = { } # A dictionary of precomputed FIRST(x) symbols self.Follow = { } # A dictionary of precomputed FOLLOW(x) symbols self.Precedence = { } # Precedence rules for each terminal. Contains tuples of the # form ('right',level) or ('nonassoc', level) or ('left',level) self.UsedPrecedence = { } # Precedence rules that were actually used by the grammer. # This is only used to provide error checking and to generate # a warning about unused precedence rules. self.Start = None # Starting symbol for the grammar def __len__(self): return len(self.Productions) def __getitem__(self,index): return self.Productions[index] # ----------------------------------------------------------------------------- # set_precedence() # # Sets the precedence for a given terminal. assoc is the associativity such as # 'left','right', or 'nonassoc'. level is a numeric level. # # ----------------------------------------------------------------------------- def set_precedence(self,term,assoc,level): assert self.Productions == [None],"Must call set_precedence() before add_production()" if term in self.Precedence: raise GrammarError("Precedence already specified for terminal '%s'" % term) if assoc not in ['left','right','nonassoc']: raise GrammarError("Associativity must be one of 'left','right', or 'nonassoc'") self.Precedence[term] = (assoc,level) # ----------------------------------------------------------------------------- # add_production() # # Given an action function, this function assembles a production rule and # computes its precedence level. # # The production rule is supplied as a list of symbols. For example, # a rule such as 'expr : expr PLUS term' has a production name of 'expr' and # symbols ['expr','PLUS','term']. # # Precedence is determined by the precedence of the right-most non-terminal # or the precedence of a terminal specified by %prec. # # A variety of error checks are performed to make sure production symbols # are valid and that %prec is used correctly. # ----------------------------------------------------------------------------- def add_production(self,prodname,syms,func=None,file='',line=0): if prodname in self.Terminals: raise GrammarError("%s:%d: Illegal rule name '%s'. Already defined as a token" % (file,line,prodname)) if prodname == 'error': raise GrammarError("%s:%d: Illegal rule name '%s'. error is a reserved word" % (file,line,prodname)) if not _is_identifier.match(prodname): raise GrammarError("%s:%d: Illegal rule name '%s'" % (file,line,prodname)) # Look for literal tokens for n,s in enumerate(syms): if s[0] in "'\"": try: c = eval(s) if (len(c) > 1): raise GrammarError("%s:%d: Literal token %s in rule '%s' may only be a single character" % (file,line,s, prodname)) if not c in self.Terminals: self.Terminals[c] = [] syms[n] = c continue except SyntaxError: pass if not _is_identifier.match(s) and s != '%prec': raise GrammarError("%s:%d: Illegal name '%s' in rule '%s'" % (file,line,s, prodname)) # Determine the precedence level if '%prec' in syms: if syms[-1] == '%prec': raise GrammarError("%s:%d: Syntax error. Nothing follows %%prec" % (file,line)) if syms[-2] != '%prec': raise GrammarError("%s:%d: Syntax error. %%prec can only appear at the end of a grammar rule" % (file,line)) precname = syms[-1] prodprec = self.Precedence.get(precname,None) if not prodprec: raise GrammarError("%s:%d: Nothing known about the precedence of '%s'" % (file,line,precname)) else: self.UsedPrecedence[precname] = 1 del syms[-2:] # Drop %prec from the rule else: # If no %prec, precedence is determined by the rightmost terminal symbol precname = rightmost_terminal(syms,self.Terminals) prodprec = self.Precedence.get(precname,('right',0)) # See if the rule is already in the rulemap map = "%s -> %s" % (prodname,syms) if map in self.Prodmap: m = self.Prodmap[map] raise GrammarError("%s:%d: Duplicate rule %s. " % (file,line, m) + "Previous definition at %s:%d" % (m.file, m.line)) # From this point on, everything is valid. Create a new Production instance pnumber = len(self.Productions) if not prodname in self.Nonterminals: self.Nonterminals[prodname] = [ ] # Add the production number to Terminals and Nonterminals for t in syms: if t in self.Terminals: self.Terminals[t].append(pnumber) else: if not t in self.Nonterminals: self.Nonterminals[t] = [ ] self.Nonterminals[t].append(pnumber) # Create a production and add it to the list of productions p = Production(pnumber,prodname,syms,prodprec,func,file,line) self.Productions.append(p) self.Prodmap[map] = p # Add to the global productions list try: self.Prodnames[prodname].append(p) except KeyError: self.Prodnames[prodname] = [ p ] return 0 # ----------------------------------------------------------------------------- # set_start() # # Sets the starting symbol and creates the augmented grammar. Production # rule 0 is S' -> start where start is the start symbol. # ----------------------------------------------------------------------------- def set_start(self,start=None): if not start: start = self.Productions[1].name if start not in self.Nonterminals: raise GrammarError("start symbol %s undefined" % start) self.Productions[0] = Production(0,"S'",[start]) self.Nonterminals[start].append(0) self.Start = start # ----------------------------------------------------------------------------- # find_unreachable() # # Find all of the nonterminal symbols that can't be reached from the starting # symbol. Returns a list of nonterminals that can't be reached. # ----------------------------------------------------------------------------- def find_unreachable(self): # Mark all symbols that are reachable from a symbol s def mark_reachable_from(s): if reachable[s]: # We've already reached symbol s. return reachable[s] = 1 for p in self.Prodnames.get(s,[]): for r in p.prod: mark_reachable_from(r) reachable = { } for s in list(self.Terminals) + list(self.Nonterminals): reachable[s] = 0 mark_reachable_from( self.Productions[0].prod[0] ) return [s for s in list(self.Nonterminals) if not reachable[s]] # ----------------------------------------------------------------------------- # infinite_cycles() # # 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 infinite_cycles(self): terminates = {} # Terminals: for t in self.Terminals: terminates[t] = 1 terminates['$end'] = 1 # Nonterminals: # Initialize to false: for n in self.Nonterminals: terminates[n] = 0 # Then propagate termination until no change: while 1: some_change = 0 for (n,pl) in self.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 infinite = [] for (s,term) in terminates.items(): if not term: if not s in self.Prodnames and not s in self.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: infinite.append(s) return infinite # ----------------------------------------------------------------------------- # undefined_symbols() # # Find all symbols that were used the grammar, but not defined as tokens or # grammar rules. Returns a list of tuples (sym, prod) where sym in the symbol # and prod is the production where the symbol was used. # ----------------------------------------------------------------------------- def undefined_symbols(self): result = [] for p in self.Productions: if not p: continue for s in p.prod: if not s in self.Prodnames and not s in self.Terminals and s != 'error': result.append((s,p)) return result # ----------------------------------------------------------------------------- # unused_terminals() # # Find all terminals that were defined, but not used by the grammar. Returns # a list of all symbols. # ----------------------------------------------------------------------------- def unused_terminals(self): unused_tok = [] for s,v in self.Terminals.items(): if s != 'error' and not v: unused_tok.append(s) return unused_tok # ------------------------------------------------------------------------------ # unused_rules() # # Find all grammar rules that were defined, but not used (maybe not reachable) # Returns a list of productions. # ------------------------------------------------------------------------------ def unused_rules(self): unused_prod = [] for s,v in self.Nonterminals.items(): if not v: p = self.Prodnames[s][0] unused_prod.append(p) return unused_prod # ----------------------------------------------------------------------------- # unused_precedence() # # Returns a list of tuples (term,precedence) corresponding to precedence # rules that were never used by the grammar. term is the name of the terminal # on which precedence was applied and precedence is a string such as 'left' or # 'right' corresponding to the type of precedence. # ----------------------------------------------------------------------------- def unused_precedence(self): unused = [] for termname in self.Precedence: if not (termname in self.Terminals or termname in self.UsedPrecedence): unused.append((termname,self.Precedence[termname][0])) return unused # ------------------------------------------------------------------------- # _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(self,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 self.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 # ------------------------------------------------------------------------- # compute_first() # # Compute the value of FIRST1(X) for all symbols # ------------------------------------------------------------------------- def compute_first(self): if self.First: return self.First # Terminals: for t in self.Terminals: self.First[t] = [t] self.First['$end'] = ['$end'] # Nonterminals: # Initialize to the empty set: for n in self.Nonterminals: self.First[n] = [] # Then propagate symbols until no change: while 1: some_change = 0 for n in self.Nonterminals: for p in self.Prodnames[n]: for f in self._first(p.prod): if f not in self.First[n]: self.First[n].append( f ) some_change = 1 if not some_change: break return self.First # --------------------------------------------------------------------- # compute_follow() # # Computes all of the follow sets for every non-terminal symbol. The # follow set is the set of all symbols that might follow a given # non-terminal. See the Dragon book, 2nd Ed. p. 189. # --------------------------------------------------------------------- def compute_follow(self,start=None): # If already computed, return the result if self.Follow: return self.Follow # If first sets not computed yet, do that first. if not self.First: self.compute_first() # Add '$end' to the follow list of the start symbol for k in self.Nonterminals: self.Follow[k] = [ ] if not start: start = self.Productions[1].name self.Follow[start] = [ '$end' ] while 1: didadd = 0 for p in self.Productions[1:]: # Here is the production set for i in range(len(p.prod)): B = p.prod[i] if B in self.Nonterminals: # Okay. We got a non-terminal in a production fst = self._first(p.prod[i+1:]) hasempty = 0 for f in fst: if f != '<empty>' and f not in self.Follow[B]: self.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 self.Follow[p.name]: if f not in self.Follow[B]: self.Follow[B].append(f) didadd = 1 if not didadd: break return self.Follow # ----------------------------------------------------------------------------- # 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(self): for p in self.Productions: lastlri = p i = 0 lr_items = [] while 1: if i > len(p): lri = None else: lri = LRItem(p,i) # Precompute the list of productions immediately following try: lri.lr_after = self.Prodnames[lri.prod[i+1]] except (IndexError,KeyError): lri.lr_after = [] try: lri.lr_before = lri.prod[i-1] except IndexError: lri.lr_before = None lastlri.lr_next = lri if not lri: break lr_items.append(lri) lastlri = lri i += 1 p.lr_items = lr_items # ----------------------------------------------------------------------------- # == Class LRTable == # # This basic class represents a basic table of LR parsing information. # Methods for generating the tables are not defined here. They are defined # in the derived class LRGeneratedTable. # ----------------------------------------------------------------------------- class VersionError(YaccError): pass class LRTable(object): def __init__(self): self.lr_action = None self.lr_goto = None self.lr_productions = None self.lr_method = None def read_table(self,module): if isinstance(module,types.ModuleType): parsetab = module else: if sys.version_info[0] < 3: exec("import %s as parsetab" % module) else: env = { } exec("import %s as parsetab" % module, env, env) parsetab = env['parsetab'] if parsetab._tabversion != __tabversion__: raise VersionError("yacc table file version is out of date") self.lr_action = parsetab._lr_action self.lr_goto = parsetab._lr_goto self.lr_productions = [] for p in parsetab._lr_productions: self.lr_productions.append(MiniProduction(*p)) self.lr_method = parsetab._lr_method return parsetab._lr_signature def read_pickle(self,filename): try: import cPickle as pickle except ImportError: import pickle in_f = open(filename,"rb") tabversion = pickle.load(in_f) if tabversion != __tabversion__: raise VersionError("yacc table file version is out of date") self.lr_method = pickle.load(in_f) signature = pickle.load(in_f) self.lr_action = pickle.load(in_f) self.lr_goto = pickle.load(in_f) productions = pickle.load(in_f) self.lr_productions = [] for p in productions: self.lr_productions.append(MiniProduction(*p)) in_f.close() return signature # Bind all production function names to callable objects in pdict def bind_callables(self,pdict): for p in self.lr_productions: p.bind(pdict) # ----------------------------------------------------------------------------- # === LR Generator === # # The following classes and functions are used to generate LR parsing tables on # a grammar. # ----------------------------------------------------------------------------- # ----------------------------------------------------------------------------- # 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]] = MAXINT F[stack[-1]] = F[x] element = stack.pop() while element != x: N[stack[-1]] = MAXINT F[stack[-1]] = F[x] element = stack.pop() class LALRError(YaccError): pass # ----------------------------------------------------------------------------- # == LRGeneratedTable == # # This class implements the LR table generation algorithm. There are no # public methods except for write() # ----------------------------------------------------------------------------- class LRGeneratedTable(LRTable): def __init__(self,grammar,method='LALR',log=None): if method not in ['SLR','LALR']: raise LALRError("Unsupported method %s" % method) self.grammar = grammar self.lr_method = method # Set up the logger if not log: log = NullLogger() self.log = log # Internal attributes self.lr_action = {} # Action table self.lr_goto = {} # Goto table self.lr_productions = grammar.Productions # Copy of grammar Production array self.lr_goto_cache = {} # Cache of computed gotos self.lr0_cidhash = {} # Cache of closures self._add_count = 0 # Internal counter used to detect cycles # Diagonistic information filled in by the table generator self.sr_conflict = 0 self.rr_conflict = 0 self.conflicts = [] # List of conflicts self.sr_conflicts = [] self.rr_conflicts = [] # Build the tables self.grammar.build_lritems() self.grammar.compute_first() self.grammar.compute_follow() self.lr_parse_table() # Compute the LR(0) closure operation on I, where I is a set of LR(0) items. def lr0_closure(self,I): self._add_count += 1 # Add everything in I to J J = I[:] didadd = 1 while didadd: didadd = 0 for j in J: for x in j.lr_after: if getattr(x,"lr0_added",0) == self._add_count: continue # Add B --> .G to J J.append(x.lr_next) x.lr0_added = self._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(self,I,x): # First we look for a previously cached entry g = self.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 = self.lr_goto_cache.get(x,None) if not s: s = { } self.lr_goto_cache[x] = s gs = [ ] for p in I: n = p.lr_next if n and n.lr_before == 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 = self.lr0_closure(gs) s['$end'] = g else: s['$end'] = gs self.lr_goto_cache[(id(I),x)] = g return g # Compute the LR(0) sets of item function def lr0_items(self): C = [ self.lr0_closure([self.grammar.Productions[0].lr_next]) ] i = 0 for I in C: self.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: g = self.lr0_goto(I,x) if not g: continue if id(g) in self.lr0_cidhash: continue self.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). # # ----------------------------------------------------------------------------- # ----------------------------------------------------------------------------- # compute_nullable_nonterminals() # # Creates a dictionary containing all of the non-terminals that might produce # an empty production. # ----------------------------------------------------------------------------- def compute_nullable_nonterminals(self): nullable = {} num_nullable = 0 while 1: for p in self.grammar.Productions[1:]: if p.len == 0: nullable[p.name] = 1 continue for t in p.prod: if not t 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(self,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 self.grammar.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(self,C,trans,nullable): dr_set = { } state,N = trans terms = [] g = self.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 self.grammar.Terminals: if a not in terms: terms.append(a) # This extra bit is to handle the start state if state == 0 and N == self.grammar.Productions[0].prod[0]: terms.append('$end') return terms # ----------------------------------------------------------------------------- # reads_relation() # # Computes the READS() relation (p,A) READS (t,C). # ----------------------------------------------------------------------------- def reads_relation(self,C, trans, empty): # Look for empty transitions rel = [] state, N = trans g = self.lr0_goto(C[state],N) j = self.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(self,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 self.grammar.Terminals: break # No forget it if not p.prod[li] in nullable: break li = li + 1 else: # Appears to be a relation between (j,t) and (state,N) includes.append((j,t)) g = self.lr0_goto(C[j],t) # Go to next set j = self.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 not i in includedict: includedict[i] = [] includedict[i].append((state,N)) lookdict[(state,N)] = lookb return lookdict,includedict # ----------------------------------------------------------------------------- # 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(self,C, ntrans, nullable): FP = lambda x: self.dr_relation(C,x,nullable) R = lambda x: self.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(self,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(self,lookbacks,followset): for trans,lb in lookbacks.items(): # Loop over productions in lookback for state,p in lb: if not state 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(self,C): # Determine all of the nullable nonterminals nullable = self.compute_nullable_nonterminals() # Find all non-terminal transitions trans = self.find_nonterminal_transitions(C) # Compute read sets readsets = self.compute_read_sets(C,trans,nullable) # Compute lookback/includes relations lookd, included = self.compute_lookback_includes(C,trans,nullable) # Compute LALR FOLLOW sets followsets = self.compute_follow_sets(trans,readsets,included) # Add all of the lookaheads self.add_lookaheads(lookd,followsets) # ----------------------------------------------------------------------------- # lr_parse_table() # # This function constructs the parse tables for SLR or LALR # ----------------------------------------------------------------------------- def lr_parse_table(self): Productions = self.grammar.Productions Precedence = self.grammar.Precedence goto = self.lr_goto # Goto array action = self.lr_action # Action array log = self.log # Logger for output actionp = { } # Action production array (temporary) log.info("Parsing method: %s", self.lr_method) # Step 1: Construct C = { I0, I1, ... IN}, collection of LR(0) items # This determines the number of states C = self.lr0_items() if self.lr_method == 'LALR': self.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 st_action = { } st_actionp = { } st_goto = { } log.info("") log.info("state %d", st) log.info("") for p in I: log.info(" (%d) %s", p.number, str(p)) log.info("") for p in I: if p.len == p.lr_index + 1: if p.name == "S'": # Start symbol. Accept! st_action["$end"] = 0 st_actionp["$end"] = p else: # We are at the end of a production. Reduce! if self.lr_method == 'LALR': laheads = p.lookaheads[st] else: laheads = self.grammar.Follow[p.name] for a in laheads: actlist.append((a,p,"reduce using rule %d (%s)" % (p.number,p))) r = st_action.get(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[st_actionp[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. st_action[a] = -p.number st_actionp[a] = p if not slevel and not rlevel: log.info(" ! shift/reduce conflict for %s resolved as reduce",a) self.sr_conflicts.append((st,a,'reduce')) Productions[p.number].reduced += 1 elif (slevel == rlevel) and (rprec == 'nonassoc'): st_action[a] = None else: # Hmmm. Guess we'll keep the shift if not rlevel: log.info(" ! shift/reduce conflict for %s resolved as shift",a) self.sr_conflicts.append((st,a,'shift')) 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: st_action[a] = -p.number st_actionp[a] = p chosenp,rejectp = pp,oldp Productions[p.number].reduced += 1 Productions[oldp.number].reduced -= 1 else: chosenp,rejectp = oldp,pp self.rr_conflicts.append((st,chosenp,rejectp)) log.info(" ! reduce/reduce conflict for %s resolved using rule %d (%s)", a,st_actionp[a].number, st_actionp[a]) else: raise LALRError("Unknown conflict in state %d" % st) else: st_action[a] = -p.number st_actionp[a] = p Productions[p.number].reduced += 1 else: i = p.lr_index a = p.prod[i+1] # Get symbol right after the "." if a in self.grammar.Terminals: g = self.lr0_goto(I,a) j = self.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 = st_action.get(a,None) if r is not None: # Whoa have a shift/reduce or shift/shift conflict if r > 0: if r != j: raise LALRError("Shift/shift conflict in state %d" % 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[st_actionp[a].number].prec sprec,slevel = Precedence.get(a,('right',0)) if (slevel > rlevel) or ((slevel == rlevel) and (rprec == 'right')): # We decide to shift here... highest precedence to shift Productions[st_actionp[a].number].reduced -= 1 st_action[a] = j st_actionp[a] = p if not rlevel: log.info(" ! shift/reduce conflict for %s resolved as shift",a) self.sr_conflicts.append((st,a,'shift')) elif (slevel == rlevel) and (rprec == 'nonassoc'): st_action[a] = None else: # Hmmm. Guess we'll keep the reduce if not slevel and not rlevel: log.info(" ! shift/reduce conflict for %s resolved as reduce",a) self.sr_conflicts.append((st,a,'reduce')) else: raise LALRError("Unknown conflict in state %d" % st) else: st_action[a] = j st_actionp[a] = p # Print the actions associated with each terminal _actprint = { } for a,p,m in actlist: if a in st_action: if p is st_actionp[a]: log.info(" %-15s %s",a,m) _actprint[(a,m)] = 1 log.info("") # Print the actions that were not used. (debugging) not_used = 0 for a,p,m in actlist: if a in st_action: if p is not st_actionp[a]: if not (a,m) in _actprint: log.debug(" ! %-15s [ %s ]",a,m) not_used = 1 _actprint[(a,m)] = 1 if not_used: log.debug("") # Construct the goto table for this state nkeys = { } for ii in I: for s in ii.usyms: if s in self.grammar.Nonterminals: nkeys[s] = None for n in nkeys: g = self.lr0_goto(I,n) j = self.lr0_cidhash.get(id(g),-1) if j >= 0: st_goto[n] = j log.info(" %-30s shift and go to state %d",n,j) action[st] = st_action actionp[st] = st_actionp goto[st] = st_goto st += 1 # ----------------------------------------------------------------------------- # write() # # This function writes the LR parsing tables to a file # ----------------------------------------------------------------------------- def write_table(self,modulename,outputdir='',signature=""): basemodulename = modulename.split(".")[-1] filename = os.path.join(outputdir,basemodulename) + ".py" try: f = open(filename,"w") f.write(""" # %s # This file is automatically generated. Do not edit. _tabversion = %r _lr_method = %r _lr_signature = %r """ % (filename, __tabversion__, self.lr_method, signature)) # Change smaller to 0 to go back to original tables smaller = 1 # Factor out names to try and make smaller if smaller: items = { } for s,nd in self.lr_action.items(): for name,v in nd.items(): i = items.get(name) if not i: i = ([],[]) items[name] = i i[0].append(s) 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]): if not _x in _lr_action: _lr_action[_x] = { } _lr_action[_x][_k] = _y del _lr_action_items """) else: f.write("\n_lr_action = { "); for k,v in self.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 s,nd in self.lr_goto.items(): for name,v in nd.items(): i = items.get(name) if not i: i = ([],[]) items[name] = i i[0].append(s) 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]): if not _x in _lr_goto: _lr_goto[_x] = { } _lr_goto[_x][_k] = _y del _lr_goto_items """) else: f.write("\n_lr_goto = { "); for k,v in self.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 self.lr_productions: if p.func: f.write(" (%r,%r,%d,%r,%r,%d),\n" % (p.str,p.name, p.len, p.func,p.file,p.line)) else: f.write(" (%r,%r,%d,None,None,None),\n" % (str(p),p.name, p.len)) f.write("]\n") f.close() except IOError: e = sys.exc_info()[1] sys.stderr.write("Unable to create '%s'\n" % filename) sys.stderr.write(str(e)+"\n") return # ----------------------------------------------------------------------------- # pickle_table() # # This function pickles the LR parsing tables to a supplied file object # ----------------------------------------------------------------------------- def pickle_table(self,filename,signature=""): try: import cPickle as pickle except ImportError: import pickle outf = open(filename,"wb") pickle.dump(__tabversion__,outf,pickle_protocol) pickle.dump(self.lr_method,outf,pickle_protocol) pickle.dump(signature,outf,pickle_protocol) pickle.dump(self.lr_action,outf,pickle_protocol) pickle.dump(self.lr_goto,outf,pickle_protocol) outp = [] for p in self.lr_productions: if p.func: outp.append((p.str,p.name, p.len, p.func,p.file,p.line)) else: outp.append((str(p),p.name,p.len,None,None,None)) pickle.dump(outp,outf,pickle_protocol) outf.close() # ----------------------------------------------------------------------------- # === INTROSPECTION === # # The following functions and classes are used to implement the PLY # introspection features followed by the yacc() function itself. # ----------------------------------------------------------------------------- # ----------------------------------------------------------------------------- # get_caller_module_dict() # # This function returns a dictionary containing all of the symbols defined within # a caller further down the call stack. This is used to get the environment # associated with the yacc() call if none was provided. # ----------------------------------------------------------------------------- def get_caller_module_dict(levels): try: raise RuntimeError except RuntimeError: e,b,t = sys.exc_info() f = t.tb_frame while levels > 0: f = f.f_back levels -= 1 ldict = f.f_globals.copy() if f.f_globals != f.f_locals: ldict.update(f.f_locals) return ldict # ----------------------------------------------------------------------------- # parse_grammar() # # This takes a raw grammar rule string and parses it into production data # ----------------------------------------------------------------------------- def parse_grammar(doc,file,line): grammar = [] # Split the doc string into lines pstrings = 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: raise SyntaxError("%s:%d: Misplaced '|'" % (file,dline)) prodname = lastp syms = p[1:] else: prodname = p[0] lastp = prodname syms = p[2:] assign = p[1] if assign != ':' and assign != '::=': raise SyntaxError("%s:%d: Syntax error. Expected ':'" % (file,dline)) grammar.append((file,dline,prodname,syms)) except SyntaxError: raise except Exception: raise SyntaxError("%s:%d: Syntax error in rule '%s'" % (file,dline,ps.strip())) return grammar # ----------------------------------------------------------------------------- # ParserReflect() # # This class represents information extracted for building a parser including # start symbol, error function, tokens, precedence list, action functions, # etc. # ----------------------------------------------------------------------------- class ParserReflect(object): def __init__(self,pdict,log=None): self.pdict = pdict self.start = None self.error_func = None self.tokens = None self.files = {} self.grammar = [] self.error = 0 if log is None: self.log = PlyLogger(sys.stderr) else: self.log = log # Get all of the basic information def get_all(self): self.get_start() self.get_error_func() self.get_tokens() self.get_precedence() self.get_pfunctions() # Validate all of the information def validate_all(self): self.validate_start() self.validate_error_func() self.validate_tokens() self.validate_precedence() self.validate_pfunctions() self.validate_files() return self.error # Compute a signature over the grammar def signature(self): parts = [] try: if self.start: parts.append(self.start) if self.prec: parts.append(''.join([''.join(p) for p in self.prec])) if self.tokens: parts.append(' '.join(self.tokens)) for f in self.pfuncs: if f[3]: parts.append(f[3]) except (TypeError, ValueError): pass return ''.join(parts) # ----------------------------------------------------------------------------- # validate_file() # # This method 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_files(self): # Match def p_funcname( fre = re.compile(r'\s*def\s+(p_[a-zA-Z_0-9]*)\(') for filename in self.files.keys(): 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: continue counthash = { } for linen,l in enumerate(lines): linen += 1 m = fre.match(l) if m: name = m.group(1) prev = counthash.get(name) if not prev: counthash[name] = linen else: self.log.warning("%s:%d: Function %s redefined. Previously defined on line %d", filename,linen,name,prev) # Get the start symbol def get_start(self): self.start = self.pdict.get('start') # Validate the start symbol def validate_start(self): if self.start is not None: if not isinstance(self.start,str): self.log.error("'start' must be a string") # Look for error handler def get_error_func(self): self.error_func = self.pdict.get('p_error') # Validate the error function def validate_error_func(self): if self.error_func: if isinstance(self.error_func,types.FunctionType): ismethod = 0 elif isinstance(self.error_func, types.MethodType): ismethod = 1 else: self.log.error("'p_error' defined, but is not a function or method") self.error = 1 return eline = func_code(self.error_func).co_firstlineno efile = func_code(self.error_func).co_filename self.files[efile] = 1 if (func_code(self.error_func).co_argcount != 1+ismethod): self.log.error("%s:%d: p_error() requires 1 argument",efile,eline) self.error = 1 # Get the tokens map def get_tokens(self): tokens = self.pdict.get("tokens",None) if not tokens: self.log.error("No token list is defined") self.error = 1 return if not isinstance(tokens,(list, tuple)): self.log.error("tokens must be a list or tuple") self.error = 1 return if not tokens: self.log.error("tokens is empty") self.error = 1 return self.tokens = tokens # Validate the tokens def validate_tokens(self): # Validate the tokens. if 'error' in self.tokens: self.log.error("Illegal token name 'error'. Is a reserved word") self.error = 1 return terminals = {} for n in self.tokens: if n in terminals: self.log.warning("Token '%s' multiply defined", n) terminals[n] = 1 # Get the precedence map (if any) def get_precedence(self): self.prec = self.pdict.get("precedence",None) # Validate and parse the precedence map def validate_precedence(self): preclist = [] if self.prec: if not isinstance(self.prec,(list,tuple)): self.log.error("precedence must be a list or tuple") self.error = 1 return for level,p in enumerate(self.prec): if not isinstance(p,(list,tuple)): self.log.error("Bad precedence table") self.error = 1 return if len(p) < 2: self.log.error("Malformed precedence entry %s. Must be (assoc, term, ..., term)",p) self.error = 1 return assoc = p[0] if not isinstance(assoc,str): self.log.error("precedence associativity must be a string") self.error = 1 return for term in p[1:]: if not isinstance(term,str): self.log.error("precedence items must be strings") self.error = 1 return preclist.append((term,assoc,level+1)) self.preclist = preclist # Get all p_functions from the grammar def get_pfunctions(self): p_functions = [] for name, item in self.pdict.items(): if name[:2] != 'p_': continue if name == 'p_error': continue if isinstance(item,(types.FunctionType,types.MethodType)): line = func_code(item).co_firstlineno file = func_code(item).co_filename p_functions.append((line,file,name,item.__doc__)) # Sort all of the actions by line number p_functions.sort() self.pfuncs = p_functions # Validate all of the p_functions def validate_pfunctions(self): grammar = [] # Check for non-empty symbols if len(self.pfuncs) == 0: self.log.error("no rules of the form p_rulename are defined") self.error = 1 return for line, file, name, doc in self.pfuncs: func = self.pdict[name] if isinstance(func, types.MethodType): reqargs = 2 else: reqargs = 1 if func_code(func).co_argcount > reqargs: self.log.error("%s:%d: Rule '%s' has too many arguments",file,line,func.__name__) self.error = 1 elif func_code(func).co_argcount < reqargs: self.log.error("%s:%d: Rule '%s' requires an argument",file,line,func.__name__) self.error = 1 elif not func.__doc__: self.log.warning("%s:%d: No documentation string specified in function '%s' (ignored)",file,line,func.__name__) else: try: parsed_g = parse_grammar(doc,file,line) for g in parsed_g: grammar.append((name, g)) except SyntaxError: e = sys.exc_info()[1] self.log.error(str(e)) self.error = 1 # Looks like a valid grammar rule # Mark the file in which defined. self.files[file] = 1 # Secondary validation step that looks for p_ definitions that are not functions # or functions that look like they might be grammar rules. for n,v in self.pdict.items(): if n[0:2] == 'p_' and isinstance(v, (types.FunctionType, types.MethodType)): continue if n[0:2] == 't_': continue if n[0:2] == 'p_' and n != 'p_error': self.log.warning("'%s' not defined as a function", n) if ((isinstance(v,types.FunctionType) and func_code(v).co_argcount == 1) or (isinstance(v,types.MethodType) and func_code(v).co_argcount == 2)): try: doc = v.__doc__.split(" ") if doc[1] == ':': self.log.warning("%s:%d: Possible grammar rule '%s' defined without p_ prefix", func_code(v).co_filename, func_code(v).co_firstlineno,n) except Exception: pass self.grammar = grammar # ----------------------------------------------------------------------------- # yacc(module) # # Build a parser # ----------------------------------------------------------------------------- def yacc(method='LALR', debug=yaccdebug, module=None, tabmodule=tab_module, start=None, check_recursion=1, optimize=0, write_tables=1, debugfile=debug_file,outputdir='', debuglog=None, errorlog = None, picklefile=None): global parse # Reference to the parsing method of the last built parser # If pickling is enabled, table files are not created if picklefile: write_tables = 0 if errorlog is None: errorlog = PlyLogger(sys.stderr) # Get the module dictionary used for the parser if module: _items = [(k,getattr(module,k)) for k in dir(module)] pdict = dict(_items) else: pdict = get_caller_module_dict(2) # Collect parser information from the dictionary pinfo = ParserReflect(pdict,log=errorlog) pinfo.get_all() if pinfo.error: raise YaccError("Unable to build parser") # Check signature against table files (if any) signature = pinfo.signature() # Read the tables try: lr = LRTable() if picklefile: read_signature = lr.read_pickle(picklefile) else: read_signature = lr.read_table(tabmodule) if optimize or (read_signature == signature): try: lr.bind_callables(pinfo.pdict) parser = LRParser(lr,pinfo.error_func) parse = parser.parse return parser except Exception: e = sys.exc_info()[1] errorlog.warning("There was a problem loading the table file: %s", repr(e)) except VersionError: e = sys.exc_info() errorlog.warning(str(e)) except Exception: pass if debuglog is None: if debug: debuglog = PlyLogger(open(debugfile,"w")) else: debuglog = NullLogger() debuglog.info("Created by PLY version %s (http://www.dabeaz.com/ply)", __version__) errors = 0 # Validate the parser information if pinfo.validate_all(): raise YaccError("Unable to build parser") if not pinfo.error_func: errorlog.warning("no p_error() function is defined") # Create a grammar object grammar = Grammar(pinfo.tokens) # Set precedence level for terminals for term, assoc, level in pinfo.preclist: try: grammar.set_precedence(term,assoc,level) except GrammarError: e = sys.exc_info()[1] errorlog.warning("%s",str(e)) # Add productions to the grammar for funcname, gram in pinfo.grammar: file, line, prodname, syms = gram try: grammar.add_production(prodname,syms,funcname,file,line) except GrammarError: e = sys.exc_info()[1] errorlog.error("%s",str(e)) errors = 1 # Set the grammar start symbols try: if start is None: grammar.set_start(pinfo.start) else: grammar.set_start(start) except GrammarError: e = sys.exc_info()[1] errorlog.error(str(e)) errors = 1 if errors: raise YaccError("Unable to build parser") # Verify the grammar structure undefined_symbols = grammar.undefined_symbols() for sym, prod in undefined_symbols: errorlog.error("%s:%d: Symbol '%s' used, but not defined as a token or a rule",prod.file,prod.line,sym) errors = 1 unused_terminals = grammar.unused_terminals() if unused_terminals: debuglog.info("") debuglog.info("Unused terminals:") debuglog.info("") for term in unused_terminals: errorlog.warning("Token '%s' defined, but not used", term) debuglog.info(" %s", term) # Print out all productions to the debug log if debug: debuglog.info("") debuglog.info("Grammar") debuglog.info("") for n,p in enumerate(grammar.Productions): debuglog.info("Rule %-5d %s", n, p) # Find unused non-terminals unused_rules = grammar.unused_rules() for prod in unused_rules: errorlog.warning("%s:%d: Rule '%s' defined, but not used", prod.file, prod.line, prod.name) if len(unused_terminals) == 1: errorlog.warning("There is 1 unused token") if len(unused_terminals) > 1: errorlog.warning("There are %d unused tokens", len(unused_terminals)) if len(unused_rules) == 1: errorlog.warning("There is 1 unused rule") if len(unused_rules) > 1: errorlog.warning("There are %d unused rules", len(unused_rules)) if debug: debuglog.info("") debuglog.info("Terminals, with rules where they appear") debuglog.info("") terms = list(grammar.Terminals) terms.sort() for term in terms: debuglog.info("%-20s : %s", term, " ".join([str(s) for s in grammar.Terminals[term]])) debuglog.info("") debuglog.info("Nonterminals, with rules where they appear") debuglog.info("") nonterms = list(grammar.Nonterminals) nonterms.sort() for nonterm in nonterms: debuglog.info("%-20s : %s", nonterm, " ".join([str(s) for s in grammar.Nonterminals[nonterm]])) debuglog.info("") if check_recursion: unreachable = grammar.find_unreachable() for u in unreachable: errorlog.warning("Symbol '%s' is unreachable",u) infinite = grammar.infinite_cycles() for inf in infinite: errorlog.error("Infinite recursion detected for symbol '%s'", inf) errors = 1 unused_prec = grammar.unused_precedence() for term, assoc in unused_prec: errorlog.error("Precedence rule '%s' defined for unknown symbol '%s'", assoc, term) errors = 1 if errors: raise YaccError("Unable to build parser") # Run the LRGeneratedTable on the grammar if debug: errorlog.debug("Generating %s tables", method) lr = LRGeneratedTable(grammar,method,debuglog) if debug: num_sr = len(lr.sr_conflicts) # Report shift/reduce and reduce/reduce conflicts if num_sr == 1: errorlog.warning("1 shift/reduce conflict") elif num_sr > 1: errorlog.warning("%d shift/reduce conflicts", num_sr) num_rr = len(lr.rr_conflicts) if num_rr == 1: errorlog.warning("1 reduce/reduce conflict") elif num_rr > 1: errorlog.warning("%d reduce/reduce conflicts", num_rr) # Write out conflicts to the output file if debug and (lr.sr_conflicts or lr.rr_conflicts): debuglog.warning("") debuglog.warning("Conflicts:") debuglog.warning("") for state, tok, resolution in lr.sr_conflicts: debuglog.warning("shift/reduce conflict for %s in state %d resolved as %s", tok, state, resolution) already_reported = {} for state, rule, rejected in lr.rr_conflicts: if (state,id(rule),id(rejected)) in already_reported: continue debuglog.warning("reduce/reduce conflict in state %d resolved using rule (%s)", state, rule) debuglog.warning("rejected rule (%s) in state %d", rejected,state) errorlog.warning("reduce/reduce conflict in state %d resolved using rule (%s)", state, rule) errorlog.warning("rejected rule (%s) in state %d", rejected, state) already_reported[state,id(rule),id(rejected)] = 1 warned_never = [] for state, rule, rejected in lr.rr_conflicts: if not rejected.reduced and (rejected not in warned_never): debuglog.warning("Rule (%s) is never reduced", rejected) errorlog.warning("Rule (%s) is never reduced", rejected) warned_never.append(rejected) # Write the table file if requested if write_tables: lr.write_table(tabmodule,outputdir,signature) # Write a pickled version of the tables if picklefile: lr.pickle_table(picklefile,signature) # Build the parser lr.bind_callables(pinfo.pdict) parser = LRParser(lr,pinfo.error_func) parse = parser.parse return parser