def FirstOfTail(self, Rule, TailIndex, Token=None):
''' computing the "first" of the tail of a rule followed by an optional
terminal.
doesn't include NULLTOKEN
requires self.First to be computed
'''
Result = kjSet.NewSet( [] )
# go through all tokens in rule tail so long as there is a
# null derivation for the remainder
Nullprefix = 1
BodyLength = len(Rule.Body)
ThisIndex = TailIndex
while Nullprefix and ThisIndex < BodyLength:
RToken = Rule.Body[ThisIndex]
(RTtype, RTname) = RToken
if RTtype == NONTERMFLAG:
for FToken in kjSet.Neighbors(self.First, RToken):
if FToken != NULLTOKEN:
kjSet.addMember(FToken, Result)
#endfor
# check whether this symbol might have a null production
if not kjSet.HasArc(self.First, RToken, NULLTOKEN):
Nullprefix = 0
elif RTtype in [KEYFLAG, TERMFLAG]:
kjSet.addMember(RToken, Result)
Nullprefix = 0
else:
raise TokenError, "unknown token type in rule body"
ThisIndex = ThisIndex + 1
#endwhile
# add the optional token if given and Nullprefix still set
if Nullprefix and Token != None:
kjSet.addMember(Token, Result)
return Result
def SLRFixDFA(self):
DFA = self.DFA
NFA = self.SLRNFA
# look through the states (except 0=success) of the DFA
# initially don't add any new states, just record
# actions to be done
# uses convention that 0 is successful final state
# ToDo is a dictionary which maps
# (State, Token) to a item to reduce
ToDo = {}
Error = None
for State in range(1, len(DFA.States) ):
# look for a final item for a rule in this state
fromNFAindices = kjSet.get_elts(DFA.States[State][1])
for NFAindex in fromNFAindices:
item = NFA.States[NFAindex][1]
# if the item is final remember to do the reductions...
if self.SLRItemIsFinal(item):
(ruleindex, position) = item
Rule = self.Rules[ruleindex]
Head = Rule.Nonterm
Following = kjSet.Neighbors( self.Follow, Head )
for Token in Following:
key = (State, Token)
if not ToDo.has_key(key):
ToDo[ key ] = item
else:
# it might be okay if the items are identical?
item2 = ToDo[key]
if item != item2:
print "reduce/reduce conflict on ",key
self.ItemDump(item)
self.ItemDump(item2)
Error = " apparent reduce/reduce conflict"
#endif
#endfor
#endif
#endfor NFAindex
#endfor State
# for each (State,Token) pair which indicates a reduction
# record the reduction UNLESS the map is already set for the pair
for key in ToDo.keys():
(State,Token) = key
item = ToDo[key]
(rulenum, dotpos) = item
ExistingMap = DFA.map( State, Token )
if ExistingMap[0] == NOMATCHFLAG:
DFA.SetReduction( State, Token, rulenum )
else:
print "apparent shift/reduce conflict"
print "reduction: ", key, ": "
self.ItemDump(item)
print "existing map ", ExistingMap
Error = " apparent shift/reduce conflict"
#endfor
if Error and ABORTONERROR:
raise NotSLRError, Error
def CompFirst(self):
# uses the special null production token NULLTOKEN
# snarfed directly from Aho+Ullman (terminals glossed)
First = kjSet.NewDG([])
# repeat the while loop until no change is made to First
done = 0
while not done:
done = 1 # assume we're done until a change is made to First
# iterate through all rules looking for a new arc to add
# indicating Terminal > possible first token derivation
#
for R in self.Rules:
GoalNonterm = R.Nonterm
Bodylength = len(R.Body)
# look through the body of the rule up to the token with
# no epsilon production (yet seen)
Bodyindex = 0
Processindex = 1
while Processindex:
# unless otherwise indicated below, don't go to next token
Processindex = 0
# if index is past end of body then record
# an epsilon production for this nonterminal
if Bodyindex >= Bodylength:
if not kjSet.HasArc(First, GoalNonterm, NULLTOKEN):
kjSet.AddArc(First, GoalNonterm, NULLTOKEN)
done = 0 # change made to First
else:
# otherwise try to add firsts of this token
# to firsts of the Head of the rule.
Token = R.Body[Bodyindex]
(type, name) = Token
if type in (KEYFLAG, TERMFLAG):
# try to add this terminal to First for GoalNonterm
if not kjSet.HasArc(First, GoalNonterm, Token):
kjSet.AddArc(First, GoalNonterm, Token)
done = 0
elif type == NONTERMFLAG:
# try to add each First entry for nonterminal
# to First entry for GoalNonterm
for FToken in kjSet.Neighbors(First, Token):
if not kjSet.HasArc(First, GoalNonterm,
FToken):
kjSet.AddArc(First, GoalNonterm, FToken)
done = 0
# does this nonterminal have a known e production?
if kjSet.HasArc(First, Token, NULLTOKEN):
# if so, process next token in rule
Processindex = 1
else:
raise TokenError, "unknown token type in rule body"
#endif
Bodyindex = Bodyindex + 1
#endwhile Processindex
#endfor R in self.Rules
#endwhile not done
self.First = First
def Eclosure(self, Epsilon, DoNullMaps=0):
''' return the epsilon closure of the FSM as a new FSM
DoNullMap, if set, will map unexpected tokens to
the "empty" state (usually creating a really big fsm)
'''
Closure = CFSMachine( self.root_nonTerminal )
# compute the Epsilon Graph between states
EGraph = kjSet.NewDG([])
for State in range(0,self.maxState+1):
# every state is E-connected to self
kjSet.AddArc( EGraph, State, State )
# add possible transition on epsilon (ONLY ONE SUPPORTED!)
key = (State, Epsilon)
if self.StateTokenMap.has_key(key):
keymap = self.StateTokenMap[key]
if keymap[0][0] != MOVETOFLAG:
raise TypeError, "unexpected map type in StateTokenMap"
for (Flag,ToState) in keymap:
kjSet.AddArc( EGraph, State, ToState )
#endfor
# transitively close EGraph
kjSet.TransClose( EGraph )
# Translate EGraph into a dictionary of lists
EMap = {}
for State in range(0,self.maxState+1):
EMap[State] = kjSet.Neighbors( EGraph, State )
# make each e-closure of each self.state a state of the closure FSM.
# here closure states assumed transient -- reset elsewhere.
# first do the initial state
Closure.States[ Closure.initial_state ] = \
[TRANSFLAG, kjSet.NewSet(EMap[self.initial_state]) ]
# do all other states (save initial and successful final states)
#for State in range(0,self.maxState+1):
# if State != self.initial_state \
# and State != self.successful_final_state:
# Closure.NewSetState(TRANSFLAG, kjSet.NewSet(EMap[State]) )
##endfor
# compute set of all known tokens EXCEPT EPSILON
Tokens = kjSet.NewSet( [] )
for (State, Token) in self.StateTokenMap.keys():
if Token != Epsilon:
kjSet.addMember(Token, Tokens)
# tranform it into a list
Tokens = kjSet.get_elts(Tokens)
# for each state of the the closure FSM (past final) add transitions
# and add new states as needed until all states are processed
# (uses convention that states are allocated sequentially)
ThisClosureState = 1
while ThisClosureState <= Closure.maxState:
MemberStates = kjSet.get_elts(Closure.States[ThisClosureState][1])
# for each possible Token, compute the union UTrans of all
# e-closures for all transitions for all member states,
# on the Token, make UTrans a new state (if needed),
# and transition ThisClosureState to UTrans on Token
for Token in Tokens:
UTrans = kjSet.NewSet( [] )
for MState in MemberStates:
# if MState has a transition on Token, include
# EMap for the destination state
key = (MState, Token)
if self.StateTokenMap.has_key(key):
DStateTup = self.StateTokenMap[key]
if DStateTup[0][0] != MOVETOFLAG:
raise TypeError, "unknown map type"
for (DFlag, DState) in DStateTup:
for EDState in EMap[DState]:
kjSet.addMember(EDState, UTrans)
#endif
#endfor MState
# register UTrans as a new state if needed
UTState = Closure.NewSetState(TRANSFLAG, UTrans)
# record transition from
# ThisClosureState to UTState on Token
if DoNullMaps:
Closure.SetMap( ThisClosureState, Token, UTState)
else:
if not kjSet.Empty(UTrans):
Closure.SetMap( ThisClosureState, Token, UTState)
#endfor Token
ThisClosureState = ThisClosureState +1
#endwhile
return Closure
def compFollowRule(self, Follow, R):
done = 1
# work backwards in the rule body to
# avoid retesting for epsilon nonterminals
Bodylength = len(R.Body)
# the tail of rule may expand to null
EpsilonTail = 1
# loop starts at the last
for BodyIndex in range(Bodylength-1, -1, -1):
Token = R.Body[BodyIndex]
(Ttype,Tname) = Token
if Ttype not in (KEYFLAG, TERMFLAG, NONTERMFLAG):
raise TokenError, "unknown token type in rule body"
if Ttype in (KEYFLAG,TERMFLAG):
# keywords etc cancel epsilon tail, otherwise ignore
EpsilonTail = 0
continue
# if the tail expands to epsilon, map
# follow for the goal nonterminal to this token
# and also follow for the tail nonterms
if EpsilonTail:
# add follow for goal
for FToken in kjSet.Neighbors(Follow,R.Nonterm):
if not kjSet.HasArc(Follow, Token, FToken):
kjSet.AddArc(Follow, Token, FToken)
# follow changed, loop again
done = 0
# add follow for tail members
#for Index2 in range(BodyIndex+1, Bodylength):
# TailToken = R.Body[Index2]
# for FToken in kjSet.Neighbors(Follow,TailToken):
# if not kjSet.HasArc(Follow,Token,FToken):
# kjSet.AddArc(Follow,Token,FToken)
# done = 0
#endif EpsilonTail
# if we are not at the end use First set for next token
if BodyIndex != Bodylength-1:
NextToken = R.Body[BodyIndex+1]
(NTtype, NTname) = NextToken
if NTtype in (KEYFLAG,TERMFLAG):
if not kjSet.HasArc(Follow, Token, NextToken):
kjSet.AddArc(Follow, Token, NextToken)
done = 0
elif NTtype == NONTERMFLAG:
for FToken in kjSet.Neighbors(self.First, NextToken):
if FToken != NULLTOKEN:
if not kjSet.HasArc(Follow, Token, FToken):
kjSet.AddArc(Follow, Token, FToken)
done = 0
continue
# next token expands to epsilon:
# add its follow, unless already done above
for FToken in kjSet.Neighbors(Follow, NextToken):
if not kjSet.HasArc(Follow, Token, FToken):
kjSet.AddArc(Follow, Token, FToken)
done = 0
else:
raise TokenError, "unknown token type in rule body"
# finally, check whether next iteration has epsilon tail
if not kjSet.HasArc(self.First, Token, NULLTOKEN):
EpsilonTail = 0
return done
def CompFollow(self):
Follow = kjSet.NewDG( [] )
# put end marker on follow of start nonterminal
kjSet.AddArc(Follow, self.StartNonterm, kjParser.ENDOFFILETOKEN)
# now compute other follows using the rules;
# repeat the loop until no change to Follow.
done = 0
while not done:
done = 1 # assume done unless Follow changes
for R in self.Rules:
#print R
# work backwards in the rule body to
# avoid retesting for epsilon nonterminals
Bodylength = len(R.Body)
EpsilonTail = 1 # the tail of rule may expand to null
BodyIndex = Bodylength - 1
Last = 1 # loop starts at the last
from types import TupleType
while BodyIndex >= 0:
Token = R.Body[BodyIndex]
(Ttype,Tname) = Token
if Ttype in (KEYFLAG,TERMFLAG):
# keywords etc cancel epsilon tail, otherwise ignore
EpsilonTail = 0
elif Ttype == NONTERMFLAG:
# if the tail expands to epsilon, map
# follow for the goal nonterminal to this token
# and also follow for the tail nonterms
if EpsilonTail:
# add follow for goal
for FToken in kjSet.Neighbors(Follow,R.Nonterm):
if not kjSet.HasArc(Follow,Token,FToken):
kjSet.AddArc(Follow,Token,FToken)
#if type(FToken[0])==TupleType:
# raise ValueError, "bad FToken"+`FToken`
#print "new", Token, FToken
done = 0 # follow changed, loop again
# add follow for tail members
#for Index2 in range(BodyIndex+1, Bodylength):
# TailToken = R.Body[Index2]
# for FToken in kjSet.Neighbors(Follow,TailToken):
# if not kjSet.HasArc(Follow,Token,FToken):
# kjSet.AddArc(Follow,Token,FToken)
# done = 0
#endif EpsilonTail
# if we are not at the end use First set for next token
if not Last:
NextToken = R.Body[BodyIndex+1]
(NTtype, NTname) = NextToken
if NTtype in (KEYFLAG,TERMFLAG):
if not kjSet.HasArc(Follow,Token,NextToken):
kjSet.AddArc(Follow,Token,NextToken)
#print "next", Token, NextToken
done = 0
elif NTtype == NONTERMFLAG:
for FToken in kjSet.Neighbors(self.First, NextToken):
if FToken != NULLTOKEN:
if not kjSet.HasArc(Follow,Token,FToken):
kjSet.AddArc(Follow,Token,FToken)
#print "neighbor", Token, FToken
done = 0
else:
# next token expands to epsilon:
# add its follow, unless already done above
#if not EpsilonTail:
for FToken in kjSet.Neighbors(Follow,NextToken):
if not kjSet.HasArc(Follow,Token,FToken):
kjSet.AddArc(Follow,Token,FToken)
#print "epsilon", Token, FToken
done = 0
else:
raise TokenError, "unknown token type in rule body"
#endif not Last
# finally, check whether next iteration has epsilon tail
if not kjSet.HasArc(self.First, Token, NULLTOKEN):
EpsilonTail = 0
else:
raise TokenError, "unknown token type in rule body"
BodyIndex = BodyIndex - 1
Last = 0 # no longer at the last token of the rule
#endwhile
#endfor
#endwhile
self.Follow = Follow
