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Null rules work in RNGLR now, but there seems to be a bug where somehow some states/rules get no lookahead.

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This commit is contained in:
Nathan Braswell
2013-08-02 15:21:42 -04:00
parent 49d149bc1f
commit d5b33efb22
5 changed files with 54 additions and 14 deletions
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52
src/RNGLRParser.cpp
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@@ -33,7 +33,12 @@ NodeTree<Symbol*>* RNGLRParser::parseInput(std::string inputString) {
while (*currentToken != *EOFSymbol) {
std::cout << EOFSymbol->toString() << " " << currentToken->toString() << std::endl;
currentToken = lexer.next();
input.push_back(currentToken);
if (currentToken != NULL) {
input.push_back(currentToken);
} else {
std::cout << "Rejected, lexer unable to fully tokenize sentence" << std::endl;
return new NodeTree<Symbol*>();
}
}
std::cout << "\n\n\nDone with Lexing\n\n\n" << std::endl;
@@ -210,8 +215,8 @@ void RNGLRParser::addStates(std::vector< State* >* stateSets, State* state) {
table.add(stateNum(state), (*lookahead)[j], new ParseAction(ParseAction::REDUCE, (*currStateTotal)[i]));
// } else if (*((*currStateTotal)[i]->getAtNextIndex()) == *nullSymbol) {
//If this has an appropriate ruduction to null, get the reduce trees out
} else if (std::vector<NodeTree<Symbol*>*>* reduceTrees = (*currStateTotal)[i]->nullReductions(), reduceTrees) {
std::cout << "REDUCE TREES" << std::endl;
} else if (reducesToNull((*currStateTotal)[i])) {
std::cout << (*currStateTotal)[i]->toString() << " REDUCES TO NULL" << std::endl;
//If is a rule that produces only NULL, add in the approprite reduction, but use a new rule with a right side of length 0. (so we don't pop off stack)
ParseRule* nullRule = (*currStateTotal)[i]->clone();
nullRule->setRightSide(* new std::vector<Symbol*>());
@@ -240,4 +245,43 @@ void RNGLRParser::addStates(std::vector< State* >* stateSets, State* state) {
table.add(stateNum(state), currStateSymbol, new ParseAction(ParseAction::SHIFT, stateSets->size()-1));
}
}
}
}
bool RNGLRParser::reducesToNull(ParseRule* rule) {
std::vector<Symbol*> avoidList;
return reducesToNull(rule, avoidList);
}
bool RNGLRParser::reducesToNull(ParseRule* rule, std::vector<Symbol*> avoidList) {
for (std::vector<Symbol*>::size_type i = 0; i < avoidList.size(); i++)
if (*(rule->getLeftSide()) == *(avoidList[i]))
return false;
avoidList.push_back(rule->getLeftSide());
std::vector<Symbol*> rightSide = rule->getRightSide();
bool reduces = true;
for (std::vector<Symbol*>::size_type i = 0; i < rightSide.size(); i++) {
if (*rightSide[i] == *nullSymbol)
continue;
if (rightSide[i]->isTerminal()) {
reduces = false;
break;
}
bool subSymbolReduces = false;
for (std::vector<ParseRule*>::size_type j = 0; j < loadedGrammer.size(); j++) {
if (*(loadedGrammer[j]->getLeftSide()) == *(rightSide[i])) {
if(reducesToNull(loadedGrammer[j], avoidList)) {
subSymbolReduces = true;
break;
}
}
}
if (!subSymbolReduces) {
reduces = false;
break;
}
}
return reduces;
}