/**
* This is the reduce implementation
*
* @param rule the rule to reduce by
*/
private void reduce(int rule) throws SyntaxError {
// get the rule number to reduce by
int num = Math.abs(rule);
// this section is for generating code
if (num == 27 || num == 28 || num == 29 || num == 30 || num == 31 || num == 32 || num == 33
|| num == 37 || num == 39 || num == 41) {
gen.reduce(num);
}
// popping empty from the stack, just push
if (GrammarTable.grammar[num].length != 1) {
// start popping and matching stuff
int input = 0;
for (int i = GrammarTable.grammar[num].length - 1; i > 0; i--) {
stack.pop();
input = stack.pop();
if (GrammarTable.grammar[num][i] == input) {
continue;
} else {
throw new SyntaxError("Syntax error in source file on line " + scanner.getLine());
}
}
}
// push the LHS
curState = stack.peek();
// push the left hand side
stack.push(GrammarTable.getRule(num)[0]);
curState = pTable.getNextState(curState, GrammarTable.getRule(num)[0]);
stack.push(curState);
}
/**
* Parse the input file
*
* @return true if the input is a part of the language, false if it is not
*/
public boolean parse() {
pTable = new ParseTable();
boolean notFound = true;
curState = stack.peek();
Token next = null;
int nextState;
String name = "";
try {
while (notFound) {
next = scanner.scan();
nextState = pTable.getNextState(curState, next.getP());
if (nextState == 9999) {
System.err.println("Error in parsing on line " + scanner.getLine());
return false;
} // next state is negative, reduce
else if (nextState < 0) {
while (nextState < 0) {
reduce(nextState);
nextState = pTable.getNextState(curState, next.getP());
}
shift(nextState, next.getP());
curState = nextState;
} // next state is positive and not a goto, shift
else if (nextState > 0) { // took out && nextState < 100
shift(nextState, next.getP());
curState = nextState;
} // next state is accept (only happens in state 6)
if (nextState == 6) {
gen.reduce(0);
return true;
}
if (curState == 9999) {
System.err.println("Error state reached while parsing.");
System.err.println("Error on line: " + scanner.getLine());
return false;
}
}
} catch (java.io.IOException ie) {
ie.printStackTrace();
} catch (SyntaxError ex) {
System.err.println("Syntax Error on line " + scanner.getLine() + " while parsing.");
return false;
} catch (compiler.CScanner.MaxIDSizeError me) {
System.err.println(me.getMessage());
return false;
}
return false;
}