/**
* Parses and returns a valid 'leftside' of an expression. If the left side starts with a prefix,
* it consumes other expressions with a lower priority than itself. If the left side does not have
* a prefix it must be an expr0.
*
* @param commaIsEndMarker used when the leftside is part of and argument list of expressions
* @param maxPriority operators with a higher priority than this will effectivly end the
* expression
* @return a wrapper of: 1. term correctly structured and 2. the priority of its root operator
* @throws InvalidTermException
*/
private IdentifiedTerm parseLeftSide(boolean commaIsEndMarker, int maxPriority)
throws InvalidTermException, IOException {
// 1. prefix expression
Token f = tokenizer.readToken();
if (f.isOperator(commaIsEndMarker)) {
int FX = opManager.opPrio(f.seq, "fx");
int FY = opManager.opPrio(f.seq, "fy");
if (f.seq.equals("-")) {
Token t = tokenizer.readToken();
if (t.isNumber())
/*Michele Castagna 06/2011*/
// return new IdentifiedTerm(0, Parser.createNumber("-" + t.seq));
return identifyTerm(0, Parser.createNumber("-" + t.seq), tokenStart);
/**/
else tokenizer.unreadToken(t);
}
// check that no operator has a priority higher than permitted
if (FY > maxPriority) FY = -1;
if (FX > maxPriority) FX = -1;
// FX has priority over FY
boolean haveAttemptedFX = false;
if (FX >= FY && FX >= OperatorManager.OP_LOW) {
IdentifiedTerm found = exprA(FX - 1, commaIsEndMarker); // op(fx, n) exprA(n - 1)
if (found != null)
/*Castagna 06/2011*/
// return new IdentifiedTerm(FX, new Struct(f.seq, found.result));
return identifyTerm(FX, new Struct(f.seq, found.result), tokenStart);
/**/
else haveAttemptedFX = true;
}
// FY has priority over FX, or FX has failed
if (FY >= OperatorManager.OP_LOW) {
IdentifiedTerm found =
exprA(FY, commaIsEndMarker); // op(fy,n) exprA(1200) or op(fy,n) exprA(n)
if (found != null)
/*Castagna 06/2011*/
// return new IdentifiedTerm(FY, new Struct(f.seq, found.result));
return identifyTerm(FY, new Struct(f.seq, found.result), tokenStart);
/**/
}
// FY has priority over FX, but FY failed
if (!haveAttemptedFX && FX >= OperatorManager.OP_LOW) {
IdentifiedTerm found = exprA(FX - 1, commaIsEndMarker); // op(fx, n) exprA(n - 1)
if (found != null)
/*Castagna 06/2011*/
// return new IdentifiedTerm(FX, new Struct(f.seq, found.result));
return identifyTerm(FX, new Struct(f.seq, found.result), tokenStart);
/**/
}
}
tokenizer.unreadToken(f);
// 2. expr0
return new IdentifiedTerm(0, expr0());
}