/**
* 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());
}
private IdentifiedTerm exprA(int maxPriority, boolean commaIsEndMarker)
throws InvalidTermException, IOException {
IdentifiedTerm leftSide = exprB(maxPriority, commaIsEndMarker);
// if (leftSide == null)
// return null;
// {op(yfx,n) exprA(n-1) | op(yf,n)}*
Token t = tokenizer.readToken();
for (; t.isOperator(commaIsEndMarker); t = tokenizer.readToken()) {
int YFX = opManager.opPrio(t.seq, "yfx");
int YF = opManager.opPrio(t.seq, "yf");
// YF and YFX has a higher priority than the left side expr and less then top limit
// if (YF < leftSide.priority && YF > OperatorManager.OP_HIGH) YF = -1;
if (YF < leftSide.priority || YF > maxPriority) YF = -1;
// if (YFX < leftSide.priority && YFX > OperatorManager.OP_HIGH) YFX = -1;
if (YFX < leftSide.priority || YFX > maxPriority) YFX = -1;
// YFX has priority over YF
if (YFX >= YF && YFX >= OperatorManager.OP_LOW) {
IdentifiedTerm ta = exprA(YFX - 1, commaIsEndMarker);
if (ta != null) {
/*Castagna 06/2011*/
// leftSide = new IdentifiedTerm(YFX, new Struct(t.seq, leftSide.result, ta.result));
leftSide = identifyTerm(YFX, new Struct(t.seq, leftSide.result, ta.result), tokenStart);
/**/
continue;
}
}
// either YF has priority over YFX or YFX failed
if (YF >= OperatorManager.OP_LOW) {
/*Castagna 06/2011*/
// leftSide = new IdentifiedTerm(YF, new Struct(t.seq, leftSide.result));
leftSide = identifyTerm(YF, new Struct(t.seq, leftSide.result), tokenStart);
/**/
continue;
}
break;
}
tokenizer.unreadToken(t);
return leftSide;
}
private IdentifiedTerm exprB(int maxPriority, boolean commaIsEndMarker)
throws InvalidTermException, IOException {
// 1. op(fx,n) exprA(n-1) | op(fy,n) exprA(n) | expr0
IdentifiedTerm left = parseLeftSide(commaIsEndMarker, maxPriority);
// 2.left is followed by either xfx, xfy or xf operators, parse these
Token operator = tokenizer.readToken();
for (; operator.isOperator(commaIsEndMarker); operator = tokenizer.readToken()) {
int XFX = opManager.opPrio(operator.seq, "xfx");
int XFY = opManager.opPrio(operator.seq, "xfy");
int XF = opManager.opPrio(operator.seq, "xf");
// check that no operator has a priority higher than permitted
// or a lower priority than the left side expression
if (XFX > maxPriority || XFX < OperatorManager.OP_LOW) XFX = -1;
if (XFY > maxPriority || XFY < OperatorManager.OP_LOW) XFY = -1;
if (XF > maxPriority || XF < OperatorManager.OP_LOW) XF = -1;
// XFX
boolean haveAttemptedXFX = false;
if (XFX >= XFY && XFX >= XF && XFX >= left.priority) { // XFX has priority
IdentifiedTerm found = exprA(XFX - 1, commaIsEndMarker);
if (found != null) {
/*Castagna 06/2011*/
// Struct xfx = new Struct(operator.seq, left.result, found.result);
// left = new IdentifiedTerm(XFX, xfx);
left = identifyTerm(XFX, new Struct(operator.seq, left.result, found.result), tokenStart);
/**/
continue;
} else haveAttemptedXFX = true;
}
// XFY
if (XFY >= XF && XFY >= left.priority) { // XFY has priority, or XFX has failed
IdentifiedTerm found = exprA(XFY, commaIsEndMarker);
if (found != null) {
/*Castagna 06/2011*/
// Struct xfy = new Struct(operator.seq, left.result, found.result);
// left = new IdentifiedTerm(XFY, xfy);
left = identifyTerm(XFY, new Struct(operator.seq, left.result, found.result), tokenStart);
/**/
continue;
}
}
// XF
if (XF >= left.priority) // XF has priority, or XFX and/or XFY has failed
/*Castagna 06/2011*/
// return new IdentifiedTerm(XF, new Struct(operator.seq, left.result));
return identifyTerm(XF, new Struct(operator.seq, left.result), tokenStart);
/**/
// XFX did not have top priority, but XFY failed
if (!haveAttemptedXFX && XFX >= left.priority) {
IdentifiedTerm found = exprA(XFX - 1, commaIsEndMarker);
if (found != null) {
/*Castagna 06/2011*/
// Struct xfx = new Struct(operator.seq, left.result, found.result);
// left = new IdentifiedTerm(XFX, xfx);
left = identifyTerm(XFX, new Struct(operator.seq, left.result, found.result), tokenStart);
/**/
continue;
}
}
break;
}
tokenizer.unreadToken(operator);
return left;
}