[antlr-interest] Re: antlr bug or grammar problem?

[kozchris]

shouldn't a line like this 

> > ( BECAME_TRUE | BECAME_FALSE | CHANGED ) => expr

produce code like this

> > 		switch ( LA(1)) {
> > 		case BECAME_TRUE:
> > 		case BECAME_FALSE:
> > 		case CHANGED:
> > 		{
> > 			expr();



--- In antlr-interest at yahoogroups.com, Monty Zukowski <monty at c...> wrote:
> A syntactic predicate doesn't work by modifying the lookahead, it 
> actually tests the grammar fragment in 'guessing' mode and then if that 
> is ok it will proceed.  I don't think you've found a bug in ANTLR.  
> However, you were looking at the code for a reason.  What's the 
> original bug?
> 
> Monty
> 
> ANTLR & Java Consultant -- http://www.codetransform.com
> ANSI C/GCC transformation toolkit -- 
> http://www.codetransform.com/gcc.html
> Embrace the Decay -- http://www.codetransform.com/EmbraceDecay.html
> 
> On Sep 23, 2004, at 11:10 AM, kozchris wrote:
> 
> > I'm using antlr 2.7.4.
> > I've run the grammar building both a cpp and java version with same
> > results.
> >
> > You can see the grammar file here
> > http://www.synergyss.com/SCRExpression.g.
> > and the java output here
> > http://www.synergyss.com/SCRExpressionParser.java
> >
> > The issue is showing up in the parser code generated for rule
> > eventExpr on line 279.
> > The line:
> >   ( BECAME_TRUE | BECAME_FALSE | CHANGED ) => expr {printf("processing
> > simple event expr\n");}
> >
> > is showing up as this in the generated parser.
> >
> > <<<< begin code snip
> > 		switch ( LA(1)) {
> > 		case BOOLEAN:
> > 		case DoubleDoubleConst:
> > 		case FloatDoubleConst:
> > 		case LongDoubleConst:
> > 		case IntBinaryConst:
> > 		case IntHexConst:
> > 		case LongHexConst:
> > 		case UnsignedHexConst:
> > 		case IntOctalConst:
> > 		case LongOctalConst:
> > 		case UnsignedOctalConst:
> > 		case IntIntConst:
> > 		case LongIntConst:
> > 		case UnsignedIntConst:
> > 		case LPAREN:
> > 		case PLUS:
> > 		case MINUS:
> > 		case LNOT:
> > 		case BNOT:
> > 		case BECAME_TRUE:
> > 		case BECAME_FALSE:
> > 		case CHANGED:
> > 		case ID:
> > 		{
> > 			expr();
> > 			astFactory.addASTChild(currentAST, returnAST);
> > 			if ( inputState.guessing==0 ) {
> > 				printf("processing simple event expr\n");
> > 			}
> > 			eventExpr_AST = (AST)currentAST.root;
> > 			break;
> > 		}
> > <<<< end code snip
> >
> > What is strange is that if I change line 281 from:
> >   ( BECAME_TRUE | BECAME_FALSE | CHANGED ) => expr {printf("processing
> > simple event expr\n");}
> >
> > to:
> >
> >   ( BECAME_TRUE | BECAME_FALSE | CHANGED ) => simpleEventExpr
> > {printf("processing simple event expr\n");}
> >
> > the code generated is correct.
> >
> > <<<< begin code snip
> > 		switch ( LA(1)) {
> > 		case BECAME_TRUE:
> > 		case BECAME_FALSE:
> > 		case CHANGED:
> > 		{
> > 			simpleEventExpr();
> > 			astFactory.addASTChild(currentAST, returnAST);
> > 			if ( inputState.guessing==0 ) {
> > 				printf("processing simple event expr\n");
> > 			}
> > 			eventExpr_AST = (AST)currentAST.root;
> > 			break;
> > 		}
> > <<<< end code snip
> >
> > Any ideas on how to solve this problem?
> >
> > Thanks for the help.
> > Chris
> >
> >
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >



 
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