[antlr-interest] Using code inserts in syntactic predicates

[Mike Gadsdon]

Hi all,

I'm trying to use syntactic predicates in conjuction with testing token text
to resolve parsing ambiguity. Problem is that the code inserts I use end up
surrounded by a condition on inputState.guessing==0, which means that my
token text code only runs when the rule is NOT being run as a syntactic
predicate, but I need it to run always.

Is there any way I can insert code such that it runs independent of the
guessing state?

I did think I could workaround by resetting inputState.guessing to zero by a
code insert in the syntactic predicate call and then setting back to its
correct value after making my checks, but this code insert is also
conditional on inputState.guessing = 0 !

any other ideas ?

Grammar extract is :-


standardObjectPropertyName
	: (sopnConfirmationStatus) => sopnConfirmationStatus
	| (sopnValidityStatus) => sopnValidityStatus
	| (sopnValue) => sopnValue
	| ({inputState.guessing = 0;}sopnMonitoringStatus) => sopnMonitoringStatus
	| (sopnStatusConsistencyCheckStatus) => sopnStatusConsistencyCheckStatus
	| (sopnLimitCheckStatus) => sopnLimitCheckStatus
	| (sopnDeltaCheckStatus) => sopnDeltaCheckStatus
	| sopnExpectedCheckStatus
	;

// following rules define the standard object properties, checking the token
text is
// correct in each case
sopnConfirmationStatus
	: a:CONFIRMATION b:IDENTIFIER_WORD
	  {if (!b.getText().equalsIgnoreCase("status")) {throw new
RecognitionException();}}
	  {a_AST.setType(Parse.IDENTIFIER_WORD);}
	;

sopnValidityStatus
	: a:IDENTIFIER_WORD b:IDENTIFIER_WORD
	  {if (!a.getText().equalsIgnoreCase("validity") ||
!b.getText().equalsIgnoreCase("status")) {throw new
RecognitionException();}}
	;

sopnValue
	: a:VALUE
	  {a_AST.setType(Parse.IDENTIFIER_WORD);}
	;

sopnMonitoringStatus
	: a:IDENTIFIER_WORD b:IDENTIFIER_WORD
	  {if (!a.getText().equalsIgnoreCase("monitoring") ||
!b.getText().equalsIgnoreCase("status")) {throw new
RecognitionException();}}
	;


Code generated is (for one rule) :-

	public final void sopnMonitoringStatus() throws RecognitionException,
TokenStreamException {

		returnAST = null;
		ASTPair currentAST = new ASTPair();
		AST sopnMonitoringStatus_AST = null;
		Token  a = null;
		AST a_AST = null;
		Token  b = null;
		AST b_AST = null;

		try {      // for error handling
			a = LT(1);
			a_AST = astFactory.create(a);
			astFactory.addASTChild(currentAST, a_AST);
			match(IDENTIFIER_WORD);
			b = LT(1);
			b_AST = astFactory.create(b);
			astFactory.addASTChild(currentAST, b_AST);
			match(IDENTIFIER_WORD);
			if ( inputState.guessing==0 ) {
				if (!a.getText().equalsIgnoreCase("monitoring") ||
!b.getText().equalsIgnoreCase("status")) {throw new RecognitionException();}
			}
			sopnMonitoringStatus_AST = (AST)currentAST.root;
		}
		catch (RecognitionException ex) {
			if (inputState.guessing==0) {
				reportError(ex);
				consume();
				consumeUntil(_tokenSet_49);
			} else {
			  throw ex;
			}
		}
		returnAST = sopnMonitoringStatus_AST;
	}


==============================================================
Mike Gadsdon                   mailto:m.gadsdon at rheagroup.com
Rhea System S.A                Tel +44 (0)20 8891 0702
                               Fax +44 (0)20 8891 6702
==============================================================