[antlr-interest] Semantic Predicates inside syntactic ones?

[Ric Klaren]

On Tue, Dec 09, 2003 at 11:55:06AM +0100, Ric Klaren wrote:
> assignment:
>    ( #( "=" id:IDENTIFIER { isClock(#id->getSymbol() ) }? (INT|FLOAT) ) ) =>
>       #( "=" IDENTIFIER ( INT | FLOAT ) )
>    {
>       // generate clock reset code
>    }
> |  #( "=" write_expr[output,false]     { output << "->setValue( "; }
>           write_expr[output,true] )
>    {
>       output << " )";
>    }
> | ... ;

Actually.. it can be solved quite nice without antlr tampering by adding an
extra rule:

isClockReset returns [bool ok]:
	#( "=" id:IDENTIFIER	( i:INT | f:FLOAT ) )
	{
		double val;
		if( #i )
		{
			std::istringstream rf(#i->getText());
			rf >> val;
		}
		if( #f )
		{
			std::istringstream rf(#f->getText());
			rf >> val;
		}
		SymbolInformation* si = data.getModel()->getSymbolInformation();
		ok = si->is_clock(#id->getSymbol()) && val == 0;
	}
;
exception
	catch [antlr::RecognitionException &ex]
	{
		// prevent exceptions from obstructing things
		ok = false;
	}

assignment:
	{ isClockReset(#assignment_in) }? #( "=" lhs0:write_expr[output,false] ( INT | FLOAT ) )
	{
		output << "->setValue( model->getGlobalClock() )";
		varname_collector->execute( lhs0, vars );
	}
|	#( "=" lhs1:write_expr[output,false]		{ output << "->setValue( "; }
			 rhs1:write_expr[output,true] )
	{ output << " )"; }
| ...;

Guess the motto is if one predicate does not the work the other will, it's
only tedious that antlr does not help very much with this..

Cheers,

Ric
--
-----+++++*****************************************************+++++++++-------
    ---- Ric Klaren ----- j.klaren at utwente.nl ----- +31 53 4893722  ----
-----+++++*****************************************************+++++++++-------
  "You know how to use that thing?" [pointing to the sword]
  "Sure.. The pointy end goes into the other guy."
  --- The Mask of Zorro

 

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