[antlr-interest] ANTLR Optional statements

[mzukowski at bco.com]

What version of antlr?  Have you tried 2.7.2a2?

Monty

> -----Original Message-----
> From: jg z [mailto:zjg1964 at yahoo.com]
> Sent: Friday, April 05, 2002 7:31 AM
> To: antlr-interest at yahoogroups.com
> Subject: RE: [antlr-interest] ANTLR Optional statements
> 
> 
> The generated code is like this,
> 
> 		switch ( LA(1)) {
> 		case ID:
> 		{
> 			match(ID);
> 			{
> 			switch ( LA(1)) {
> 			case COLON:
> 			{
> 				base_clause();
> 				break;
> 			}
> 			case ANTLR_USE_NAMESPACE(antlr)Token::EOF_TYPE:
> 			{
> 				break;
> 			}
> 			default:
> 			{
> 				throw
> ANTLR_USE_NAMESPACE(antlr)NoViableAltException(LT(1),
> getFilename());
> 			}
> 			}
> 			}
> 			break;
> 		}
> 		case ANTLR_USE_NAMESPACE(antlr)Token::EOF_TYPE:
> 		{
> 			break;
> 		}
> 		default:
> 		{
> 			throw
> ANTLR_USE_NAMESPACE(antlr)NoViableAltException(LT(1),
> getFilename());
> 		}
> 		}
> 
> The problem is, if there is no "ID", it would go into
> default and throw an Exception.  It shouldn't do like
> this as an optional statement, should it?   
> --- mzukowski at bco.com wrote:
> > What does it produce that's not right?
> > 
> > > -----Original Message-----
> > > From: jg z [mailto:zjg1964 at yahoo.com]
> > > Sent: Friday, April 05, 2002 6:44 AM
> > > To: antlr-interest at yahoogroups.com
> > > Subject: [antlr-interest] ANTLR Optional
> > statements
> > > 
> > > 
> > > We are trying to convert a C++ Parser from PCCTS
> > to
> > > ANTLR, and becoming increasingly frustrated by the
> > > differences between the two systems.
> > > 
> > > For instance;
> > > 
> > > In cplusplus.g we have,
> > > 
> > > class_head
> > >    :  (  STRUCT  
> > >       |  UNION 
> > >       |  CLASS 
> > >       )
> > >       {ID { base_clause } }
> > >    ;
> > > 
> > > which works fine in PCCTS.
> > > 
> > > For ANTLR we have converted this to,
> > > 
> > > class_head
> > >    :	
> > >     (  STRUCT  
> > >     |  UNION 
> > >     |  CLASS 
> > >     )
> > >     (ID ( base_clause)? )?
> > >    ;
> > > 
> > > However, the optional statements shown at the end
> > of
> > > this production no longer produces a properly
> > optional
> > > construction in the generated .cpp file.
> > > 
> > > What are we supposed to do?
> > > 
> > > David.
> > > 
> > > 
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> 
> 
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