[antlr-interest] Are token aliases possible?

[Jim Idle]

Get a reference to the token and just set the type property.

Jim

> -----Original Message-----
> From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-
> bounces at antlr.org] On Behalf Of Christian
> Sent: Friday, October 28, 2011 4:46 AM
> To: antlr-interest at antlr.org
> Subject: Re: [antlr-interest] Are token aliases possible?
>
> Yes, I know that one can use rewrite rules. Thank you anyway. In some
> cases however, I do not want to repeat the rules following the CLASS
> token and write an arrow etc. In such cases, it is shorter to just
> replace the CLASS by CLASS_DECL and add a few operators instead of a
> rewrite rule.
>
> As an example, I want to transform the following rule:
>
> class_declaration
>   : CLASS  type_or_generic   class_base?
> type_parameter_constraints_clauses?   class_body   ';'?
>
> into
>
> class_declaration
>   : CLASS_DECL  type_or_generic   class_base?
> type_parameter_constraints_clauses?   class_body   ';'!?
>
> versus
>
> class_declaration
>   : CLASS  type_or_generic   class_base?
> type_parameter_constraints_clauses?   class_body   ';'?
>       -> ^(CLASS_DECL type_or_generic class_base?
> type_parameter_constraints_clauses? class_body)
>     ;
>
> I think everyone, especially me, would prefer the first solution.
>
> Am 28.10.2011 13:34, schrieb Sam Barnett-Cormack:
> > I don't know for sure, buut my immediate thought is that it isn't
> > likely to be possible (as tokens are generated without reference to
> > parse context, and must be unambiguous except where code manually
> > deals with the ambiguity). You could however create it as a dummy
> > token name, and rewrite to it in the parser, such that the AST
> > generated has a 'virtual' CLASS_DECL token generated from the 'real'
> > CLASS token. Pretty sure there are examples of this in the wiki.
> >
> > On 28/10/2011 12:27, Christian wrote:
> >> CLASS is only the token name. However, CLASS_DECL represents the
> >> semantics of what was parsed. It allows to be more consequent when
> >> analyzing the generated AST by names like CLASS_DECL, METHOD_DECL,
> >> FIELD_DECL etc.
> >>
> >> Example:
> >>
> >> switch (node.getType()) {
> >>     case CsRewriteRulesParser.NAMESPACE_DECL:
> >>        // TODO
> >>        break;
> >>     case CsRewriteRulesParser.METHOD_DECL:
> >>        // TODO
> >>        break;
> >>     case CsRewriteRulesParser.CLASS_DECL:
> >>        // TODO
> >>        break;
> >> }
> >>
> >> It would be just another name for the integer constant CLASS.
> >>
> >> Am 28.10.2011 13:19, schrieb Sam Barnett-Cormack:
> >>> I think the immediate answer is, "why?"
> >>>
> >>> On 28/10/2011 09:02, Christian wrote:
> >>>> Hi community,
> >>>>
> >>>> if there is a real token, say
> >>>>       CLASS : 'class';
> >>>> can a define an alias, say
> >>>>       CLASS_DECL = CLASS
> >>>> in some way?
> >>>>
> >>>> Regards,
> >>>> Christian
> >>>>
> >>>> List: http://www.antlr.org/mailman/listinfo/antlr-interest
> >>>> Unsubscribe:
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> addr
> >>>> ess
> >>>
> >>
> >>
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> >
>
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