[antlr-interest] Are token aliases possible?

[Christian]

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
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>>>
>>
>>
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