[antlr-interest] Semantic predicates during AST construction

[Oliver B. Fischer]

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It is possible, if you call the ctor directly, but this is a language
dependend solution.

Here is an example:

- -> ^(PLUS $ruleA $ruleB
     {(true != false) ? new SymbolTree(INT2FLOAT) : null })

I would like to have a more generic solution...


Gavin Lambert schrieb:
> At 20:30 6/10/2008, Oliver B. Fischer wrote:
>>I would like to express things like:
>>
>>-> ^(ROOT A ({condition}? B | C)
>>
>>Evaluates condition to true, I would like to get ^(ROOT A B).
>>Otherwise the result should be ^(ROOT A C).
> 
> If B and C are tokens that exist on the matching side (left of the
> arrow) then I think you can do this (haven't tried it, though, so I
> could be wrong):
> 
> A b=B c=C -> ^(ROOT A { (condition) ? $b : $c })
> 
> It's probably possible to do this sort of thing with imaginary tokens as
> well, although I'm not sure exactly what the syntax would be.
> 

- --
Oliver B. Fischer, Schönhauser Allee 64, 10437 Berlin
Tel. +49 30 44793251, Mobil: +49 178 7903538
Mail: o.b.fischer at gmx.de Blog: http://www.sw-blog.net
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