[antlr-interest] manual tree construction

[Monty Zukowski]

On Sep 15, 2005, at 8:39 AM, Michael Laszlo wrote:

> My parser includes the rules below for declarations that look like  
> this:
>     var a = 2, b = 3+4;
>
>
> decl_statement SEMI!
>  : "var"! ID DEC_ASSIGN^ expr (DEC_COMMA^ var_decl)*
>  ;
>
> var_decl!     // construct these subtrees manually
>  : ID DEC_ASSIGN expr { #var_decl = #(DEC_ASSIGN ID expr); }
>  ;
>
> antlr.Tool gives me this error message:
> ANTLR Parser Generator   Version 2.7.5 (20050128)   1989-2005  
> jGuru.com
> calc.g:35:27: Syntax error in action: calc.g:35:27: expecting ')',  
> found 'I'
> Exiting due to errors.
> This error message flags the second reference to ID in the var_decl  
> rule. The documentation (ANTLR Tree Construction) suggests that  
> this should work.
>
> I'm using heterogeneous trees, and am basically trying to construct  
> a tree that looks like this:
> #(DEC_COMMA #(DEC_ASSIGN ID expr) #(DEC_ASSIGN ID expr)). Here  
> DEC_COMMA serves as the backbone for the subtrees for the variable  
> bindings.
>

Use labels.  When you use #(TOKEN ...) ANTLR thinks you are building  
a node, not a tree.

i:ID d:DEC_ASSIGN expr { #var_decl = #(i d expr); }


Monty
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