[antlr-interest] AST NODE CHOICE

[Ric Klaren]

On Wed, Jul 09, 2003 at 12:47:52PM -0000, colettekirwan wrote:
> I was wondering is it possible using the antlr grammar to  generate a 
> tree node based on a choice i.e
> 
> I have the following grammar in my Parser
> 
> test_statement:!
>  e2:node1_list e1:node2_list e3:(node3_list | node4_list)
>         {## = #([TEST_STATEMENT,"TEST_STATEMENT"],#e2,#e1,#e3);}
>        
>  ; 
> 
> I want the last node e3 to be either node3_list or node4_list 
> depending on the User's input. The above grammar compiles but does 
> not work i.e my Parser code does not generate any code relating to e3.

Labeled subrules do not work e.g. label:( x|y|z ).

Something like this should do the job if I understood the problem correctly
(assuming java & I did not typo/laps in C++ somewhere):

e2:node1_list e1:node2_list (e3:node3_list | e4:node4_list)
{
	AST t;
	if ( #e3 )
		t = #e3;
	else
		t = #e4;
	## = #([TEST_STATEMENT,"TEST_STATEMENT"],#e2,#e1,t);
}

Cheers,

Ric
--
-----+++++*****************************************************+++++++++-------
    ---- Ric Klaren ----- j.klaren at utwente.nl ----- +31 53 4893722  ----
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  Before they invented drawing boards, what did they go back to?


 

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