[antlr-interest] why <if(y==2 )> in Stringtemplate does not work?

[Terence Parr]

On Mar 6, 2009, at 3:46 PM, YingAnnie wrote:

>
>  So, what I expect is that when the code is "a=b*c", and c==2, then  
> change * to /.
>
> multiplicativeExpression
>     :^(STAR u1=unaryExpression u2=unaryExpression)  ->  
> assgin(x={$u1.text},y={$u2.text},z={"/"})
>     ;
>
> group T;
> assgin(x,y,z)::= <<
> <if(y==2)><x><z><y><else><"error"><endif>
>
> If I can not test the value of attributes within ST,Then it has to  
> be done in the tree grammar. can I do something like this:
>
> multiplicativeExpression
>     :^(STAR u1=unaryExpression u2='2')  ->  
> assgin(x={$u1.text},y={$u2.text},z={"/"})
>     ;

Almost.  you need predicated -> alternatives

-> {..}?  template one
-> {...}? template two
-> else template

T