[antlr-interest] New article on StringTemplates and Treewalkers

[Terence Parr]

On Jan 10, 2006, at 1:14 PM, sohail at taggedtype.net wrote:
> I was struck by the example of 5 lines of C code being folded into one
> line of Java code. Why couldn't you have a tree parser do this? It  
> would
> be inefficient, but I don't know if that is the point of the article.

Hi.  My impression from reading his article was that Andy was  
interpreting tree walker to be the simple visitor pattern where all  
you can see is "I'm at node function definition" as opposed to the  
more powerful grammar-based tree pattern matching:

funcdef
	: ^(FUNCDEF ID args body)
	;

Specifically he asked where one would worry about whether or not a  
return statement was present in the body.  Seems straightforward to  
have an action after the body rule reference that checked a boolean  
set by body.  You might do this (using the new dynamic scope stuff):

funcdef
scope {
   boolean hasReturn;
}
@init {
   hasReturn = false;
}
	: ^(FUNCDEF ID args body) {if ($hasReturn) ...}
	;

body : stat+ ;

stat : ... | ^(RETURN expr) {$funcdef::hasReturn=true;} | ... ;

Andy, is this easier or harder than you imagined?  Does it address  
your point?

Ter