[antlr-interest] TreeParser efficiency: Can TreeParsers ignore arbitary subtrees?

[Terence Parr]

On Tuesday, May 13, 2003, at 05:11  AM, micheal_jor wrote:

> Hi,
>
> I just wondered if it is possible to generate TreeParsers that ignore
> (i.e. do not "visit") the nodes in arbitary subtrees.

Sure. :)  Use wildcard:

expr : #(MULTIPLY . .) ;

will match just the multiply and ensure there are two children.  I use 
this all the time for efficiency when doing simple phases.  For 
example, if you don't care about what's inside a method body, just use 
dot for the body and it won't be parsed. :)

Terence
>
> I have an AST in which only a few nodes have attributes I am
> interested in processing with a TreeParser. Because every TreeParser
> grammar describes the whole tree(?), all nodes are still visited even
> if no action code exists to be executed.
>
> Is it possible to effectively say in the TreeParser grammar "I won't
> be doing anything in this node/subtree so don't even generate code to
> visit it?
>
> Cheers,
>
> Micheal
>
>
>
>
>
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>
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