[antlr-interest] "explosion" rewrite

[Terence Parr]

On May 1, 2009, at 5:03 PM, Steve Ebersole wrote:

> Lets say sortKey comes back as
> ^( VECTOR_EXPR
>    ^( COLUMN
>        ALIAS_REF["a"] IDENTIFIER["col1"]
>    )
>    ^( COLUMN
>        ALIAS_REF["a"] IDENTIFIER["col2"]
>    )
> )
>
> I'd really like sortSpecification to go from:
>
> ^( SORT_SPEC ^( VECTOR_EXPR["see above"] ) )
>
> to:
>
> ^( SORT_SPEC ^( COLUMN ALIAS_REF["a"] IDENTIFIER["col1"] ) )
> ^( SORT_SPEC ^( COLUMN ALIAS_REF["a"] IDENTIFIER["col2"] ) )
>
> so its gets split from one Tree to two

Ok, that's easy enough I think. Have sortKey not return VECTOR_EXPR as  
the root; you don't want it. THen, if we are ignoring the other rules  
for now, this is what you want:

> sortSpecification : sortKey  -> ^( SORT_SPEC sortKey  )+  ;

The + on the outside duplicates the root, one for each child pulled  
from sortKey...ack, wait.  Will it see the tree coming back from  
sortKey as a "list" or a single element...hmm...try that first and see  
what happens.

Then, if that works, we can think about the rule references I deleted.

Ter