[antlr-interest] Duplicating Tree Nodes (in rewrite grammar)

[Robin Hamilton-Pennell]

Thanks for the reply.

Actually, that won't work in my case, since the number of duplicates
is not based on any existing tokens, but on some member variables set
during semantic analysis (I actually have a Set<String> containing the
"names" for each of the generated blocks). Unfortunately the specifics
of my grammar are pretty esoteric, and so explaining it is difficult.

There's no repeated elements in the rule I want to do the duplication
in (this is an actual clip of the grammar, slightly simplified):

statement
	: ^(TYPEDEF l=lvalue b=basicBlock)			->  // ?????
	| // other rules...
        ;

So, let's say after semantic analysis, I determine I need 6 duplicates
of $b above. What could I put on the right side of the rule to do
this? Is it possible to create 6 imaginary tokens based on some
context variables, and then use the technique you showed? I'm sorry if
I'm being dense, I just have a hard time wrapping my mind around what
I need to do...

Thanks again for your help,
Robin

On Fri, May 30, 2008 at 4:11 PM, Terence Parr <parrt at cs.usfca.edu> wrote:
> ANTLRWill automatically build duplicates as necessary. Is this what you
> want?
>
> d : type ID (',' ID)* -> ^(DECL type ID)+ ;
>
> ANTLR should make n copies of DECL and n-1 copies of type's tree.
> Ter
> On May 30, 2008, at 3:08 PM, Robin Hamilton-Pennell wrote:
>
>> Hi all,
>>
>> Been stumbling against a problem lately which I'd like to get some
>> feedback on.
>>
>> I need to duplicate a tree node at a certain point in my AST rewrite
>> grammar, including all of its children (recursively). If I knew the
>> number of copies necessary in advance, I imagine I could do something
>> like this:
>>
>> foo:
>>   ^(BAR baz)  ->  ^(BAR baz)  ^(BAR baz)  ^(BAR baz)
>>   ;
>>
>> However, the number of copies necessary is not knowable until runtime.
>>
>> I tried simply using CommonTree.dupNode(), but it doesn't copy the
>> children (after reading through the source I know this is correct
>> behavior).
>>
>> So I guess my question is this: How can I make an arbitrary number of
>> copies of a tree node and all sub-trees? I don't actually care about
>> making changes to the tree yet, I just want a verbatim copy.
>>
>> Any advice would be appreciated.
>>
>> Thanks in advance,
>> Robin
>
>