[antlr-interest] Tree transformations

[Bryan Ewbank]

You can do it with code, but it's perhaps better to use the ANTLR constructs:

  refactor { RefAST ctree; }
  : #( A ctree=brule erule[ctree] F ) ;

  brule returning [ RefAST ctree ]
  : #( b:B c:C d:D ) { ## = #( b d ); ctree = #c; } ;

  crule : C ;

  erule [ RefAST ctree ]
  : #( e:E children ) { ## = #( e, ctree, #children ); } ;

This is not quite right - no access to compiler at the moment - but
it's close.  Beware of dangling links in the intermediate tree (ctree)
that is passed around; the factory has a "dupTree" method that might
come in handy.

Sorry for being sketchy...
- Bryan


On 7/14/05, Tarun Khanna <tarunkhanna at gmail.com> wrote:
> I guess yes. You can do something like 
>  
>  E.addChild(B.getFirstChild());
>  and then set the child of B to NULL
>  B.setFirstChild(null) or
> B.setFirstChild(B.getFirstChild().getNextSibling());
>  
>  All you ANTLR experts, please let me know if the above procedure is
> correct. I would appreciate if you can point out the flaw as I spent a
> couple of days in trying to understand the AST stuff in ANTLR and if the
> above is flawed then I need to spend some more time.
>  
>  Tarun
> 
> 
> On 7/14/05, Jeff Dahl <jddahl at micron.com> wrote:
> > When transforming a tree, is it possible to move a subtree to some
> > arbitrary node?  For example, given the tree:
> > 
> >     A
> >     |-- B
> >     |   |-- C
> >     |   |   |-- attribute1
> >     |   |   |   `-- value 1
> >     |   |   |-- attribute2
> >     |   |   |   `-- value 2
> >     |   |   `-- attribute3
> >     |   |       `-- value 3
> >     |   `-- D
> >     |       `-- attribute4
> >     |           `-- value 4
> >     |-- E
> >     |   `-- attribute5 
> >     |       `-- value 5
> >     `-- F
> >         `-- attribute6
> >             `-- value 6
> > 
> > is it possible to move subtree "C" to subtree "E" as illustrated below?
> > 
> >     A
> >     |-- B
> >     |   `-- D
> >     |       `-- attribute4
> >     |           `-- value 4
> >     |-- E
> >     |   |-- C
> >     |   |   |-- attribute1
> >     |   |   |   `-- value 1
> >     |   |   |-- attribute2
> >     |   |   |   `-- value 2 
> >     |   |   `-- attribute3
> >     |   |       `-- value 3
> >     |   `-- attribute5
> >     |       `-- value 5
> >     `-- F
> >         `-- attribute6
> >             `-- value 6
> > 
> > Thanks,
> > Jeff
> > 
> > 
>  
> 
> 
> -- 
> Tarun Khanna