[antlr-interest] AST factory / heterogeneous tree enhancement

[Terence Parr]

Ok, Loring and I have discussed the tree factory problems.  
"micheal_jor" <open.zone at virgin.net> brought them up regarding C# and 
Ric seems to have fixed this for C++.  So, now the Java solution.

Here is the problem as I understand it.

1. #[FOO] always builds an AST node of the default type because
     the ASTFactory only knows about the default.  In future if you say

     tokens {
         PLUS<AST=PLUSNode>;
         ...
     }

     then I'll make action #[PLUS] create the right node.  You can also 
say
     #[ID,"foo","VarNode"] (3rd arg is the type of node to create).

2. dup methods of ASTFactory don't respect the type of the nodes; it
     uses default node type.  In future, i'll use 
t.getClass().newInstance()
     to do the dup.

3. hetero tree construction does not call the factory.  E.g.,

     anIntRule : INT<AST=INTNode> ;

     generates

     INTNode v = new INTNode(LT(1));

     but we need to instead generate:

     AST v = (AST)astFactory.create(LT(1),"INTNode");

     where the create(...) method is new and specifies the type to
     create.  This will use newInstance() instead of "new" by default.

4. If you define ID<AST=T> in tokens section then all code in grammar 
"id:ID" should
     define labels as "T id" not "AST id" nor labelASTType id.

Make sense to folks?  I think this is the "type table in the ast 
factory" problem that Ric fixed in the C++ output.

Ter
PS	Michael let's talk about C# integration.
--
Co-founder, http://www.jguru.com
Creator, ANTLR Parser Generator: http://www.antlr.org
Lecturer in Comp. Sci., University of San Francisco


 

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