[antlr-interest] repeating the parsing of a subtree

[Claude Moulin]

I never had a good solution to the problem that I resolved before using
(or rendering public) the getNodeIndex method of the
CommonTreeNodeStream

class.

I have the following tree:

^(REPEAT a = atom list = .)

Where list can be parsed with a specific rule: list_instructions. 

atom returns an integer giving the number of times (maybe 0) the list of
instructions has to be executed.

The semantics of the instruction is then clear.

In the previous version of antlr I used the following interpreting Java
code:

{

 for (int i = 0; i < $a.r ; i++) {

   push(list);

   list_instructions();

   pop();

}

Where push and pop method are added to the tree parser:

private void push(CommonTree tree) {

 int n = ((CommonTreeNodeStream)input).getNodeIndex(tree);

 if (n >= 0)

   ((CommonTreeNodeStream)input).push(n);

}

private void pop() {

     ((CommonTreeNodeStream)input).pop();

  }

In version 3.2 CommonTreeNodeStream has been updated and I no longer
understand how to parse a subtree of the AST when it is needed and
possibly several times. The problem was to find the index of a Tree root
in the AST representation.

 

Can someone give the solution?

Thank you

Claude 

 

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