[antlr-interest] a left recursive walker rule

[Bryan Ewbank]

> "��͸� Jigang (Robert) Sun" <sunjigang1965 at yahoo.com.cn> wrote:
>  Hi,
> I have a rule in tree walker, which is left recursive:  A : (A|B)+ C ,
>
> so I am trying to eliminate it
> ...

I think this matches the same regex:
    A : ( (B)+ (C)+ )+ ;

This is more intuitive than anything else, by exploring the strings generated;
it therefore might be wrong (I didn't test it rigorously), but it might be good
place to start explorations.

Look at the strings generated by "A : (A|B)+ C", assuming B and C are
terminals:  "A" must, in any final application, generate "(B)+C"; and "A"
itself ends with "C", so "B(C)+" is generated by recursion.

Hope I didn't miss something, and hope this helps a bit,
- Bryan