[antlr-interest] a left recursive walker rule

[Loring Craymer]

This looks very weird--you have no termination condition for the recursion.  Normally, recursive rules have termination conditions and the recursion-to-iteration conversion is relatively straightforward.  I cannot easily imaging how you got to this form.  What did the annotated parser rule look like that got you here?

--Loring


"��͸� 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 

A : (A|B)+ C
=> A : ( A(A|B)* | B(A|B)*) C
=> A : A(A|B)* C | B(A|B)* C
=> A : B(A|B)* C  ((A|B)* C)*
=> A : B ( (A|B)* C )+
=> A : B ( ( B((A|B)* C)+ |B )* C )+ //replace A with " B ( (A|B)* C )+ "
=> A : B( ( B [((A|B)* C)+ | ]* C)+ // need to replace A with " B ( (A|B)* C )+ " again
=> A : ... //then again and again forever, never ends

Any better solution?

Thanks

Jigang





  
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