That's the whole point of this, trying to add left recursion support to PEG.
This is a topic which has already been discussed a few times and in a few
papers.
Basically there are two reasons why you don't want to rewrite your rules:
1. In case an AST is automagically generated, have it left-associative
2. Reduce the effort of implementing existing grammars, specified using
left-recursion
>From my experience, I think that both reasons do not compensate the
complexity added by the support of left-recursion.
Hence, I personnally do not want left-recursion in PEG.
2012/2/1 Francisco Mota <fmot...@gmail.com>
> A PEG parser should never match anything with this rule, because to
> match the symbol a you must first attempt to match the symbol a. (If
> your parser matches anything with this rule, it isn't a PEG parser.)
>
> Why don't you rewrite your rule as follows?
>
> a <- ('a' / 'b')* 'a' / 'b'
>
> Best,
> - Francisco Mota
>
> On 1/31/12, Ondřej Bílka <nel...@seznam.cz> wrote:
> > What your parser does on following rule:
> > a = a* 'a' | 'b'
> > say on string ababbba
> >
> > --
> >
> > NOTICE: alloc: /dev/null: filesystem full
> >
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> >
>
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