Re: [Spirit-general] Request for comments on iter_advance parser component

[Hartmut K. <har...@gm...>]

> On 1/25/11 4:22 AM, teajay wrote:
> > Le 24/01/2011 19:22, Aaron Graham a écrit :
> >> I'm planning to submit this simple parser component to the repository.
> >> The opportunities I get to work on this are few and far between, so I
> >> thought I'd go ahead and request comments before proceeding further
> >> with documentation and tests.
> 
> [snip]
> 
> >> Some questions:
> >>
> >> 1) Should it be named "iter_advance" or just "advance"?
> >>
> >
> > How about something like skip_chars, skip or jump ?
> 
> skip sounds good!

We already have skip[]. Either we overload the existing name (which is
possible as currently a plain 'skip' is not allowed, only skip[...] and
skip(...)[...]), or we use a different name. I'd prefer a different name,
though. What about 'advance'?

> >> 2) I considered supporting negative advancement, but there are
> >> complications. One of the nice things about the current
> >> implementation is that you can't skip over the end (it will fail to
> >> parse, keeping the iterator position unmoved, if last/end is
> >> reached). Such a thing will be difficult to guarantee if negative
> >> advancement is allowed. Currently, the implementation won't prevent
> >> you from using negative advancement in the case of random access
> >> iterators, but I intend to document that it is unsupported.
> 
> forward skip is good enough, IMO.

Yes, and I believe you should check whether the requested advancement is
non-negative.

> > There's one spot that might make things tricky when using this parser
> > that should appear in the docs: it will pre-skip before advancing the
> > iterator. It all depends on how the input is formed but this could
> > lead to misinterpretations on the start position used when advancing
> > the iterator.
> 
> Why do we have to do a pre-skip in the first place?

That's exactly my question. I believe this parser component should not
pre-skip.

Regards Hartmut
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