Re: [boost] Is Boost.Range broken?

Subject: Re: [boost] Is Boost.Range broken?
From: Neil Groves (neil_at_[hidden])
Date: 2008-11-25 11:36:20

Andrew,

On Tue, Nov 25, 2008 at 4:07 PM, Andrew Sutton <andrew.n.sutton_at_[hidden]>wrote:

> >
> > I think this is the right answer (and pretty well argued by now). The
> >> behavior of the iterator_range should "inherit" (is there a better word
> >> for
> >> this?) its semantics from the underlying iterator. To do otherwise would
> >> impose requirements on iterators that may not (easily) support those
> >> semantics, making the concept less generic (as in represents fewer
> >> possible
> >> implementations).
> >>
> >
> > Well, it is fairly easy to remove some of the debug-checks from the code.
> > Do I understand you correctly in that you want them all removed?
> >
>
> No! Definitely no. As I understand it, those debug checks are kind of
> playing the role of axiomatic preconditions in debug mode, so they're
> actually reinforcing the correct behavior. I think.
>

Yes! Definately yes ;-) The checks have all manner of false-positives. They
aren't axiomatic preconditions that should apply for all or even most
iterator types used with iterator_range. The iterator_range simply cannot
reliably determine if the iterator is invalid due to it being singular.
Singularity is a property of iterators.  If singulairity requires additional
debugging infrastructure it should be added to a debugging iterator
framework. It's far too restricting upon the typical and valid usages of
iterator_range.

>
> I think from a previous post I was considering a kind of checked
> iterator_range that could provide additional diagnostics in debug mode -
> something akin to the STLPort checked iterators. Providing something like
> that as a compile-time replacement for iterator_range would free that class
> up to be as lean as possible and sans preprocessor. Completely outside the
> scope of the  discussion... sorry.
>
> Andrew Sutton
> andrew.n.sutton_at_[hidden]
>

Neil Groves

>
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