Re: [boost] difference_type size()?

Subject: Re: [boost] difference_type size()?
From: Jeffrey Lee Hellrung, Jr. (jeffrey.hellrung_at_[hidden])
Date: 2011-10-20 11:48:59

On Thu, Oct 20, 2011 at 8:32 AM, Bo Persson <bop_at_[hidden]> wrote:

> Jeffrey Lee Hellrung, Jr. wrote:
> > On Wed, Oct 19, 2011 at 12:38 PM, <andrey.semashev_at_[hidden]> wrote:
> >
> >> On Wednesday, October 19, 2011 12:27:31 Jeffrey Lee Hellrung, Jr.
> >> wrote:
> >>
> > [...]
> >
> >>>> I think the following would do:
> >>>>  typedef typename make_unsigned< difference_type >::type
> >>>> size_type;
> >>>
> >>> I was under the impression that most of the traits in
> >>> Boost.TypeTraits of this nature are only defined for builtin
> >>> types.
> >>
> >> See one of my previous replies, difference type should be a signed
> >> integer type.
> >>
> >
> > Ah, indeed.  Then I agree make_unsigned would be a legitimate
> > solution.
> >
>
> This will break if difference_type is a UDT without a make_unsigned
> specialization.
>
> Is that a good idea?
>

The wording of the standard says that difference_type is a "signed integer
type", seeming to imply that it shouldn't be a UDT.

- Jeff