Re: [boost] [iterator] Using zip_iterator with std::pair

Subject: Re: [boost] [iterator] Using zip_iterator with std::pair
From: Jeffrey Lee Hellrung, Jr. (jeffrey.hellrung_at_[hidden])
Date: 2012-10-16 08:27:48

On Tue, Oct 16, 2012 at 4:21 AM, "Claas H. Köhler" <claas.koehler_at_[hidden]>wrote:

>
>
> On 16/10/12 12:01, Giovanni Piero Deretta wrote:
> > On Tue, Oct 16, 2012 at 9:06 AM, "Claas H. Köhler" <claas.koehler_at_[hidden]>
> wrote:
> >> Hi!
> >>
> >> I would like to use the boost::zip_iterator with std::pair.
> Unfortunately this does not work out of
> >> the box, but there exists a namespace
>  boost::detail::tuple_impl_specific, which apparently needs to
> >> be specialised for each tuple type.
>

Hmmm...I guess it makes sense you might have to specialize something if
zip_iterator doesn't specifically know about your desired tuple type.

> >> I managed to re-implement tuple_meta_transform and
> tuple_meta_accumulate for std::tuple, which seems
> >> to be straightforward. However, there are functions of the form
> >>
> >> template<typename Tuple, typename Fun>
> >> complex_result_type tuple_transform(const Tuple&, Fun)
> >>
> >> which have to be overloaded as well, if I am not mistaken. However,
> overloading this with something like
> >> template<typename... Args, typename Fun>
> >> complex_result_type tuple_transform(const std::tuple<Args...>&, Fun)
> >>
> >> is probably not going to work, since this would be a partial template
> specialisation of a function.
> >
> > That's an overload actually and should work fine. Did you try it?
> >
> > HTH,
>
> Thanks for the hint. I have to admit I did not try it yet. I have just
> created a similar simple test
> case, which indeed compiles/works fine. Shame on me for not trying it out.
> For me this was always a
> classical example of template function specialisation. I guess I should
> take a look at template
> basics again :-)
>
> Sorry for that and thanks for the quick response.
>

I'm glad you got it working, but ideally, I think, zip_iterator should work
out of the box for std::pair and std::tuple. Could I trouble you to provide
patches based on what you needed to get this to work?

- Jeff