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 22:28:11

On Tue, Oct 16, 2012 at 10:06 AM, "Claas H. Köhler" <claas.koehler_at_[hidden]>wrote:

>
>
> On 16/10/12 14:27, Jeffrey Lee Hellrung, Jr. wrote:
> > 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
>
> Unfortunately things are not working yet. As far as I can judge, the
> problem is that some of the
> functions are called from within the zip_iterator.hpp header file, which
> is before I can actually
> define the overloaded functions. As a result the overloaded functions are
> not called.
>
> Should I get this working, however, I am glad to share the wisdom.
>

Well, I'd consider it fair game to edit the zip_iterator.hpp header file
directly :)

- Jeff