Re: [boost] [type_traits] Interest in is_iterator type trait?

Subject: Re: [boost] [type_traits] Interest in is_iterator type trait?
From: pfultz2 (pfultz2_at_[hidden])
Date: 2014-08-19 11:02:27

Here's something that I have been using on C++03 compilers to check if its an
iterator. It is somewhat similar, except it checks additionally for
`reference` and `pointer`.

    template<class T1 = void, class T2 = void, class T3 = void, class T4 =
void, class T5 = void>
    struct holder
    {
        typedef void type;
    };

    template<class T, class X = void>
    struct is_iterator 
    : boost::mpl::bool_<false>
    {};

    template<class T>
    struct is_iterator<T*>
    : boost::mpl::bool_<true>
    {};

    template<class Iterator>
    struct is_iterator<Iterator, typename holder
    &lt;
        typename Iterator::iterator_category, 
        typename Iterator::reference, 
        typename Iterator::pointer, 
        typename Iterator::value_type, 
        typename Iterator::difference_type 
    >::type >
    : boost::mpl::bool_<true>
    {};

> If there is interest, and John Maddock gives the OK, I'll write docs and
> integrate into type_traits, then submit a pull request. 

I definately think it is something very useful to have. Perhaps, it should
go
in Boost.Iterator instead?

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