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

On 19/08/14 19:09, pfultz2 wrote:

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Fwiw, I used something closely related in libc++ for SFINAE on the “member template members” of the containers (the ones taking iterators) to disambiguate them from the members/constructors not taking iterators, but having the same number of parameters. But instead of is_iterator, I needed is_input_iterator, is_forward_iterator, etc. These refinements are implemented similar to what Beman shows, but takes into account which std iterator tag the nested iterator_category type is implicitly convertible to.

I actually have used a `has_iterator_traversal` trait to check iterator traversal, like this:

template struct has_iterator_traversal : boost::mpl::bool_<false> {};

template struct has_iterator_traversal >::type> : boost::is_convertible::type {};

Why not just write template<class Iterator> void my_function_impl(Iterator it, std::input_iterator_tag) { ... } template<class Iterator> void my_function(Iterator it) { return my_function_impl(it, typename std::iterator_traits<Iterator>::iterator_category()); } It's simpler and it probably compiles faster too.