// Copyright David Abrahams 2003. Use, modification and distribution is // subject to the Boost Software License, Version 1.0. (See accompanying // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) #ifndef BOOST_ITERATOR_MINIMUM_CATEGORY_HPP_INCLUDED_ # define BOOST_ITERATOR_MINIMUM_CATEGORY_HPP_INCLUDED_ # include # include # include # include # include namespace boost { namespace iterators { namespace detail { template struct minimum_category_impl; template struct error_not_related_by_convertibility; template <> struct minimum_category_impl { template struct apply { typedef T2 type; }; }; template <> struct minimum_category_impl { template struct apply { typedef T1 type; }; }; template <> struct minimum_category_impl { template struct apply { BOOST_STATIC_ASSERT((is_same::value)); typedef T1 type; }; }; template <> struct minimum_category_impl { template struct apply : error_not_related_by_convertibility { }; }; } // namespace detail // // Returns the minimum category type or fails to compile // if T1 and T2 are unrelated. // template struct minimum_category { typedef boost::iterators::detail::minimum_category_impl< ::boost::is_convertible::value , ::boost::is_convertible::value > outer; typedef typename outer::template apply inner; typedef typename inner::type type; BOOST_MPL_AUX_LAMBDA_SUPPORT(2,minimum_category,(T1,T2)) }; template <> struct minimum_category { template struct apply : minimum_category {}; BOOST_MPL_AUX_LAMBDA_SUPPORT_SPEC(2,minimum_category,(mpl::_1,mpl::_2)) }; } // namespace iterators } // namespace boost #endif // BOOST_ITERATOR_MINIMUM_CATEGORY_HPP_INCLUDED_