boost/hana/min.hpp

0001 /*!
0002 @file
0003 Defines `boost::hana::min`.
0004
0005 Copyright Louis Dionne 2013-2022
0006 Distributed under the Boost Software License, Version 1.0.
0007 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
0008  */
0009
0010 #ifndef BOOST_HANA_MIN_HPP
0011 #define BOOST_HANA_MIN_HPP
0012
0013 #include <boost/hana/fwd/min.hpp>
0014
0015 #include <boost/hana/concept/orderable.hpp>
0016 #include <boost/hana/config.hpp>
0017 #include <boost/hana/core/dispatch.hpp>
0018 #include <boost/hana/if.hpp>
0019 #include <boost/hana/less.hpp>
0020
0021
0022 namespace boost { namespace hana {
0023     //! @cond
0024     template <typename X, typename Y>
0025     constexpr decltype(auto) min_t::operator()(X&& x, Y&& y) const {
0026         using T = typename hana::tag_of<X>::type;
0027         using U = typename hana::tag_of<Y>::type;
0028         using Min = BOOST_HANA_DISPATCH_IF(decltype(min_impl<T, U>{}),
0029             hana::Orderable<T>::value &&
0030             hana::Orderable<U>::value
0031         );
0032
0033     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
0034         static_assert(hana::Orderable<T>::value,
0035         "hana::min(x, y) requires 'x' to be Orderable");
0036
0037         static_assert(hana::Orderable<U>::value,
0038         "hana::min(x, y) requires 'y' to be Orderable");
0039     #endif
0040
0041         return Min::apply(static_cast<X&&>(x), static_cast<Y&&>(y));
0042     }
0043     //! @endcond
0044
0045     template <typename T, typename U, bool condition>
0046     struct min_impl<T, U, when<condition>> : default_ {
0047         template <typename X, typename Y>
0048         static constexpr decltype(auto) apply(X&& x, Y&& y) {
0049             decltype(auto) cond = hana::less(x, y);
0050             return hana::if_(static_cast<decltype(cond)&&>(cond),
0051                 static_cast<X&&>(x),
0052                 static_cast<Y&&>(y)
0053             );
0054         }
0055     };
0056 }} // end namespace boost::hana
0057
0058 #endif // !BOOST_HANA_MIN_HPP