123456789101112131415161718192021222324252627282930313233343536373839404142434445 |
- // Copyright Louis Dionne 2013-2017
- // Distributed under the Boost Software License, Version 1.0.
- // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
- #ifndef TEST_CONCEPT_CONSTANT_MINIMAL_HPP
- #define TEST_CONCEPT_CONSTANT_MINIMAL_HPP
- #include <boost/hana/concept/constant.hpp>
- #include <boost/hana/core/when.hpp>
- #include <boost/hana/fwd/core/to.hpp>
- #include <boost/hana/value.hpp>
- template <typename T>
- struct minimal_constant_tag {
- using value_type = T;
- };
- template <typename T, T v>
- struct minimal_constant {
- using hana_tag = minimal_constant_tag<T>;
- static constexpr T value_ = v;
- };
- namespace boost { namespace hana {
- template <typename T>
- struct value_impl<minimal_constant_tag<T>> {
- template <typename N>
- static constexpr T apply() { return N::value_; }
- };
- template <typename T, typename C>
- struct to_impl<minimal_constant_tag<T>, C, hana::when<
- hana::Constant<C>::value &&
- hana::is_convertible<typename C::value_type, T>::value
- >>
- : hana::embedding<hana::is_embedded<typename C::value_type, T>::value>
- {
- template <typename N>
- static constexpr auto apply(N const&)
- { return minimal_constant<T, hana::value<N>()>{}; }
- };
- }} // end namespace boost::hana
- #endif // !TEST_CONCEPT_CONSTANT_MINIMAL_HPP
|