92 lines
2.7 KiB
C++
92 lines
2.7 KiB
C++
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/*!
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@file
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Adapts `std::pair` for use with Hana.
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@copyright Louis Dionne 2013-2016
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Distributed under the Boost Software License, Version 1.0.
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(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
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*/
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#ifndef BOOST_HANA_EXT_STD_PAIR_HPP
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#define BOOST_HANA_EXT_STD_PAIR_HPP
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#include <boost/hana/config.hpp>
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#include <boost/hana/fwd/core/make.hpp>
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#include <boost/hana/fwd/core/tag_of.hpp>
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#include <boost/hana/fwd/first.hpp>
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#include <boost/hana/fwd/second.hpp>
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#include <utility>
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#ifdef BOOST_HANA_DOXYGEN_INVOKED
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namespace std {
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//! @ingroup group-ext-std
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//! Adaptation of `std::pair` for Hana.
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//!
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//!
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//! Modeled concepts
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//! ----------------
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//! A `std::pair` models exactly the same concepts as a `hana::pair`.
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//! Please refer to the documentation of `hana::pair` for details.
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//!
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//! @include example/ext/std/pair.cpp
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template <typename First, typename Second>
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struct pair { };
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}
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#endif
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BOOST_HANA_NAMESPACE_BEGIN
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namespace ext { namespace std { struct pair_tag; }}
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template <typename First, typename Second>
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struct tag_of<std::pair<First, Second>> {
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using type = ext::std::pair_tag;
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};
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//////////////////////////////////////////////////////////////////////////
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// Product
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//////////////////////////////////////////////////////////////////////////
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template <>
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struct make_impl<ext::std::pair_tag> {
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template <typename X, typename Y>
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static constexpr decltype(auto) apply(X&& x, Y&& y) {
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return std::make_pair(static_cast<X&&>(x),
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static_cast<Y&&>(y));
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}
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};
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template <>
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struct first_impl<ext::std::pair_tag> {
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template <typename T, typename U>
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static constexpr T const& apply(std::pair<T, U> const& p)
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{ return p.first; }
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template <typename T, typename U>
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static constexpr T& apply(std::pair<T, U>& p)
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{ return p.first; }
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template <typename T, typename U>
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static constexpr T&& apply(std::pair<T, U>&& p)
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{ return static_cast<T&&>(p.first); }
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};
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template <>
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struct second_impl<ext::std::pair_tag> {
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template <typename T, typename U>
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static constexpr U const& apply(std::pair<T, U> const& p)
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{ return p.second; }
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template <typename T, typename U>
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static constexpr U& apply(std::pair<T, U>& p)
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{ return p.second; }
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template <typename T, typename U>
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static constexpr U&& apply(std::pair<T, U>&& p)
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{ return static_cast<U&&>(p.second); }
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};
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_EXT_STD_PAIR_HPP
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