79 lines
3.0 KiB
C++
79 lines
3.0 KiB
C++
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/*!
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@file
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Defines concepts from the Standard library.
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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_DETAIL_CONCEPTS_HPP
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#define BOOST_HANA_DETAIL_CONCEPTS_HPP
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#include <boost/hana/config.hpp>
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#include <boost/hana/detail/std_common_type.hpp>
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#include <boost/hana/detail/void_t.hpp>
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#include <type_traits>
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BOOST_HANA_NAMESPACE_BEGIN namespace detail {
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//! @cond
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//////////////////////////////////////////////////////////////////////////
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// EqualityComparable
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//////////////////////////////////////////////////////////////////////////
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template <typename T, typename U = T, typename = void>
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struct EqualityComparable : std::false_type { };
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template <typename T>
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struct EqualityComparable<T, T, detail::void_t<
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decltype(static_cast<T&&>(*(T*)0) == static_cast<T&&>(*(T*)0) ? 0:0),
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decltype(static_cast<T&&>(*(T*)0) != static_cast<T&&>(*(T*)0) ? 0:0)
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>> : std::true_type { };
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template <typename T, typename U>
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struct EqualityComparable<T, U, typename std::enable_if<
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!std::is_same<T, U>::value, detail::void_t<
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decltype(static_cast<T&&>(*(T*)0) == static_cast<U&&>(*(U*)0) ? 0:0),
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decltype(static_cast<U&&>(*(U*)0) == static_cast<T&&>(*(T*)0) ? 0:0),
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decltype(static_cast<T&&>(*(T*)0) != static_cast<U&&>(*(U*)0) ? 0:0),
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decltype(static_cast<U&&>(*(U*)0) != static_cast<T&&>(*(T*)0) ? 0:0),
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typename detail::std_common_type<T, U>::type
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>>::type> : std::integral_constant<bool,
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EqualityComparable<T>::value &&
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EqualityComparable<U>::value &&
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EqualityComparable<typename detail::std_common_type<T, U>::type>::value
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> { };
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//////////////////////////////////////////////////////////////////////////
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// LessThanComparable
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//////////////////////////////////////////////////////////////////////////
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template <typename T, typename U = T, typename = void>
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struct LessThanComparable : std::false_type { };
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template <typename T>
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struct LessThanComparable<T, T, detail::void_t<
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decltype(static_cast<T&&>(*(T*)0) < static_cast<T&&>(*(T*)0) ? 0:0)
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>> : std::true_type { };
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template <typename T, typename U>
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struct LessThanComparable<T, U, std::enable_if_t<
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!std::is_same<T, U>::value,
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detail::void_t<
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decltype(static_cast<T&&>(*(T*)0) < static_cast<U&&>(*(U*)0) ? 0:0),
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decltype(static_cast<U&&>(*(U*)0) < static_cast<T&&>(*(T*)0) ? 0:0),
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typename detail::std_common_type<T, U>::type
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>
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>>
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: std::integral_constant<bool,
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LessThanComparable<T>::value &&
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LessThanComparable<U>::value &&
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LessThanComparable<typename detail::std_common_type<T, U>::type>::value
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>
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{ };
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//! @endcond
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} BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_DETAIL_CONCEPTS_HPP
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