/*!
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@file
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Defines `boost::hana::tag_of` and `boost::hana::tag_of_t`.
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@copyright Louis Dionne 2013-2017
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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_CORE_TAG_OF_HPP
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#define BOOST_HANA_CORE_TAG_OF_HPP
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#include <boost/hana/fwd/core/tag_of.hpp>
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#include <boost/hana/config.hpp>
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#include <boost/hana/core/when.hpp>
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#include <type_traits>
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BOOST_HANA_NAMESPACE_BEGIN
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//! @cond
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template <typename T, typename>
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struct tag_of : tag_of<T, when<true>> { };
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//! @endcond
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namespace core_detail {
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template <typename ...>
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struct is_valid { static constexpr bool value = true; };
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}
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template <typename T, bool condition>
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struct tag_of<T, when<condition>> {
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using type = T;
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};
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template <typename T>
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struct tag_of<T, when<
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core_detail::is_valid<typename T::hana_tag>::value
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>> {
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using type = typename T::hana_tag;
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};
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template <typename T> struct tag_of<T const> : tag_of<T> { };
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template <typename T> struct tag_of<T volatile> : tag_of<T> { };
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template <typename T> struct tag_of<T const volatile> : tag_of<T> { };
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template <typename T> struct tag_of<T&> : tag_of<T> { };
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template <typename T> struct tag_of<T&&> : tag_of<T> { };
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namespace detail {
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template <typename T>
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struct has_idempotent_tag
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: std::is_same<hana::tag_of_t<T>,
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std::remove_const_t<std::remove_reference_t<T>>>
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{ };
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}
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BOOST_HANA_NAMESPACE_END
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#endif // !BOOST_HANA_CORE_TAG_OF_HPP
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