// Copyright 2015-2019 Hans Dembinski
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//
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt
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// or copy at http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_HISTOGRAM_DETAIL_RELAXED_EQUAL_HPP
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#define BOOST_HISTOGRAM_DETAIL_RELAXED_EQUAL_HPP
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#include <boost/histogram/detail/priority.hpp>
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#include <type_traits>
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namespace boost {
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namespace histogram {
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namespace detail {
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struct relaxed_equal {
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template <class T, class U>
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constexpr auto impl(const T& t, const U& u, priority<1>) const noexcept
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-> decltype(t == u) const {
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return t == u;
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}
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// consider T and U not equal, if there is no operator== defined for them
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template <class T, class U>
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constexpr bool impl(const T&, const U&, priority<0>) const noexcept {
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return false;
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}
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// consider two T equal if they are stateless
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template <class T>
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constexpr bool impl(const T&, const T&, priority<0>) const noexcept {
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return std::is_empty<T>::value;
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}
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template <class T, class U>
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constexpr bool operator()(const T& t, const U& u) const noexcept {
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return impl(t, u, priority<1>{});
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}
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};
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} // namespace detail
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} // namespace histogram
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} // namespace boost
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#endif
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