//
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// Copyright Louis Dionne 2013-2017
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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.md or copy at http://boost.org/LICENSE_1_0.txt)
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//
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#ifndef BOOST_GIL_DETAIL_STD_COMMON_TYPE_HPP
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#define BOOST_GIL_DETAIL_STD_COMMON_TYPE_HPP
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#include <type_traits>
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#include <utility>
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namespace boost { namespace gil { namespace detail {
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// Defines a SFINAE-friendly version of `std::common_type`.
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//
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// Based on boost/hana/detail/std_common_type.hpp
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// Equivalent to `std::common_type`, except it is SFINAE-friendly and
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// does not support custom specializations.
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template <typename T, typename U, typename = void>
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struct std_common_type {};
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template <typename T, typename U>
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struct std_common_type
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<
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T, U,
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decltype((void)(true ? std::declval<T>() : std::declval<U>()))
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>
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{
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using type = typename std::decay
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<
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decltype(true ? std::declval<T>() : std::declval<U>())
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>::type;
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};
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}}} // namespace boost::gil::detail
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#endif
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