48 lines
1.4 KiB
C++
48 lines
1.4 KiB
C++
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// Copyright 2018-2019 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_STATIC_IF_HPP
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#define BOOST_HISTOGRAM_DETAIL_STATIC_IF_HPP
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#include <type_traits>
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#include <utility>
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namespace boost {
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namespace histogram {
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namespace detail {
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template <class T, class F, class... Args>
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constexpr decltype(auto) static_if_impl(
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std::true_type, T&& t, F&&,
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Args&&... args) noexcept(noexcept(std::declval<T>()(std::declval<Args>()...))) {
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return std::forward<T>(t)(std::forward<Args>(args)...);
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}
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template <class T, class F, class... Args>
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constexpr decltype(auto) static_if_impl(
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std::false_type, T&&, F&& f,
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Args&&... args) noexcept(noexcept(std::declval<F>()(std::declval<Args>()...))) {
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return std::forward<F>(f)(std::forward<Args>(args)...);
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}
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template <bool B, class... Ts>
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constexpr decltype(auto) static_if_c(Ts&&... ts) noexcept(
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noexcept(static_if_impl(std::integral_constant<bool, B>{}, std::declval<Ts>()...))) {
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return static_if_impl(std::integral_constant<bool, B>{}, std::forward<Ts>(ts)...);
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}
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template <class Bool, class... Ts>
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constexpr decltype(auto) static_if(Ts&&... ts) noexcept(
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noexcept(static_if_impl(Bool{}, std::declval<Ts>()...))) {
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return static_if_impl(Bool{}, std::forward<Ts>(ts)...);
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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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