88 lines
2.5 KiB
C++
88 lines
2.5 KiB
C++
/////////////////////////////////////////////////////////////////////
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// Copyright 2018 Glen Joseph Fernandes.
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// Copyright 2021 Matt Borland. Distributed under the Boost
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// Software License, Version 1.0. (See accompanying file
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// LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt
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#ifndef BOOST_MP_DETAIL_EMPTY_VALUE_HPP
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#define BOOST_MP_DETAIL_EMPTY_VALUE_HPP
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#include <utility>
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#include <boost/multiprecision/detail/standalone_config.hpp>
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#if defined(BOOST_GCC_VERSION) && (BOOST_GCC_VERSION >= 40700)
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#define BOOST_DETAIL_EMPTY_VALUE_BASE
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#elif defined(BOOST_INTEL) && defined(_MSC_VER) && (_MSC_VER >= 1800)
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#define BOOST_DETAIL_EMPTY_VALUE_BASE
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#elif defined(BOOST_MSVC) && (BOOST_MSVC >= 1800)
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#define BOOST_DETAIL_EMPTY_VALUE_BASE
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#elif defined(BOOST_CLANG) && !defined(__CUDACC__)
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#if __has_feature(is_empty) && __has_feature(is_final)
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#define BOOST_DETAIL_EMPTY_VALUE_BASE
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#endif
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#endif
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namespace boost { namespace multiprecision { namespace detail {
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template <typename T>
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struct use_empty_value_base
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{
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#if defined(BOOST_DETAIL_EMPTY_VALUE_BASE)
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static constexpr bool value = __is_empty(T) && !__is_final(T);
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#else
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static constexpr bool value = false;
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#endif
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};
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struct empty_init_t {};
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namespace empty_impl {
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template <typename T, unsigned N = 0,
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bool E = boost::multiprecision::detail::use_empty_value_base<T>::value>
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class empty_value
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{
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private:
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T value_;
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public:
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using type = T;
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empty_value() = default;
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explicit empty_value(boost::multiprecision::detail::empty_init_t) : value_ {} {}
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template <typename U, typename... Args>
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empty_value(boost::multiprecision::detail::empty_init_t, U&& value, Args&&... args) :
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value_ {std::forward<U>(value), std::forward<Args>(args)...} {}
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const T& get() const noexcept { return value_; }
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T& get() noexcept { return value_; }
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};
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template <typename T, unsigned N>
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class empty_value<T, N, true> : T
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{
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public:
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using type = T;
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empty_value() = default;
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explicit empty_value(boost::multiprecision::detail::empty_init_t) : T{} {}
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template <typename U, typename... Args>
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empty_value(boost::multiprecision::detail::empty_init_t, U&& value, Args&&... args) :
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T{std::forward<U>(value), std::forward<Args>(args)...} {}
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const T& get() const noexcept { return *this; }
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T& get() noexcept { return *this; }
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};
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} // Namespace empty impl
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using empty_impl::empty_value;
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BOOST_INLINE_CONSTEXPR empty_init_t empty_init = empty_init_t();
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}}} // Namespaces
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#endif // BOOST_MP_DETAIL_EMPTY_VALUE_HPP
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