92 lines
2.8 KiB
C++
92 lines
2.8 KiB
C++
///////////////////////////////////////////////////////////////////////////////
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// Copyright 2015 John Maddock. 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 http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_MP_IS_BACKEND_HPP
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#define BOOST_MP_IS_BACKEND_HPP
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#include <type_traits>
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#include <boost/multiprecision/detail/number_base.hpp>
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namespace boost { namespace multiprecision { namespace detail {
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template <class T>
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struct has_signed_types
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{
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template <class U>
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static double check(U*, typename U::signed_types* = nullptr);
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static char check(...);
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static T* get();
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static constexpr bool value = sizeof(check(get())) == sizeof(double);
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};
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template <class T>
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struct has_unsigned_types
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{
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template <class U>
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static double check(U*, typename U::unsigned_types* = nullptr);
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static char check(...);
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static T* get();
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static constexpr bool value = sizeof(check(get())) == sizeof(double);
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};
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template <class T>
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struct has_float_types
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{
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template <class U>
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static double check(U*, typename U::float_types* = nullptr);
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static char check(...);
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static T* get();
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static constexpr bool value = sizeof(check(get())) == sizeof(double);
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};
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template <class T>
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struct is_backend : public std::integral_constant<bool, has_signed_types<T>::value && has_unsigned_types<T>::value && has_float_types<T>::value> {};
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template <class Backend>
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struct other_backend
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{
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using type = typename std::conditional<
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std::is_same<number<Backend>, number<Backend, et_on> >::value,
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number<Backend, et_off>, number<Backend, et_on> >::type;
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};
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template <class B, class V>
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struct number_from_backend
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{
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using type = typename std::conditional<
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std::is_convertible<V, number<B> >::value,
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number<B>,
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typename other_backend<B>::type>::type;
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};
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template <bool b, class T, class U>
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struct is_first_backend_imp : public std::false_type {};
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template <class T, class U>
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struct is_first_backend_imp<true, T, U> : public std::integral_constant < bool, std::is_convertible<U, number<T, et_on> >::value || std::is_convertible<U, number<T, et_off> >::value> {};
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template <class T, class U>
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struct is_first_backend : is_first_backend_imp<is_backend<T>::value, T, U>
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{};
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template <bool b, class T, class U>
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struct is_second_backend_imp
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{
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static constexpr bool value = false;
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};
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template <class T, class U>
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struct is_second_backend_imp<true, T, U>
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{
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static constexpr bool value = (std::is_convertible<T, number<U, et_on> >::value || std::is_convertible<T, number<U, et_off> >::value) && !is_first_backend<T, U>::value;
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};
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template <class T, class U>
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struct is_second_backend : is_second_backend_imp<is_backend<U>::value, T, U>
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{};
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}
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}
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} // namespace boost::multiprecision::detail
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#endif // BOOST_MP_IS_BACKEND_HPP
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