57 lines
1.4 KiB
Plaintext
57 lines
1.4 KiB
Plaintext
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#ifndef BOOST_TYPE_TRAITS_DETAIL_MP_DEFER_HPP_INCLUDED
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#define BOOST_TYPE_TRAITS_DETAIL_MP_DEFER_HPP_INCLUDED
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//
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// Copyright 2015 Peter Dimov
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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 or copy at
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// http://www.boost.org/LICENSE_1_0.txt
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//
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#include <boost/type_traits/integral_constant.hpp>
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#include <boost/type_traits/conditional.hpp>
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namespace boost
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{
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namespace type_traits_detail
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{
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// mp_valid
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// implementation by Bruno Dutra (by the name is_evaluable)
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template<template<class...> class F, class... T>
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struct mp_valid_impl
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{
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template<template<class...> class G, class = G<T...>>
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static boost::true_type check_s(int);
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template<template<class...> class>
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static boost::false_type check_s(...);
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using type = decltype(check_s<F>(0));
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};
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template<template<class...> class F, class... T>
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using mp_valid = typename mp_valid_impl<F, T...>::type;
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// mp_defer
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struct mp_empty
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{
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};
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template<template<class...> class F, class... T> struct mp_defer_impl
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{
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using type = F<T...>;
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};
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template<template<class...> class F, class... T> using mp_defer = typename boost::conditional<mp_valid<F, T...>::value, mp_defer_impl<F, T...>, mp_empty>::type;
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} // namespace type_traits_detail
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} // namespace boost
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#endif // #ifndef BOOST_TYPE_TRAITS_DETAIL_MP_DEFER_HPP_INCLUDED
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