120 lines
2.9 KiB
C++
120 lines
2.9 KiB
C++
#ifndef BOOST_MP11_DETAIL_MP_DEFER_HPP_INCLUDED
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#define BOOST_MP11_DETAIL_MP_DEFER_HPP_INCLUDED
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// Copyright 2015-2020, 2023 Peter Dimov
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// Distributed under the Boost Software License, Version 1.0.
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// https://www.boost.org/LICENSE_1_0.txt
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#include <boost/mp11/integral.hpp>
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#include <boost/mp11/detail/config.hpp>
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namespace boost
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{
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namespace mp11
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{
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// mp_if, mp_if_c
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namespace detail
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{
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template<bool C, class T, class... E> struct mp_if_c_impl
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{
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};
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template<class T, class... E> struct mp_if_c_impl<true, T, E...>
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{
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using type = T;
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};
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template<class T, class E> struct mp_if_c_impl<false, T, E>
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{
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using type = E;
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};
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} // namespace detail
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template<bool C, class T, class... E> using mp_if_c = typename detail::mp_if_c_impl<C, T, E...>::type;
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template<class C, class T, class... E> using mp_if = typename detail::mp_if_c_impl<static_cast<bool>(C::value), T, E...>::type;
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// mp_valid
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#if BOOST_MP11_WORKAROUND( BOOST_MP11_INTEL, != 0 ) // tested at 1800
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// contributed by Roland Schulz in https://github.com/boostorg/mp11/issues/17
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namespace detail
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{
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template<class...> using void_t = void;
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template<class, template<class...> class F, class... T>
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struct mp_valid_impl: mp_false {};
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template<template<class...> class F, class... T>
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struct mp_valid_impl<void_t<F<T...>>, F, T...>: mp_true {};
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} // namespace detail
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template<template<class...> class F, class... T> using mp_valid = typename detail::mp_valid_impl<void, F, T...>;
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#else
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// implementation by Bruno Dutra (by the name is_evaluable)
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namespace detail
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{
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template<template<class...> class F, class... T> struct mp_valid_impl
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{
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template<template<class...> class G, class = G<T...>> static mp_true check(int);
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template<template<class...> class> static mp_false check(...);
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using type = decltype(check<F>(0));
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};
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} // namespace detail
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template<template<class...> class F, class... T> using mp_valid = typename detail::mp_valid_impl<F, T...>::type;
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#endif
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template<class Q, class... T> using mp_valid_q = mp_valid<Q::template fn, T...>;
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// mp_defer
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namespace detail
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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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struct mp_no_type
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{
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};
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#if BOOST_MP11_WORKAROUND( BOOST_MP11_CUDA, >= 9000000 && BOOST_MP11_CUDA < 10000000 )
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template<template<class...> class F, class... T> struct mp_defer_cuda_workaround
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{
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using type = mp_if<mp_valid<F, T...>, detail::mp_defer_impl<F, T...>, detail::mp_no_type>;
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};
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#endif
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} // namespace detail
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#if BOOST_MP11_WORKAROUND( BOOST_MP11_CUDA, >= 9000000 && BOOST_MP11_CUDA < 10000000 )
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template<template<class...> class F, class... T> using mp_defer = typename detail::mp_defer_cuda_workaround< F, T...>::type;
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#else
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template<template<class...> class F, class... T> using mp_defer = mp_if<mp_valid<F, T...>, detail::mp_defer_impl<F, T...>, detail::mp_no_type>;
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#endif
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} // namespace mp11
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} // namespace boost
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#endif // #ifndef BOOST_MP11_DETAIL_MP_DEFER_HPP_INCLUDED
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