39 lines
855 B
C++
39 lines
855 B
C++
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#ifndef BOOST_MP11_DETAIL_MP_FRONT_HPP_INCLUDED
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#define BOOST_MP11_DETAIL_MP_FRONT_HPP_INCLUDED
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// Copyright 2015-2021 Peter Dimov.
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//
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// Distributed under the Boost Software License, Version 1.0.
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//
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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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namespace boost
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{
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namespace mp11
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{
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// mp_front<L>
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namespace detail
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{
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template<class L> struct mp_front_impl
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{
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// An error "no type named 'type'" here means that the argument to mp_front
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// is either not a list, or is an empty list
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};
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template<template<class...> class L, class T1, class... T> struct mp_front_impl<L<T1, T...>>
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{
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using type = T1;
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};
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} // namespace detail
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template<class L> using mp_front = typename detail::mp_front_impl<L>::type;
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} // namespace mp11
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} // namespace boost
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#endif // #ifndef BOOST_MP11_DETAIL_MP_FRONT_HPP_INCLUDED
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