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- #ifndef BOOST_MP11_DETAIL_MP_FRONT_HPP_INCLUDED
- #define BOOST_MP11_DETAIL_MP_FRONT_HPP_INCLUDED
- // Copyright 2015-2021 Peter Dimov.
- //
- // Distributed under the Boost Software License, Version 1.0.
- //
- // See accompanying file LICENSE_1_0.txt or copy at
- // http://www.boost.org/LICENSE_1_0.txt
- namespace boost
- {
- namespace mp11
- {
- // mp_front<L>
- namespace detail
- {
- template<class L> struct mp_front_impl
- {
- // An error "no type named 'type'" here means that the argument to mp_front
- // is either not a list, or is an empty list
- };
- template<template<class...> class L, class T1, class... T> struct mp_front_impl<L<T1, T...>>
- {
- using type = T1;
- };
- } // namespace detail
- template<class L> using mp_front = typename detail::mp_front_impl<L>::type;
- } // namespace mp11
- } // namespace boost
- #endif // #ifndef BOOST_MP11_DETAIL_MP_FRONT_HPP_INCLUDED
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