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//  Copyright 2015-2023 Peter Dimov.
//  Distributed under the Boost Software License, Version 1.0.
//  See accompanying file LICENSE_1_0.txt or copy at

#include <boost/mp11/detail/mp_value.hpp>
#include <boost/mp11/detail/config.hpp>

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;


template<template<auto...> class L, auto A1, auto... A> struct mp_front_impl<L<A1, A...>>
    using type = mp_value<A1>;


} // namespace detail

template<class L> using mp_front = typename detail::mp_front_impl<L>::type;

} // namespace mp11
} // namespace boost