Boost C++ Libraries

boost/mp11/detail/mp_fold.hpp

#ifndef BOOST_MP11_DETAIL_MP_FOLD_HPP_INCLUDED
#define BOOST_MP11_DETAIL_MP_FOLD_HPP_INCLUDED

//  Copyright 2015-2017 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

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

namespace boost
{
namespace mp11
{

// mp_fold<L, V, F>
namespace detail
{

template<class L, class V, template<class...> class F> struct mp_fold_impl
{
// An error "no type named 'type'" here means that the first argument to mp_fold is not a list
};

#if BOOST_MP11_WORKAROUND( BOOST_MP11_MSVC, <= 1800 )

template<template<class...> class L, class... T, class V, template<class...> class F> struct mp_fold_impl<L<T...>, V, F>
{
    static_assert( sizeof...(T) == 0, "T... must be empty" );
    using type = V;
};

#else

template<template<class...> class L, class V, template<class...> class F> struct mp_fold_impl<L<>, V, F>
{
    using type = V;
};

#endif

template<template<class...> class L, class T1, class... T, class V, template<class...> class F> struct mp_fold_impl<L<T1, T...>, V, F>
{
    using type = typename mp_fold_impl<L<T...>, F<V, T1>, F>::type;
};

template<template<class...> class L, class T1, class T2, class T3, class T4, class T5, class T6, class T7, class T8, class T9, class T10, class... T, class V, template<class...> class F> struct mp_fold_impl<L<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T...>, V, F>
{
    using type = typename mp_fold_impl<L<T...>, F<F<F<F<F<F<F<F<F<F<V, T1>, T2>, T3>, T4>, T5>, T6>, T7>, T8>, T9>, T10>, F>::type;
};

} // namespace detail

template<class L, class V, template<class...> class F> using mp_fold = typename detail::mp_fold_impl<L, V, F>::type;
template<class L, class V, class Q> using mp_fold_q = mp_fold<L, V, Q::template fn>;

} // namespace mp11
} // namespace boost

#endif // #ifndef BOOST_MP11_DETAIL_MP_FOLD_HPP_INCLUDED