/*!
@file
Defines `boost::hana::detail::variadic::foldl1`.

@copyright Louis Dionne 2013-2017
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
 */

#ifndef BOOST_HANA_DETAIL_VARIADIC_FOLDL1_HPP
#define BOOST_HANA_DETAIL_VARIADIC_FOLDL1_HPP

#include <boost/hana/config.hpp>
#include <boost/hana/core/when.hpp>


BOOST_HANA_NAMESPACE_BEGIN namespace detail { namespace variadic {
    //! @cond
    template <unsigned int n, typename = when<true>>
    struct foldl1_impl;

    template <>
    struct foldl1_impl<1> {
        template <typename F, typename X1>
        static constexpr X1 apply(F&&, X1&& x1)
        { return static_cast<X1&&>(x1); }
    };

    template <>
    struct foldl1_impl<2> {
        template <typename F, typename X1, typename X2>
        static constexpr decltype(auto) apply(F&& f, X1&& x1, X2&& x2) {
            return static_cast<F&&>(f)(static_cast<X1&&>(x1),
                                       static_cast<X2&&>(x2));
        }
    };

    template <>
    struct foldl1_impl<3> {
        template <typename F, typename X1, typename X2, typename X3>
        static constexpr decltype(auto) apply(F&& f, X1&& x1, X2&& x2, X3&& x3) {
            return f(f(static_cast<X1&&>(x1),
                       static_cast<X2&&>(x2)),
                       static_cast<X3&&>(x3));
        }
    };

    template <>
    struct foldl1_impl<4> {
        template <typename F, typename X1, typename X2, typename X3, typename X4>
        static constexpr decltype(auto) apply(F&& f, X1&& x1, X2&& x2, X3&& x3, X4&& x4) {
            return f(f(f(static_cast<X1&&>(x1),
                         static_cast<X2&&>(x2)),
                         static_cast<X3&&>(x3)),
                         static_cast<X4&&>(x4));
        }
    };

    template <>
    struct foldl1_impl<5> {
        template <typename F, typename X1, typename X2, typename X3, typename X4, typename X5>
        static constexpr decltype(auto) apply(F&& f, X1&& x1, X2&& x2, X3&& x3, X4&& x4, X5&& x5) {
            return f(f(f(f(static_cast<X1&&>(x1),
                           static_cast<X2&&>(x2)),
                           static_cast<X3&&>(x3)),
                           static_cast<X4&&>(x4)),
                           static_cast<X5&&>(x5));
        }
    };

    template <>
    struct foldl1_impl<6> {
        template <typename F, typename X1, typename X2, typename X3, typename X4, typename X5, typename X6>
        static constexpr decltype(auto) apply(F&& f, X1&& x1, X2&& x2, X3&& x3, X4&& x4, X5&& x5, X6&& x6) {
            return f(f(f(f(f(static_cast<X1&&>(x1),
                             static_cast<X2&&>(x2)),
                             static_cast<X3&&>(x3)),
                             static_cast<X4&&>(x4)),
                             static_cast<X5&&>(x5)),
                             static_cast<X6&&>(x6));
        }
    };

    template <unsigned int n>
    struct foldl1_impl<n, when<(n >= 7) && (n < 14)>> {
        template <typename F, typename X1, typename X2, typename X3, typename X4, typename X5, typename X6, typename X7, typename ...Xn>
        static constexpr decltype(auto)
        apply(F&& f
              , X1&& x1, X2&& x2, X3&& x3, X4&& x4, X5&& x5, X6&& x6, X7&& x7
              , Xn&& ...xn)
        {
            return foldl1_impl<sizeof...(xn) + 1>::apply(
                f,
                f(f(f(f(f(f(static_cast<X1&&>(x1),
                            static_cast<X2&&>(x2)),
                            static_cast<X3&&>(x3)),
                            static_cast<X4&&>(x4)),
                            static_cast<X5&&>(x5)),
                            static_cast<X6&&>(x6)),
                            static_cast<X7&&>(x7)),
                static_cast<Xn&&>(xn)...
            );
        }
    };

    template <unsigned int n>
    struct foldl1_impl<n, when<(n >= 14) && (n < 28)>> {
        template <
              typename F
            , typename X1, typename X2, typename X3,  typename X4,  typename X5,  typename X6,  typename X7
            , typename X8, typename X9, typename X10, typename X11, typename X12, typename X13, typename X14
            , typename ...Xn
        >
        static constexpr decltype(auto)
        apply(F&& f
              , X1&& x1, X2&& x2, X3&& x3,   X4&& x4,   X5&& x5,   X6&& x6,   X7&& x7
              , X8&& x8, X9&& x9, X10&& x10, X11&& x11, X12&& x12, X13&& x13, X14&& x14
              , Xn&& ...xn)
        {
            return foldl1_impl<sizeof...(xn) + 1>::apply(
                f,
                f(f(f(f(f(f(f(f(f(f(f(f(f(
                    static_cast<X1&&>(x1),  static_cast<X2&&>(x2)), static_cast<X3&&>(x3)),   static_cast<X4&&>(x4)),   static_cast<X5&&>(x5)),   static_cast<X6&&>(x6)),   static_cast<X7&&>(x7)),
                    static_cast<X8&&>(x8)), static_cast<X9&&>(x9)), static_cast<X10&&>(x10)), static_cast<X11&&>(x11)), static_cast<X12&&>(x12)), static_cast<X13&&>(x13)), static_cast<X14&&>(x14))
                , static_cast<Xn&&>(xn)...);

        }
    };

    template <unsigned int n>
    struct foldl1_impl<n, when<(n >= 28) && (n < 56)>> {
        template <
              typename F
            , typename X1,  typename X2,  typename X3,  typename X4,  typename X5,  typename X6,  typename X7
            , typename X8,  typename X9,  typename X10, typename X11, typename X12, typename X13, typename X14
            , typename X15, typename X16, typename X17, typename X18, typename X19, typename X20, typename X21
            , typename X22, typename X23, typename X24, typename X25, typename X26, typename X27, typename X28
            , typename ...Xn
        >
        static constexpr decltype(auto)
        apply(F&& f
              , X1&& x1,   X2&& x2,   X3&& x3,   X4&& x4,   X5&& x5,   X6&& x6,   X7&& x7
              , X8&& x8,   X9&& x9,   X10&& x10, X11&& x11, X12&& x12, X13&& x13, X14&& x14
              , X15&& x15, X16&& x16, X17&& x17, X18&& x18, X19&& x19, X20&& x20, X21&& x21
              , X22&& x22, X23&& x23, X24&& x24, X25&& x25, X26&& x26, X27&& x27, X28&& x28
              , Xn&& ...xn)
        {
            return foldl1_impl<sizeof...(xn) + 1>::apply(
                f,
                f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(
                    static_cast<X1&&>(x1),    static_cast<X2&&>(x2)),   static_cast<X3&&>(x3)),   static_cast<X4&&>(x4)),   static_cast<X5&&>(x5)),   static_cast<X6&&>(x6)),   static_cast<X7&&>(x7)),
                    static_cast<X8&&>(x8)),   static_cast<X9&&>(x9)),   static_cast<X10&&>(x10)), static_cast<X11&&>(x11)), static_cast<X12&&>(x12)), static_cast<X13&&>(x13)), static_cast<X14&&>(x14)),
                    static_cast<X15&&>(x15)), static_cast<X16&&>(x16)), static_cast<X17&&>(x17)), static_cast<X18&&>(x18)), static_cast<X19&&>(x19)), static_cast<X20&&>(x20)), static_cast<X21&&>(x21)),
                    static_cast<X22&&>(x22)), static_cast<X23&&>(x23)), static_cast<X24&&>(x24)), static_cast<X25&&>(x25)), static_cast<X26&&>(x26)), static_cast<X27&&>(x27)), static_cast<X28&&>(x28))
                , static_cast<Xn&&>(xn)...);
        }
    };

    template <unsigned int n>
    struct foldl1_impl<n, when<(n >= 56)>> {
        template <
              typename F
            , typename X1,  typename X2,  typename X3,  typename X4,  typename X5,  typename X6,  typename X7
            , typename X8,  typename X9,  typename X10, typename X11, typename X12, typename X13, typename X14
            , typename X15, typename X16, typename X17, typename X18, typename X19, typename X20, typename X21
            , typename X22, typename X23, typename X24, typename X25, typename X26, typename X27, typename X28
            , typename X29, typename X30, typename X31, typename X32, typename X33, typename X34, typename X35
            , typename X36, typename X37, typename X38, typename X39, typename X40, typename X41, typename X42
            , typename X43, typename X44, typename X45, typename X46, typename X47, typename X48, typename X49
            , typename X50, typename X51, typename X52, typename X53, typename X54, typename X55, typename X56
            , typename ...Xn
        >
        static constexpr decltype(auto)
        apply(F&& f
              , X1&& x1,   X2&& x2,   X3&& x3,   X4&& x4,   X5&& x5,   X6&& x6,   X7&& x7
              , X8&& x8,   X9&& x9,   X10&& x10, X11&& x11, X12&& x12, X13&& x13, X14&& x14
              , X15&& x15, X16&& x16, X17&& x17, X18&& x18, X19&& x19, X20&& x20, X21&& x21
              , X22&& x22, X23&& x23, X24&& x24, X25&& x25, X26&& x26, X27&& x27, X28&& x28
              , X29&& x29, X30&& x30, X31&& x31, X32&& x32, X33&& x33, X34&& x34, X35&& x35
              , X36&& x36, X37&& x37, X38&& x38, X39&& x39, X40&& x40, X41&& x41, X42&& x42
              , X43&& x43, X44&& x44, X45&& x45, X46&& x46, X47&& x47, X48&& x48, X49&& x49
              , X50&& x50, X51&& x51, X52&& x52, X53&& x53, X54&& x54, X55&& x55, X56&& x56
              , Xn&& ...xn)
        {
            return foldl1_impl<sizeof...(xn) + 1>::apply(
                f,
                f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(f(
                    static_cast<X1&&>(x1),    static_cast<X2&&>(x2)),   static_cast<X3&&>(x3)),   static_cast<X4&&>(x4)),   static_cast<X5&&>(x5)),   static_cast<X6&&>(x6)),   static_cast<X7&&>(x7)),
                    static_cast<X8&&>(x8)),   static_cast<X9&&>(x9)),   static_cast<X10&&>(x10)), static_cast<X11&&>(x11)), static_cast<X12&&>(x12)), static_cast<X13&&>(x13)), static_cast<X14&&>(x14)),
                    static_cast<X15&&>(x15)), static_cast<X16&&>(x16)), static_cast<X17&&>(x17)), static_cast<X18&&>(x18)), static_cast<X19&&>(x19)), static_cast<X20&&>(x20)), static_cast<X21&&>(x21)),
                    static_cast<X22&&>(x22)), static_cast<X23&&>(x23)), static_cast<X24&&>(x24)), static_cast<X25&&>(x25)), static_cast<X26&&>(x26)), static_cast<X27&&>(x27)), static_cast<X28&&>(x28)),
                    static_cast<X29&&>(x29)), static_cast<X30&&>(x30)), static_cast<X31&&>(x31)), static_cast<X32&&>(x32)), static_cast<X33&&>(x33)), static_cast<X34&&>(x34)), static_cast<X35&&>(x35)),
                    static_cast<X36&&>(x36)), static_cast<X37&&>(x37)), static_cast<X38&&>(x38)), static_cast<X39&&>(x39)), static_cast<X40&&>(x40)), static_cast<X41&&>(x41)), static_cast<X42&&>(x42)),
                    static_cast<X43&&>(x43)), static_cast<X44&&>(x44)), static_cast<X45&&>(x45)), static_cast<X46&&>(x46)), static_cast<X47&&>(x47)), static_cast<X48&&>(x48)), static_cast<X49&&>(x49)),
                    static_cast<X50&&>(x50)), static_cast<X51&&>(x51)), static_cast<X52&&>(x52)), static_cast<X53&&>(x53)), static_cast<X54&&>(x54)), static_cast<X55&&>(x55)), static_cast<X56&&>(x56))
                , static_cast<Xn&&>(xn)...);
        }
    };
    //! @endcond

    struct foldl1_t {
        template <typename F, typename X1, typename ...Xn>
        constexpr decltype(auto) operator()(F&& f, X1&& x1, Xn&& ...xn) const {
            return foldl1_impl<sizeof...(xn) + 1>::apply(
                static_cast<F&&>(f), static_cast<X1&&>(x1), static_cast<Xn&&>(xn)...
            );
        }
    };

    constexpr foldl1_t foldl1{};
    constexpr auto foldl = foldl1;
}} BOOST_HANA_NAMESPACE_END

#endif // !BOOST_HANA_DETAIL_VARIADIC_FOLDL1_HPP
