build/_deps/metal-src/include/metal/value/fold_left.hpp

#ifndef METAL_VALUE_FOLD_LEFT_HPP
#define METAL_VALUE_FOLD_LEFT_HPP

#include "../config.hpp"
#include "../detail/sfinae.hpp"

namespace metal {
/// \cond
namespace detail {
    template <class lbd>
    struct _fold_left;
}
/// \endcond

/// \ingroup value
///
/// ### Description
/// Computes the recursive invocation of a binary \lambda with the result of
/// the previous invocation and each \value, from the first to the last.
///
/// ### Usage
/// For any \lambda `lbd`, and \values `val_0, ..., val_n-1`
/// \code
///     using result = metal::fold_left<lbd, val_0, ..., val_n-1>;
/// \endcode
///
/// \returns: \value
/// \semantics:
///     Equivalent to
///     \code
///         using result =
///             lbd(... lbd(lbd(val_0, val_1), val_2), ..., val_n-1)
///     \endcode
///     where `lbd(x, y)` stands for `metal::invoke<lbd, x, y>`.
///
/// ### Example
/// \snippet value.cpp fold_left
///
/// ### See Also
/// \see fold_right
template <class lbd, class... vals>
using fold_left = detail::call<detail::_fold_left<lbd>::template type, vals...>;
}

#include "../lambda/lambda.hpp"
#include "../value/identity.hpp"

#include <cstddef>

namespace metal {
/// \cond
namespace detail {
    template <
        class state,
        class _00, class _01, class _02, class _03, class _04, class _05,
        class _06, class _07, class _08, class _09, class _10, class _11,
        class _12, class _13, class _14, class _15, class _16, class _17,
        class _18, class _19, class _20, class _21, class _22, class _23,
        class _24, class _25, class _26, class _27, class _28, class _29,
        class _30, class _31, class _32, class _33, class _34, class _35,
        class _36, class _37, class _38, class _39, class _40, class _41,
        class _42, class _43, class _44, class _45, class _46, class _47,
        class _48, class _49, class _50, class _51, class _52, class _53,
        class _54, class _55, class _56, class _57, class _58, class _59,
        class _60, class _61, class _62, class _63, class _64, class _65,
        class _66, class _67, class _68, class _69, class _70, class _71,
        class _72, class _73, class _74, class _75, class _76, class _77,
        class _78, class _79, class _80, class _81, class _82, class _83,
        class _84, class _85, class _86, class _87, class _88, class _89,
        class _90, class _91, class _92, class _93, class _94, class _95,
        class _96, class _97, class _98, class _99>
    struct left_folder_100 {
            template<template<class...> class expr>
            using type =
                expr<expr<expr<expr<expr<expr<expr<expr<expr<expr<
                expr<expr<expr<expr<expr<expr<expr<expr<expr<expr<
                expr<expr<expr<expr<expr<expr<expr<expr<expr<expr<
                expr<expr<expr<expr<expr<expr<expr<expr<expr<expr<
                expr<expr<expr<expr<expr<expr<expr<expr<expr<expr<
                expr<expr<expr<expr<expr<expr<expr<expr<expr<expr<
                expr<expr<expr<expr<expr<expr<expr<expr<expr<expr<
                expr<expr<expr<expr<expr<expr<expr<expr<expr<expr<
                expr<expr<expr<expr<expr<expr<expr<expr<expr<expr<
                expr<expr<expr<expr<expr<expr<expr<expr<expr<expr<
                    forward<state::template type, expr>,
                _00>, _01>, _02>, _03>, _04>, _05>, _06>, _07>, _08>, _09>,
                _10>, _11>, _12>, _13>, _14>, _15>, _16>, _17>, _18>, _19>,
                _20>, _21>, _22>, _23>, _24>, _25>, _26>, _27>, _28>, _29>,
                _30>, _31>, _32>, _33>, _34>, _35>, _36>, _37>, _38>, _39>,
                _40>, _41>, _42>, _43>, _44>, _45>, _46>, _47>, _48>, _49>,
                _50>, _51>, _52>, _53>, _54>, _55>, _56>, _57>, _58>, _59>,
                _60>, _61>, _62>, _63>, _64>, _65>, _66>, _67>, _68>, _69>,
                _70>, _71>, _72>, _73>, _74>, _75>, _76>, _77>, _78>, _79>,
                _80>, _81>, _82>, _83>, _84>, _85>, _86>, _87>, _88>, _89>,
                _90>, _91>, _92>, _93>, _94>, _95>, _96>, _97>, _98>, _99>;
    };

    template <
        class state,
        class _00, class _01, class _02, class _03, class _04,
        class _05, class _06, class _07, class _08, class _09>
    struct left_folder_10 {
        template <template <class...> class expr>
        /* clang-format off */
            using type =
                expr<expr<expr<expr<expr<expr<expr<expr<expr<expr<
                    forward<state::template type, expr>,
                _00>, _01>, _02>, _03>, _04>, _05>, _06>, _07>, _08>, _09>;
        /* clang-format on */
    };

    template <class state, class _00>
    struct left_folder_1 {
        template <template <class...> class expr>
        using type = expr<forward<state::template type, expr>, _00>;
    };

    template <class state>
    struct left_folder_0 {
        template <template <class...> class>
        using type = identity<state>;
    };

    template <std::size_t n>
    struct _fold_left_impl
        /* clang-format off */
        : _fold_left_impl<(n > 100) ? 100 : (n > 10) ? 10 : (n > 1)> {
        /* clang-format on */
    };

    template <>
    struct _fold_left_impl<100> {
        template <
            class state,
            class _00, class _01, class _02, class _03, class _04,
            class _05, class _06, class _07, class _08, class _09,
            class _10, class _11, class _12, class _13, class _14,
            class _15, class _16, class _17, class _18, class _19,
            class _20, class _21, class _22, class _23, class _24,
            class _25, class _26, class _27, class _28, class _29,
            class _30, class _31, class _32, class _33, class _34,
            class _35, class _36, class _37, class _38, class _39,
            class _40, class _41, class _42, class _43, class _44,
            class _45, class _46, class _47, class _48, class _49,
            class _50, class _51, class _52, class _53, class _54,
            class _55, class _56, class _57, class _58, class _59,
            class _60, class _61, class _62, class _63, class _64,
            class _65, class _66, class _67, class _68, class _69,
            class _70, class _71, class _72, class _73, class _74,
            class _75, class _76, class _77, class _78, class _79,
            class _80, class _81, class _82, class _83, class _84,
            class _85, class _86, class _87, class _88, class _89,
            class _90, class _91, class _92, class _93, class _94,
            class _95, class _96, class _97, class _98, class _99,
            class... tail>
        using type = typename _fold_left_impl<sizeof...(tail)>::
            template type<
                left_folder_100<
                    state,
                    _00, _01, _02, _03, _04, _05, _06, _07, _08, _09, _10,
                    _11, _12, _13, _14, _15, _16, _17, _18, _19, _20, _21,
                    _22, _23, _24, _25, _26, _27, _28, _29, _30, _31, _32,
                    _33, _34, _35, _36, _37, _38, _39, _40, _41, _42, _43,
                    _44, _45, _46, _47, _48, _49, _50, _51, _52, _53, _54,
                    _55, _56, _57, _58, _59, _60, _61, _62, _63, _64, _65,
                    _66, _67, _68, _69, _70, _71, _72, _73, _74, _75, _76,
                    _77, _78, _79, _80, _81, _82, _83, _84, _85, _86, _87,
                    _88, _89, _90, _91, _92, _93, _94, _95, _96, _97, _98,
                    _99>,
                tail...>;
    };

    template <>
    struct _fold_left_impl<10> {
        template <
            class state,
            class _00, class _01, class _02, class _03, class _04,
            class _05, class _06, class _07, class _08, class _09,
            class... tail>
        using type = typename _fold_left_impl<sizeof...(tail)>::
            template type<left_folder_10<state, _00, _01, _02, _03, _04, _05, _06, _07, _08, _09>, tail...>;
    };

    template <>
    struct _fold_left_impl<1> {
        template <class state, class _00, class... tail>
        using type = typename _fold_left_impl<sizeof...(tail)>::
            template type<left_folder_1<state, _00>, tail...>;
    };

    template <>
    struct _fold_left_impl<0> {
        template <class state, class...>
        using type = state;
    };

    template <class state, class... vals>
    struct left_folder
        : _fold_left_impl<sizeof...(vals)>::
              template type<left_folder_0<state>, vals...> {
    };

    template <class lbd>
    struct _fold_left {
    };

    template <template <class...> class expr>
    struct _fold_left<lambda<expr>> {
        template <class... vals>
        using type = forward<left_folder<vals...>::template type, expr>;
    };
}
/// \endcond
}

#endif