vmap/libs/generic/functional.h

#if !defined( INCLUDED_FUNCTIONAL_H )
#define INCLUDED_FUNCTIONAL_H

#include <functional>
#include <tuple>

namespace detail {

    template<int N>
    struct rank : rank<N - 1> {
    };

    template<>
    struct rank<0> {
    };

    struct get_func {

        template<class T>
        struct wrapper {
            using type = T;
        };

        template<class F>
        using func_member = wrapper<typename F::func>;

        template<class F>
        static wrapper<func_member<F>> test(rank<2>) { return {}; }

        template<class F>
        struct func_lambda {
            using type = typename func_lambda<decltype(&F::operator())>::type;
        };

        template<class R, class... Ts>
        struct func_lambda<R(*)(Ts...)> {
            using type = R(Ts...);
        };

        template<class Object, class R, class... Ts>
        struct func_lambda<R(Object::*)(Ts...) const> {
            using type = R(Ts...);
        };

        template<class Object, class R, class... Ts>
        struct func_lambda<R(Object::*)(Ts...)> {
            using type = R(Ts...);
        };

        template<class F, class = func_lambda<F>>
        static wrapper<func_lambda<F>> test(rank<1>) { return {}; }
    };

    template<class F>
    struct Fn;

    template<class R, class... Ts>
    struct Fn<R(Ts...)> {
        using result_type = R;

        template<int N>
        using get = typename std::tuple_element<N, std::tuple<Ts...>>::type;
    };
}

template<class Caller>
using get_func = typename decltype(detail::get_func::test<Caller>(detail::rank<2>{}))::type::type;

template<class Caller>
using get_result_type = typename detail::Fn<get_func<Caller>>::result_type;

template<class Caller, int N>
using get_argument = typename detail::Fn<get_func<Caller>>::template get<N>;

namespace detail {

    template<class F>
    class FunctionN;

    template<class R, class... Ts>
    class FunctionN<R(Ts...)> {
    public:
        template<R(*f)(Ts...)>
        class instance {
        public:
            using func = R(Ts...);

            static R call(Ts... args) {
                return (f)(args...);
            }
        };
    };

}

template<class F, F *func>
using Function = typename detail::FunctionN<F>::template instance<func>;

namespace detail {
    template<class Object, class F>
    struct MemberFunction;

    template<class Object, class R, class... Ts>
    struct MemberFunction<Object, R(Ts...)> {
        using type = R(Object::*)(Ts...);
        using type_const = R(Object::*)(Ts...) const;
    };
}

namespace detail {
    template<class Object, class F>
    class MemberN;

    template<class Object, class R, class... Ts>
    class MemberN<Object, R(Ts...)> {
    public:
        template<R(Object::*f)(Ts...)>
        class instance {
        public:
            using func = R(Object &, Ts...);

            static R call(Object &object, Ts... args) {
                return (object.*f)(args...);
            }
        };
    };
}

template<class Object, class F>
using MemberFunction = typename detail::MemberFunction<Object, F>::type;

template<class Object, class F, MemberFunction<Object, F> func>
using Member = typename detail::MemberN<Object, F>::template instance<func>;

namespace detail {
    template<class Object, class F>
    class ConstMemberN;

    template<class Object, class R, class... Ts>
    class ConstMemberN<Object, R(Ts...)> {
    public:
        template<R(Object::*f)(Ts...) const>
        class instance {
        public:
            using func = R(const Object &, Ts...);

            static R call(const Object &object, Ts... args) {
                return (object.*f)(args...);
            }
        };
    };
}

template<class Object, class F>
using ConstMemberFunction = typename detail::MemberFunction<Object, F>::type_const;

template<class Object, class F, ConstMemberFunction<Object, F> func>
using ConstMember = typename detail::ConstMemberN<Object, F>::template instance<func>;

// misc

namespace detail {
    template<int ...>
    struct seq {
    };

    template<int N, int... S>
    struct gens : gens<N - 1, N - 1, S...> {
    };

    template<int... S>
    struct gens<0, S...> {
        using type = seq<S...>;
    };

    template<int N>
    using seq_new = typename gens<N>::type;

    template<class Functor, class F>
    class FunctorNInvoke;

    template<class Functor, class R, class... Ts>
    class FunctorNInvoke<Functor, R(Ts...)> {
        std::tuple<Ts...> args;

        template<class T>
        struct caller;

        template<int ...I>
        struct caller<seq<I...>> {
            static inline R call(FunctorNInvoke<Functor, R(Ts...)> *self, Functor functor) {
                (void) self;
                return functor(std::get<I>(self->args)...);
            }
        };

    public:
        FunctorNInvoke(Ts... args) : args(args...) {
        }

        inline R operator()(Functor functor) {
            return caller<seq_new<sizeof...(Ts)>>::call(this, functor);
        }
    };
}

template<class Functor>
using FunctorInvoke = detail::FunctorNInvoke<Functor, get_func<Functor>>;

#endif