core/modules/Meta.cppm

export module Core.Meta;

namespace Core {
    template<typename T>
    struct BaseRemovePointer final {
        using Type = T;
    };

    template<typename T>
    struct BaseRemovePointer<T*> final {
        using Type = T;
    };

    template<typename T>
    struct BaseRemoveReference final {
        using Type = T;
    };

    template<typename T>
    struct BaseRemoveReference<T&> final {
        using Type = T;
    };

    template<typename T>
    struct BaseRemoveReference<T&&> final {
        using Type = T;
    };

    template<typename A, typename B>
    struct BaseIsSame final {
        static constexpr bool value = false;
    };

    template<typename T>
    struct BaseIsSame<T, T> final {
        static constexpr bool value = true;
    };

    template<bool C, typename A, typename B>
    struct BaseIf final {
        using Type = A;
    };

    template<typename A, typename B>
    struct BaseIf<false, A, B> final {
        using Type = B;
    };
}

export namespace Core {
    template<typename T>
    concept Iterable = requires(T& t) {
        t.begin();
        t.end();
    };

    template<typename T>
    using RemovePointer = BaseRemovePointer<T>::Type;

    template<typename T>
    using RemoveReference = BaseRemoveReference<T>::Type;

    template<typename T, typename U>
    constexpr bool IsSame = BaseIsSame<T, U>::value;

    template<bool C, typename A, typename B>
    using If = BaseIf<C, A, B>::Type;

    template<typename T>
    constexpr RemoveReference<T>&& move(T&& t) noexcept {
        return static_cast<RemoveReference<T>&&>(t);
    }

    template<typename T>
    concept Moveable = requires(T t) {
        requires noexcept(T(Core::move(t)));
        requires noexcept(t = T(Core::move(t)));
    };

    template<typename T>
    constexpr T&& forward(RemoveReference<T>& t) noexcept {
        return static_cast<T&&>(t);
    }

    template<typename T>
    constexpr T&& forward(RemoveReference<T>&& t) noexcept {
        return static_cast<T&&>(t);
    }

    template<Moveable T>
    void swap(T& a, T& b) noexcept {
        T tmp = Core::move(a);
        a = Core::move(b);
        b = Core::move(tmp);
    }
}