cppmp/include/cppmp/core/conditionals.h

#pragma once

#include "types.h"

namespace cppmp
{

    namespace __impl
    {

        /* eval_if_c_impl */

        template<bool B, typename T, template<typename...> class E, typename... A>
        struct eval_if_impl;

    }

    /* enable_if */

    /**
     * @brief Defines T as ::type if B is true, otherwise the resulting type is empty.
     */
    template<bool B, typename T = void>
    struct enable_if
        : public std::enable_if<B, T>
        { };

    /**
     * @brief Resulting type is T if B is true. If B is false the resulting type is invalid.
     */
    template<bool B, typename T = void>
    using enable_if_t = typename enable_if<B, T>::type;

    /* conditional/if */

    /**
     * @brief Defines T as ::type if B is true, F otherwise.
     */
    template<bool B, typename T, typename F>
    struct conditional
        : public std::conditional<B, T, F>
        { };

    /**
     * @brief Evaluates to T if B is true, to F otherwise.
     */
    template<bool B, typename T, typename F>
    using conditional_t = typename conditional<B, T, F>::type;

    /**
     * @brief Same as conditional.
     */
    template<bool B, typename T, typename F>
    struct if_
        : public conditional<B, T, F>
        { };

    /**
     * @brief Same as conditional_t.
     */
    template<bool B, typename T, typename F>
    using if_t = typename if_<B, T, F>::type;

    /* eval_if */

    /**
     * @brief Defines T as ::type if B is true, evaluates E<A...> otherwise.
     */
    template<bool B, typename T, template<typename...> class E, typename... A>
    struct eval_if
        : public __impl::eval_if_impl<B, T, E, A...>
        { };

    /**
     * @brief Evaluates to T if B is true, to E<A...> otherwise.
     */
    template<bool B, typename T, template<typename...> class E, typename... A>
    using eval_if_t = typename eval_if<B, T, E, A...>::type;

    /* conjunction/and */

#if __cplusplus >= 201703L

    /**
     * @brief Evaluates to true_t if all passed arguments are also true_t.
     */
    template<typename... T>
    struct conjunction
        : public std::conjunction<T...>
        { };

    /**
     * @brief It to true if all passed arguments are also true_t.
     */
    template<typename... T>
    constexpr decltype(auto) conjunction_v = conjunction<T...>::value;

    /**
     * @brief Same as conjunction.
     */
    template<typename... T>
    struct and_
        : public conjunction<T...>
        { };

    /**
     * @brief Same as conjunction_v.
     */
    template<typename... T>
    constexpr decltype(auto) and_v = conjunction<T...>::value;

#endif

    /* disjunction/or */

#if __cplusplus >= 201703L

    /**
     * @brief Evaluates to true_t if at least one passed arguments is true_t.
     */
    template<typename... T>
    struct disjunction
        : public std::disjunction<T...>
        { };

    /**
     * @brief Is true if at least one passed arguments is true_t.
     */
    template<typename... T>
    constexpr decltype(auto) disjunction_v = disjunction<T...>::value;

    /**
     * @brief Same as disjunction.
     */
    template<typename... T>
    struct or_
        : public disjunction<T...>
        { };

    /**
     * @brief Same as disjunction_v.
     */
    template<typename... T>
    constexpr decltype(auto) or_v = disjunction<T...>::value;

#endif

}

#include "conditionals.inl"