add_long, remove_long, has_long type traits

long_type_traits.hpp

#include <type_traits>

namespace bxlx {
  namespace impl {
    template<typename T, typename = void>
    struct add_long {
        using type = T;
    };

    template<>
    struct add_long<char> {
        using type = char;
    };

    template<>
    struct add_long<int> {
        using type = long int;
    };

    template<>
    struct add_long<long int> {
        using type = long long int;
    };

    template<typename T>
    struct add_long<T, std::enable_if_t<std::is_const_v<T>>> {
        using type = std::add_const_t<typename add_long<std::remove_const_t<T>>::type>;
    };

    template<typename T>
    struct add_long<T, std::enable_if_t<!std::is_const_v<T> && std::is_volatile_v<T>>> {
        using type = std::add_volatile_t<typename add_long<std::remove_volatile_t<T>>::type>;
    };

    template<typename T>
    struct add_long<T, std::enable_if_t<!std::is_const_v<T> && !std::is_volatile_v<T> && std::is_unsigned_v<T>>> {
        using type = std::make_unsigned_t<typename add_long<std::make_signed_t<T>>::type>;
    };


    template<typename T, typename = void>
    struct remove_long {
        using type = T;
    };

    template<>
    struct remove_long<char> {
        using type = char;
    };

    template<>
    struct remove_long<long int> {
        using type = int;
    };

    template<>
    struct remove_long<long long int> {
        using type = long int;
    };

    template<typename T>
    struct remove_long<T, std::enable_if_t<std::is_const_v<T>>> {
        using type = std::add_const_t<typename remove_long<std::remove_const_t<T>>::type>;
    };

    template<typename T>
    struct remove_long<T, std::enable_if_t<!std::is_const_v<T> && std::is_volatile_v<T>>> {
        using type = std::add_volatile_t<typename remove_long<std::remove_volatile_t<T>>::type>;
    };

    template<typename T>
    struct remove_long<T, std::enable_if_t<!std::is_const_v<T> && !std::is_volatile_v<T> && std::is_unsigned_v<T>>> {
        using type = std::make_unsigned_t<typename remove_long<std::make_signed_t<T>>::type>;
    };
  }

  template<typename T>
  using add_long = impl::add_long<T>;

  template<typename T>
  using remove_long = impl::remove_long<T>;

  template<typename T>
  using has_long = std::bool_constant<!std::is_same_v<remove_long<T>, T>>;

  template<typename T>
  using add_long_t = typename add_long<T>::type;

  template<typename T>
  using remove_long_t = typename remove_long<T>::type;

  template<typename T>
  [[maybe_unused]]
  constexpr static inline auto has_long_v = has_long<T>::value;
}