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type_traits: added value_list

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This commit is contained in:
Michele Caini
2020-12-02 15:49:05 +01:00
parent cf176719a8
commit b1369582e1
2 changed files with 81 additions and 0 deletions
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68
src/entt/core/type_traits.hpp
View File

@@ -229,6 +229,74 @@ template<class List, typename Type>
inline constexpr auto type_list_contains_v = type_list_contains<List, Type>::value;
/**
* @brief A class to use to push around lists of constant values, nothing more.
* @tparam Value Values provided by the value list.
*/
template<auto... Value>
struct value_list {
/*! @brief Value list type. */
using type = value_list;
/*! @brief Compile-time number of elements in the value list. */
static constexpr auto size = sizeof...(Value);
};
/**
* @brief Concatenates multiple value lists.
* @tparam Value Values provided by the first value list.
* @tparam Other Values provided by the second value list.
* @return A value list composed by the values of both the value lists.
*/
template<auto... Value, auto... Other>
constexpr value_list<Value..., Other...> operator+(value_list<Value...>, value_list<Other...>) { return {}; }
/*! @brief Primary template isn't defined on purpose. */
template<typename...>
struct value_list_cat;
/*! @brief Concatenates multiple value lists. */
template<>
struct value_list_cat<> {
/*! @brief A value list composed by the values of all the value lists. */
using type = value_list<>;
};
/**
* @brief Concatenates multiple value lists.
* @tparam Value Values provided by the first value list.
* @tparam Other Values provided by the second value list.
* @tparam List Other value lists, if any.
*/
template<auto... Value, auto... Other, typename... List>
struct value_list_cat<value_list<Value...>, value_list<Other...>, List...> {
/*! @brief A value list composed by the values of all the value lists. */
using type = typename value_list_cat<value_list<Value..., Other...>, List...>::type;
};
/**
* @brief Concatenates multiple value lists.
* @tparam Value Values provided by the value list.
*/
template<auto... Value>
struct value_list_cat<value_list<Value...>> {
/*! @brief A value list composed by the values of all the value lists. */
using type = value_list<Value...>;
};
/**
* @brief Helper type.
* @tparam List Value lists to concatenate.
*/
template<typename... List>
using value_list_cat_t = typename value_list_cat<List...>::type;
/**
* @brief Provides the member constant `value` to true if a given type is
* equality comparable, false otherwise.

13
test/entt/core/type_traits.cpp
View File

@@ -56,6 +56,19 @@ TEST(TypeTraits, TypeList) {
static_assert(!entt::type_list_contains_v<type, double>);
}
TEST(TypeTraits, ValueList) {
using value = entt::value_list<0, 2>;
using other = entt::value_list<1>;
static_assert(value::size == 2u);
static_assert(other::size == 1u);
static_assert(std::is_same_v<decltype(value{} + other{}), entt::value_list<0, 2, 1>>);
static_assert(std::is_same_v<entt::value_list_cat_t<value, other, value, other>, entt::value_list<0, 2, 1, 0, 2, 1>>);
static_assert(std::is_same_v<entt::value_list_cat_t<value, other>, entt::value_list<0, 2, 1>>);
static_assert(std::is_same_v<entt::value_list_cat_t<value, value>, entt::value_list<0, 2, 0, 2>>);
}
TEST(TypeTraits, IsEqualityComparable) {
static_assert(entt::is_equality_comparable_v<int>);
static_assert(!entt::is_equality_comparable_v<void>);