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type_traits: added type_list_element[_t] and value_list_element[_v]

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This commit is contained in:
Michele Caini
2020-12-15 12:20:20 +01:00
parent a7c2a5c49b
commit 9950b2ea34
2 changed files with 84 additions and 0 deletions
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76
src/entt/core/type_traits.hpp
View File

@@ -132,6 +132,44 @@ struct type_list {
};
/*! @brief Primary template isn't defined on purpose. */
template<std::size_t, typename>
struct type_list_element;
/**
* @brief Provides compile-time indexed access to the types of a type list.
* @tparam Index Index of the type to return.
* @tparam Type First type provided by the type list.
* @tparam Other Other types provided by the type list.
*/
template<std::size_t Index, typename Type, typename... Other>
struct type_list_element<Index, type_list<Type, Other...>>
: type_list_element<Index - 1u, type_list<Other...>>
{};
/**
* @brief Provides compile-time indexed access to the types of a type list.
* @tparam Type First type provided by the type list.
* @tparam Other Other types provided by the type list.
*/
template<typename Type, typename... Other>
struct type_list_element<0u, type_list<Type, Other...>> {
/*! @brief Searched type. */
using type = Type;
};
/**
* @brief Helper type.
* @tparam Index Index of the type to return.
* @tparam List Type list to search into.
*/
template<std::size_t Index, typename List>
using type_list_element_t = typename type_list_element<Index, List>::type;
/**
* @brief Concatenates multiple type lists.
* @tparam Type Types provided by the first type list.
@@ -265,6 +303,44 @@ struct value_list {
};
/*! @brief Primary template isn't defined on purpose. */
template<std::size_t, typename>
struct value_list_element;
/**
* @brief Provides compile-time indexed access to the values of a value list.
* @tparam Index Index of the value to return.
* @tparam Value First value provided by the value list.
* @tparam Other Other values provided by the value list.
*/
template<std::size_t Index, auto Value, auto... Other>
struct value_list_element<Index, value_list<Value, Other...>>
: value_list_element<Index - 1u, value_list<Other...>>
{};
/**
* @brief Provides compile-time indexed access to the types of a type list.
* @tparam Value First value provided by the value list.
* @tparam Other Other values provided by the value list.
*/
template<auto Value, auto... Other>
struct value_list_element<0u, value_list<Value, Other...>> {
/*! @brief Searched value. */
static constexpr auto value = Value;
};
/**
* @brief Helper type.
* @tparam Index Index of the value to return.
* @tparam List Value list to search into.
*/
template<std::size_t Index, typename List>
inline constexpr auto value_list_element_v = value_list_element<Index, List>::value;
/**
* @brief Concatenates multiple value lists.
* @tparam Value Values provided by the first value list.

8
test/entt/core/type_traits.cpp
View File

@@ -54,6 +54,10 @@ TEST(TypeTraits, TypeList) {
static_assert(entt::type_list_contains_v<type, int>);
static_assert(entt::type_list_contains_v<type, char>);
static_assert(!entt::type_list_contains_v<type, double>);
static_assert(std::is_same_v<entt::type_list_element_t<0u, type>, int>);
static_assert(std::is_same_v<entt::type_list_element_t<1u, type>, char>);
static_assert(std::is_same_v<entt::type_list_element_t<0u, other>, double>);
}
TEST(TypeTraits, ValueList) {
@@ -67,6 +71,10 @@ TEST(TypeTraits, ValueList) {
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>>);
static_assert(entt::value_list_element_v<0u, value> == 0);
static_assert(entt::value_list_element_v<1u, value> == 2);
static_assert(entt::value_list_element_v<0u, other> == 1);
}
TEST(TypeTraits, IsEqualityComparable) {