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#ifndef ENTT_CORE_TUPLE_HPP
#define ENTT_CORE_TUPLE_HPP
#include <tuple>
#include <type_traits>
#include <utility>
namespace entt {
/*! @cond TURN_OFF_DOXYGEN */
namespace internal {
template<typename>
struct is_tuple_impl: std::false_type {};
template<typename... Args>
struct is_tuple_impl<std::tuple<Args...>>: std::true_type {};
} // namespace internal
/*! @endcond */
/**
* @brief Provides the member constant `value` to true if a given type is a
* tuple, false otherwise.
* @tparam Type The type to test.
*/
template<typename Type>
struct is_tuple: internal::is_tuple_impl<std::remove_cv_t<Type>> {};
/**
* @brief Helper variable template.
* @tparam Type The type to test.
*/
template<typename Type>
inline constexpr bool is_tuple_v = is_tuple<Type>::value;
/**
* @brief Utility function to unwrap tuples of a single element.
* @tparam Type Tuple type of any sizes.
* @param value A tuple object of the given type.
* @return The tuple itself if it contains more than one element, the first
* element otherwise.
*/
template<typename Type>
constexpr decltype(auto) unwrap_tuple(Type &&value) noexcept {
if constexpr(std::tuple_size_v<std::remove_reference_t<Type>> == 1u) {
return std::get<0>(std::forward<Type>(value));
} else {
return std::forward<Type>(value);
}
}
/**
* @brief Utility class to forward-and-apply tuple objects.
* @tparam Func Type of underlying invocable object.
*/
template<typename Func>
struct forward_apply: private Func {
/**
* @brief Constructs a forward-and-apply object.
* @tparam Args Types of arguments to use to construct the new instance.
* @param args Parameters to use to construct the instance.
*/
template<typename... Args>
constexpr forward_apply(Args &&...args) noexcept(std::is_nothrow_constructible_v<Func, Args...>)
: Func{std::forward<Args>(args)...} {}
/**
* @brief Forwards and applies the arguments with the underlying function.
* @tparam Type Tuple-like type to forward to the underlying function.
* @param args Parameters to forward to the underlying function.
* @return Return value of the underlying function, if any.
*/
template<typename Type>
constexpr decltype(auto) operator()(Type &&args) noexcept(noexcept(std::apply(std::declval<Func &>(), args))) {
return std::apply(static_cast<Func &>(*this), std::forward<Type>(args));
}
/*! @copydoc operator()() */
template<typename Type>
constexpr decltype(auto) operator()(Type &&args) const noexcept(noexcept(std::apply(std::declval<const Func &>(), args))) {
return std::apply(static_cast<const Func &>(*this), std::forward<Type>(args));
}
};
/**
* @brief Deduction guide.
* @tparam Func Type of underlying invocable object.
*/
template<typename Func>
forward_apply(Func) -> forward_apply<std::remove_reference_t<std::remove_cv_t<Func>>>;
} // namespace entt
#endif
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