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@airglow923
Last active November 23, 2021 02:34
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SFINAE and concept comparison
#include <concepts>
#include <iostream>
#include <type_traits>
struct BothAssignable {
constexpr auto operator=(const BothAssignable&) noexcept -> BothAssignable& = default;
constexpr auto operator=(BothAssignable&&) noexcept -> BothAssignable& = default;
};
struct CopyAssignable {
constexpr auto operator=(const CopyAssignable&) noexcept -> CopyAssignable& = default;
constexpr auto operator=(CopyAssignable&&) noexcept -> CopyAssignable& = delete;
};
struct MoveAssignable {
constexpr auto operator=(const MoveAssignable&) noexcept -> MoveAssignable& = delete;
constexpr auto operator=(MoveAssignable&&) noexcept -> MoveAssignable& = default;
};
template <typename T,
typename std::enable_if_t<!std::is_move_assignable_v<T> &&
std::is_copy_assignable_v<T>,
bool> = true>
auto func_sfinae() -> void {
std::cout << "is_copy_assignable\n";
}
template <typename T,
typename std::enable_if_t<std::is_move_assignable_v<T>, bool> = false>
auto func_sfinae() -> void {
std::cout << "is_move_assignable\n";
}
template <typename T>
requires (!std::is_move_assignable_v<T> && std::is_copy_assignable_v<T>)
auto func_concept() -> void {
std::cout << "is_copy_assignable\n";
}
template <typename T>
requires std::is_move_assignable_v<T>
auto func_concept() -> void {
std::cout << "is_move_assignable\n";
}
auto main() -> int {
func_sfinae<BothAssignable>(); // is_move_assignable
func_sfinae<CopyAssignable>(); // is_copy_assignable
func_sfinae<MoveAssignable>(); // is_move_assignable
func_concept<BothAssignable>(); // is_move_assignable
func_concept<CopyAssignable>(); // is_copy_assignable
func_concept<MoveAssignable>(); // is_move_assignable
}
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