[C++] is_swappable/is_nothrow_swappable/is_swappable_with/is_nothrow_swappable_with

개요

• swap 가능 여부 확인

예제

• 코드

   #include <algorithm>
   #include <cstring>
   #include <iostream>
   #include <string>
   #include <string_view>
   #include <type_traits>
      
   using namespace std;
      
   class A {};
      
   class B {
   	public:
   		B() {}
   		B(const B &b) {}
   };
      
   class C {
   	public:
   		C() {}
   		C(const C &c) noexcept {}
   };
      
   class D {
   	public:
   		D() {}
   		D(const D &d) = delete;
   };
      
   void swap(A &a, B &b) {}
      
   template <typename T> constexpr string_view type_name() {
   	const string s = __PRETTY_FUNCTION__;
   	const int prefixSize = s.find("[with T = ") + strlen("[with T = ");
      
   	return string_view(s.data() + prefixSize, s.find(';') - prefixSize);
   }
      
   int main() {
   	auto func1 = [](auto t) {
   		cout << "is_swappable<" << type_name<decltype(t)>() << ">::value - "
   			 << is_swappable<decltype(t)>::value << endl;
   		cout << "is_nothrow_swappable<" << type_name<decltype(t)>()
   			 << ">::value - " << is_nothrow_swappable<decltype(t)>::value
   			 << endl;
   	};
      
   	auto func2 = [](auto t1, auto t2) {
   		cout << "is_swappable_with<" << type_name<decltype(t1)>() << ", "
   			 << type_name<decltype(t2)>() << ">::value - "
   			 << is_swappable_with<decltype(t1), decltype(t2)>::value << endl;
      
   		cout << "is_nothrow_swappable_with<" << type_name<decltype(t1)>()
   			 << ", " << type_name<decltype(t2)>() << ">::value - "
   			 << is_nothrow_swappable_with<decltype(t1), decltype(t2)>::value
   			 << endl;
   	};
      
   	func1(int());
   	cout << "------" << endl;
   	func1(A());
   	cout << "------" << endl;
   	func1(B());
   	cout << "------" << endl;
   	func1(C());
   	cout << "------" << endl;
   	func1(D());
   	cout << "------" << endl;
   	func2(int(), int());
   	cout << "------" << endl;
   	func2(int(), A());
   	cout << "------" << endl;
   	func2(A(), B());
   	cout << "------" << endl;
   	func2(C(), D());
      
   	return 0;
   }
  

• 실행 결과

   is_swappable<int>::value - 1
   is_nothrow_swappable<int>::value - 1
   ------
   is_swappable<A>::value - 1
   is_nothrow_swappable<A>::value - 1
   ------
   is_swappable<B>::value - 1
   is_nothrow_swappable<B>::value - 0
   ------
   is_swappable<C>::value - 1
   is_nothrow_swappable<C>::value - 1
   ------
   is_swappable<D>::value - 0
   is_nothrow_swappable<D>::value - 0
   ------
   is_swappable_with<int, int>::value - 0
   is_nothrow_swappable_with<int, int>::value - 0
   ------
   is_swappable_with<int, A>::value - 0
   is_nothrow_swappable_with<int, A>::value - 0
   ------
   is_swappable_with<A, B>::value - 0
   is_nothrow_swappable_with<A, B>::value - 0
   ------
   is_swappable_with<C, D>::value - 0
   is_nothrow_swappable_with<C, D>::value - 0