头文件:
#include
模板类别:
template< class T >
struct is_trivially_move_constructible;
句法:
std::is_trivially_move_constructible::value
参数:模板std :: is_trivially_move_constructible接受单个参数T(Trait class)来检查T是否是平凡的可构造类型。
返回值:模板std :: is_trivially_move_constructible返回一个布尔变量,如下所示:
- 正确:如果类型T是可平移的可构造对象。
- False:如果类型T不是平凡的可构造对象。
下面是演示C++中std :: is_trivially_move_constructible的程序:
程序1:
// C++ program to demonstrate
// std::is_trivially_move_constructible
#include
#include
using namespace std;
// Declaration of classes
class A {
};
class B {
B() {}
};
enum class C : int { x,
y,
z };
class D {
int v1;
double v2;
public:
D(int n)
: v1(n), v2()
{
}
D(int n, double f)
noexcept : v1(n), v2(f) {}
};
int main()
{
cout << boolalpha;
// Check if int is trivially
// move constructible or not
cout << "int: "
<< is_trivially_move_constructible::value
<< endl;
// Check if class A is trivially
// move constructible or not
cout << "class A: "
<< is_trivially_move_constructible::value
<< endl;
// Check if class B is trivially
// move constructible or not
cout << "class B: "
<< is_trivially_move_constructible::value
<< endl;
// Check if enum class C is trivially
// move constructible or not
cout << "enum class C: "
<< is_trivially_move_constructible::value
<< endl;
// Check if class D is trivially
// move constructible or not
std::cout << "class D: "
<< is_trivially_move_constructible::value
<< endl;
return 0;
}
输出:
int: true
class A: true
class B: true
enum class C: true
class D: true
程式2:
// C++ program to demonstrate
// std::is_trivially_move_constructible
#include
#include
using namespace std;
// Declare structures
struct Ex1 {
Ex1() {}
Ex1(Ex1&&)
{
cout << "Throwing move constructor!";
}
Ex1(const Ex1&)
{
cout << "Throwing copy constructor!";
}
};
struct Ex2 {
Ex2() {}
Ex2(Ex2&&) noexcept
{
cout << "Non-throwing move constructor!";
}
Ex2(const Ex2&) noexcept
{
cout << "Non-throwing copy constructor!";
}
};
// Driver Code
int main()
{
cout << boolalpha;
// Check if struct Ex1 is move
// constructible or not
cout << "Ex1 is move-constructible? "
<< is_move_constructible::value
<< '\n';
// Check if struct Ex1 is trivially
// move constructible or not
cout << "Ex1 is trivially move-constructible? "
<< is_trivially_move_constructible::value
<< '\n';
// Check if struct Ex2 is trivially
// move constructible or not
cout << "Ex2 is trivially move-constructible? "
<< is_trivially_move_constructible::value
<< '\n';
}
输出:
Ex1 is move-constructible? true
Ex1 is trivially move-constructible? false
Ex2 is trivially move-constructible? false
参考: http://www.cplusplus.com/reference/type_traits/is_trivially_move_constructible/
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