std::is_nothrow_move_constructible

STD：：是[医]移动[医]可构造的，STD：：is[医]琐碎[医]移动[医]可构造的，STD：：is[医]无抛[医]移动[医]可构造

Defined in header
template< class T > struct is_move_constructible;	(1)	(since C++11)
template< class T > struct is_trivially_move_constructible;	(2)	(since C++11)
template< class T > struct is_nothrow_move_constructible;	(3)	(since C++11)

1%29T不是可引用的类型%28i。E.，可能是cv-符合条件的void类的函数类型。简历-限定符-seq或者是参-限定符%29，提供成员常量。value等于false否则，提供成员常量。value等于std::is_constructible<T, T&&>::value...

2%29与%281%29相同，但使用std::is_trivially_constructible<T, T&&>...

3%29与%281%29相同，但使用std::is_nothrow_constructible<T, T&&>...

T为完整类型，%28可能是cv-合格%29void，或者一系列未知的界限。否则，行为就没有定义。

辅助变量模板

template< class T > inline constexpr bool is_move_constructible_v = is_move_constructible::value;		(since C++17)
template< class T > inline constexpr bool is_trivially_move_constructible_v = is_trivially_move_constructible<T>::value;		(since C++17)
template< class T > inline constexpr bool is_nothrow_move_constructible_v = is_nothrow_move_constructible<T>::value;		(since C++17)

继承自STD：积分[医]常量

成员常数

value static	true if T is move-constructible , false otherwise (public static member constant)

成员函数

operator bool	converts the object to bool, returns value (public member function)
operator() (C++14)	returns value (public member function)

成员类型

Type	Definition
value_type	bool
type	std::integral_constant<bool, value>

可能的实施

模板<class T>结构是[医]移动[医]可构造性：std：：is[医]可构造<T，type Name std：：add[医]r值[医]参照系<T>*类型>{}；模板<class T>结构是[医]琐碎[医]移动[医]可构造性：std：：is[医]琐碎[医]可构造<T，type Name std：：add[医]r值[医]参照系<T>*类型>{}；模板<class T>结构是[医]无抛[医]移动[医]可构造性：std：：is[医]无抛[医]可构造<T，type Name std：：add[医]r值[医]参照系<T>*类型>{}；

*。

注记

类型，但不使用移动构造函数，而是使用可接受的复制构造函数。const T&论点，满足std::is_move_constructible...

Move构造函数通常为NoOPTION，因为否则它们在任何提供强异常保证的代码中都是不可用的。

在许多实现中，is_nothrow_move_constructible还检查析构函数是否抛出，因为它有效。noexept(T(arg)).同样适用于is_trivially_move_constructible，在这些实现中，还要求析构函数是微不足道的：gcc bug 51452lwg第2116期...

例

二次

#include <iostream>
#include <type_traits>
 
struct Ex1 {
    std::string str; // member has a non-trivial but non-throwing move ctor
};
struct Ex2 {
    int n;
    Ex2(Ex2&&) = default; // trivial and non-throwing
};
struct NoMove {
    // prevents implicit declaration of default move constructor
    // however, the class is still move-constructible because its
    // copy constructor can bind to an rvalue argument
    NoMove(const NoMove&) {}
};
 
int main() {
    std::cout << std::boolalpha << "Ex1 is move-constructible? "
              << std::is_move_constructible<Ex1>::value << '\n'
              << "Ex1 is trivially move-constructible? "
              << std::is_trivially_move_constructible<Ex1>::value << '\n'
              << "Ex1 is nothrow move-constructible? "
              << std::is_nothrow_move_constructible<Ex1>::value << '\n'
              << "Ex2 is trivially move-constructible? "
              << std::is_trivially_move_constructible<Ex2>::value << '\n'
              << "Ex2 is nothrow move-constructible? "
              << std::is_nothrow_move_constructible<Ex2>::value << '\n';
 
    std::cout << std::boolalpha
              << "NoMove is move-constructible? "
              << std::is_move_constructible<NoMove>::value << '\n'
              << "NoMove is nothrow move-constructible? "
              << std::is_nothrow_move_constructible<NoMove>::value << '\n';
}

二次

产出：

二次

Ex1 is move-constructible? true
Ex1 is trivially move-constructible? false
Ex1 is nothrow move-constructible? true
Ex2 is trivially move-constructible? true
Ex2 is nothrow move-constructible? true
NoMove is move-constructible? true
NoMove is nothrow move-constructible? false

二次

另见

is_constructibleis_trivially_constructibleis_nothrow_constructible (C++11)(C++11)(C++11)	checks if a type has a constructor for specific arguments (class template)
is_default_constructibleis_trivially_default_constructibleis_nothrow_default_constructible (C++11)(C++11)(C++11)	checks if a type has a default constructor (class template)
is_copy_constructibleis_trivially_copy_constructibleis_nothrow_copy_constructible (C++11)(C++11)(C++11)	checks if a type has a copy constructor (class template)
move_if_noexcept (C++11)	obtains an rvalue reference if the move constructor does not throw (function template)

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