类模板
<type_traits>
std::is_nothrow_assignable
template <class T, class U> struct is_nothrow_assignable;
Is assignable throwing no exceptions
Trait class that identifies whether U is a type assignable to T, and such operation is known not to throw any exception.
模板参数
- T, U
- 完整类型，或void（可能带 cv 限定），或者一个未知边界的数组。
示例
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// is_nothrow_assignable example
#include <iostream>
#include <type_traits>
struct A { };
struct B {
B& operator= (const A&) noexcept {return *this;}
B& operator= (const B&) {return *this;}
};
int main() {
std::cout << std::boolalpha;
std::cout << "is_nothrow_assignable:" << std::endl;
std::cout << "A=A: " << std::is_nothrow_assignable<A,A>::value << std::endl;
std::cout << "B=A: " << std::is_nothrow_assignable<B,A>::value << std::endl;
std::cout << "B=B: " << std::is_nothrow_assignable<B,B>::value << std::endl;
return 0;
}
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输出
is_nothrow_assignable:
A=A: true
B=A: true
B=B: false
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