C++ std::is_nothrow_constructible用法及代码示例

<type_traits>头文件中提供了C++ STL的std::is_nothrow_constructible模板。 C++ STL的std::is_nothrow_constructible模板用于检查给定类型T是否是带有参数集的可构造类型，并且众所周知，它不会引发任何异常。如果T为可构造类型，则返回布尔值true，否则返回false。

头文件：

#include<type_traits>

模板类别：

template< class T, class... Args >
struct is_nothrow_constructible;

用法:

std::is_nothrow_constructible<T, Args..>::value

参数：模板std::is_nothrow_constructible接受以下参数：

T:它代表一种数据类型。
Args:它表示数据类型T的列表。

返回值：模板std::is_nothrow_constructible返回一个布尔变量，如下所示：

True:如果类型T是可从Args构造的。
False:如果T类型无法从Args构造。

下面是演示C++中std::is_nothrow_constructible的程序：

程序1:

// C++ program to illustrate 
// std::is_nothrow_constructible 
#include <bits/stdc++.h> 
#include <type_traits> 
using namespace std; 
  
// Declare structures 
struct X { 
}; 
  
struct Y { 
    Y() {} 
    Y(X&) 
    noexcept {} 
}; 
  
struct Z { 
    int n; 
    Z() = default; 
}; 
  
// Driver Code 
int main() 
{ 
    cout << boolalpha; 
  
    cout << "int is_nothrow_constructible? "
         << is_nothrow_constructible<int>::value 
         << endl; 
  
    cout << "X() is is_nothrow_constructible? "
         << is_nothrow_constructible<X>::value 
         << endl; 
  
    cout << "Y(X) is is_nothrow_constructible? "
         << is_nothrow_constructible<Y, X>::value 
         << endl; 
  
    cout << "Z() is is_nothrow_constructible? "
         << is_nothrow_constructible<Z>::value 
         << endl; 
    return 0; 
}

输出：

int is_nothrow_constructible? true
X() is is_nothrow_constructible? true
Y(X) is is_nothrow_constructible? false
Z() is is_nothrow_constructible? true

程序2:

// C++ program to illustrate 
// std::is_nothrow_constructible 
#include <bits/stdc++.h> 
#include <type_traits> 
using namespace std; 
  
// Class GfG 
class GfG { 
    int v1; 
    float v2; 
  
public:
    GfG(int n) 
        :v1(n), v2() 
    { 
    } 
    GfG(int n, double f) noexcept:v1(n), v2(f) {} 
}; 
  
// Declare Structure 
  
struct X { 
    int n; 
    X() = default; 
}; 
  
// Driver Code 
int main() 
{ 
  
    cout << boolalpha; 
  
    cout << "GfG is Nothrow-constructible from int? "
         << is_nothrow_constructible<GfG, int>::value 
         << '\n'; 
  
    cout << "GfG is Nothrow-constructible from int and float? "
         << is_nothrow_constructible<GfG, int, float>::value 
         << '\n'; 
  
    cout << "GfG is Nothrow-constructible from struct X? "
         << is_nothrow_constructible<GfG, X>::value 
         << '\n'; 
}

输出：

GfG is Nothrow-constructible from int? false
GfG is Nothrow-constructible from int and float? true
GfG is Nothrow-constructible from struct X? false

参考：http://www.cplusplus.com/reference/type_traits/is_nothrow_constructible/

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注：本文由纯净天空筛选整理自bansal_rtk_大神的英文原创作品 std::is_nothrow_constructible in C++ with Examples。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。