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C++ std::is_nothrow_constructible用法及代碼示例


<type_traits>頭文件中提供了C++ STL的std::is_nothrow_constructible模板。 C++ STL的std::is_nothrow_constructible模板用於檢查給定類型T是否是帶有參數集的可構造類型,並且眾所周知,它不會引發任何異常。如果T為可構造類型,則返回布爾值true,否則返回false。

頭文件:

#include<type_traits>

模板類別:

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

用法:

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

參數:模板std::is_nothrow_constructible接受以下參數:



  • T:它代表一種數據類型。
  • Args:它表示數據類型T的列表。

返回值:模板std::is_nothrow_constructible返回一個布爾變量,如下所示:

  • True:如果類型T是可從Args構造的。
  • False:如果T類型無法從Args構造。

下麵是演示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; 
}
輸出:
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'; 
}
輸出:
GfG is Nothrow-constructible from int? false
GfG is Nothrow-constructible from int and float? true
GfG is Nothrow-constructible from struct X? false

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




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注:本文由純淨天空篩選整理自bansal_rtk_大神的英文原創作品 std::is_nothrow_constructible in C++ with Examples。非經特殊聲明,原始代碼版權歸原作者所有,本譯文未經允許或授權,請勿轉載或複製。