std::is_nothrow_default_constructible in C++ with Examples

The std::is_nothrow_default_constructible template of C++ STL is present in the <type_traits> header file. The std::is_nothrow_default_constructible template of C++ STL is used to check whether the given type T is default constructible type or not and this is known for not to throw any exception. It return the boolean value true if T is default constructible type, Otherwise return false.

Header File:

#include<type_traits>

Template Class:

template <class T>
struct is_nothrow_default_constructible;

Syntax:

std::is_nothrow_default_constructible::value

Parameters: The template std::is_nothrow_default_constructible accepts a single parameter T(Trait class) to check whether T is default constructible type or not.

Return Value: This template returns a boolean variable as shown below:

• True: If the type T is a is_nothrow_default_constructible.
• False: If the type T is not a is_nothrow_default_constructible.

Below is the program to illustrates the std::is_nothrow_default_constructible template in C/C++:

Program 1:

// C++ program to illustrate
// std::is_nothrow_default_constructible
#include <bits/stdc++.h>
#include <type_traits>
using namespace std;

// Declare structures
struct X {
    X(int, float){};
};

struct Y {
    Y(const Y&) {}
};

struct Z {
    int n;
    Z() = default;
};

// Driver Code
int main()
{

    cout << boolalpha;

    // Check if int is nothrow default
    // constructible or not
    cout << "int: "
         << is_nothrow_default_constructible<int>::value
         << endl;

    // Check if struct X is nothrow default
    // constructible or not
    cout << "struct X: "
         << is_nothrow_default_constructible<X>::value
         << endl;

    // Check if struct Y is nothrow default
    // constructible or not
    cout << "struct Y: "
         << is_nothrow_default_constructible<Y>::value
         << endl;

    // Check if struct Z is nothrow default
    // constructible or not
    cout << "struct Z: "
         << is_nothrow_default_constructible<Z>::value
         << endl;

    // Check if constructor X(int, float) is
    // nothrow default constructible or not
    cout << "constructor X(int, float): "
         << is_nothrow_default_constructible<X(int, float)>::value
         << endl;
    return 0;
}

Output:

int: true
struct X: false
struct Y: false
struct Z: true
constructor X(int, float): false

Reference: http://www.cplusplus.com/reference/type_traits/is_nothrow_default_constructible/