std::is_nothrow_constructible in C++ with Examples

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

Header File:

#include<type_traits>

Template Class:

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

Syntax:

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

Parameter: The template std::is_nothrow_constructible accepts the following parameters:

• T: It represent a data type.
• Args: It represent the list of data type T.

Return Value: The template std::is_nothrow_constructible returns a boolean variable as shown below:

• True: If the type T is constructible from Args.
• False: If the type T is not constructible from Args.

Below is the program to demonstrate std::is_nothrow_constructible in C++:

Program 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;
}

Output:

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

Program 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';
}

Output:

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

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