std::is_nothrow_copy_constructible in C++ with Examples

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

Header File:

#include<type_traits>

Template Class:

template <class T>
struct is_nothrow_copy_constructible

Syntax:

is_nothrow_copy_constructible<T>::value

Parameter: The template std::is_nothrow_copy_constructible accepts a single parameter T(Trait class) to check whether T is copy constructible type or not.

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

• True: If type T is a copy constructible type.
• False: If type T is not a copy constructible type.

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

Program 1:

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

// Define Classes
class X {
};

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

// Driver Code
int main()
{

    cout << boolalpha;

    // Check if int is no throw copy
    // constructible
    cout << "int: "
         << is_nothrow_copy_constructible<int>::value
         << endl;

    // Check if class X is no throw copy
    // constructible
    cout << "class X: "
         << is_nothrow_copy_constructible<X>::value
         << endl;

    // Check if class Y is no throw copy
    // constructible
    cout << "class Y: "
         << is_nothrow_copy_constructible<Y>::value
         << endl;

    return 0;
}

Output:

int: true
class X: true
class Y: false

Program 2:

// C++ program to illustrate
// std::is_nothrow_copy_constructible
#include <iostream>
#include <type_traits>
using namespace std;

// Declare structures
struct A {
};

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

struct C {
    C(const C&)
    noexcept {}
};

// Driver Code
int main()
{

    cout << boolalpha;
    cout << "is_nothrow_copy_constructible:"
         << endl;

    cout << "int is_nothrow_copy_constructible? "
         << is_nothrow_copy_constructible<int>::value
         << endl;

    cout << "A is_nothrow_copy_constructible? "
         << is_nothrow_copy_constructible<A>::value
         << endl;

    cout << "B is_nothrow_copy_constructible? "
         << is_nothrow_copy_constructible<B>::value
         << endl;

    cout << "C is_nothrow_copy_constructible? "
         << is_nothrow_copy_constructible<C>::value
         << endl;

    return 0;
}

Output:

is_nothrow_copy_constructible:
int is_nothrow_copy_constructible? true
A is_nothrow_copy_constructible? true
B is_nothrow_copy_constructible? false
C is_nothrow_copy_constructible? true

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