#include <type_traits>

template <class T>
struct is_default_constructible;

std::is_default_constructible<class T>::value

// C++ program to illustrate
// std::is_default_constructible
#include <bits/stdc++.h>
#include <type_traits>
using namespace std;
  
// Declare structures
struct A {
};
  
struct B {
    int n;
    B() = default;
};
  
// Class
class classA {
    ~classA() = delete;
};
  
// Inherited class
class classB : classA {
};
  
// Driver Code
int main()
{
    cout << boolalpha;
  
    // Check if int is default constructible?
    cout << "int : "
         << is_default_constructible<int>::value
         << endl;
  
    // Check if struct A is default constructible?
    cout << "struct A: "
         << is_default_constructible<A>::value
         << endl;
  
    // Check if struct B is default constructible?
    cout << "struct B: "
         << is_default_constructible<B>::value
         << endl;
  
    // Check if classA is default constructible?
    cout << "classA: "
         << is_default_constructible<classA>::value
         << endl;
  
    // Check if classB is default constructible?
    cout << "classB: "
         << is_default_constructible<classB>::value
         << endl;
  
    return 0;
}

int : true
struct A: true
struct B: true
classA: false
classB: false