std::underlying_type in C++ with Example

The std::underlying_type template of C++ STL is present in the <type_traits> header file. The std::underlying_type template of C++ STL is used to get the underlying type of enum type T.

Header File:

#include<type_traits>

Template Class:

template <class T>
struct underlying_type;

Syntax:

std::underlying_type<class T>::value

Parameter: The template std::underlying_type accepts a single parameter T(Trait class).

Return Value: The template std::underlying_type return the underlying type of enum type T.

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

Program:

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

// ENUM Class GFG
enum GFG {};

// Class gfg
enum class gfg : int {};

// Driver Code
int main()
{
    bool GFG1
        = is_same<unsigned,
                  typename underlying_type<GFG>::type>::value;

    bool gfg1
        = is_same<int,
                  typename underlying_type<gfg>::type>::value;

    cout << "underlying type for 'GFG' is "
         << (GFG1 ? "unsigned" : "non-unsigned")
         << endl;

    cout << "underlying type for 'gfg' is "
         << (gfg1 ? "int" : "non-int")
         << endl;

    return 0;
}

Output:

underlying type for 'GFG' is unsigned
underlying type for 'gfg' is int

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

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