std::is_same template in C++ with Examples

The std::is_same template of C++ STL is present in the <type_traits> header file. The std::is_same template of C++ STL is used to check whether the type A is same type as of B or not. It return the boolean value true if both are same, otherwise return false.

Header File:

#include<type_traits>

Template Class:

template <class A, class B>
struct is_same

template <class A, class B>
inline constexpr 
       bool is_same_v
         = is_same<A, B>::value

Syntax:

std::is_same<A, B>::value

Parameters: This std::is_same template accepts the following parameters:

• A: It represent the first type.
• B: It represent the second type.

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

• True: If the type A is same as the type B.
• False: If the type A is not same as the type B.

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

Program:

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

// Driver Code
int main()
{

    cout << boolalpha;

    cout << "is int & int32_t is same? "
         << is_same<int, int32_t>::value
         << endl;

    cout << "is int & int64_t is same? "
         << is_same<int, int64_t>::value
         << endl;

    cout << "is float & int32_t is same? "
         << is_same<float, int32_t>::value
         << endl;

    cout << "is int & int is same? "
         << is_same<int, int>::value << endl;
    cout << "is int & unsigned int is same? "
         << is_same<int, unsigned int>::value
         << endl;

    cout << "is int & signed int is same? "
         << is_same<int, signed int>::value
         << endl;

    return 0;
}

Output:

is int & int32_t is same? true
is int & int64_t is same? false
is float & int32_t is same? false
is int & int is same? true
is int & unsigned int is same? false
is int & signed int is same? true

Program 2:

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

typedef int integer_type;

// Declare structures
struct A {
    int x, y;
};
struct B {
    int x, y;
};
typedef A C;

// Driver Code
int main()
{

    cout << boolalpha;

    cout << "is_same:" << endl;
    cout << "int, const int is_same: "
         << is_same<int, const int>::value
         << endl;

    cout << "int, integer_type is_same: "
         << is_same<int, integer_type>::value
         << endl;

    cout << "A, B is_same: "
         << is_same<A, B>::value
         << endl;

    cout << "A, C is_same: "
         << is_same<A, C>::value
         << endl;

    cout << "signed char, int8_t is_same: "
         << is_same<signed char, int8_t>::value
         << endl;

    return 0;
}

Output:

is_same:
int, const int is_same: false
int, integer_type is_same: true
A, B is_same: false
A, C is_same: true
signed char, int8_t is_same: true

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