std::is_same template in C++ with Examples - GeeksforGeeks

08 Jun, 2020
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 Codeint 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;}
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 structuresstruct A {    int x, y;};struct B {    int x, y;};typedef A C;  // Driver Codeint 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;}
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/
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