std::is_same

Defined in header `<type_traits>`
template< class T, class U > struct is_same;		(since C++11)

If T and U name the same type (including const/volatile qualifications), provides the member constant value equal to true. Otherwise value is false.

Commutativity is satisfied, i.e. for any two types T and U, is_same<T, U>::value == true if and only if is_same<U, T>::value == true.

Helper variable template

template< class T, class U >
inline constexpr bool is_same_v = is_same<T, U>::value;

(since C++17)

Inherited from std::integral_constant

Member constants

value

[static]

true if T and U is the same type , false otherwise
(public static member constant)

Member functions

operator bool	converts the object to `bool`, returns `value` (public member function)
operator() (C++14)	returns `value` (public member function)

Member types

Type	Definition
`value_type`	`bool`
`type`	`std::integral_constant<bool, value>`

Possible implementation

template<class T, class U>
struct is_same : std::false_type {};
 
template<class T>
struct is_same<T, T> : std::true_type {};

Example

#include <iostream>
#include <type_traits>
#include <cstdint>
 
void print_separator()
{
    std::cout << "-----\n";
}
 
int main()
{
    std::cout << std::boolalpha;
 
    // some implementation-defined facts
    std::cout << std::is_same<int, std::int32_t>::value << '\n';
    // usually true if 'int' is 32 bit
    std::cout << std::is_same<int, std::int64_t>::value << '\n';
    // possibly true if ILP64 data model is used
 
    print_separator();
 
    // 'float' is never an integral type
    std::cout << std::is_same<float, std::int32_t>::value << '\n'; // false
 
    print_separator();
 
    // 'int' is implicitly 'signed'
    std::cout << std::is_same<int, int>::value << "\n";          // true
    std::cout << std::is_same<int, unsigned int>::value << "\n"; // false
    std::cout << std::is_same<int, signed int>::value << "\n";   // true
 
    print_separator();
 
    // unlike other types, 'char' is neither 'unsigned' nor 'signed'
    std::cout << std::is_same<char, char>::value << "\n";          // true
    std::cout << std::is_same<char, unsigned char>::value << "\n"; // false
    std::cout << std::is_same<char, signed char>::value << "\n";   // false
}

Possible output:

true
false
-----
false
-----
true
false
true
-----
true
false
false

is_integral (C++11)	checks if a type is an integral type (class template)
make_signed (C++11)	makes the given integral type signed (class template)
make_unsigned (C++11)	makes the given integral type unsigned (class template)