##### cppreference.com

##### Search

Create account

##### Namespaces

- Page
- Discussion

##### Variants

##### Views

- View
- Edit
- History

##### Actions

# std::is_same

From cppreference.com
< cpp‎ | types

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

If `T` and `U` name the same type with the same const-volatile qualifications, provides the member constant `value` equal to true. Otherwise `value` is false.

### [edit] Helper variable template

template< class T, class U > inline constexpr bool is_same_v = is_same<T, U>::value; |  | (since C++17)

[edit]

## 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>

### [edit] Possible implementation

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

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

### [edit] Example

Run this code

    #include <iostream>
    #include <type_traits>
    #include <cstdint>

    void print_separator()
    {
        std::cout << "-----\n";
    }

    int main()
    {
        std::cout << std::boolalpha;

        std::cout << std::is_same<int, int32_t>::value << '\n';   // true
        std::cout << std::is_same<int, int64_t>::value << '\n';   // false
        std::cout << std::is_same<float, int32_t>::value << '\n'; // false

        print_separator();

        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 not 'unsigned' and not '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
    }

Output:

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

### [edit] See also

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

Retrieved from "http://en.cppreference.com/mwiki/index.php?title=cpp/types/is_same&oldid=90985"