| 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.
Helper variable template
template< class T, class U > 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;
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
See also
| (C++11) | checks if a type is integral type (class template) |
| (C++11) | makes the given integral type signed (class template) |
| (C++11) | makes the given integral type unsigned (class template) |
| std::experimental::is_same_v
(library fundamentals TS) | variable template alias of std::is_same::value (variable template) |
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