std::is_same
From cppreference.com
| Defined in header <type_traits>
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| 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
Run this code
#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
See also
| (C++11) |
checks if a type is an integral type (class template) |
| (C++11) |
makes the given integral type signed (class template) |
| (C++11) |
makes the given integral type unsigned (class template) |