std::is_same(3)

NAME
std::is_same - std::is_same

Synopsis
   Defined in header <type_traits>
   template< class T, class U > (since C++11)
   struct is_same;
   If T and U name the same type (taking into account 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.
   The behavior of a program that adds specializations for is_same
   or is_same_v
   (since C++17) is undefined.
  Helper variable template
   template< class T, class U > (since C++17)
   inline constexpr bool is_same_v = is_same<T, U>::value; Inherited from std::integral_constant

Member constants
   value true if T and U are the same type , false otherwise
   [static] (public static member constant)

Member functions
   operator bool converts the object to bool, returns value
                 (public member function)
   operator() returns value
   (C++14) (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
     // usually true if 'int' is 32 bit
     std::cout << std::is_same<int, std::int32_t>::value << ' '; // ~ true
     // possibly true if ILP64 data model is used
     std::cout << std::is_same<int, std::int64_t>::value << ' '; // ~ false
     // same tests as above, except using C++17's `std::is_same_v<T, U>` format
     std::cout << std::is_same_v<int, std::int32_t> << ' '; // ~ true
     std::cout << std::is_same_v<int, std::int64_t> << '\n'; // ~ false
     print_separator();
     // compare the types of a couple variables
     long double num1 = 1.0;
     long double num2 = 2.0;
     std::cout << std::is_same_v<decltype(num1), decltype(num2)> << '\n'; // true
     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 << ' '; // true
     std::cout << std::is_same<int, unsigned int>::value << ' '; // 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 << ' '; // true
     std::cout << std::is_same<char, unsigned char>::value << ' '; // false
     std::cout << std::is_same<char, signed char>::value << '\n'; // false
     // const-qualified type T is not same as non-const T
     static_assert( not std::is_same<const int, int>() );
 }

Possible output:
 true false true false
 -----
 true
 -----
 false
 -----
 true false true
 -----
 true false false

See also
   same_as specifies that a type is the same as another type
   (C++20) (concept)
   decltype specifier(C++11) obtains the type of an expression or an entity