std::is_scalar (3) - Linux Man Pages

std::is_scalar: std::is_scalar

NAME

std::is_scalar - std::is_scalar

Synopsis


Defined in header <type_traits>
template< class T > (since C++11)
struct is_scalar;


If T is a scalar_type (that is a possibly cv-qualified arithmetic, pointer, pointer_to_member, enumeration, or std::nullptr_t type), provides the member constant value equal true. For any other type, value is false.

Template parameters


T - a type to check


Helper variable template


template< class T > (since C++17)
inline constexpr bool is_scalar_v = is_scalar<T>::value;


Inherited from std::integral_constant

Member constants


value true if T is a scalar type , false otherwise
         (public static member constant)
[static]

Member functions


              converts the object to bool, returns value
operator bool (public member function)


operator() returns value
              (public member function)
(C++14)

Member types


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

Notes


Each individual memory location in the C++ memory model, including the hidden memory locations used by language features (e.g virtual table pointer), has scalar type (or is a sequence of adjacent bit-fields of non-zero length). Sequencing of side-effects in expression evaluation, interthread synchronization, and dependency ordering are all defined in terms of individual scalar objects.

Possible implementation


  template< class T >
  struct is_scalar : std::integral_constant<bool,
                       std::is_arithmetic<T>::value ||
                       std::is_enum<T>::value ||
                       std::is_pointer<T>::value ||
                       std::is_member_pointer<T>::value ||
                       std::is_null_pointer<T>::value> {};

Example


// Run this code


  #include <iostream>
  #include <type_traits>


  int main() {
      class cls {};
      std::cout << (std::is_scalar<int>::value
                       ? "T is a scalar"
                       : "T is not a scalar") << '\n';
      std::cout << (std::is_scalar<cls>::value
                       ? "T is a scalar"
                       : "T is not a scalar") << '\n';
  }

Output:


  T is a scalar
  T is not a scalar

See also


is_arithmetic checks if a type is an arithmetic type
                  (class template)
(C++11)


is_enum checks if a type is an enumeration type
                  (class template)
(C++11)


is_pointer checks if a type is a pointer type
                  (class template)
(C++11)


is_member_pointer checks if a type is a pointer to an non-static member function or object
                  (class template)
(C++11)