< cpp‎ | types
Type support
Basic types
Fundamental types
Fixed width integer types (C++11)
Numeric limits
C numeric limits interface
Runtime type information
Type traits
Type categories
Type properties
(C++11)(until C++20)
(C++11)(deprecated in C++20)
Type trait constants
Constant evaluation context
Supported operations
Relationships and property queries
Type modifications
Type transformations
(C++11)(until C++20)(C++17)
Defined in header <type_traits>
template< class T >
struct is_scalar;
(since C++11)

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.

The behavior of a program that adds specializations for is_scalar or is_scalar_v (since C++17) is undefined.


[edit] Template parameters

T - a type to check

[edit] Helper variable template

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

Inherited from std::integral_constant

Member constants

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

Member functions

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

Member types

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

[edit] 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.

[edit] 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> {};

[edit] Example

#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';


T is a scalar
T is not a scalar

[edit] See also

checks if a type is an arithmetic type
(class template) [edit]
checks if a type is an enumeration type
(class template) [edit]
checks if a type is a pointer type
(class template) [edit]
checks if a type is a pointer to an non-static member function or object
(class template) [edit]