# std::is_scalar

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< cpp‎ | types

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.

### Template parameters

T | - | a type to check

### 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

value [static] | 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)
operator() (C++14) | returns `value` (public member function)

### 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 (C++11) | checks if a type is an arithmetic type (class template)
is_enum (C++11) | checks if a type is an enumeration type (class template)
is_pointer (C++11) | checks if a type is a pointer type (class template)
is_member_pointer (C++11) | checks if a type is a pointer to an non-static member function or object (class template)

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