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
.
T | - | a type to check |
template< class T > inline constexpr bool is_scalar_v = is_scalar<T>::value; | (since C++17) |
value
[static] | true if T is a scalar type , false otherwise (public static member constant) |
operator bool | converts the object to bool , returns value (public member function) |
operator()
(C++14) | returns value (public member function) |
Type | Definition |
---|---|
value_type | bool |
type | std::integral_constant<bool, value> |
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.
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> {}; |
#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
(C++11) | checks if a type is an arithmetic type (class template) |
(C++11) | checks if a type is an enumeration type (class template) |
(C++11) | checks if a type is a pointer type (class template) |
(C++11) | checks if a type is a pointer to an non-static member function or object (class template) |
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