Defined in header <type_traits> template< class T >
struct is_compound; (since C++11)
If T is a compound type (that is, array, function, object pointer, function pointer, member object pointer, member function pointer, reference, class, union, or enumeration, including any cv-qualified variants), 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&