std::is_abstract (3) Linux Manual Page

std::is_abstract – std::is_abstract

Synopsis

Defined in header<type_traits>

    template <class T>
    (since C++ 11)

        struct is_abstract;

If T is an abstract_class (that is, a non-union class that declares or inherits at least one pure virtual function), provides the member constant value equal true. For any other type, value is false.
If T is a non-union class type, T shall be a complete type; otherwise, the behavior is undefined.

Template parameters

T – a type to check

Helper variable template

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

Inherited from std::integral_constant

Member constants

value true if T is an abstract_class 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>

Example

// Run this code

#include <iostream>

#include <type_traits>
struct A {
    int m;
};
struct B {
    virtual void foo();
};
struct C {
    virtual void foo() = 0;
};
struct D : C {
};
int main()

{
    std::cout << std::boolalpha;
    std::cout << std::is_abstract<A>::value << '\n';
    std::cout << std::is_abstract<B>::value << '\n';
    std::cout << std::is_abstract<C>::value << '\n';
    std::cout << std::is_abstract<D>::value << '\n';
}

Output:

  false
  false
  true
  true

See also

is_class checks if a type is a non-union class type
               (class template)
(C++11)
is_polymorphic checks if a type is a polymorphic class type
               (class template)
(C++11)