std::derived_from

 

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Concepts library

Core language concepts same_as (C++20) derived_from (C++20) convertible_to (C++20) common_reference_with (C++20) common_with (C++20) integral (C++20) signed_integral (C++20) unsigned_integral (C++20) floating_point (C++20) swappableswappable_with (C++20)(C++20) destructible (C++20) constructible_from (C++20) default_initializable (C++20)   move_constructible (C++20) copy_constructible (C++20) assignable_from (C++20)

Comparison concepts equality_comparableequality_comparable_with (C++20)(C++20) totally_orderedtotally_ordered_with (C++20)(C++20) Object concepts movable (C++20) copyable (C++20) semiregular (C++20) regular (C++20) Callable concepts invocableregular_invocable (C++20)(C++20) predicate (C++20) relation (C++20) equivalence_relation (C++20) strict_weak_order (C++20)

Exposition-only concepts boolean-testable  (C++20)

 

Defined in header <concepts>
template< class Derived, class Base > concept derived_from =     std::is_base_of_v<Base, Derived> &&     std::is_convertible_v<const volatile Derived*, const volatile Base*>;		(since C++20)

The concept derived_from<Derived, Base> is satisfied if and only if Base is a class type that is either Derived or a public and unambiguous base of Derived, ignoring cv-qualifiers.

Note that this behavior is different to std::is_base_of when Base is a private or protected base of Derived.

Example

Run this code

#include <concepts>
 
class A {};
 
class B : public A {};
 
class C : private A {};
 
/ std::derived_from == true only for public inheritance or exact same class
static_assert(std::derived_from<B, B> == true);      / same class: true
static_assert(std::derived_from<int, int> == false); / same primitive type: false
static_assert(std::derived_from<B, A> == true);      / public inheritance: true
static_assert(std::derived_from<C, A> == false);     / private inheritance: false
 
/ std::is_base_of == true also for private inheritance
static_assert(std::is_base_of_v<B, B> == true);      / same class: true
static_assert(std::is_base_of_v<int, int> == false); / same primitive type: false
static_assert(std::is_base_of_v<A, B> == true);      / public inheritance: true
static_assert(std::is_base_of_v<A, C> == true);      / private inheritance: true
 
int main() {}

References

• C++23 standard (ISO/IEC 14882:2024):

• 18.4.3 Concept derived_from [concept.derived]

• C++20 standard (ISO/IEC 14882:2020):

• 18.4.3 Concept derived_from [concept.derived]

See also

is_base_of (C++11)	checks if a type is a base of the other type (class template)
is_convertibleis_nothrow_convertible (C++11)(C++20)	checks if a type can be converted to the other type (class template)

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