is_base_of

Applicability

Product	Supported
Atlas A3 training products/Atlas A3 inference products	√
Atlas A2 training products/Atlas A2 inference products	√
Atlas 200I/500 A2 inference products	x
Atlas inference product's AI Core	x
Atlas inference product's Vector Core	x
Atlas training products	x

Function

Checks whether a type is a base class of another type during program building as a type characteristics tool defined in the <type_traits> header file. This API can be used in template metaprogramming, type checking, and conditional building to capture potential type errors during building, improving code robustness.

Prototype

template <typename Base, typename Derived>
struct is_base_of;

Parameters

**Table 1** Template parameters
Parameter	Description
Base	Base class type to be checked, that is, whether the Base type is the base class of the Derived type.
Derived	Derived class type to be checked, that is, whether the Base type is the base class of the Derived type.

Restrictions

None

Returns

The static constant member value of is_base_of is used to obtain the returned Boolean value. The values of is_base_of<Base, Derived>::value are as follows:

true: The Base type is a base class of Derived (including the case where Base and Derived are the same type).
false: The Base type is not a base class of Derived.

Example

class Base {};
class Derived : public Base {};
class Unrelated {};

// Derived class of virtual inheritance
class Derived2 : virtual public Base {};

// Define the derived class of virtual inheritance.
class VirtualDerived : virtual public Base {};

// Define the derived class of multiple inheritance.
class MultiDerived : public Base, public VirtualDerived {};

//Base class of the template
template <typename T>
class BaseTemplate {
public:
    T value;
};

// Derived class of the template
template <typename T>
class DerivedTemplate : public BaseTemplate<T> {};

// Check whether Base is the base class of Derived.
AscendC::PRINTF("Is Base a base of Derived? %d\n" , AscendC::Std::is_base_of<Base, Derived>::value);

// Check whether Derived is the base class of Base (the value should be false).
AscendC::PRINTF("Is Derived a base of Base? %d\n" , AscendC::Std::is_base_of<Derived, Base>::value);

// Check whether Base is the base class of Unrelated (the value should be false).
AscendC::PRINTF("Is Base a base of Unrelated? %d\n" , AscendC::Std::is_base_of<Base, Unrelated>::value);

AscendC::PRINTF("Is Base a base of Derived (virtual inheritance)? %d\n", AscendC::Std::is_base_of<Base, Derived2>::value);

AscendC::PRINTF("Is BaseTemplate<int> a base of DerivedTemplate<int>? %d\n", AscendC::Std::is_base_of<BaseTemplate<int>, DerivedTemplate<int>>::value);

// Check whether Base is the base class of VirtualDerived (virtual inheritance).
AscendC::PRINTF("Is Base a base of VirtualDerived? %d\n" , AscendC::Std::is_base_of<Base, VirtualDerived>::value);
// Check whether Base is the base class of MultiDerived (multiple inheritance).
AscendC::PRINTF("Is Base a base of MultiDerived? %d\n" , AscendC::Std::is_base_of<Base, MultiDerived>::value);

// Execution result:
Is Base a base of Derived? 1
Is Derived a base of Base? 0
Is Base a base of Unrelated? 0
Is Base a base of Derived (virtual inheritance)? 1
Is BaseTemplate<int> a base of DerivedTemplate<int>? 1
Is Base a base of VirtualDerived? 1
Is Base a base of MultiDerived? 1

Parent topic: Type Traits