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The inheritance hierarchy of an object is fixed at instantiation when the object's type is selected and does not change with time. For example, the inheritance graph does not allow a Student object to become an Employee object while retaining the state of its Person superclass.
The C++ examples in this section demonstrate the principle of using composition and interfaces to achieve code reuse and polymorphism. Due to the C++ language not having a dedicated keyword to declare interfaces, the following C++ example uses inheritance from a pure abstract base class.
It is sometimes called "Upside-Down Inheritance" [5] [6] due to the way it allows class hierarchies to be extended by substituting different base classes. The Microsoft Implementation of CRTP in Active Template Library (ATL) was independently discovered, also in 1995, by Jan Falkin, who accidentally derived a base class from a derived class.
A good example of the has-a relationship is containers in the C++ STL. To summarize the relations, we have hypernym-hyponym (supertype-subtype) relations between types (classes) defining a taxonomic hierarchy, where for an inheritance relation: a hyponym (subtype, subclass) has a type-of (is-a) relationship with its hypernym (supertype ...
The concept of class hierarchy in computer science is very similar to taxonomy, the classifications of species. The relationships are specified in the science of object-oriented design and object interface standards defined by popular use, language designers ( Java , C++ , Smalltalk , Visual Prolog ) and standards committees for software design ...
The singly rooted hierarchy, in object-oriented programming, is a characteristic of most (but not all) OOP-based programming languages.In most such languages, in fact, all classes inherit directly or indirectly from a single root, usually with a name similar to Object; all classes then form a common inheritance hierarchy.
Multiple inheritance is a feature of some object-oriented computer programming languages in which an object or class can inherit features from more than one parent object or parent class. It is distinct from single inheritance, where an object or class may only inherit from one particular object or class.
The g++ compiler implements the multiple inheritance of the classes B1 and B2 in class D using two virtual method tables, one for each base class. (There are other ways to implement multiple inheritance, but this is the most common.) This leads to the necessity for "pointer fixups", also called thunks, when casting. Consider the following C++ code: