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Polymorphism can be distinguished by when the implementation is selected: statically (at compile time) or dynamically (at run time, typically via a virtual function). This is known respectively as static dispatch and dynamic dispatch, and the corresponding forms of polymorphism are accordingly called static polymorphism and dynamic polymorphism.
[citation needed] Examples of strictly object-based languages – supporting an object feature but not inheritance or subtyping – are early versions of Ada, [2] Visual Basic 6 (VB6), and Fortran 90. Some classify prototype-based programming as object-based even though it supports inheritance and subtyping albeit not via a class concept.
Liskov's notion of a behavioural subtype defines a notion of substitutability for objects; that is, if S is a subtype of T, then objects of type T in a program may be replaced with objects of type S without altering any of the desirable properties of that program (e.g. correctness).
This technique achieves a similar effect to the use of virtual functions, without the costs (and some flexibility) of dynamic polymorphism. This particular use of the CRTP has been called "simulated dynamic binding" by some. [10] This pattern is used extensively in the Windows ATL and WTL libraries.
Duck typing is similar to, but distinct from, structural typing.Structural typing is a static typing system that determines type compatibility and equivalence by a type's structure, whereas duck typing is dynamic and determines type compatibility by only that part of a type's structure that is accessed during runtime.
Some languages like Go do not support inheritance at all. Go states that it is object-oriented, [37] and Bjarne Stroustrup, author of C++, has stated that it is possible to do OOP without inheritance. [38] The doctrine of composition over inheritance advocates implementing has-a relationships using composition instead of inheritance. For ...
In computer science, dynamic dispatch is the process of selecting which implementation of a polymorphic operation (method or function) to call at run time.It is commonly employed in, and considered a prime characteristic of, object-oriented programming (OOP) languages and systems.
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.