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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.
In programming language theory, subtyping (also called subtype polymorphism or inclusion polymorphism) is a form of type polymorphism.A subtype is a datatype that is related to another datatype (the supertype) by some notion of substitutability, meaning that program elements (typically subroutines or functions), written to operate on elements of the supertype, can also operate on elements of ...
C++ template functions exhibit structural typing on type arguments. Haxe uses structural typing, but classes are not structurally subtyped. In languages which support subtype polymorphism, a similar dichotomy can be formed based on how the subtype relationship is defined.
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 .
Another example is C++ RTTI. More generally, most programming languages include mechanisms for dispatching over different 'kinds' of data, such as disjoint unions, runtime polymorphism, and variant types. Even when not interacting with type annotations or type checking, such mechanisms are materially similar to dynamic typing implementations.
In object-oriented programming, polymorphism more specifically refers to subtyping or subtype polymorphism, where a function can work with a specific interface and thus manipulate entities of different classes in a uniform manner. [61] For example, imagine a program has two shapes: a circle and a square. Both come from a common class called ...
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. The TypeScript, [6] Elm [7] and Python [8] languages support structural typing to varying ...
Polymorphism (computer science), the ability in programming to present the same programming interface for differing underlying forms; Ad hoc polymorphism, applying polymorphic functions to arguments of different types; Parametric polymorphism, abstracts types, so that multiple can be used with a single implementation