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Impredicative polymorphism (also called first-class polymorphism) is the most powerful form of parametric polymorphism. [1]: 340 In formal logic, a definition is said to be impredicative if it is self-referential; in type theory, it refers to the ability for a type to be in the domain of a quantifier it contains. This allows the instantiation ...
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.
Roberts (p. 171) gives a related example in Java, using a Class to represent a stack frame. The example given is a solution to the Tower of Hanoi problem wherein a stack simulates polymorphic recursion with a beginning, temporary and ending nested stack substitution structure. [5]
In addition to providing data-driven algorithm-determined parameters across virtual network interfaces, [1] it also allows for a specific type of polymorphism . The implementation in the subclass overrides (replaces) the implementation in the superclass by providing a method that has same name, same parameters or signature, and same return type ...
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.
It can still be referred to, and its other properties can be accessed via its external behaviour associated with the identity. The identity provides a mechanism for referring to such parts of the object that are not exposed in the interface. Thus, identity is the basis for polymorphism in object-oriented programming.
Polymorphism is an ideology that follows with the object oriented programming paradigm, where methods can be overridden or overloaded (methods with the same name in a child class which will take priority over a method written in a parent class). The definition of methods is based on a skeleton framework defined by the syntax of the language. [9]
For example, in the GHC standard library, the class IArray expresses a general immutable array interface. In this class, the type class constraint IArray a e means that a is an array type that contains elements of type e. (This restriction on polymorphism is used to implement unboxed array types, for example.)