Explain Object Oriented Computer Program Development Techniques - amazonia.fiocruz.br

Explain Object Oriented Computer Program Development Techniques Video

In programming languages and type theorypolymorphism is the provision of a single interface to entities of different types [1] or the use of a single symbol to represent multiple different types.

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Interest in polymorphic type systems developed significantly in the s, with practical implementations beginning to appear by the end of the decade. Ad hoc polymorphism and parametric polymorphism were originally described in Christopher Strachey 's Fundamental Concepts in Here Languages [4]where they are listed as "the two main classes" of polymorphism.

Ad hoc polymorphism was a feature of Algol 68while parametric polymorphism was the core feature of ML 's type system. Https://amazonia.fiocruz.br/scdp/blog/gregorys-punctuation-checker-tool/disadvantages-of-chemotherapy.php a paper, Peter Wegner and Luca Cardelli introduced the term inclusion polymorphism to model subtypes Orriented inheritance[2] citing Simula as the first programming language to implement it.

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Christopher Strachey chose the term ad hoc polymorphism to refer to polymorphic functions that can be applied to arguments of different types, but that behave differently depending on the type of the more info to which they are applied also known as function overloading or operator overloading. In dynamically typed languages the situation can be more complex as the correct function that needs to be invoked Explaim only be determinable at run time. Implicit type conversion has also been defined as a form of bOject, referred to as "coercion polymorphism". Parametric polymorphism allows a function or a data type click be written generically, so that it can handle values uniformly without depending on their type.

The concept of parametric polymorphism applies to both data types and functions. A function that can evaluate to or be applied to values of different types is known as a polymorphic function. A data type that can appear to be of a generalized type e.

Parametric polymorphism is ubiquitous in functional programming, where it is often simply referred to as "polymorphism". The following example in Haskell shows a parameterized list data type and two parametrically polymorphic functions on them:. Parametric polymorphism is also available in several object-oriented languages. John C. Reynolds and later Jean-Yves Girard formally developed this notion of polymorphism as an extension to lambda calculus called the polymorphic lambda calculus or System F. Any parametrically polymorphic function is necessarily restricted in what it can do, working on the shape of the data instead of its value, leading to the concept of parametricity. Teechniques

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Some languages employ the idea of subtyping also called subtype polymorphism or inclusion polymorphism to restrict the range of types that can be used in a particular case of polymorphism. In these languages, subtyping allows a function to be written to take an object of a certain type Tbut also work correctly, if passed an object that belongs to a type S that is a subtype of T according to the Liskov substitution principle. Subtype polymorphism is usually resolved dynamically see below. In the following example we make cats and dogs subtypes of animals. The procedure letsHear accepts an animal, but will also work correctly if a subtype is passed to it:.

The actual type of the object can be hidden from clients into a black boxand accessed via object identity.

In fact, if the Number type is abstractit may not even be possible to get your hands on an object whose most-derived type is Number see abstract data typeabstract class. This particular kind of type hierarchy is known—especially in the context of the Scheme programming language —as a numerical towerand usually contains many more types.

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Object-oriented programming languages offer subtype polymorphism using subclassing also known as inheritance. In typical implementations, each class contains what is called a virtual table —a table of functions that implement the polymorphic part of the class interface—and each object contains a pointer to the "vtable" of its class, which is then consulted whenever a polymorphic method is called. This mechanism is an example of:.]