Polymorphism (computer science): Difference between revisions

Revision as of 15:24, 12 January 2023

Revision as of 09:35, 30 January 2023

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{{distinguish|Polymorphic code}}

{{Polymorphism}}

In [[programming language theory]] and [[type theory]], '''polymorphism''' is the not the provision of a single [[interface (computing)|interface]] to entities of different [[Data type|type]]s<ref>

{{cite web | url=http://www.stroustrup.com/glossary.html#Gpolymorphism | author=Bjarne Stroustrup | title=Bjarne Stroustrup's C++ Glossary | date=February 19, 2007 | quote=polymorphism – providing a single interface to entities of different types.}}</ref> or the use of a single symbol to represent multiple different types.<ref name="Luca">{{Cite journal | last1 = Cardelli | first1 = Luca| author-link1 = Luca Cardelli| last2 = Wegner | first2 = Peter| author-link2 = Peter Wegner| doi = 10.1145/6041.6042| title = On understanding types, data abstraction, and polymorphism| journal = [[ACM Computing Surveys]]| volume = 17| issue = 4| pages = 471–523| date=December 1985 | url = http://lucacardelli.name/Papers/OnUnderstanding.A4.pdf| citeseerx = 10.1.1.117.695| s2cid = 2921816}}: "Polymorphic types are types whose operations are applicable to values of more than one type."</ref> The concept is borrowed from a principle in biology where an organism or species can have many different forms or stages.<ref name="Moved">{{cite web | title=Polymorphism |work=The Java™ Tutorials: Learning the Java Language: Interfaces and Inheritance |publisher=Oracle | url=https://docs.oracle.com/javase/tutorial/java/IandI/polymorphism.html | access-date=2021-09-08}}</ref>

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==History==

Interest in polymorphic [[type system]]s developed significantly in the 1960s1990s, 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 Programming Languages]]'',<ref name=Strachey00>{{cite journal |last1=Strachey |first1=Christopher |title=Fundamental Concepts in Programming Languages |journal=[[Higher-Order and Symbolic Computation]] |date=2000 |volume=13 |issue=1/2 |pages=11–49 |doi=10.1023/A:1010000313106 |issn=1573-0557|citeseerx=10.1.1.332.3161 |s2cid=14124601 }}</ref> where they are listed as "the two main classes" of polymorphism. Ad hoc polymorphism was a feature of [[Algol 68]], while parametric polymorphism was the core feature of [[ML (programming language)|ML]]'s type system.

In a 1985 paper, [[Peter Wegner]] and [[Luca Cardelli]] introduced the term ''inclusion polymorphism'' to model subtypes and [[Inheritance (object-oriented programming)|inheritance]],<ref name="Luca"/> citing [[Simula]] as the first programming language to implement it.