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In programming languages and type theory, polymorphism (from Greek πολύς, polys, "many, much" and μορφή, morphē, "form, shape") is the provision of a single interface to entities of different types.〔 〕 A polymorphic type is one whose operations can also be applied to values of some other type, or types.〔: "Polymorphic types are types whose operations are applicable to values of more than one type."〕 There are several fundamentally different kinds of polymorphism: * ''Ad hoc polymorphism'': when a function denotes different and potentially heterogeneous implementations depending on a limited range of individually specified types and combinations. Ad hoc polymorphism is supported in many languages using function overloading. * ''Parametric polymorphism'': when code is written without mention of any specific type and thus can be used transparently with any number of new types. In the object-oriented programming community, this is often known as ''generics'' or ''generic programming''. In the functional programming community, this is often shortened to ''polymorphism''. * ''Subtyping'' (also called ''subtype polymorphism'' or ''inclusion polymorphism''): when a name denotes instances of many different classes related by some common superclass.〔Booch, et all 2007 ''Object-Oriented Analysis and Design with Applications.'' Addison-Wesley.〕 In the object-oriented programming community, this is often simply referred to as ''polymorphism''. The interaction between parametric polymorphism and subtyping leads to the concepts of variance and bounded quantification. ==History== Ad hoc polymorphism and parametric polymorphism were originally described in ''Fundamental Concepts in Programming Languages'', a set of lecture notes written in 1967 by British computer scientist Christopher Strachey.〔C. Strachey - ''Fundamental Concepts in Programming Languages'' http://www.itu.dk/courses/BPRD/E2009/fundamental-1967.pdf〕 In a 1985 paper, Peter Wegner and Luca Cardelli introduced the term ''inclusion polymorphism'' to model subtypes and inheritance.〔 However, implementations of subtyping and inheritance predate the term "inclusion polymorphism", having appeared with Simula in 1967. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Polymorphism (computer science)」の詳細全文を読む スポンサード リンク
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