Programming Language Support For Genericity
Genericity facilities have existed in high-level languages since at least the 1970s in languages such as CLU and Ada, and were subsequently adopted by many object-based and object-oriented languages, including BETA, C++, D, Eiffel, Java, and DEC's now defunct Trellis-Owl language. Implementations of generics in languages such as Java and C# are formally based on the notion of parametricity, due to John C. Reynolds.
Genericity is implemented and supported differently in various programming languages; the term "generic" has also been used differently in various programming contexts. For example, in Forth the compiler can execute code while compiling and one can create new compiler keywords and new implementations for those words on the fly. It has few words that expose the compiler behaviour and therefore naturally offers genericity capacities which, however, are not referred to as such in most Forth texts. The term has been used in functional programming, specifically in Haskell-like languages, which use a structural type system where types are always parametric and the actual code on those types is generic. These usages still serve a similar purpose of code-saving and the rendering of an abstraction.
Arrays and structs can be viewed as predefined generic types. Every usage of an array or struct type instantiates a new concrete type, or reuses a previous instantiated type. Array element types and struct element types are parameterized types, which are used to instantiate the corresponding generic type. All this is usually built-in in the compiler and the syntax differs from other generic constructs. Some extensible programming languages try to unify built-in and user defined generic types.
A broad survey of genericity mechanisms in programming languages follows. For a specific survey comparing suitability of mechanisms for generic programming, see.
Read more about this topic: Generic Programming
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