In computer science, a type class is a type system construct that supports ad-hoc polymorphism. This is achieved by adding constraints to type variables in parametrically polymorphic types. Such a constraint typically involves a type class T and a type variable a, and means that a can only be instantiated to a type whose members support the overloaded operations associated with T.
Type classes first appeared in the Haskell programming language, and were originally conceived as a way of implementing overloaded arithmetic and equality operators in a principled fashion. In contrast with the "eqtypes" of Standard ML, overloading the equality operator through the use of type classes in Haskell does not require extensive modification of the compiler frontend or the underlying type system.
Since their creation, many other applications of type classes have been discovered.
Read more about Type Class: Overview, Higher-kinded Polymorphism, Multi-parameter Type Classes, Functional Dependencies, Other Approaches To Operator Overloading, Related Notions
Famous quotes containing the words type and/or class:
“The more characteristic American hero in the earlier day, and the more beloved type at all times, was not the hustler but the whittler.”
—Mark Sullivan (1874–1952)
“I read, with a kind of hopeless envy, histories and legends of people of our craft who “do not write for money.” It must be a pleasant experience to be able to cultivate so delicate a class of motives for the privilege of doing one’s best to express one’s thoughts to people who care for them. Personally, I have yet to breathe the ether of such a transcendent sphere. I am proud to say that I have always been a working woman, and always had to be ...”
—Elizabeth Stuart Phelps (1844–1911)