# functor

Also found in: Dictionary, Acronyms, Wikipedia.

## functor

[′fəŋk·tər] (computer science)

(mathematics)

A function between categories which associates objects with objects and morphisms with morphisms.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

## functor

In category theory, a functor F is an operator on types. F
is also considered to be a polymorphic operator on functions
with the type

F : (a -> b) -> (F a -> F b).

Functors are a generalisation of the function "map". The type operator in this case takes a type T and returns type "list of T". The map function takes a function and applies it to each element of a list.

F : (a -> b) -> (F a -> F b).

Functors are a generalisation of the function "map". The type operator in this case takes a type T and returns type "list of T". The map function takes a function and applies it to each element of a list.

This article is provided by FOLDOC - Free Online Dictionary of Computing (

**foldoc.org**)Want to thank TFD for its existence? Tell a friend about us, add a link to this page, or visit the webmaster's page for free fun content.

Link to this page: