Maps As Functions
In many branches of mathematics, the term is used to mean a function with a specific property of particular importance to that branch. For instance, a "map" is a continuous function in topology, a linear transformation in linear algebra, etc.
In contrast, in category theory, "map" is often used as a synonym for morphism or arrow, thus for something more general than a function.
Some authors, such as Serge Lang, use "map" as a general term for an association of an element in the range with each element in the domain, and "function" only to refer to maps in which the range is a field.
Sets of maps of special kinds are the subjects of many important theories: see for instance Lie group, mapping class group, permutation group.
In formal logic, the term is sometimes used for a functional predicate, whereas a function is a model of such a predicate in set theory.
In the theory of dynamical systems, a map denotes an evolution function used to create discrete dynamical systems. See also Poincaré map.
A partial map is a partial function, and a total map is a total function. Related terms like domain, codomain, injective, continuous, etc. can be applied equally to maps and functions, with the same meaning. All these usages can be applied to "maps" as general functions or as functions with special properties.
Read more about this topic: Functions And Mappings
Famous quotes containing the words maps and/or functions:
“And at least you know
That maps are of time, not place, so far as the army
Happens to be concerned—the reason being,
Is one which need not delay us.”
—Henry Reed (1914–1986)
“Let us stop being afraid. Of our own thoughts, our own minds. Of madness, our own or others’. Stop being afraid of the mind itself, its astonishing functions and fandangos, its complications and simplifications, the wonderful operation of its machinery—more wonderful because it is not machinery at all or predictable.”
—Kate Millett (b. 1934)