View source for Functional programming

In [[computer science]], '''functional programming''' is a [[programming paradigm]] that treats [[computation]] as the [[evaluation]] of [[Function (mathematics)|mathematical functions]] and avoids changing-[[State (computer science)|state]] and [[Immutable object|mutable data]].

== Description ==

It uses a [[Declarative programming|declarative programming paradigm]]:  programming is done with [[Expression (computer science)|expressions]].

== Depends only on the arguments ==
In functional code, the [[Computing (output)|output value]] of a [[Function (mathematics)|function]] depends only on the [[arguments]] that are [[Input (computing)|input]] to the function

Therefore calling a function f twice with the same value for an argument x will produce the same result f(x) each time.

== Eliminating side effects ==

Eliminating side effects, i.e. changes in state that do not depend on the function inputs, can make it much easier to understand and predict the behavior of a program, which is one of the key motivations for the development of functional programming.

== History ==

Functional programming has its roots in [[lambda calculus]], a [[formal system]] developed in the 1930s to investigate:

* [[Computability]]
* The [[Entscheidungsproblem]]
* [[Function definition]]
* [[Function application]]
* [[Recursion]]

Many functional programming languages can be viewed as elaborations on the lambda calculus.

== Logic programming ==

Another well-known declarative programming paradigm, [[logic programming]], is based on [[relations]].

== Imperative programming ==

In contrast, [[imperative programming]] changes state with commands in the source language, the most simple example being [[assignment]].

== See also ==

* [[Comparison of programming paradigms]]
* [[Computer program]]
* [[Computer programming]]
* [[Computer science]]
* [[Declarative programming]]
* [[Eager evaluation]]
* [[Entscheidungsproblem]]
* [[Expression (computer science)]]
* [[Formal system]]
* [[Function (mathematics)]]
* [[Functional reactive programming]]
* [[Immutable object]]
* [[Lambda calculus]]
* [[Inductive functional programming]]
* [[List of functional programming topics]]
* [[Logic programming]]
* [[Nested function]]
* [[Programming paradigm]]
* [[Purely functional programming]]
* [[Recursion]]
* [[State (computer science)]]

== External links ==

* [https://en.wikipedia.org/wiki/Functional_programming Functional programming] @ Wikipedia
*[http://cryto.net/~joepie91/blog/2015/05/04/functional-programming-in-javascript-map-filter-reduce/ Functional programming in JavaScript:  Map, Filter, and Reduce] @ cryto.net

[[Category:Computer programming]]
[[Category:Computing]]
[[Category:Programming languages]]