Iteration

: This article discusses a concept which is exploited in computer programming (but which originated before it). For use in the Japanese and Chinese languages see iteration mark.

Iteration is the repetition of a Process, typically within a computer program. It can be used both as a general term, synonymous with repetition, and to describe a specific form of repetition with a Mutable object state.

When used in the first sense, Recursion is an example of iteration , but typically using a recursive notation , which is typically not the case for iteration .

However, when used in the second (more restricted) sense, iteration describes the style of programming used in imperative programming languages. This contrasts with recursion, which has a more declarative approach. Here an example of iteration, in imperative Pseudocode:

var i, a := 0 // initialize a before iteration for i from 1 to 3 { // loop three times a := a + i // increment a by the current value of i } print a // the number 6 is printed

In this program fragment, the value of the variable i changes over time, taking the values 1, 2 and 3. This changing value—or mutable state —is characteristic of iteration.

Iteration can be done in functional programming languages. The following example is in Scheme programming language:

(define (sum n) (define (iter n i) (if (= n 0) i (iter (- n 1)(+ n i)) )) (iter n 1))

An Iterator is an object that wraps iteration.

=See also=

*Iterative method *Iterator *For loop *While loop