[ri-kur-zhuh
n] 
| the process of defining a function or calculating a number by the repeated application of an algorithm. |
| re·cur·sion (rĭ-kûr'zhən) n. Mathematics
[Late Latin recursiō, recursiōn-, a running back, from Latin recursus, past participle of recurrere, to run back; see recur.] re·cur'sive adj. |
recursion mathematics, programming
When a function (or procedure) calls itself. Such a function is called "recursive". If the call is via one or more other functions then this group of functions are called "mutually recursive".
If a function will always call itself, however it is called, then it will never terminate. Usually however, it first performs some test on its arguments to check for a "base case" - a condition under which it can return a value without calling itself.
The canonical example of a recursive function is factorial:
factorial 0 = 1 factorial n = n * factorial (n-1)
Functional programming languages rely heavily on recursion, using it where a procedural language would use iteration.
See also recursion, recursive definition, tail recursion.
[The Jargon File]
(1996-05-11)