recursion
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}.
[{Jargon File}]
(1996-05-11)