recursive -->
recursion
computing dictionary

<mathematics, computer 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.

(01 Feb 1996)

recursive -->
recursion
medical dictionary

The act of recurring; return. (Math) The calculation of a mathematical expression (or a quantity) by repeating an operation on another expression which was derived by application of the same operation, on an expression which itself was the result of similar repeated applications of that same operation on prior results. The series of operations is terminated by specifying an initial or terminal condition. (Computers) A programming technique in which a function calls itself as a subfunction. Such calls may be repeated in series to arbitrary depth, provided that a terminating condition is given so that the final (deepest) call will return a value (rather than continue to recurse), which then permits the next higher call to return a value, and so forth, until the original call returns a value to the calling program.

Origin: L. Recursio. See Recur.

(01 Mar 1998)