Recursive algorithm

A recursive algorithm is in essence an programming code block which calls itself over and over again, eventually terminating when an end condition is met.

In the C computer programming language, the following is an example of a recursive factorial function (algorithm):

int Factorial(n)
{
  if (n <= 1)
    return 1;
  else
    return n * Factorial(n - 1);
}

If you examine this short code block, you can see how it functions. For example, if the function Factorial is called with n = 3, it runs like this:

1. Factorial function called with n = 3
2. Else branch is taken
3. Return value of Factorial, this time with argument of n = 2
4. In new function call, Else branch is chosen again
5. Return value of Factorial with arg n = 1
6. New functional call of Factorial terminates on If statement, and returns value of 1
7. Next function return yields 2 * 1
8. Last function return yields 3 * 2 * 1, and terminates with a value of 6.

The computer running this sequence uses what is known as a stack to hold these function calls with their associated values until each is resolved in reverse order. These wait in line to be resolved one at a time.

Factorial(1) Factorial(2) Factorial(3)

Recursive algorithms are used for many purposes. They can be used to clear an overload of a holograms interactive matrix, or used to retrieve missing data from a log. (ENT: "Affliction"; VOY: "Nothing Human", "Warhead", "Renaissance Man")

Most Cardassian access codes are based on a recursive encryption algorithm. (DS9: "In Purgatory's Shadow")

See also

• Subspace infrared algorithm

External Links

• Recursion at Wikipedia