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[REBOL] Re: Tail end recursion

From: gedb01:yaho:o at: 9-Oct-2003 14:29

You probably know that recursion is when a function calls itself. With tail end recursion LISP ensures that recursion is as efficient as iteration [1]. Instead of iteration: repeat count 3 [ print ["count: " count] ] You would use: recursive: func [count target][ print ["recursive count: " count] if count < target [recursive count + 1 target] ] recursive 1 3 In this simple example iteration looks much better. The recursive approach looks complicated and difficult to understand. So why is tail end recursion desirable? Well, consider a alogrithm for Longest Common Subsequence [2]. As link 2 shows, the initial recursive form is very easy to derive and understand, but you have to work a lot harder to get a decent iterative solution. [1] [2]