> (2*[)/\ 2 3 4 > 2 4 4 Prefixes:
<\ 2 3 4 ┌─┬───┬─────┐ │2│2 3│2 3 4│ └─┴───┴─────┘ Applying a function on these prefixes like you did gives: (2*[)/ 2 2 Here there is no left argument so it uses the unit element of '*', which is 1. (2*[)/ 2 3 4 (2*[)/ 2 3 4 4 Explanation of the result of the last prefix array: f=.2*[ f/ 2 3 4 <===> 2 f 3 f 4 2 f (3 f 4) 2 f 6 4 If you really want the desired result this way, then use e.g.: inc2=. 2+] note the difference with your (2+[) 4 inc2/\@:$ 2 2 4 6 8 but I would not do that, instead I would use: 4 +/\@:$ 2 2 4 6 8 But this is focused on the result and not on the concept of recursion. -- Met vriendelijke groet, =@@i ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
