Thanks Bill! > I guess a pattern of "filter" is > (#~ filter) y > where filter is a monad verb that return 0 or 1 > For your case, it would (untested) > (#~ odd) i.9
odd=: 2&| (#~ odd) i.9 1 3 5 7 Yes, great, the hook works as expected, and as per Chris's example Where I'm stuck is in making the filter verb _itself_ filter =: (#~ [) doesn't work, neither filter =: (#~ [) ] I guess what I'm trying to say, is that as much as I like the challenge of Chris's elegant example, I think a far more readable entry point for a beginner would be filter =: ...whatever... prime =: 1&=...@#@q: prime filter i.9 2 3 5 7 which of course would also allow nice, useful bindings like prime&filter, odd&filter, etc. I also note that "prime" in the boolean function given above, probably won't work with our pattern for "filter", due to reasons of rank, but I'm not sure, I'm leaving that for later. ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
