> Van: Peter B. Kessler > Verzonden: maandag 30 juli 2012 22:12 (...) > > This doesn't address the case where both inputs have 1's in the same column > > ]C=:2 5 $ 1 0 0 1 0 0 1 0 1 0 > 1 0 0 1 0 > 0 1 0 1 0 > (>./-<./)+/\+/1 _1 *C > 1 > > The original statement of the problem doesn't say what to do with > simultaneous 1's, but I would think they fail the "alternating" > description.
IMO this case is not included in the specs of the problem. Or one could even think it qualifies. > I am a total newb when it comes to J programming, though I did some APL > programming in the early 1970's. I find that what's missing > from this example (and lots of other examples of J programs) is a statement > of why it is written the way it is. I am not in the education business, others are better in that area, unless non-trivial questions arise, since I assume people (of our age) with interest in J very well know how to teach themselves. > For example, I love the use of "+/\" in the above to propagate the state of > the match. > (Though, I worry a little about the efficiency of it, if prefix really > reapplies the verb to each of the possible prefixes, especially as the > inputs get long.) Compare performances of (+/\) with (plus/\) where (plus=.+ ) . As a newbie, performance should not be one of the first things to worry about. R.E. Boss ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
