RM=Randy MacDonald, DB=me RM> A good explanation for my original question is: dyadic use RM> of (f g h &]) allows the right verb in the fork to ignore the RM> fork's left argument.
Actually, it is the dyadic use of (f g h @:]) which allows the right verb of a fork to ignore the fork's left argument. I suspect Raul had a typo when he wrote &] (and he didn't notice the error because it wouldn't be apparent unless he tried to invoke the fork dyadically). As an intersting aside, &] is sort of an "identity adverb", in that (u y) -: u&] y and (x u y) -: x u&] y . RM> (Now, where in the manual one could put that statement, I don't know.) It's a couple of paragraphs down from the part where it says 2+3 is 5 :) DB> PPS: In x 6!:2 y I assumed x would be constrained to the positive DB> integers. But I tried 0 (with the expected result) and negative DB> numbers (with unexpected results) RM> What do you see as the expected result? Well, in advance of trying it, I expected an error. But if you said to me "if 0 (6!:2) y produces a result, what is it?", I would have said "0" because that's how long it takes to execute a(ny) sentence zero times. So when I saw the result (indeed, 0 ), I was not surprised. Similarly, before I tried (-x) 6!:2 y I expected a domain error (again), but this time I was surprised when I didn't get one. I got a very small negative result, no matter what y I used. Unlike the case for zero, I cannot reconcile this result with the definition of the foreign (maybe if (-x) 6!:2 y were just - (x 6!:2 y) I could be talked into it). I suspect the result of (-x) 6!:2 y is an unintentional artifact of its implementation (in C code). RM> What about fractional left arguments? I did try fractional, infinite, and complex left arguments, and got the errors I expected. If I had to come up with a consistent definition with fractional x , it might be something like "time executing the sentence (<.x) times, add to that the time it takes to execute (x-<.x) times [by stopping the sentence partway through] and divide the result by x ". But in practice that's silly. -Dan ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
