I think the more puzzling behavior here isn't that ?. is different from ? but that ?. is giving a manifestly incorrect result wrt its definition. Whatever rank ?. is, each element of its result should be strictly less than the corresponding atom of its argument. Also an output of _ is just nonsensical, no matter what the input.
I appreciate Raul's comment re the distaste for ?. generally, but I think that's more applicable to your observation re rank than REB's re _ , which is a bug and should be fixed. -Dan Please excuse typos; composed on a handheld device. -----Original Message----- From: Mark Niemiec <[email protected]> Sender: [email protected] Date: Mon, 8 Aug 2011 07:20:35 To: J Programming Forum<[email protected]> Reply-To: Programming forum <[email protected]> Subject: [Jprogramming] Subject: monadic rank of roll and deal "R.E. Boss" <[email protected]> wrote: > ? b. 0 > > 0 0 0 > > > > ?. b. 0 > > _ 0 0 > > > > Is this intended? ?.10#10 6 5 9 2 4 9 0 7 0 4 ?."0]10#10 6 6 6 6 6 6 6 6 6 6 Before 6.02, ?. had rank 0, which caused inconsistent behavior, since "0 should have no effect on a verb that is already rank 0. It is impossible to write a user-defined verb that emulates the behavior of ?. without making its rank infinite. As far as I know, this was the only J primitive that had this kind of behavior. -- Mark D. Niemiec <[email protected]> ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
