Of course, I meant F=: FB^:FT^:_ . By the way, you also meant F=: FB^:FT^:_, not F=: FB^:FT^:_ y . Did you not? ;)
Can you think of any verb that cannot be rewritten in that fashion? I guess the task description is not clear enough for you; that is unfortunate. On Thu, Jan 11, 2018 at 6:06 PM, Raul Miller <[email protected]> wrote: > On Thu, Jan 11, 2018 at 5:50 PM, Jose Mario Quintana > <[email protected]> wrote: > >> Perhaps you could shed a bit more light on whatever it is that you are > >> trying to talk about? > > > > "Because no restrictions on the nature of FB and FT are imposed" my > > reaction to > > > >> If I have a recursive verb (F y) implemented in J, which satisfies the > >> constraints for tail recursion, I believe that there is always a pair > >> of companion functions (FB y) (FT y) such that an F workalike can be > >> written: > >> > >> F=: FB^:FT^:_ y > > Well, ok, in the sense that either FB or FT could call quicksort. > > They still have to represent a tail recursive function for this to be > meaningful. But even tail recursive routines can call quicksort > (though, granted, I do not have any clear ideas, right now, about what > useful tail recursive routine would call quicksor). > > > (so far) is that the part "which satisfies the constraints for tail > > recursion," is gratuitous. (Can you exhibit a verb F which does not > > satisfy the constraints for tail recursion and an F workalike cannot be > > written as F=: FB^:^:_ ?) > > > > I could be mistaken though and I am willing to be educated. > > At this point I don't even know what you are talking about. But I > think you asked me to rewrite a non-tail recursive routine in a > syntactically invalid fashion. > > Consider, for example: > > FB=: 0 >. <: > FB 2 > 1 > FB^:^:_(2) > |syntax error > > > If I had to guess what you might have in mind for FB and FT in connection > > to tail recursion then I would think that the form F=: FB^:FT^:_ might be > > almost correct. However, I rather not guess; I would like to be > enlighted > > instead, if possible. That is one reason why I suggested the verb > > evolve as a subject matter. > > The only examples I have found for evolve are either: > > (a) identity functions (which do nothing whatsoever), or > (b) throw errors. > > How is this relevant? > > -- > Raul > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
