Agreed that negative rank must not change. And I would love to see f"g x<-> f"(g x) x . I have wished for that a couple of times, though I don't remember why now.
Even though I use f"g in a couple of places, I would welcome the change. I could always do f"(g b. 0), right? Henry Rich On 11/10/2010 4:26 PM, Roger Hui wrote: > On the other hand, one could look at the current definition > of f"g as some sort of mistake (and the infrequency of > its use is an indication of that), and a different meaning > might have been more useful. e.g. f"g x<-> f"(g x) x > > Anyway, even given the current definition of f"g, I don't > think there is a case for changing anything. You want > f"f to be the same as f, but what if a rank of f is negative? > Or even the noun case:<"r is not necessarily the same > as<"r"r if r is negative. > > > > ----- Original Message ----- > From: Dan Bron<[email protected]> > Date: Wednesday, November 10, 2010 11:19 > Subject: Re: [Jprogramming] Atop u...@v with v of negative monadic rank > To: J Programming<[email protected]> > >> Yes, or you might have an expression like 3 2 0 p. x which >> relies on the definition of x+0 without explicitly >> stating it, or without the author of the expression even knowing >> it (see Ambrus' comments later in this thread). >> >> In other words, you need identities to make algebra >> reliable. In other words, edge cases are the bane of >> formalisms (and one of the joys of J is that so very often it >> handles them elegantly and transparently. This feature is >> mostly derived from the thoughtful and sometimes seemingly >> prophetic definitions of its words). In other words, the >> more guarantees J makes, the less I have to worry (including >> worrying about whether I should be worrying, as you& Roger are >> doing). >> Anyway, if you're looking for an analog to x+y , then think >> about modifiers like "f (or 1 :'u"f' or whatever) >> which one would like to "work" without worrying about the value >> of the argument (even if sometimes it's exactly f). Yes, >> abstractions over verbs are rarer than abstractions over nouns >> (and J's grammar encourages this, viz Lisp), but they are not >> insignificant, and I personally make great use of them [1]. >> >> Bear in mind, I am not arguing for or against Ambrus' proposal >> (which I still haven't had time to study). I am only >> pointing out 'who needs f"f ?' is not an argument against it and >> is invidious logic. >> >> It is obvious that f -: f"f should be a tautology ("f is the >> same as f with the rank of f"); we can choose to sacrifice this >> self-consistency for some benefit, but we should do so >> consciously and for good reasons (not because we can't think of >> uses for self-consistency). >> >> -Dan >> >> >> [1] We all know modifiers are one of J's strengths - we have >> +/ */ and ^/ where math has big-sigma, big-pi and big-nada >> respectively. >> >> >> Please excuse typos; composed on a handheld device. >> >> -----Original Message----- >> From: Raul Miller<[email protected]> >> Sender: [email protected] >> Date: Wed, 10 Nov 2010 12:57:58 >> To: Programming forum<[email protected]> >> Reply-To: Programming forum<[email protected]> >> Subject: Re: [Jprogramming] Atop u...@v with v of negative monadic rank >> >> On Wed, Nov 10, 2010 at 10:29 AM, Dan Bron<[email protected]> wrote: >>> Why would you ever say x+0 or y*1 ? >> >> I am not sure that I do? >> >> But I might say x+y where y was 1 0 1. > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
