Yes, I can see at least one problem: If X1, X2 and X3 are in the list, the tolerant equality might have X1=X2 and X2=X3, but X1~:X3. In which case, the "specification is problematic".
But does this not also mean that - in theory, if not in practice with Paul's data - Oleg's solution (and just about any other solution you can think of) will suffer from "the same problem"? -----Original Message----- From: Roger Hui [mailto:[EMAIL PROTECTED] Sent: 6. juni 2007 19:28 To: General forum Subject: Re: [Jgeneral] Re: Challenge to expert J'ers > If I got this right, your need for it actually arises from the > fact that > neither APL nor J take comparison tolerance into account when sorting > floating-point values, probably for the same reason (cost seemed > to outweigh > the benefits). Tolerance is not used in grade and sort not because of any difficulties in implementation, but because the specifications would be problematic. ----- Original Message ----- From: Morten Kromberg <[EMAIL PROTECTED]> Date: Wednesday, June 6, 2007 9:56 am Subject: RE: [Jgeneral] Re: Challenge to expert J'ers > Paul, > > You have correctly identified the fact that (float i. float) is not > special-cased in Dyalog APL (unless comparison tolerance is zero, > in which > case we DO hash it); we do a linear search and that is slow when > the arrays > get big. A public bashing on the J forum still isn't quite enough > to get the > Dyalog development team fired up about this, mostly because our > imaginationfails us as to what sort of (sensible) applications > there are for fast fuzzy > searching of floats. > > If I got this right, your need for it actually arises from the > fact that > neither APL nor J take comparison tolerance into account when sorting > floating-point values, probably for the same reason (cost seemed > to outweigh > the benefits). > > I think your comment that we have thereby contributed to rotting > the brains > of generations of APLers is *slightly* over the top :-). I think Olegs > elegant solution WOULD have occurred to many APL programmers, in > fact I seem > to remember having seen this as a puzzle solution a decade or two ago. > > Congratulations to Roger on his excellent implementation! If > someone comes > up with a convincing set of examples to motivate further work on > this case, > we may change our minds (but please don't use the J forums for > this). We ARE > doing a significant amount of work on optimizing various cases in > a number > of primitives in the next release of Dyalog APL. > > Morten > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > Sent: 6. juni 2007 17:48 > To: General forum > Subject: Re: [Jgeneral] Re: Challenge to expert J'ers > > Actually Roger was not aware of the definite problem with Dyalog > APL's > f{iota}f implementation which was highlighted in later posting. So > his > sentence would now probably contain more nuances. > > > Paul Gauthier > APL Software Developer - Senior > [EMAIL PROTECTED] > Phone: 312-739-3467 > Fax: 312-739-3496 > > CheckFree. The Company that Powers Payment on the WebSM. > http://www.checkfree.com/paybillsonline > > > > > Brian Schott <[EMAIL PROTECTED]> > Sent by: [EMAIL PROTECTED] > 06/06/2007 07:10 AM > Please respond to > General forum <[email protected]> > > > To > General forum <[email protected]> > cc > > Subject > Re: [Jgeneral] Re: Challenge to expert J'ers > > > > > > > Sorry to the forum and Roger. > I found the referrent finally, and I suppose Roger > is saying that that phrase was not the correct explanation. > > > On Wed, 6 Jun 2007, Brian Schott wrote: > > + Roger, > + > + I cannot understand this post. First, I cannot find > + the *previous* message to which you refer. Second, I cannot > + tell what aspect of the previous excerpt you are "Not"ing. > + > + > + On Fri, 1 Jun 2007, Roger Hui wrote: > + > + + > In J you just do /:/:y because grade on small > + + > range integers takes linear time. > + + > + + Not, because it is the straightforward thing and > + + your faithful implementor has taken care that you > + + don't pay a penalty for it. > + > + > > (B=) <----------my "sig" > > Brian Schott > Atlanta, GA, USA > schott DOT bee are eye eh en AT gee em ae eye el DOT com > http://schott.selfip.net/~brian/ ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
