I like the prepending idea because it makes explicit the expected domain and puts any unexpected elements (unlikely in the case of monadic "*" - except if complex numbers sneak in) at the end where they are out of the way but easy to find.
Just now, checking the results of signum on edge conditions, I was intrigued to find that "_1 0 1 -: *__ _. _". On Thu, Sep 23, 2010 at 9:24 AM, R.E. Boss <r.e.b...@planet.nl> wrote: > I agree. First comes correctness, then performance, then elegance. > > > R.E. Boss > > > > -----Oorspronkelijk bericht----- > > Van: programming-boun...@jsoftware.com [mailto:programming- > > boun...@jsoftware.com] Namens Brian Schott > > Verzonden: donderdag 23 september 2010 14:41 > > Aan: Programming forum > > Onderwerp: Re: [Jprogramming] Classification problem > > > > I agree that this solution is elegant, but for a large data set I > > assume that Raul's idea of prepending and then dropping 3 elements > > would be more efficient. Don't you, too? > > > > (<@}./.~ *) _1 0 1,data > > > > On Thu, Sep 23, 2010 at 8:26 AM, R.E. Boss <r.e.b...@planet.nl> wrote: > > > One of the more elegant solutions is > > > > > > ((/:&(* </. ])) *) data > > > +---------------+---+-----+ > > > |_3 _1 _10 _2 _4|0 0|1 1 6| > > > +---------------+---+-----+ > > > > > > > > > R.E. Boss > > > > > > > > >> -----Oorspronkelijk bericht----- > > >> Van: programming-boun...@jsoftware.com [mailto:programming- > > >> boun...@jsoftware.com] Namens Marshall Lochbaum > > >> Verzonden: woensdag 22 september 2010 23:57 > > >> Aan: Programming forum > > >> Onderwerp: Re: [Jprogramming] Classification problem > > >> > > >> It looks to me like the most terse way is > > >> ((</. /: ~...@[)~ f) data > > >> > > >> Although this computes the nub twice, unlike some earlier solutions. > > >> > > >> Marshall > > >> > > >> ________________________________________ > > >> From: programming-boun...@jsoftware.com [programming- > > >> boun...@jsoftware.com] On Behalf Of Raul Miller [ > rauldmil...@gmail.com] > > >> Sent: Wednesday, September 22, 2010 3:29 PM > > >> To: Programming forum > > >> Subject: Re: [Jprogramming] Classification problem > > >> > > >> Note, if * is the universe of interesting > > >> functions (if it does not need to be generic) then > > >> I would be tempted to use a variation on Dan's > > >> second suggestion: > > >> > > >> (<@}./.~ *) _1 0 1,data > > >> > > >> Note that this also preserves the relative > > >> ordering of the data items. > > >> > > >> -- > > >> 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 > > > > > > ---------------------------------------------------------------------- > > > For information about J forums see http://www.jsoftware.com/forums.htm > > > > > > > > > > > -- > > (B=) <-----my sig > > Brian Schott > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > -- Devon McCormick, CFA ^me^ at acm. org is my preferred e-mail ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
