The "recently" in the quoted text dates from the year 2000 in the J4.05 release notes:
http://www.jsoftware.com/help/release/iamend.htm ----- Original Message ----- From: Henry Rich <[EMAIL PROTECTED]> Date: Wednesday, October 25, 2006 5:38 am Subject: RE: [Jprogramming] Choose Operators > The forms of this idiom that assign the result to a name > benefit from some special code: > > The phrase b}x,:y for numeric x and y is equivalent to the > well-known phrase (x*b)+y*-.b . Recently, special code has > been implemented for the phrase name=: c}x,y,...,:z , with > boolean c as a special case, and the amendment is done in > place if name is x or y and c is boolean. (In-place > amendment is eschewed for integral c due to the possibility > of index error.) > > Henry Rich > > > -----Original Message----- > > From: [EMAIL PROTECTED] > > [EMAIL PROTECTED] On Behalf Of R.E. Boss > > Sent: Wednesday, October 25, 2006 6:45 AM > > To: 'Programming forum' > > Subject: RE: [Jprogramming] Choose Operators > > > > This is what makes J so attractive, one is pleasantly surprised > by an > > elegant solution. Perfect. > > > > Remarkable that both questions had the same solution. > > > > R.E. Boss > > > > > > > > -----Oorspronkelijk bericht----- > > Van: [EMAIL PROTECTED] > > [EMAIL PROTECTED] Namens Devon McCormick > > Verzonden: woensdag 25 oktober 2006 2:51 > > Aan: Programming forum > > Onderwerp: Re: [Jprogramming] Choose Operators > > > > This is an idiom - I don't remember where I first saw it: > > > > B=. 1=2|X0=. 999+ X1=. i.10 > > > > B,X0,:X1 > > 1 0 1 0 1 0 1 0 1 0 > > 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 > > 0 1 2 3 4 5 6 7 8 9 > > > > B}X0,:X1 > > 0 1000 2 1002 4 1004 6 1006 8 1008 > > > > > > On 10/24/06, Leigh J. Halliwell <[EMAIL PROTECTED]> wrote: > > > > > > Thank you, Roger and Cliff. On my first question I was > > indeed thinking of > > > the monadic amend. And Cliff's use of it for my second > > question is nice, > > > too. But I'd still like to know how to make the > > identity/left operator > > > work > > > one-to one, as per my second question: > > > > > > "2) X0 and X1 are numeric vectors, and B is a Boolean > > vector. They all > > > have > > > the same length. I'd like to select from X0 where B is 0, > > and from X1 > > > where > > > B is 1. I try the expression: X1 [^:B X0. But the adverb > > ^:B wants to > > > get > > > two-dimensional, i.e., to apply each B to every pair of X1 > > and X2. How > > > can > > > I make J to apply the adverb one-to-one with the arguments?" ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
