On Thu, Nov 6, 2008 at 02:04, Roger Hui <[EMAIL PROTECTED]> wrote: > ts 'p i. i.#p' > 0.00602786 1.57363e6 > > Compared to: >> ts '/:p' >> 0.00611782 1.04922e6 >> ts '(i.#p) p}p' >> 0.0112338 1.57389e6
My story is actually this. Back in 2005, someone asked an interesting puzzle in "http://www.perlmonks.com/?node_id=487200";, which asked to generate a certain spiral. In the first solution I wrote ("http://www.perlmonks.com/?node_id=487238";), I used p i. i.#p to generate the inverse of a permutation. The original solution was basically this (except that it had y. instead of y): spiral =: 3 : 0 >: (,~ y) $ (i. *: y) i.~ /: ,/ (-@>.&| , [EMAIL >PROTECTED]:@*.@(1j_1&*)@j.)"0/~ (i. y) - -:<: y ) spiral 5 1 2 3 4 5 16 17 18 19 6 15 24 25 20 7 14 23 22 21 8 13 12 11 10 9 Then, when I translated this to perl ("http://www.perlmonks.com/?node_id=487246";), I realized this, and instead used the equivalent of ((i.#p) p} p). Much later, in 2007, when this topic came up in the jprogramming list, I rewrote my J solution to use ((i.#p) p} p) instead: "http://www.jsoftware.com/pipermail/programming/2007-December/009009.html";. I also copied this back to the perlmonks thread. Ambrus ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
