Exactly what I've been sidetracked into doing for the last hour or so... :-)
My dissertation was in this very area. But 40 years is a long time to forget things. Do you know, my eye originally skated over the definitions of A. and C. without realising their significance? Back then, as a government scientist, I got to borrow one of the biggest non-military computers in England to trawl through the permutations (ordered as A. would order them) looking for a certain sort of finite group. I'm tempted to repeat my calculations in J. "You're getting old when..." -you find this sort of thing amazing. On Fri, Apr 29, 2011 at 2:41 PM, Dan Bron <[email protected]> wrote: > Apply the monad C. to the output of foo to discover the LHA required by the > dyad C. to permute i. to foo . > > Similarly for A. > > -Dan > > > Please excuse typos; composed on a handheld device. > > -----Original Message----- > From: Ian Clark <[email protected]> > Sender: [email protected] > Date: Fri, 29 Apr 2011 14:23:26 > To: Programming forum<[email protected]> > Reply-To: Programming forum <[email protected]> > Subject: Re: [Jprogramming] A permutation of i.y > > Nice one, Henry. > > And thanks for the idea to use C. , Dan -- it almost does what I want > but it floats DOWN the LAST element instead of floating up the > first... > (but I can use it with minor adaptation) > > fi=: [ C.^:_1 [: i. ] > 3 fi 9 > 0 1 2 8 3 4 5 6 7 > > > On Fri, Apr 29, 2011 at 1:22 PM, Henry Rich <[email protected]> wrote: >> 3 /:@(0} i.) 9 >> 1 2 0 3 4 5 6 7 8 >> >> Henry Rich >> >> On 4/29/2011 8:03 AM, Ian Clark wrote: >>> My brain's a mess this morning... >>> >>> Let foo be a dyadic verb which simply returns i.y with the zero >>> floated up to position x . >>> (Forget the cases of x<1 and x>y) >>> >>> foo=: 4 : '(1|.i.x) , (x}.i.y)' >>> 3 foo 9 >>> 1 2 0 3 4 5 6 7 8 >>> >>> That's a distressing way of doing it, but it's the best I can manage. >>> There's got to be a neater solution. Using # maybe? >>> ---------------------------------------------------------------------- >>> 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 > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
