You are right to question the symbology of C.!.2, and right to be suspicious of having to look up it in the manual. _All_ cases of u!.n have a scent of arbitrariness about them because you can not readily deduce what exactly they do.
----- Original Message ----- From: Marshall Lochbaum <[email protected]> Date: Monday, October 4, 2010 18:08 Subject: Re: [Jprogramming] Distinct Numbers in Rows and Columns To: 'Programming forum' <[email protected]> > My best shot with expansion by minors, if anyone's interested in > O(n!):((i.3) -: [: /:~ -.&_1)"1 , .(_1:`...@.=)"2 q > > I retract my comment about <: being unnecessary, though. I > have been using > (i.n) instead of (1+i.n). > > The real reason C.!.2 bothers me is that it makes it seem that > C.!.1 is > taken. I agree that the function can be useful. > > Marshall > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Henry Rich > Sent: Monday, October 04, 2010 8:14 PM > To: Programming forum > Subject: Re: [Jprogramming] Distinct Numbers in Rows and Columns > > I got to > > -.@(0&e.)@:(C.!.2)@(,|:)@:<:"2 > > as the test for whether the item is a Latin square. I have > been trying to > find some cool test, without success. > > Henry Rich > > On 10/4/2010 7:37 PM, Roger Hui wrote: > > Great minds think alike, eh? (But I think you need to > test your > > expressions ;-) Go to > http://www.jsoftware.com/jwiki/Essays/KenKen> and look about a > third of the way down, > > > > q #~ (8$15) -:"1 (+/"1 ,. +/"2) q{0,2^i.4 > > > > The initial effort in your previous msg is also similar to my > initial > > effort. > > > > > > > > ----- Original Message ----- > > From: Marshall Lochbaum<[email protected]> > > Date: Monday, October 4, 2010 16:28 > > Subject: Re: [Jprogramming] Distinct Numbers in Rows and Columns > > To: 'Programming forum'<[email protected]> > > > >> Here's a funny--and much faster--one: > >> p=.p:i.n > >> *./"1 (*/p) = (*/"2 ,. */"1) q{p > >> > >> Actually, I suppose it is better to do it with addition, so > p=.2^i.n>> *./"1 (+/p) = (+/"2 ,. +/"1) q{p > >> > >> Marshall > >> > >> -----Original Message----- > >> From: [email protected] > >> [mailto:[email protected]] On Behalf Of Roger Hui > >> Sent: Monday, October 04, 2010 6:41 PM > >> To: Programming forum > >> Subject: [Jprogramming] Distinct Numbers in Rows and Columns > >> > >> An interesting puzzle arising from the KenKen solver: > >> q is an array with shape (m,n,n) and (,q) e. 1+i.n . > >> Which items of q have 1+i.n in each row and in each column? > > --------------------------------------------------------------- > ------- > > 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
