I don't think you'd ever want to use perm dyadically. perm=. ! A.&i. ]
perm y gives all !y permutaions of y objects. x perm y gives the first x!y permutations of y objects. So dyadic perm is defined as the first x!y (or # x comb y) items of monadic perm. I think this is simply a consequence of the intended monadic definition. -----Original Message----- From: programming-boun...@jsoftware.com [mailto:programming-boun...@jsoftware.com] On Behalf Of Raul Miller Sent: Tuesday, June 26, 2012 2:14 PM To: Programming forum Subject: Re: [Jprogramming] permutation list They are certainly different. 2 comb 3 0 1 0 2 1 2 2 perm 3 0 1 2 0 2 1 1 0 2 In general, for n of m permutations and n of m combinations, the permutations are going to be longer (length m instead of length n). But the number of distinct items will be the same. -- Raul On Tue, Jun 26, 2012 at 2:09 PM, Devon McCormick <devon...@gmail.com> wrote: > I thought that in the usual mathematical definition, combinations and > permutations differ: for permutations, order matters; for > combinations, it does not. Under this definition, the combinations of > 3 things is just " i. 3 " - assuming we don't allow replacement? If > we do allow replacement, the permutations of 3 things are given by " > {3$<i.3 " and the combinations by something like " ~./:~&.>,{3$<i.3 ". > > Does this seem right? > > On Tue, Jun 26, 2012 at 12:51 PM, Raul Miller <rauldmil...@gmail.com> wrote: >> Note that the number of combinations and the number of permutions are the >> same. >> >> And, perm is just: ! A.&i. ] >> >> It seems like there ought to be a way of putting the permutations in >> 1 to 1 correspondence with the combinations (to give us a concise >> expression for combinations). >> >> -- >> Raul >> >> On Tue, Jun 26, 2012 at 12:41 PM, ed bierly <ebie...@gmail.com> wrote: >>> yes combinations not permutations >>> thought there might be a way that didn't loop thank you for the >>> references >>> >>> On Tue, Jun 26, 2012 at 12:30 PM, R.E. Boss <r.e.b...@planet.nl> wrote: >>> >>>> 4 comb 10 >>>> >>>> >>>> R.E. Boss >>>> >>>> >>>> > -----Oorspronkelijk bericht----- >>>> > Van: programming-boun...@jsoftware.com [mailto: >>>> programming-boun...@jsoftware.com] Namens ed bierly >>>> > Verzonden: dinsdag 26 juni 2012 18:15 >>>> > Aan: programming@jsoftware.com >>>> > Onderwerp: [Jprogramming] permutation list >>>> > >>>> > what is the best way to get this list of 210 vectors? >>>> > >>>> > 4!10 >>>> > ----------------------------------------------------------------- >>>> > ----- 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 > > > > -- > Devon McCormick, CFA > ^me^ at acm. > org is my > preferred e-mail > ---------------------------------------------------------------------- > 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
