Thanks to everyone who answered - there were a few that were just what I needed.

On Sat, Apr 7, 2018 at 6:48 AM, 'Pascal Jasmin' via Programming < programm...@jsoftware.com> wrote: > there is also, > > iota =: i. : (+ i.) > > > 3 iota 5 > 3 4 5 6 7 > > ([ iota >:@-~)/ 3 7 > 3 4 5 6 7 > > 3 iota _5 > 7 6 5 4 3 > > > ________________________________ > From: Joe Bogner <joebog...@gmail.com> > To: programm...@jsoftware.com > Sent: Friday, April 6, 2018 3:50 PM > Subject: Re: [Jprogramming] Expression to generate sequ > > > > Lightly tested and non-optimized and ugly, but seems to work! > > genseq=:({: + i.@:>:@:-/)@] > > seq =: (] (>/@[ \:~@]^:[ genseq) \:~) f. > > > ] (>/@[ \:~@]^:[ ({: + i.@:>:@:-/)@]) \:~ > > > seq 3 7 3 4 5 6 7 seq 7 3 7 6 5 4 3 > > > > > On Fri, Apr 6, 2018 at 3:23 PM, Devon McCormick <devon...@gmail.com> > wrote: > > > Hi - > > > > I'm working with selecting sequential items from a vector given a > starting > > and an ending point as a pair of integers. If we assume we always get > the > > pair as (lesser, greater), something like this suffices: > > > > seq=: {. + [: i. [: >: -~/ > > seq 3 7 > > 3 4 5 6 7 > > > > However, if our assumption about the order of our points is violated, we > > get nonsense: > > > > seq 7 3 > > 7 8 9 > > > > Just for robustness, how could we write a version of "seq" that would > > return the sequence in reverse order in this latter case, i.e. give the > > proper sequence from seven to three: 7 6 5 4 3 ? > > > > I generalized the "seq" verb to remove the ordering assumption: my idea > was > > to generate the ascending sequence, then flip it if >/y is true. I tried > > this with "agenda" but am not sure how to get it to work on one thing - > the > > ascending vector - on the basis of comparison of another thing - the pair > > of integers. > > > > I did achieve this using the "power" conjunction: > > > > seq=: 3 : '|.^:(>/y)](<./ + [: i. [: >: >./ - <./) y' > > seq 3 7 > > 3 4 5 6 7 > > seq 7 3 > > 7 6 5 4 3 > > > > Does anyone have any ideas for a more elegant, preferably tacit, > solution? > > > > Thanks, > > > > Devon > > -- > > > > Devon McCormick, CFA > > > > Quantitative Consultant > > ---------------------------------------------------------------------- > > 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 Quantitative Consultant ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm