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
>
> ----------------------------------------------------------------------
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> ----------------------------------------------------------------------
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>



-- 

Devon McCormick, CFA

Quantitative Consultant
----------------------------------------------------------------------
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