Sure, ... that's a bit bulkier than I prefer, but it works.
Here's another alternative:
evenodd=: , (_1 2,:_1 4)&p.@{:
evenodd evenodd 4
4 7 15 29 59
Thanks,
--
Raul
On Tue, Nov 27, 2018 at 10:44 AM 'Pascal Jasmin' via Programming
<[email protected]> wrote:
>
> Another approach,
>
> ar =: 1 : '5!:1 <''u'''
>
> even =: 3 : ' (,(+: - 1:)@{:) ar , (y`:6) ar'
> odd =: 3 : ' (,(+: + 1:)@{:) ar , (y`:6) ar'
> even odd even odd (+: - 1:) ar , 4 ar
> ┌──────────────────────────────┬──────────────┐
> │┌─┬──────────────────────────┐│┌─┬──────────┐│
> ││2│┌─┬──────────────────────┐│││0│7 15 29 59││
> ││ ││,│┌─┬──────────────────┐│││└─┴──────────┘│
> ││ ││ ││@│┌─────────────┬──┐││││ │
> ││ ││ ││ ││┌─┬─────────┐│{:│││││ │
> ││ ││ ││ │││3│┌──┬─┬──┐││ │││││ │
> ││ ││ ││ │││ ││+:│-│1:│││ │││││ │
> ││ ││ ││ │││ │└──┴─┴──┘││ │││││ │
> ││ ││ ││ ││└─┴─────────┘│ │││││ │
> ││ ││ ││ │└─────────────┴──┘││││ │
> ││ ││ │└─┴──────────────────┘│││ │
> ││ │└─┴──────────────────────┘││ │
> │└─┴──────────────────────────┘│ │
> └──────────────────────────────┴──────────────┘
>
> ________________________________
> From: Raul Miller <[email protected]>
> To: Programming forum <[email protected]>
> Sent: Tuesday, November 27, 2018 10:25 AM
> Subject: Re: [Jprogramming] Recursive verbs
>
>
>
> It's more like this, actually:
>
> seqodd=: +: - 1:
> seqevn=: +: + 1:
> (,seqevn@{:)@(,seqodd@{:)^:8]4
> 4 7 15 29 59 117 235 469 939 1877 3755 7509 15019 30037 60075 120149 240299
>
> More generally, either:
>
> a) you keep explicit track of which position in the sequence you are
> generating, so you can choose between the odd or the even method, or
>
> b) you generate the numbers in pairs
>
> If you generate the numbers in pairs, you can rearrange things in a
> variety of ways.
>
> Thanks,
>
> --
> Raul
>
>
> On Tue, Nov 27, 2018 at 7:37 AM 'Pascal Jasmin' via Programming
> <[email protected]> wrote:
> >
> > If the verb you want is repetitive double - 1 then
> >
> > 5 (1 -~ +:@])^:(<@[) 4
> > 4 7 13 25 49
> >
> > Otherwise, Mike's 2 at a time approach is the way to go.
> >
> > ________________________________
> > From: Skip Cave <[email protected]>
> > To: "[email protected]" <[email protected]>
> > Sent: Tuesday, November 27, 2018 2:10 AM
> > Subject: [Jprogramming] Recursive verbs
> >
> >
> >
> > How would you write an implicit or explicit recursive verb for this
> >
> > sequence formula?
> >
> >
> > a1=.4
> >
> >
> > a1 , (a2=.1-~2*a1) , (a3=.1+~2*a2) , (a4=.1-~2*a3) , (a5=.1+~2*a4) ...
> >
> > (an=.1(+-)~2*an-1
> >
> >
> >
> > The verb would be specified as x f y, where x is the starting integer a1,
> >
> > and y is the number of terms (n) - or vice versa.
> >
> >
> > The result will be a vector n items long. Note the alternating sign in each
> >
> > term
> >
> >
> >
> > Example:
> >
> >
> > 4 f 5
> >
> >
> > 4 7 15 29 59
> >
> >
> >
> > Skip
> >
> > ----------------------------------------------------------------------
> >
> > For information about J forums see http://www.jsoftware.com/forums.htm
>
> > ----------------------------------------------------------------------
> > For information about J forums see http://www.jsoftware.com/forums.htm
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