Ah, I see it now -- I should have looked closer at your digraphs.
Here's a fixed version:
digra=: * 2 | i.@# + +/\
dedouble=: #!.'X'~ 1 j. [: digra #{.}.=}:
(I could not think of a good name for the "compress out splits of
non-digraphs" mechanism.)
The moral of the story here is that numeric calculations can often
replace simple recursive processes. (Because numbers can be defined
recursively.)
I hope this helps,
--
Raul
On Thu, Feb 4, 2021 at 5:50 AM Ric Sherlock <tikk...@gmail.com> wrote:
>
> Sorry I should have been a bit more explicit with the specification.
>
> The reason that the double O in the 2nd example does not get an X inserted
> is that once the X is inserted for the first double, the Os are split
> between 2 digraphs and no longer require to be separated. In other words,
> after the first insertion, the digraphs need to be re-generated to see if
> further insertions are required.
>
> _2 ]\ dedouble 'THEEQUICKBROWFOOX'
> TH
> EX
> EQ
> UI
> CK
> BR
> OW
> FO
> OX
>
> A simple non-looping solution doesn't leap out at me!
>
>
> On Thu, Feb 4, 2021 at 6:20 PM Raul Miller <rauldmil...@gmail.com> wrote:
>
> > I would be tempted to go with
> >
> > dedouble=: #!.'X'~ 1 j. #{.}.=}:
> >
> > But I do not understand why the double O in your second example does
> > not get an X inserted. So maybe I am missing something.
> >
> > I hope this helps,
> >
> > --
> > Raul
> >
> > On Wed, Feb 3, 2021 at 11:02 PM Ric Sherlock <tikk...@gmail.com> wrote:
> > >
> > > I need to separate any digraphs in a string, that consist of 2 letters
> > the
> > > same, by inserting an 'X' between them.
> > > _2 ]\ 'THEEQUICKBROWFFOX'
> > > TH
> > > EE
> > > QU
> > > IC
> > > KB
> > > RO
> > > WF
> > > FO
> > > X
> > >
> > > 'EE' is a digraph that needs an 'X' inserted. Doing so will result in:
> > >
> > > TH
> > > EX
> > > EQ
> > > UI
> > > CK
> > > BR
> > > OW
> > > FF
> > > OX
> > >
> > > So now we also need to separate the 'FF' digraph.
> > >
> > > I want to define a verb "dedouble" that will process a string so:
> > > dedouble 'THEEQUICKBROWFFOX'
> > > THEXEQUICKBROWFXFOX
> > > But:
> > > dedouble 'THEEQUICKBROWFOOX'
> > > THEXEQUICKBROWFOOX
> > >
> > > I have implemented a solution at
> > > https://rosettacode.org/wiki/Playfair_cipher#J but am interested in
> > > alternative implementations.
> > > ----------------------------------------------------------------------
> > > 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
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