Thanks that's much nicer.
The only case it doesn't handle is the empty arg (which I didn't put in my
spec!).
mergeRow i.0
|length error: mergeRow
| mergeRow i.0
A quick fix:
mergeRow=: ((-.@] # [ (+/@:{~ <:,:])`(<:@])`[} I.@]) mergeMask) :: ((i.0)"_)
$mergeRow i.0
0
On Wed, Jun 8, 2016 at 9:29 AM, Raul Miller <[email protected]> wrote:
> Best I can think of is something like this:
>
> mergeMask=: [: ;@(+/\@(0 1&E.) <@(* ~:/\)/. ]) 0, 2 =/\ ]
> mergeRow=: (-.@] # [ (+/@:{~ <:,:])`(<:@])`[} I.@]) mergeMask
>
> Hopefully that makes sense?
>
> Thanks,
>
> --
> Raul
>
>
> On Tue, Jun 7, 2016 at 5:15 PM, Ric Sherlock <[email protected]> wrote:
> > I'm looking for a J-like approach to a verb for merging adjacent numbers
> in
> > a row where the numbers are the same. For example
> >
> > mergerow 4 4 4 4
> >
> > 8 8
> >
> > mergerow 8 8
> >
> > 16
> >
> > mergerow 16
> >
> > 16
> >
> > mergerow 4 4 4
> >
> > 8 4
> >
> > mergerow 8 4
> >
> > 8 4
> >
> > mergerow 4 8 8 4
> >
> > 4 16 4
> >
> >
> > My version below which I've used as part of the answer to a RosettaCode
> task
> > <http://rosettacode.org/wiki/2048#J> is very non J-like:
> >
> > mergerow=: verb define
> > len=. <:@# y
> > row=. i. i=. 0
> > while. (i <: len) *. len >: 0 do.
> > if. =/ (i , i+1) { y,_9 do.
> > row=. row, +: i { y
> > i=. i + 2
> > else.
> > row=. row, i { y
> > i=. i + 1
> > end.
> > end.
> > row
> > )
> >
> > I thought I had a good solution with:
> >
> > mergerow=: rplc (2&# ; +:)&>@~.
> >
> > But this seemed to cause unpredictable behaviour when used as part of the
> > whole solution.
> > ----------------------------------------------------------------------
> > 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
