This is nice.

I would package it as:

validalt=: 1 = [: (>./-<./) [: +/\ 1 _1 +/ .* ]

Thanks,

-- 
Raul

On Sat, Jul 28, 2012 at 7:12 AM, R.E. Boss <[email protected]> wrote:
> My 2 cents:
>
>    (>./-<./)+/\+/1 _1 *A
> 1
>
>    (>./-<./)+/\+/1 _1 *B
> 2
>
> So A qualifies, B does not.
>
>
> R.E. Boss
>
>
>> -----Oorspronkelijk bericht-----
>> Van: [email protected] 
>> [mailto:[email protected]] Namens Linda Alvord
>> Verzonden: zaterdag 28 juli 2012 9:43
>> Aan: [email protected]
>> Onderwerp: Re: [Jprogramming] Determining an 'alternating' binary array
>>
>> In this case the tacit version leads to a better explicit definition:
>>
>>
>>    al=: 13 :'(-:((2 2$0 1 1 0)$~#))(|: y) -. 0 0'
>>    al
>> [: (-: ((2 2$0 1 1 0) $~ #)) 0 0 -.~ |:
>>
>>    al2=: 13 :'(-:(2 2$0 1 1 0)$~#)0 0 -.~|:y'
>>    al2
>> [: (-: ((2 2$0 1 1 0) $~ #)) 0 0 -.~ |:
>>
>> Linda
>>
>> -----Original Message-----
>> From: [email protected]
>> [mailto:[email protected]] On Behalf Of Linda Alvord
>> Sent: Saturday, July 28, 2012 3:14 AM
>> To: [email protected]
>> Subject: Re: [Jprogramming] Determining an 'alternating' binary array
>>
>> This seems to work as well:
>>
>>    (|:A)-: |: A/:A
>> 1
>>    al=: 13 :'(-:((2 2$0 1 1 0)$~#))(|: y) -. 0 0'
>>    al
>> [: (-: ((2 2$0 1 1 0) $~ #)) 0 0 -.~ |:
>>
>>    al A
>> 1
>>    al B
>>
>> -----Original Message-----
>> From: [email protected]
>> [mailto:[email protected]] On Behalf Of Linda Alvord
>> Sent: Saturday, July 28, 2012 2:45 AM
>> To: [email protected]
>> Subject: Re: [Jprogramming] Determining an 'alternating' binary array
>>
>> Here's an alternative to 'alternative'
>>
>>     ]A=:2 8$  0 0 1 0 0 0 0 1 1 0 0 0 1 0 0 0
>> 0 0 1 0 0 0 0 1
>> 1 0 0 0 1 0 0 0
>>    ]B=:2 5$1 0 0 0 1 0 1 1 0 0
>> 1 0 0 0 1
>> 0 1 1 0 0
>>    alt=: 13 :'(-:((2 2$0 1 1 0)$~#))(|: y /:y) -. 0 0'
>>    alt
>> [: (-: ((2 2$0 1 1 0) $~ #)) 0 0 -.~ [: |: /:~
>>
>>    alt A
>> 1
>>    alt B
>> 0
>>
>> Linda
>>
>> -----Original Message-----
>> From: [email protected]
>> [mailto:[email protected]] On Behalf Of Marshall
>> Lochbaum
>> Sent: Friday, July 27, 2012 11:56 AM
>> To: [email protected]
>> Subject: Re: [Jprogramming] Determining an 'alternating' binary array
>>
>> Here's another option: convert the two rows into one using base 2, discard
>> the ones that are 0, and check if the remaining ones are 1 2 1...
>> I borrowed the sort in Raul's solution so that they must be in that order,
>> not 2 1 2... .
>>
>> alternate =: (-: 1 2$~$)@:(0 -.~ #.@|:)@:/:~
>>
>> Note that we don't have to convert to binary. In this case, we end up with
>>
>> alternate =: (-: (0 1,:1 0)$~#)@:(0 0 -.~ |:)@:/:~
>>
>> Marshall
>>
>> On Fri, Jul 27, 2012 at 10:39 AM, Brian Schott
>> <[email protected]>wrote:
>>
>> > Another approach?
>> >
>> > alternates =: [: -. 1 e. [: +/ 0 1 |."0 1 ] #"_ 1~ +./ noAnds =:
>> > *./@(-.@(*./)) check =: noAnds *. alternates
>> >
>> >
>> >
>> >
>> > --
>> > (B=)
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