Just for the record, I include my solution for guard in the following.
I wanted to find a purely tacit version of guard but I couldn't. You
can see the struggle; it's complex. As you might notice, I tried to
follow the repetitive pattern shown in my original 3d version. Of
course the final code is more complex than Raul's guard, which takes
use of "take."
enc=: 0,~0,]
er=: enc"
erstep=: 3 : '(>:r) ; (r=.>{.y) er >{:y'
guard=:[: >@{: ([EMAIL PROTECTED]:([EMAIL PROTECTED]@[) (1 ; ]))
guard >:i. 2
0 1 2 0
guard >:i. 2 3
0 0 0 0 0
0 1 2 3 0
0 4 5 6 0
0 0 0 0 0
guard >:i. 2 3 4
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 1 2 3 4 0
0 5 6 7 8 0
0 9 10 11 12 0
0 0 0 0 0 0
0 0 0 0 0 0
0 13 14 15 16 0
0 17 18 19 20 0
0 21 22 23 24 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
2008/6/17 June Kim <[EMAIL PROTECTED]>:
> 2008/6/17 Raul Miller <[EMAIL PROTECTED]>:
>> On 6/17/08, June Kim <[EMAIL PROTECTED]> wrote:
>>> Now, the next part. You want to make the code general, so it can treat
>>> n-dimension.
>> ...
>>> How would you generalize guard code in J style? I believe there is a
>>> simple solution.
>>
>> guard=: ({.~ _1 - $)@({.~ 1 + $)
>
> Great. I always tend to underestimate the power and usefulness of "take".
>
>
>> guard 1 2 3
>> 0 1 2 3 0
>> guard 1 2 3,:4 5 6
>> 0 0 0 0 0
>> 0 1 2 3 0
>> 0 4 5 6 0
>> 0 0 0 0 0
>>
>> --
>> Raul
>> ----------------------------------------------------------------------
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>>
>
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