Yes.
(2 2 $ 1 2 3 4)
1 2
3 4
i.1 2
0 1
i.3 4
0 1 2 3
4 5 6 7
8 9 10 11
(i.1 2),: i.3 4
0 1 0 0
0 0 0 0
0 0 0 0
0 1 2 3
4 5 6 7
8 9 10 11
i. (2 2 $ 1 2 3 4)
0 1 0 0
0 0 0 0
0 0 0 0
0 1 2 3
4 5 6 7
8 9 10 11
I tried to describe this behavior in section "The Monadic Array
Operation Helper Program" in this manual:
https://github.com/andrimne/JWithATwist.DocBook/raw/master/target/en/JWithATwistReferenceManual.pdf
As far as my tests show J and JWithATwist behaves the same in this regard.
I doubt you can find reasonably accurate descriptions of this
functionality (these four helper programs) anywhere else.
To understand J you have to understand this functionality, as I see it.
It is essential in everything you do in J.
Cheers,
Erling Hellenäs
Den 2017-12-13 kl. 00:34, skrev 'Jon Hough' via Programming:
The zero-padding is happening because i. acts on each row but returns different
shaped results for each row.
Try this:
i.&.> <"1[2 2 $ 1 2 3 4
This will give boxed results of the correct shape for each row.
Another example of this kind of zero-padding is
q: 5 100000
q: will get the prime factors of each number. 5 only has one factor, itself,
whereas 100000 has many factors. J will zero pad
the result of q: 5 to match the shape of q: 100000.
Doing something like this:
q:&.> <"0[ 5 100000
will give non-zero-padded results. The results are boxed.
--------------------------------------------
On Wed, 12/13/17, TongKe Xue <[email protected]> wrote:
Subject: [Jprogramming] i. (2 2 $ 1 2 3 4)
To: [email protected]
Date: Wednesday, December 13, 2017, 7:49 AM
Hi,
I understand what (2 2 $ 1 2 3
4) does.
I understand what i. 1 2 does
I understand what i. 3 4 does.
I have read http://www.jsoftware.com/help/jforc/loopless_code_i_verbs_have_r.htm#_Toc191734331
I understand the concept of
verb-rank, of frames + cells, of
"promoting one frame to another if they
share the same prefix."
I don't understand how the 0
padding in
i. (2 2 $ 1 2 3 4) works
What is the mechanism by which
0-padding is happening?
Thanks,
--TongKe
====
2 2 $ 1 2 3 4
1 2
3 4
i. 1 2
0 1
i. 3 4
0 1 2 3
4 5 6 7
8 9 10 11
i. (2 2 $ 1 2 3 4)
0 1 0 0
0 0 0 0
0 0 0 0
0 1 2 3
4 5 6 7
8 9 10 11
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