Dan and Linda, I will describe how I think of ic 1j2 . ic 1j2 is the ravel of
a complex form of the Cartesian product of i: 1 and i: 2 .
Here, from the Vocabulary page for Catalogue { is a definition plus example of
Cartesian product:
CP=: {@(,&<)
0 1 CP 2 3 4
+---+---+---+
|0 2|0 3|0 4|
+---+---+---+
|1 2|1 3|1 4|
+---+---+---+
Then
(i: 1) CP i: 2
+-----+-----+----+----+----+
|_1 _2|_1 _1|_1 0|_1 1|_1 2|
+-----+-----+----+----+----+
|0 _2 |0 _1 |0 0 |0 1 |0 2 |
+-----+-----+----+----+----+
|1 _2 |1 _1 |1 0 |1 1 |1 2 |
+-----+-----+----+----+----+
j./&> (i: 1) CP i: 2
_1j_2 _1j_1 _1 _1j1 _1j2
0j_2 0j_1 0 0j1 0j2
1j_2 1j_1 1 1j1 1j2
My mind went straight to this last array. I wanted its ravel to be the result
of ic 1j2 .
Kip
Sent from my iPad
On Jan 20, 2013, at 9:43 PM, "Dan Bron" <[email protected]> wrote:
> Linda wrote:
>> ic=:[: , ([: i: 9&o.) j./ ([: i: 11&o.)
>> ic2=: [: , j./&i:/@+.
>> ic3=: 13 :'j./ i:+.y'
>
> Please post a description, in English, of the algorithm behind ic3. What is
> that verb attempting to accomplish? In operational terms, how does it
> transform its input to its output?
>
> If you can provide an analysis, similar to the one I posted yesterday, where
> you describe how you came to believe that ic3 is equivalent to ic (or ic2,
> whichever), that would be most helpful. Barring that, please provide a
> description of the algorithm behind ic (or ic2), as you understand it, which
> we could compare/contrast to your description of the algorithm underlying
> ic3.
>
> In short: from my perspective, ic and ic3 are different verbs, and I have no
> reason to believe that given identical inputs, they will produce identical
> outputs (and, as you noticed, the J interpreter shares this perspective, at
> least for certain inputs). I would like to understand why you believe
> differently.
>
> Bear in mind I ask this not in order to help you repair ic3 (which is
> trivial), but in order to understand your general approach to programming in
> J. I would honestly like to teach you to fish, as it were, rather than
> forcing you to continue to rely on others to catch fish for you.
>
> My first attempt at that was taking time and effort to write-up a formal
> procedure for transforming ic to ic2, to see if it could help you meet your
> goals of educating with J. I'm certainly willing to continue that effort in
> good faith - if you are.
>
> -Dan
>
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