On the lines of ascii art, I found at Ewart Shaw's site (
http://www.ewartshaw.co.uk/jwhat.html) this jem:
{&'#.' @ (2:<|) @ ((+*:)^:400 0:) (18 %~ i:_20) j.~/ 28 %~ _59+i.75
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Fractals look nice on a t-shirt...
~Yuva
On 5/17/07, Dan Bron <[EMAIL PROTECTED]> wrote:
I call these phrases "jems": J gems.
The problem with elegant phrases is they only impress if you already know
the language.
Which is to say, it's hard to impress non-Jers with jems.
Non-Jers are more likely to be impressed by pretty pictures, and since
graphics aren't defined by the J language, phrases which produce graphics
can not be termed jems.
Jers, on the other hand, are more likely to be impressed by J phrases
which make elegant of the language, and reduce complex word problems to
minute J expressions (e.g. the Josephus Problem (A)).
I therefore conclude that the best candidates for jems are concise phrases
which produce ASCII art. Such phrases are poised to astound the elect and
the hoi polloi alike.
Here's a great example:
|._31]\,(,.~,])^:4,:'* '
*
* *
* *
* * * *
* *
* * * *
* * * *
* * * * * * * *
* *
* * * *
* * * *
* * * * * * * *
* * * *
* * * * * * * *
* * * * * * * *
* * * * * * * * * * * * * * * *
This concise formulation of the Sierpinski Triangle is was a collaborative
effort, with the final expression due to Raul Miller (B).
The creme de la creme are those jems which exploit subtle or surprising
mathematical identities. For example, John Randall pointed out that the
triangle can be calculated with Pascal's Triangle mod 2 (C):
' *'{~'1'=(-|."_1[:":2|!/~)i.-16
*
* *
* *
* * * *
* *
* * * *
* * * *
* * * * * * * *
* *
* * * *
* * * *
* * * * * * * *
* * * *
* * * * * * * *
* * * * * * * *
* * * * * * * * * * * * * * * *
Having said all that, one of my personal favorites doesn't produce ASCII
art at all. The problem (D) called for a verb which would create a table
which could be visualized thus:
http://upload.wikimedia.org/wikipedia/commons/4/43/JPEG_ZigZag.svg
which is obviously hard to represent in ASCII art. Nevertheless, the
solution in J was, to me, one of the best and most compelling examples of
the language:
zz =: ($ [: /:@; [: <@|.`< /. i.)@,~
Again, this was a collaborative effort, but the final form was due to Oleg
Kobchenko (E). Depending on your taste, the use of a gerund argument
to \. is either innovative or precious (in the pejorative sense). If the
latter, you might prefer this formulation:
zz =: ($ [: /:@; [: <@(A.~_2|#)/. i.)@,~
In either case:
zz 4
0 1 5 6
2 4 7 12
3 8 11 13
9 10 14 15
-Dan
(A) http://www.jsoftware.com/jwiki/Essays/Josephus_Problem
(B)
http://www.jsoftware.com/pipermail/programming/2006-September/003206.html
(C)
http://www.jsoftware.com/pipermail/programming/2006-April/002043.html
(D)
http://www.jsoftware.com/pipermail/programming/2006-November/004150.html
(E)
http://www.jsoftware.com/pipermail/programming/2006-November/004159.html
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