Xash:
(3 ({. ~: {:)\ 0,],0:)
That's brilliant! It only took me 5 minutes to understand what this means
this time :-)
Elijah:
Thank you for the clarification. The adverb rule is foreign to me, I will
have to explore some examples to see why it makes sense for it to be
different from the verb rule.
> Now why steps 10-13 result in the next row of a sierpinski triangle, I
> don't know, I guess it has to do with generating a Pascal triangle.
It's not that important for learning J, but it gives a hint why the
seemingly confusing `72#:~8#2` was used. `bm{~3#.\row` maps three consecutive
bits to
I know this question is about understanding some J code, but perhaps it is
worth noting that the Jqt Studio|Showcase|isigraph demo has other examples,
including Cliff Reiter's elegant:
load 'viewmat'
viewmat (,,.~)^:8 ,1
--
On Wed, 2 Feb 2022, Andrew P wrote:
A question that I have is: can V0 V1 V2 V3 V4 can become V0 V1 V2 (V3
V4) instead of V0 V1 (V2 V3 V4)?
Nope. A way to think about it is that the parser eats verbs from the
right, as many as it can handle. So if you start with V0 V1 V2 V3 V4 V5,
it first
Hello everyone,
First of all, thank you so much for all the responses. After reading each
one multiple times and spending several hours looking at this program, I
think that I have made progress.
Hauke:
I hadn't noticed that parentheses were, as a rule of thumb, matched.
About dissect: it is not
It's probably worth noting here that the {: here is used to grab the
last row of the partial result which is being built.
Initially, this is a list of y zeros, followed by a 1, followed by y zeros.
,: 1 (15)} (>:+:15) $ 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Note
Andrew, your observations are correct.
Now consider this part which is an amend to create
and amend a long list of zeroes.
1 (15)} (>:+:15) $ 0NB. beware, of long result
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
$,:1 (15)} (>:+:15) $ 0 NB. ,: forces a new dimension
another approach that could be helpful
with respect to that question:
try removing that , and rearranging
)@{:)^:y
to become
)^:y)@{:
in the definition
what does it compute now?
Sierpinski =: {{ (((72#:~8#2){~3#.\0,],0:)^:y)@{: ,: 1 y} (>:+:y) $ 0 }}
' #'{~ Sierpinski"0 i.>:15
This gives
20:10
To: programm...@jsoftware.com
Subject: Re: [Jprogramming] Sierpinski triangle
Hello,
Besides dissect that I really like, Art's flowtree (
https://code.jsoftware.com/wiki/User:Art_Anger/FlowTree) looks pretty
interesting too, but I haven't used it much yet.
Best regards,
On Tue, Feb 1, 2022 a
Hello,
Besides dissect that I really like, Art's flowtree (
https://code.jsoftware.com/wiki/User:Art_Anger/FlowTree) looks pretty
interesting too, but I haven't used it much yet.
Best regards,
On Tue, Feb 1, 2022 at 7:59 PM Hauke Rehr wrote:
> You already understood that some kinds of
You already understood that some kinds of brackets
don’t come in balanced pairs. But parentheses () nearly
always do, the exceptions being inside of strings,
obviously, and closing ) on a line of its own
(which doesn’t occur here, so I won’t explain that).
(oh, and {{…}} introduced another
I have found in a forum the following J code that generates a Sierpinski
triangle, and am trying to understand how it works.
sierpinski =: {{ (, ((72#:~8#2){~3#.\0,],0:)@{:)^:y ,: 1 y} (>:+:y) $ 0 }}
' #'{~ sierpinski 15
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