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AviFS
AviFS
3:45 AM
@xpqz Ooh, that's really nice! I think I saw it in its infancy, but then I forgot about it. I haven't seen all this! And the APL Cultivation lessons converted to a more easily readable and slightly curated/edited format is super nice. I like that a lot!
Does anyone have any recommendations for good books, or nice essays, on J? I've been completely at a loss the past several times I've tried to find reading material to whet my appetite..
 
Adám
Adám
 
AviFS
AviFS
(Ideally, it's not just a textbook-like/encyclopedic guide to all the primitives and concepts. Something more like presenting a problem, and then an interesting solution in J. And ideally, it's not a character-for-character transliteration of the APL solution. Either a different approach than APL would take, or something APL isn't as good at.

Alternatively, maybe something like presenting the mathematics behind the language. Or the CS theory/alternative array paradigms that inspired it. Or a thoughtful something on the linguistic influence/why the names draw on parts of speech. Or somethin…
On second thought, all of the above but for K would also be interesting. I think I'm currently slightly skewed towards J, but K would also be great if there's good reading material at that level.
 
Adám
Adám
K people tend to not write about the language; neither discussion, nor documentation.
 
AviFS
AviFS
@Adám I've looked through all of that! It's after being surprised that I wasn't able to find anything appealing that I ask.
I'm especially surprised since I've read/heard that one of the pros of J is that there's a lot of mathematical stuff written for it. So that it's great for math education, or at least the recommendation goes that it's better for math education than Dyalog/other dialects. Math would be great! But I wasn't able to find much beyond some pieces that looked more like calculus/linear algebra textbooks, but with J code.
On the other hand, I commend the Dyalog community for such great and inviting learning resources! I hadn't appreciated it at the time, until now that I'm wanting to look at others.
 
Adám
Adám
@AviFS You could ask in the APL Farm's #j-edi-counsel channel.
 
AviFS
AviFS
4:00 AM
@Adám Interesting, wonder where these cultural things come from. Related to the fact that it was originally proprietary and largely used in industry, as opposed to the open-source of J, and J/APL slightly more academic origins?
@Adám Is there such a thing? I'll do that right away! Thanks Adám. This has been bothering me for a while!
 
Adám
Adám
Both J and APL started as closed source.
 
AviFS
AviFS
@Adám Oh wow. I knew about the APLs, but I figured J was always open source.
Did they ever make much money on J, before open sourcing?
 
Adám
Adám
Free ≠ open source.
 
 
6 hours later…
xpqz
xpqz
10:29 AM
@AviFS I wrote some stuff on k, too -- not quite as comprehensive: xpqz.github.io/kbook
I've not yet got the bug for J.
 
 
4 hours later…
Adám
Adám
2:56 PM
Announcement: BAA webinar (open session) in 5 minutes: Zoom 858 532 665 (zoom.us/j/858532665), passcode: ⎕←×/1920 12 17
 
TryAPL
TryAPL
@Adám 391680
 
 
3 hours later…
Jeremy gee
Jeremy gee
6:15 PM
I am converting degrees into degree minutes seconds. For example 42.125 degrees is 42 degrees 7 minutes and 30 seconds. I figured a way to split the 42.125 into 42 and 0.125 but I'm not sure how to apply the answer repeatedly. 60×2⊃60 1⊤42.125
 
Adám
Adám
@Jeremygee ⎕←0 60 60⊤3600×42.125
 
TryAPL
TryAPL
@Adám 42 7 30
 
Adám
Adám
This (and the inverse) should go on APLcart.
 
Jeremy gee
Jeremy gee
thank you!
 
Adám
Adám
@Jeremygee Does it matter that it fails on negative numbers?
How should negative values be represented? ¯42 ¯7 ¯30 or ¯42 7 30?
 
Jeremy gee
Jeremy gee
6:30 PM
Added an issue to the github,
not sure will think
 
Adám
Adám
Either 
(××0 60 60⊤3600×|)N
(3600÷⍨60∘⊥)N
or 
(×(×@1)0 60 60⊤3600×|)N
(3600÷⍨×∘⊃×60⊥|)N
 
Jeremy gee
Jeremy gee
I am just learning trig so may not be the best resource. Mathworks degree to dms documentation says the following. "In any given row of DMS, the sign of the first nonzero element indicates the sign of the overall angle. A positive number indicates north latitude or east longitude; a negative number indicates south latitude or west longitude. Any remaining elements in that row will have nonnegative values."
 
Adám
Adám
Right, of course you can't just use the first element, as it may be 0, but what they describe is really inconsistent, if I understand it right. −1°0′0″ + 0°−2′3″ = −1°2′3″
I think I prefer negating all elements, as then addition just works.
I can of course include entries for both, but the MathWorks system is going to be ugly.
 
whiskrs
whiskrs
7:00 PM
Friends, for a decade i've been trying to rewrite APL84 in C so my dad can run his old code. Learned a lot about APL and C but no complete luck. Any hints?
 
Adám
Adám
APL84?
 
whiskrs
whiskrs
It's a version. Upgraded from the original APL.
 
rak1507
rak1507
@whiskrs it might still run in dyalog
 
whiskrs
whiskrs
?! Gonna give it a try.
 
Adám
Adám
Never heard of APL84.
 
whiskrs
whiskrs
7:04 PM
(Whatever dyalog is. Will find out.)
 
Adám
Adám
What year is it from? 84?
 
whiskrs
whiskrs
It's from the 70s.
 
Adám
Adám
Then it should run in Dyalog with little to no changes.
 
whiskrs
whiskrs
Checking that out. Thank you!
 
rak1507
rak1507
if it doesn't, feel free to post some code here and people will probably be able to help port it
 
whiskrs
whiskrs
7:07 PM
The subject is public. 10,000 dimensional random vectors acting as orthogonal vectors.
 
Adám
Adám
Yeah, the only thing I'd thin might be incompatible are uses of ; for output, and uses of ⌶. Both are trivial to replace with modern things.
 
whiskrs
whiskrs
^ well noted
. . . message sent. The old guy can figure things out from there. THANK YOU!
 
Jeremy gee
Jeremy gee
@Adám Wikipedia has the following example conversion formulas. Just passing these on incase they help. Thanks so much @adam
Decimal degrees
Decimal degrees (DD) is a notation for expressing latitude and longitude geographic coordinates as decimal fractions of a degree. DD are used in many geographic information systems (GIS), web mapping applications such as OpenStreetMap, and GPS devices. Decimal degrees are an alternative to using sexagesimal degrees (degrees, minutes, and seconds - DMS notation). As with latitude and longitude, the values are bounded by ±90° and ±180° respectively. Positive latitudes are north of the equator, negative latitudes are south of the equator. Positive longitudes are east of the Prime Meridian; negative...
 
whiskrs
whiskrs
7:22 PM
(off we go, with a smile, see you next time)
 
Adám
Adám
7:58 PM
@Jeremygee Interesting:
> Note that with this formula only D can be negative and only S may have a fractional value.
So would −0.5 become −0 30 0?
 
Jeremy gee
Jeremy gee
8:14 PM
I think so. That's what ISO 6709 indicates. (Standard representation of geographic point location by coordinates)
However it may only hold for Latitude and Longitude calculations.
 
Adám
Adám
8:26 PM
But then that's not a numeric vector format any more. Even a language with negative zero couldn't do that because [-0,30,0] would compare equal to [0,30,0 when they are far apart.
 
Jeremy gee
Jeremy gee
ah I confess I am out of my depth on this.
 
LdBeth
LdBeth
get an extra sign bit
 
Jeremy gee
Jeremy gee
I believe we have reached null island
 

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