Awesome resource; however both J and K are evolving, so we either have multitude of various versions of the languages or a comparison which is outdated - referring to the latest versions of the languages.

J is quite stable. In a set of simple examples, everything would be backwards compatible.

Seems a bit strange to put spaces around (some!) J primitives, but not around K primtives.

i thought that was author's impression of the prevailing coding styles in each language.

i think the only consistently whitespace-abundant k (not q!) code i have seen is by bob armstrong: http://cosy.com/K/CoSy.htm

Related:

J vs. K by Example - https://news.ycombinator.com/item?id=26041598 - Feb 2021 (13 comments)

Were APL, K, J, etc. ever used in production? Array programming seems like a cool idea (albeit being counterintuitive sometimes), and it's maybe one of the tersest syntaxes I've ever seen.

I've heard it's seen limited adoption in finance.

https://github.com/interregna/arraylanguage-companies

I mainly work in financial markets. I have personally seen it used many times in some places at most of the places I have worked at. KDB/Q is an important component for historical data and order capture here at OSL. The only issue I have is there are few developers and they cost a lot of money. We are lucky we have a very good one.

How much is "a lot"?

APL came out a LONG time ago and was sold by IBM for awhile. If you look for Dyalog's customers you'll see some recognizable names. Volvo has their entire inventory system in Dyalog APL or something like that if iirc. Kdb+ is used a good bit on Wall Street and also by F1 racing and a few other places. I'm sure J is in use somewhere, but it's probably a bit rarer.

https://www.dyalog.com/case-studies/hercules.htm

APL had non trivial uptake during its heyday.

J is apparently somewhat popular with actuaries and similar.

K/Q is used by a number of finance companies, via the KDB vector database. Here the selling point was that the overall system was great for in memory vector processing of stock tick data.

Arthur Witney also built a language named A+ while at Morgan Stanley that was used in production as an improvement over various previous APL apps.

They're odd languages but have found successful niches.

I read the K (K9) manual[0] and it points to https://shakti.com/ as the authoritative place to download K, but the download link is gone and Wayback Machine hasn't helped

[0] https://estradajke.github.io/k9-simples/k9/Introduction.html...

There's also a number of different open source implementations of various versions of K listed on the K wiki:

https://k.miraheze.org/wiki/Running_K

Thanks, I appreciate the link. As it turns out, it is really hard to google "K"

Yeah. Arthur Whitney's old company is Kx Systems which sells a vector in memory database for things like financial stock ticker analysis called Kdb+. I forget which version of K it is on. It mostly doesn't matter as most folks use the q-sql DSL on top of it. He then started another company called Shakti with some changes and what I guess is a later version of K. He had a download link up for a bit, but took it down iirc. I wish the site had more about the product listed, but we're not exactly the target audience (more for big banks).

Look at one of the captures around the end of 2021.