hckrnws

Only APL and K see real industry use. Both are actively developed. K is really a family of mutually incompatible languages, called K3, K4, K5, etc. Financial applications and most of the development is on K4, as far as I understand.

> Which APL derivatives (with an active/healthy userbase) besides k would you recommend to take a closer look at?

But why not APL? Dyalog has a team actively working on their interpreter, and industry has mostly converged around Dyalog APL now. If you want something well-worn through real-world use, then it's basically the only choice, unless you have money to drop on K4 or Shakti. Also, the literature is dominated by APL.

If you're more interested in array languages for their mathematical appeal and for tinkering on puzzle problems, then BQN will probably suit your tastes. If you don't like the symbols and want something open-source, then J is a strong option. If you wonder what kind of baby APL and Forth would have, then Uiua is just for you.

Note that while J and BQN can be considered APL variants, K is somewhat of a separate beast.

Have fun!

I've written and worked on real-world APL applications, and this doesn't fit my experience. APL allows writing some of the most readable code out there, specifically because it makes whole-application architecture imminently more visible.

I like APL because it keeps me from bike-shedding on boilerplate or ceremony and forces me to consistently think about fundamental issues in the problem domain.

That said, APL by beginners (including myself, years ago) can be pretty terrible and effectively write-only. The steep learning curve is very real, and learning to write good APL is synonymous with learning good application architecture and UX.