For production software I program in Python, C#, Java, PHP, HTML5/JS but to keep my language skills and curiosity happy, I play around with different Lisps (including Clojure/Shen), APLs (including Q), Forths and languages made for formal verification (Idris/Coq). It is very interesting what people do with these languages and I like playing with most of them, but besides niche jobs, I don't cannot use them for production. It is simply not sellable to companies who are not used to them.

I have a copy of the first Q for Mortals (I bought it a while ago); thanks for this one for free.

KDB might be niche, but that niche is finance and there are a decent number of open KDB positions. I get a couple of unsolicited emails a week for them. And they pay very well.

tluyben2

Yes, Clojure (that Lisp variety) as well. Forth for embedded as well. But they are niche; it depends where you live etc on which opportunities there are for each of those. But yes, you are right; Kdb (and Clojure btw) are good in some parts of finance and pay well.

Edit: what i'm basically saying is that practicing any of these languages will help you in potentially more than one way; it will open your mind to interesting paradigms and constructs as well as give you job opportunities you would not think of possibly later on.

Edit2: https://github.com/JohnEarnest/ok is interesting for playing around by the way