The APLs and especially, for me, j and k, are really interesting languagues. For one, I agree with Whitney, the creator of k, that you should not have to scroll to read your software. I think making sure at least every function points fits on a phone screen is a large boon for readability and maintainability. It is not the fact that it fits there, it is more so that if it does, you can work on that implementation mentally focused: without jumping pages or even files. I know a lot of people find j,k and even Forth unreadable, but that is really just practice. When I got used to it, I found, for instance, c# a lot more annoying to read. It is somewhat (this is a bit over the top, but you get the idea) the difference between reading Godel his original whitepaper (in German ofcourse) and Godel, Escher Bach explaining that whitepaper. Both are good reads, but the original paper, when you have the background context, is easier to read and debug that that enormous volume.

I hope to find more time to explore these avenues. For now, k and forth mixtures are my favorite to mess around with; I created a little language to do live coding on my phone for Xamarin and the forth/k mix I use is actually the first thing that is not annoying to work with on a phone screen. Because most happens in your brain and what you type is a few hieroglyphs, the development is interactive, you can walk around doing it. I hope to clean it up enough to release it (I am old, I do not like this releasing of half baked stuff usually, unless it is game related): it saves me a lot hell doing edit/compile/wait/test cycles.

For playing around, check out oK : it is a k implementation in JS, it is slow but works everywhere and has some cool features for making graphics and little games.