J is probably the best language in the world to craft native GUIs (something k could never do very well, and now doesn't do at all).
It also has a wonderful amount of books on it, most of them Creative Commons-licensed now (as all/most of Iverson's books are, I believe). It's significantly easier to learn for someone new to array languages yet who doesn't have the sort of hands-on training you can get with APL & k; you could go into the woods with nothing but the J interpreter tarball for a week and come out pretty having internalized the language, and it's even easier with some of the other books available.
I was kinda thinking the exact same thing with regards to J.
Btw Scott, I've been meaning to ask you about what tools you're using for your work for awhile, but don't see an email address anywhere on your blog.
It seems like you've tried Lush, Clojure, Lua (Torch 7), J, R, and a bunch of other technologies. I've had the chance to try some of these for hobby purposes, but nothing for work yet, so I would trust your evaluation more than mine. Have you given up on array languages all together?
Lush is worth people's attention for its design, but I didn't feel like getting involved with language maintenance: my strengths are elsewhere. J also solves all the problems Lush did and has a larger user community.
Clojure was cool, but JVM is basically worthless to me.
It also has a wonderful amount of books on it, most of them Creative Commons-licensed now (as all/most of Iverson's books are, I believe). It's significantly easier to learn for someone new to array languages yet who doesn't have the sort of hands-on training you can get with APL & k; you could go into the woods with nothing but the J interpreter tarball for a week and come out pretty having internalized the language, and it's even easier with some of the other books available.
It's, of course, free software.