[pierrec]

I've been slowly learning J on and off for the past year or so (well, I wanted to learn it ever since I saw this [1]). It still feels pretty write-only to me, and I wouldn't make any large project in it, but as a brainstorming, research and experimentation tool, it's gold. This especially applies if you're working with matrices or things that can be well represented by arrays of any dimension.

The jqt environment that comes with the standard package is polished, and encourages an interactive workflow where you progressively build your sentences while looking at the output. This way also greatly eases the learning curve.

Another useful tool to help learning is the cheat sheet [2]. I'm not really into dead trees but I still printed it on paper because I'm not surrounded by monitors, and it really helps to have a quick reference to the very rich and concise J vocabulary. Applying unexplored verbs to problems that interest you is a fun exercise.

One thing that struck me it that it's difficult to look up examples to help you as you go, in part because the one-letter name is not search engine-friendly, but more importantly because of the small size of the J corpus out there on the web. This is good because it force you to find solutions yourself, but it's bad because you never know if you're limiting yourself to a sub-optimal solution.

[1]: https://news.ycombinator.com/item?id=1041500

[2]: http://www.jsoftware.com/jwiki/HenryRich?action=AttachFile&d...

[RodgerTheGreat]

I have been teaching myself K, and one useful resource for me has been http://codegolf.stackexchange.com. There are a handful of active users who write solutions in J, so it might be a good way to compare your solutions with those of another J programmer.