[myco_logic]

I also came here to mention this video. Watching the solution emerge line-by-line is a profound experience, and highly revelatory towards the kind of iterative problem-solving workflow possible in the Iversonian languages.

In the same vein, John Scholes' collection of APL code in the Dfns workspace[0] is positively wonderful to read through. I think it's probably one of the finest repositories of annotated code ever assembled.

[0]: http://dfns.dyalog.com/