Well, then I also remember that theoretical computer science exists.
Which is pretty much the background of the guy who wrote the code. So I can't say I was especially surprised by it, but it's still exasperating when I have to find a bug in the code.
Add to that that it's in clojure and heavily uses macros, and you end up with 100 lines of code in which I'm wandering around for hours now and am still not sure of what they do.
It's not quite Swearjure, but it is definitely reminiscent of old-school "efficient" C-code as far as readability is concerned.