>>Wonder what's up with functional languages that leads them to do this.

One way to teach dry math'y concepts is to make them fun to learn. Serious Math people mind find them irritating but for the remainder crowd it is a fun exercise.

Sure, though I suppose fun is in the eye of the beholder. Grokking Algorithms is illustrated with cartoons and examples that kids could understand, but it doesn't indulge in the same weird quirky whimsy that some of these texts do. It's almost as if they're written in some lost lolcat dialect.