[hyperthesis]

He learnt about recursion in a fp workshop(?), and as a first exercise, tried applying it to sort.

You pick a number in the list, then put lesser numbers into a left-list, and greater into a right-list. Recurse.

It's very slow as intuitive, simple and elegant fp, because it's creating new lists like crazy; but a mutable, in-place version (e.g. in C) is super fast. Maybe the origin of the folklore "learn fp to be a better coder, not to code fp"? I don't think he expected it to be so good; he was just doing him. A very smart man.