Funny moment in LP this morning; Frank's teaching us "difference lists", a funny technique in logic programming that seems a bit nontrivial in the case of doing queues, a little bit less impressive in the case of merely implementing reverse.

Because of this, Ruy asks something like "what's the difference between this difference list implementation and just treating it like an ordinary accumulator-passing function with two inputs and one output?"

Frank, with a completely straight face: "Ah, this has a much fancier name."