Good point about reusing variables, I've renamed all except the ones introduced locally. I would only say that these are "isomorphic to" others; in the real wo

Good point about reusing variables, I've renamed all except the ones introduced locally. I would only say that these are "isomorphic to" others; in the real world people do think of them differently, so it is important to enumerate them. And in particular people do think "the function", even though different the functions act differently. (the real question is, did I ever see "left-idempotent" and "right-idempotent" somewhere?)