It ought to be the contamination of the mental images of a graph and a steep hill (which is hard to climb). Neither a pedagogical nor an intuitive analogy -- b

It ought to be the contamination of the mental images of a graph and a steep hill (which is hard to climb). Neither a pedagogical nor an intuitive analogy -- but fun! Since I don't write parsers for natural languages, I like that kind of expressions more than they irritate me. vi fans might think that is related to me prefering emacs... :-) Edit: Grammar, spelling. Sigh.