(defn complement
"Takes a fn f and returns a fn that takes the same arguments as f,
has the same effects, if any, and returns the opposite truth value."
{:added "1.0"
:static true}
[f]
(fn
([] (not (f)))
([x] (not (f x)))
([x y] (not (f x y)))
([x y & zs] (not (apply f x y zs)))))