Make.1-OrdA total ordering function This is a two-argument function f such that f e1 e2 is zero if the values e1 and e2 are equal, f e1 e2 is strictly negative if e1 is smaller than e2, and f e1 e2 is strictly positive if e1 is greater than e2. Example: a suitable ordering function is the generic structural comparison function Pervasives.compare.