module type OrderedType = Set.OrderedType
type
t
val compare : t -> t -> int
f
such that
f e1 e2
is zero if the elements 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
.