module Union_find: Union_find
type 'a t
type 'a t is the type of objects, where each object is part of an
equivalence class that is associated with a single value of type 'a.
val create : 'a -> 'a t
create v returns a new object in its own equivalence class that has value v.
val get : 'a t -> 'a
get t returns the value of the class of t.
val set : 'a t -> 'a -> unit
set t v sets the value of the class of t to v.
val same_class : 'a t -> 'a t -> bool
same_class t1 t2 returns true iff t1 and t2 are in the same equivalence class.
val union : 'a t -> 'a t -> unit
union t1 t2 makes the class of t1 and the class of t2 be the same (if they are
already equal, then nothing changes). The value of the combined class is the value of
t1 or t2; it is unspecified which. After union t1 t2, it will always be the
case that same_class t1 t2.