let bind_set (u: 'a set) (f: 'a -> 'b set) =
List.concat (List.map f u);;
-The following will be useful later: persuade yourself that `List.filter (test : 'a -> bool) (u : 'a set) : 'a set` is the same as:
+ The following will be useful later: persuade yourself that `List.filter (test : 'a -> bool) (u : 'a set) : 'a set` is the same as:
bind_set u (fun a -> if test a then unit_set a else empty_set)