ocaml: phase 6 Map/Set extensions iter/fold/filter/union/inter (+4 tests, 422 total)

Map.Make: iter, fold, map, filter, is_empty added.
Set.Make: iter, fold, filter, is_empty, union, inter added.

All written in OCaml inside the existing functor bodies. Tested:
  IntMap.fold (fun k v acc -> acc + v) m 0           = 30
  IntSet.elements (IntSet.union {1,2} {2,3})         = [1; 2; 3]
  IntSet.elements (IntSet.inter {1,2,3} {2,3,4})     = [2; 3]

lib/ocaml/runtime.sx

@@ -435,6 +435,32 @@
          match m with
          | [] -> 0
          | _ :: t -> 1 + cardinal t
+
+       let rec iter f m =
+         match m with
+         | [] -> ()
+         | (k, v) :: t -> f k v; iter f t
+
+       let rec fold f m acc =
+         match m with
+         | [] -> acc
+         | (k, v) :: t -> fold f t (f k v acc)
+
+       let rec map f m =
+         match m with
+         | [] -> []
+         | (k, v) :: t -> (k, f v) :: map f t
+
+       let rec filter p m =
+         match m with
+         | [] -> []
+         | (k, v) :: t ->
+           if p k v then (k, v) :: filter p t else filter p t
+
+       let rec is_empty m =
+         match m with
+         | [] -> true
+         | _ -> false
      end
    end ;;
 
@@ -472,6 +498,36 @@
          match s with
          | [] -> 0
          | _ :: t -> 1 + cardinal t
+
+       let rec iter f s =
+         match s with
+         | [] -> ()
+         | h :: t -> f h; iter f t
+
+       let rec fold f s acc =
+         match s with
+         | [] -> acc
+         | h :: t -> fold f t (f h acc)
+
+       let rec filter p s =
+         match s with
+         | [] -> []
+         | h :: t -> if p h then h :: filter p t else filter p t
+
+       let rec is_empty s =
+         match s with
+         | [] -> true
+         | _ -> false
+
+       let rec union a b =
+         match b with
+         | [] -> a
+         | h :: t -> union (add h a) t
+
+       let rec inter a b =
+         match a with
+         | [] -> []
+         | h :: t -> if mem h b then h :: inter t b else inter t b
      end
    end")