diff --git a/enum.ml b/enum.ml
index 544de648..d1274a16 100644
--- a/enum.ml
+++ b/enum.ml
@@ -424,6 +424,9 @@ let combinations n enum =
   assert (n >= 0);
   failwith "not implemented" (* TODO *)
 
+let powerSet enum =
+  failwith "not implemented"
+
 (** {2 Basic conversion functions} *)
 
 let to_list enum =
diff --git a/enum.mli b/enum.mli
index 85089402..3e44dce5 100644
--- a/enum.mli
+++ b/enum.mli
@@ -155,10 +155,14 @@ val product : 'a t -> 'b t -> ('a * 'b) t
   (** Cartesian product *)
 
 val permutations : 'a t -> 'a t t
-  (** Permutations of the enum *)
+  (** Permutations of the enum. Each permutation becomes unavailable once
+      the next one is produced. *)
 
 val combinations : int -> 'a t -> 'a t t
-  (** Combinations of given length *)
+  (** Combinations of given length. *)
+
+val powerSet : 'a t -> 'a t t
+  (** All subsets of the enum (in no particular order) *)
 
 (** {2 Basic conversion functions} *)