diff --git a/src/core/CCList.ml b/src/core/CCList.ml
index 8087df0d..d7426cd1 100644
--- a/src/core/CCList.ml
+++ b/src/core/CCList.ml
@@ -654,71 +654,69 @@ let filter_map f l =
       [ 1; 2; 3; 4; 5; 6 ])
 *)
 
-module Set = struct
-  let mem ?(eq=(=)) x l =
-    let rec search eq x l = match l with
-      | [] -> false
-      | y::l' -> eq x y || search eq x l'
-    in search eq x l
+let mem ?(eq=(=)) x l =
+  let rec search eq x l = match l with
+    | [] -> false
+    | y::l' -> eq x y || search eq x l'
+  in search eq x l
 
-  let add ?(eq=(=)) x l =
-    if mem ~eq x l then l else x::l
+let add_nodup ?(eq=(=)) x l =
+  if mem ~eq x l then l else x::l
 
-  let remove ?(eq=(=)) x l =
-    let rec remove_one ~eq x acc l = match l with
-      | [] -> assert false
-      | y :: tl when eq x y -> List.rev_append acc tl
-      | y :: tl -> remove_one ~eq x (y::acc) tl
-    in
-    if mem ~eq x l then remove_one ~eq x [] l else l
+let remove_one ?(eq=(=)) x l =
+  let rec remove_one ~eq x acc l = match l with
+    | [] -> assert false
+    | y :: tl when eq x y -> List.rev_append acc tl
+    | y :: tl -> remove_one ~eq x (y::acc) tl
+  in
+  if mem ~eq x l then remove_one ~eq x [] l else l
 
-  (*$Q
-    Q.(pair int (list int)) (fun (x,l) -> \
-      Set.remove x (Set.add x l) = l)
-    Q.(pair int (list int)) (fun (x,l) -> \
-      Set.mem x l || List.length (Set.add x l) = List.length l + 1)
-    Q.(pair int (list int)) (fun (x,l) -> \
-      not (Set.mem x l) || List.length (Set.remove x l) = List.length l - 1)
-  *)
+(*$Q
+  Q.(pair int (list int)) (fun (x,l) -> \
+    remove_one x (add_nodup x l) = l)
+  Q.(pair int (list int)) (fun (x,l) -> \
+    mem x l || List.length (add_nodup x l) = List.length l + 1)
+  Q.(pair int (list int)) (fun (x,l) -> \
+    not (mem x l) || List.length (remove_one x l) = List.length l - 1)
+*)
 
-  let subset ?(eq=(=)) l1 l2 =
-    List.for_all
-      (fun t -> mem ~eq t l2)
-      l1
+let subset ?(eq=(=)) l1 l2 =
+  List.for_all
+    (fun t -> mem ~eq t l2)
+    l1
 
-  let uniq ?(eq=(=)) l =
-    let rec uniq eq acc l = match l with
-      | [] -> List.rev acc
-      | x::xs when List.exists (eq x) xs -> uniq eq acc xs
-      | x::xs -> uniq eq (x::acc) xs
-    in uniq eq [] l
+let uniq ?(eq=(=)) l =
+  let rec uniq eq acc l = match l with
+    | [] -> List.rev acc
+    | x::xs when List.exists (eq x) xs -> uniq eq acc xs
+    | x::xs -> uniq eq (x::acc) xs
+  in uniq eq [] l
 
-  (*$T
-    Set.uniq [1;1;2;2;3;4;4;2;4;1;5] |> List.sort Pervasives.compare = [1;2;3;4;5]
-  *)
+(*$T
+  uniq [1;1;2;2;3;4;4;2;4;1;5] |> List.sort Pervasives.compare = [1;2;3;4;5]
+*)
 
-  let union ?(eq=(=)) l1 l2 =
-    let rec union eq acc l1 l2 = match l1 with
-      | [] -> List.rev_append acc l2
-      | x::xs when mem ~eq x l2 -> union eq acc xs l2
-      | x::xs -> union eq (x::acc) xs l2
-    in union eq [] l1 l2
+let union ?(eq=(=)) l1 l2 =
+  let rec union eq acc l1 l2 = match l1 with
+    | [] -> List.rev_append acc l2
+    | x::xs when mem ~eq x l2 -> union eq acc xs l2
+    | x::xs -> union eq (x::acc) xs l2
+  in union eq [] l1 l2
 
-  (*$T
-    Set.union [1;2;4] [2;3;4;5] = [1;2;3;4;5]
-  *)
+(*$T
+  union [1;2;4] [2;3;4;5] = [1;2;3;4;5]
+*)
 
-  let inter ?(eq=(=)) l1 l2 =
-    let rec inter eq acc l1 l2 = match l1 with
-      | [] -> List.rev acc
-      | x::xs when mem ~eq x l2 -> inter eq (x::acc) xs l2
-      | _::xs -> inter eq acc xs l2
-    in inter eq [] l1 l2
+let inter ?(eq=(=)) l1 l2 =
+  let rec inter eq acc l1 l2 = match l1 with
+    | [] -> List.rev acc
+    | x::xs when mem ~eq x l2 -> inter eq (x::acc) xs l2
+    | _::xs -> inter eq acc xs l2
+  in inter eq [] l1 l2
 
-  (*$T
-    Set.inter [1;2;4] [2;3;4;5] = [2;4]
-  *)
-end
+(*$T
+  inter [1;2;4] [2;3;4;5] = [2;4]
+*)
 
 module Idx = struct
   let mapi f l =
diff --git a/src/core/CCList.mli b/src/core/CCList.mli
index 41cd0888..5dcbc579 100644
--- a/src/core/CCList.mli
+++ b/src/core/CCList.mli
@@ -251,35 +251,36 @@ module Idx : sig
       too high. *)
 end
 
-(** {2 Set Operators} *)
+(** {2 Set Operators}
 
-module Set : sig
-  val add : ?eq:('a -> 'a -> bool) -> 'a -> 'a t -> 'a t
-  (** [add x set] adds [x] to [set] if it was not already present. Linear time.
-      @since 0.11 *)
+    Those operations maintain the invariant that the list does not
+    contain duplicates (if it already satisfies it) *)
 
-  val remove : ?eq:('a -> 'a -> bool) -> 'a -> 'a t -> 'a t
-  (** [remove x set] removes one occurrence of [x] from [set]. Linear time.
-      @since 0.11 *)
+val add_nodup : ?eq:('a -> 'a -> bool) -> 'a -> 'a t -> 'a t
+(** [add_nodup x set] adds [x] to [set] if it was not already present. Linear time.
+    @since 0.11 *)
 
-  val mem : ?eq:('a -> 'a -> bool) -> 'a -> 'a t -> bool
-  (** Membership to the list. Linear time *)
+val remove_one : ?eq:('a -> 'a -> bool) -> 'a -> 'a t -> 'a t
+(** [remove_one x set] removes one occurrence of [x] from [set]. Linear time.
+    @since 0.11 *)
 
-  val subset : ?eq:('a -> 'a -> bool) -> 'a t -> 'a t -> bool
-  (** Test for inclusion *)
+val mem : ?eq:('a -> 'a -> bool) -> 'a -> 'a t -> bool
+(** Membership to the list. Linear time *)
 
-  val uniq : ?eq:('a -> 'a -> bool) -> 'a t -> 'a t
-  (** List uniq. Remove duplicates w.r.t the equality predicate.
-      Complexity is quadratic in the length of the list, but the order
-      of elements is preserved. If you wish for a faster de-duplication
-      but do not care about the order, use {!sort_uniq}*)
+val subset : ?eq:('a -> 'a -> bool) -> 'a t -> 'a t -> bool
+(** Test for inclusion *)
 
-  val union : ?eq:('a -> 'a -> bool) -> 'a t -> 'a t -> 'a t
-  (** List union. Complexity is product of length of inputs. *)
+val uniq : ?eq:('a -> 'a -> bool) -> 'a t -> 'a t
+(** Remove duplicates w.r.t the equality predicate.
+    Complexity is quadratic in the length of the list, but the order
+    of elements is preserved. If you wish for a faster de-duplication
+    but do not care about the order, use {!sort_uniq}*)
 
-  val inter : ?eq:('a -> 'a -> bool) -> 'a t -> 'a t -> 'a t
-  (** List intersection. Complexity is product of length of inputs. *)
-end
+val union : ?eq:('a -> 'a -> bool) -> 'a t -> 'a t -> 'a t
+(** List union. Complexity is product of length of inputs. *)
+
+val inter : ?eq:('a -> 'a -> bool) -> 'a t -> 'a t -> 'a t
+(** List intersection. Complexity is product of length of inputs. *)
 
 (** {2 Other Constructors} *)