diff --git a/src/data/CCDeque.ml b/src/data/CCDeque.ml
index bbcfaf8f..e253922d 100644
--- a/src/data/CCDeque.ml
+++ b/src/data/CCDeque.ml
@@ -121,6 +121,14 @@ let append_front ~into q = iter (push_front into) q
 
 let append_back ~into q = iter (push_back into) q
 
+(*$R
+  let q = of_list [3;4] in
+  append_front ~into:q (of_list [2;1]);
+  assert_equal [1;2;3;4] (to_list q);
+  append_back ~into:q (of_list [5;6]);
+  assert_equal [1;2;3;4;5;6] (to_list q);
+*)
+
 let fold f acc d =
   match !d with
   | None -> acc
@@ -171,6 +179,14 @@ let of_list l =
   List.iter (push_back q) l;
   q
 
+(*$R
+  let q = of_list [1;2;3] in
+  assert_equal 1 (take_front q);
+  assert_equal 3 (take_back q);
+  assert_equal 2 (take_front q);
+  assert_equal true (is_empty q)
+*)
+
 let to_rev_list q = fold (fun l x -> x::l) [] q
 
 let to_list q = List.rev (to_rev_list q)
diff --git a/src/data/CCDeque.mli b/src/data/CCDeque.mli
index aa3b5cb6..804c776b 100644
--- a/src/data/CCDeque.mli
+++ b/src/data/CCDeque.mli
@@ -57,16 +57,16 @@ val push_back : 'a t -> 'a -> unit
 (** Push value at the back *)
 
 val peek_front : 'a t -> 'a
-(** First value, or Empty *)
+(** First value, or @raise Empty if empty *)
 
 val peek_back : 'a t -> 'a
-(** Last value, or Empty *)
+(** Last value, or @raise Empty if empty *)
 
 val take_back : 'a t -> 'a
-(** Take last value, or raise Empty *)
+(** Take last value, or @raise Empty if empty *)
 
 val take_front : 'a t -> 'a
-(** Take first value, or raise Empty *)
+(** Take first value, or @raise Empty if empty *)
 
 val append_front : into:'a t -> 'a t -> unit
 (** [append_front ~into q] adds all elements of [q] at the front