add Dllist.iter_l, reset

lib/data/dllist.ml

@@ -25,6 +25,12 @@ let create () =
 
 let is_empty seq = seq.next == seq
 
+let reset seq =
+  begin
+    seq.next <- seq;
+    seq.prev <- seq;
+  end
+
 let remove node =
   if node.node_active then begin
     node.node_active <- false;
@@ -74,6 +80,15 @@ let fold_r f seq acc =
   in
   loop seq.prev acc
 
+let iter_l f seq =
+  let rec loop curr =
+    if curr != seq then
+      let node = node_of_seq curr in
+      if node.node_active then f node.node_data;
+      loop node.node_next
+  in
+  loop seq.next
+
 let find f seq =
   let rec loop curr =
     if curr == seq then

lib/data/dllist.mli

@@ -21,6 +21,9 @@ val create : unit -> 'a t
 val is_empty : 'a t -> bool
   (** Returns [true] iff the given sequence is empty *)
 
+val reset : 'a t -> unit
+  (** [reset ()] is a lazy way to remove all the elements from the sequence *)
+
 val add_l : 'a -> 'a t -> 'a node
   (** [add_l x s] adds [x] to the left of the sequence [s] *)
 
@@ -57,6 +60,10 @@ val fold_r : ('a -> 'b -> 'b) -> 'a t -> 'b -> 'b
       where [e1], [e2], ..., [en] are the elements of [s]
   *)
 
+val iter_l : ('a -> unit) -> 'a t -> unit
+  (** [iter_l f s] applies [f] on all elements of [s] starting from
+      the left *)
+
 val find : ('a -> bool) -> 'a t -> 'a
   (** [find_node_l f s] returns the first element of [s] starting from the left
       that satisfies [f] or raises [Not_found] if none exists. *)