1 files changed, 5 insertions, 1 deletions
diff --git a/src/sheet.mli b/src/sheet.mli
index 11881cc..d768b8f 100755
--- a/src/sheet.mli
+++ b/src/sheet.mli
@@ -31,11 +31,12 @@ module Raw: sig
 end
 
 type yank
+type history
 
 type t = {
   selected: Selection.t;    (* The selected cell *)
   data: Raw.t;
-  history: t list;          (* Unlimited history *)
+  history: history;    (* Unlimited history *)
   yank: yank list           (* All the selected cells *)
 }
 
@@ -68,6 +69,9 @@ val search: search -> t -> t option
 
 val paste: t -> t * int
 
+(** Add or update the sheet.
+    The expression is added at current selection.
+    @return A set containing all updated cells, and the tree updated. *)
 val add: Expression.t -> t -> Cell.Set.t * t
 
 (** Create an empty sheet *)