1 files changed, 29 insertions, 15 deletions
diff --git a/sheet.ml b/sheet.ml
index b604c03..38a45d7 100755
--- a/sheet.ml
+++ b/sheet.ml
@@ -1,7 +1,9 @@
+module Option = Tools.Option
+
 type cell = int * int
 
 type search = [
-  | `Pattern of ScTypes.result
+  | `Pattern of ScTypes.result option
   | `Next
   | `Previous
 ]
@@ -17,7 +19,7 @@ module Raw = struct
 
   type content = {
     expr    : Expression.t; (** The expression *)
-    value   : ScTypes.result; (** The content evaluated *)
+    value   : ScTypes.result option; (** The content evaluated *)
     sink    : Cell.Set.t;   (** All the cell which references this one *)
   }
 
@@ -29,7 +31,7 @@ module Raw = struct
   (** An empty cell which does contains nothing *)
   let empty_cell = {
     expr = Expression.load @@ UTF8.empty;
-    value = ScTypes.Result ScTypes.Undefined;
+    value = None;
     sink = Cell.Set.empty;
   }
 
@@ -37,7 +39,7 @@ module Raw = struct
 
   let get_value id t = begin
     try (Map.find id t).value
-    with Not_found ->  ScTypes.Result ScTypes.Undefined
+    with Not_found ->  None
   end
 
   let get_expr id t = begin
@@ -48,7 +50,7 @@ module Raw = struct
   (** Extract a value from a reference.
       This function is given to the evaluator for getting the values from a reference.
    *)
-  let get_ref from t ref = begin
+  let get_ref from t ref : ScTypes.types option ScTypes.Refs.range = begin
 
     let extract_values = begin function
       | ScTypes.Result v -> v
@@ -56,21 +58,27 @@ module Raw = struct
     end in
 
     ScTypes.Refs.collect ref
-      |> ScTypes.Refs.map (fun coord -> extract_values (get_value coord t))
+      |> ScTypes.Refs.map (fun coord -> Option.map extract_values (get_value coord t))
 
   end
 
   (** Update the value for the given cell.
       Evaluate the new expression and compare it with the previous value.
-      @return the map updated if the result differ.
+      @return Some map if the map has been updated
    *)
   let update cell content t = begin
     let new_val = Expression.eval content.expr (get_ref cell t) in
-    if not (ScTypes.Result.(=) new_val content.value) then
-      Some (Map.add cell { content with value = new_val } t)
-    else
-      (* If there is no changes, do not update the map *)
-      None
+    match content.value with
+    | None ->
+      (* If the previous value wasn't defined, update the map *)
+      Some (Map.add cell { content with value = Some new_val } t)
+    | Some old_value ->
+      (* If the previous value was defined, update only if both differs *)
+      if not (ScTypes.Result.(=) new_val old_value) then
+        Some (Map.add cell { content with value = Some new_val } t)
+      else
+        (* If there is no changes, do not update the map *)
+        None
   end
 
   (** Parse all the successors from [init] and call [f] for each of them.
@@ -176,7 +184,7 @@ module Raw = struct
     else
       let f cell t = { cell with
         expr = expression ;
-        value = Expression.eval expression (get_ref id t)
+        value = Some (Expression.eval expression (get_ref id t))
       } in
       add_element id f t
   end
@@ -186,7 +194,7 @@ module Raw = struct
     let f cell t =
       { cell with
         expr = expr ;
-        value = Expression.eval expr (get_ref id t)
+        value = Some (Expression.eval expr (get_ref id t))
       } in
     add_element id f t
   end
@@ -206,8 +214,14 @@ module Raw = struct
     try (Map.find id t).sink
     with Not_found -> Cell.Set.empty
 
+  (** Fold over each defined value *)
   let fold f a t = begin
-    Map.fold (fun key content a -> f a key (content.expr, content.value)) t a
+    Map.fold (fun key content a ->
+      match content.value with
+      | None -> a
+      | Some x ->
+        f a key (content.expr, x)
+    ) t a
   end
 
 end