1 files changed, 5 insertions, 2 deletions
diff --git a/expression.ml b/expression.ml
index 1feb62e..155e1b9 100755
--- a/expression.ml
+++ b/expression.ml
@@ -6,6 +6,7 @@ let u = UTF8.from_utf8string
 type t =
   | Basic of ScTypes.types            (** A direct type *)
   | Formula of formula                (** A formula *)
+  | Undefined                         (** The content is not defined *)
 
 and formula =
   | Expression of ScTypes.expression  (** A valid expression *)
@@ -13,7 +14,7 @@ and formula =
 
 
 let is_defined = function
-  | Basic ScTypes.Undefined -> false
+  | Undefined -> false
   | _ -> true
 
 let load content = begin
@@ -41,7 +42,7 @@ let load content = begin
     )
   ) else (
     (* If the string in empty, build an undefined value *)
-    Basic ScTypes.Undefined
+    Undefined
   )
 end
 
@@ -60,6 +61,7 @@ let eval expr sources = begin
     | Basic value -> ScTypes.Result value
     | Formula (Expression f) -> ScTypes.Result (eval_exp f)
     | Formula (Error (i, s)) -> ScTypes.Error ScTypes.Error
+    | Undefined -> ScTypes.Error Not_found
     with ex -> ScTypes.Error ex
   end
 
@@ -91,6 +93,7 @@ let show e =
       ScTypes.show_expr buffer f
   | Basic b -> ScTypes.Type.show buffer b
   | Formula (Error (i,s)) -> UTF8.Buffer.add_string buffer s
+  | Undefined -> ()
   end;
   UTF8.Buffer.contents buffer