27 files changed, 398 insertions, 211 deletions
diff --git a/Makefile b/Makefile
index f90a98c..bf896ac 100755
--- a/Makefile
+++ b/Makefile
@@ -31,7 +31,7 @@ doc:
 	$(OCAMLBUILD) -pkgs $(PACKAGES) -menhir -Is $(PATHS) licht.docdir/index.html
 
 test: stub
-	$(OCAMLBUILD) -pkgs $(PACKAGES),oUnit -cflag -g -lflag -g $(STUB_OPTIONS) $(MENHIR) -Is $(PATHS),tests test.byte --
+	$(OCAMLBUILD) -pkgs $(PACKAGES),oUnit -cflag -g -lflag -g $(STUB_OPTIONS) $(MENHIR) -Is $(PATHS),tests,tests/odf test.byte --
 
 relink: stub
 	rm -f _build/main.native
diff --git a/UTF8.ml b/UTF8.ml
index 33df5b4..4fa5eca 100755
--- a/UTF8.ml
+++ b/UTF8.ml
@@ -4,7 +4,11 @@ let empty = ""
 
 let decode x = Text.decode x
 
-let encode x = Text.encode x
+let encode x =
+  try Some (Text.encode x)
+  with Text.Invalid (_, _) -> None
+
+let raw_encode x = Text.encode x
 
 let from_utf8string x = x
 
diff --git a/UTF8.mli b/UTF8.mli
index c1fa400..9e957ac 100755
--- a/UTF8.mli
+++ b/UTF8.mli
@@ -16,7 +16,12 @@ val decode: string -> t
 val from_utf8string: string -> t
 
 (** Encode to the string to the user locale *)
-val encode: t -> string
+val encode: t -> string option
+
+(** Encode the string.
+    This function may raise Text.Invalid if the string cannot be encoded in current locale
+*)
+val raw_encode: t -> string
 
 val to_utf8string: t -> string
 
diff --git a/dataType.ml b/dataType.ml
index 3937465..2fcbd0d 100755
--- a/dataType.ml
+++ b/dataType.ml
@@ -109,6 +109,10 @@ module Num = struct
     | NAN -> NAN
     | N n1 -> N (Num.abs_num n1)
 
+  let neg = function
+    | NAN -> NAN
+    | N n1 -> N (Num.minus_num n1)
+
 end
 
 module Bool = struct
diff --git a/dataType.mli b/dataType.mli
index 09b0082..901346c 100755
--- a/dataType.mli
+++ b/dataType.mli
@@ -17,6 +17,8 @@ module Num: sig
 
   val to_num: t -> Num.num
 
+  val neg: t -> t
+
   val eq: t -> t -> bool
   val neq: t -> t -> bool
   val lt: t -> t -> bool
diff --git a/evaluator.ml b/evaluator.ml
index 3adf7fa..490ab43 100755
--- a/evaluator.ml
+++ b/evaluator.ml
@@ -1,8 +1,6 @@
 module D = DataType
 module T = Tools
 
-let u = UTF8.from_utf8string
-
 exception RegisteredFunction
 
 (** Data format *)
@@ -392,32 +390,25 @@ let repr mapper value = begin
     | ScTypes.Bool b    -> Result (Bool b)
     | ScTypes.Date d    -> Result (Num (Date, (D.Num.of_num d)))
     | ScTypes.Str s     -> Result (String s)
-    | ScTypes.Undefined -> raise Errors.TypeError
   end in
 
-  (** Extract the value from a raw type.
-      If the value is Undefined, provide a default result.
-   *)
-  let guess_value: type a. a typ -> ScTypes.types -> existencialResult = fun typ value -> begin
-    try extract_value value with Errors.TypeError ->
-      match typ with
+  let add_elem: type a. a typ -> a list * a dataFormat -> ScTypes.types option -> a list * a dataFormat =
+  begin fun type_of (result, format_of) next ->
+    let Result r = match next with
+    | Some x -> extract_value x
+    | None -> begin match type_of with
       | Num  ->   Result (Num (Number, (D.Num.nan)))
       | Bool ->   Result (Bool false)
-      | String -> Result (String (u""))
+      | String -> Result (String (UTF8.empty))
       | List x  -> Result (List ((default_format_for_type x), []))
       | Unit -> raise Errors.TypeError
-  end in
-
-
-  let add_elem: type a. a typ -> a list * a dataFormat -> ScTypes.types -> a list * a dataFormat =
-  begin fun type_of (result, format_of) next ->
-      let Result r = guess_value type_of next in
-      begin match compare_typ type_of (type_of_value r) with
-      | T.Eq ->
-        let l' = (get_value_content r)::result in
-        l' , (most_generic_format (format_of_value r) format_of)
-      | _ -> raise Errors.TypeError
-      end
+    end in
+    begin match compare_typ type_of (type_of_value r) with
+    | T.Eq ->
+      let l' = (get_value_content r)::result in
+      l' , (most_generic_format (format_of_value r) format_of)
+    | _ -> raise Errors.TypeError
+    end
   end in
 
   (* Return the result for any expression as an ScTypes.types result *)
@@ -449,11 +440,14 @@ let repr mapper value = begin
     (* For a reference to an external we first extract the value pointed  *)
     | ScTypes.Ref r ->
         begin match mapper r with
-        | ScTypes.Refs.Single v -> extract_value v
+        | ScTypes.Refs.Single v ->
+            begin match v with
+            | None -> raise Errors.TypeError
+            | Some v -> extract_value v
+            end
         | ScTypes.Refs.Array1 l ->
-
           (* Guess the list type from it's first defined element *)
-          let Result r = extract_value (List.find ((!=) ScTypes.Undefined) l) in
+          let Result r = extract_value (Tools.List.find_map (fun x -> x) l) in
           let format_of = format_of_value r in
           let type_of = type_of_value r in
           (* Build the list with all the elements *)
@@ -461,7 +455,8 @@ let repr mapper value = begin
           Result (List (format, elems))
         | ScTypes.Refs.Array2 l ->
           (* Guess the list type from it's first defined element *)
-          let Result r = extract_value (Tools.List.find2 ((!=) ScTypes.Undefined) l) in
+          let Result r = extract_value (Tools.List.find_map2 (fun x -> x) l) in
+
           let format_of = format_of_value r in
           let type_of = type_of_value r in
           (* Build the list with all the elements *)
@@ -526,14 +521,17 @@ let () = begin
 
   let module CompareNum = MAKE(D.Num) in
   CompareNum.register t_int;
-  register0 "rand"              f_number D.Num.rnd;
-  register2 "+"  (t_int, t_int) f_num D.Num.add;
-  register2 "-"  (t_int, t_int) f_num D.Num.sub;
-  register2 "*"  (t_int, t_int) f_number D.Num.mult;
-  register2 "/"  (t_int, t_int) f_number D.Num.div;
-  register2 "^"  (t_int, t_int) f_number D.Num.pow;
+  register0 "rand"              f_number  D.Num.rnd;
 
-  register1 "abs" t_int         f_number D.Num.abs;
+  register1 "+"  t_int          f_num     (fun x -> x);
+  register1 "-"  t_int          f_num     D.Num.neg;    (* Unary negation *)
+  register2 "+"  (t_int, t_int) f_num     D.Num.add;
+  register2 "-"  (t_int, t_int) f_num     D.Num.sub;
+  register2 "*"  (t_int, t_int) f_number  D.Num.mult;
+  register2 "/"  (t_int, t_int) f_number  D.Num.div;
+  register2 "^"  (t_int, t_int) f_number  D.Num.pow;
+
+  register1 "abs" t_int         f_number  D.Num.abs;
 
   fold "sum"     t_int f_number D.Num.add  (D.Num.of_num (Num.num_of_int 0));
   fold "product" t_int f_number D.Num.mult (D.Num.of_num (Num.num_of_int 1));
@@ -553,4 +551,14 @@ let () = begin
   let module CompareString = MAKE(D.String) in
   CompareString.register t_string;
 
+  (* Build a date *)
+  register3 "date"  (t_int, t_int, t_int) f_date (
+    fun year month day ->
+      Tools.Date.get_julian_day
+        (Num.int_of_num @@ Num.floor_num @@ D.Num.to_num year)
+        (Num.int_of_num @@ Num.floor_num @@ D.Num.to_num month)
+        (Num.int_of_num @@ Num.floor_num @@ D.Num.to_num day)
+      |> D.Num.of_num
+  )
+
 end
diff --git a/evaluator.mli b/evaluator.mli
index 9fa280b..d69bba6 100755
--- a/evaluator.mli
+++ b/evaluator.mli
@@ -1,4 +1,4 @@
-val repr: (ScTypes.refs -> ScTypes.types ScTypes.Refs.range) -> ScTypes.expression -> ScTypes.types
+val repr: (ScTypes.refs -> ScTypes.types option ScTypes.Refs.range) -> ScTypes.expression -> ScTypes.types
 
 (** Type definitions *)
 
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
 
diff --git a/expression.mli b/expression.mli
index f7f0ece..e54d2a0 100755
--- a/expression.mli
+++ b/expression.mli
@@ -1,6 +1,7 @@
 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 *)
@@ -15,7 +16,7 @@ val load_expr: t -> t
 val is_defined: t -> bool
 
 (** Evaluate the expression *)
-val eval: t -> (ScTypes.refs -> ScTypes.types ScTypes.Refs.range) -> ScTypes.result
+val eval: t -> (ScTypes.refs -> ScTypes.types option ScTypes.Refs.range) -> ScTypes.result
 
 (** Collect all the cell referenced in the expression *)
 val collect_sources: t -> Cell.Set.t
diff --git a/expressionParser.mly b/expressionParser.mly
index a4d0716..ac3f71d 100755
--- a/expressionParser.mly
+++ b/expressionParser.mly
@@ -48,6 +48,7 @@ content:
 basic:
   | num                     {Num ((snd $1), Some (u(fst $1)))}
   | MINUS num               {Num (Num.minus_num (snd $2), Some (u("-" ^(fst $2)) ))}
+  | PLUS num                {Num ((snd $2), Some (u(fst $2)))}
   | NUM DIVIDE NUM DIVIDE NUM {
                               Date (Tools.Date.get_julian_day 
                                 (Num.int_of_num @@ snd $1)
@@ -57,7 +58,8 @@ basic:
 
 expr:
   | num                     {Value (Num ((snd $1), Some (u(fst $1))))}
-  | MINUS num               {Value (Num (Num.minus_num (snd $2), Some (u("-" ^(fst $2)) )))}
+  | MINUS expr              {Call (F.sub, [$2])}
+  | PLUS expr               {Call (F.add, [$2])}
 
   | LETTERS ident LPAREN  separated_list(SEMICOLON, expr) RPAREN { Call (u($1 ^ $2), $4) }
 
diff --git a/main.ml b/main.ml
index 393d4fe..e91a9f5 100755
--- a/main.ml
+++ b/main.ml
@@ -127,8 +127,8 @@ let rec normal_mode (t, screen) = begin
   | Actions.Search ->
     let expr = Screen.search screen
     |> Expression.load in
-    let pattern = Expression.eval expr (fun _ -> ScTypes.Refs.Single ScTypes.Undefined) in
-    begin match Sheet.search (`Pattern pattern) t with
+    let pattern = Expression.eval expr (fun _ -> ScTypes.Refs.Single None) in
+    begin match Sheet.search (`Pattern (Some pattern)) t with
     | Some t' -> normal_mode @@ redraw t' screen
     | None -> normal_mode (t, screen)
     end
@@ -231,11 +231,6 @@ let () = begin
     else
       Odf.load Sys.argv.(1) in
 
-  let window = Screen.init () in
-  begin Tools.try_finally
-    (fun () ->
+  Screen.run (fun window ->
       ignore @@ normal_mode @@ redraw (Sheet.create sheet) window)
-    (fun () ->
-      ignore @@ Screen.close window; )
-  end
 end
diff --git a/odf/odf.ml b/odf/odf.ml
index df98adb..da33ba9 100755
--- a/odf/odf.ml
+++ b/odf/odf.ml
@@ -6,25 +6,27 @@ let u = UTF8.from_utf8string
 
 type t
 
-let load_attrs attrs =
-
-  let _load t = function
-  | (("urn:oasis:names:tc:opendocument:xmlns:table:1.0", "formula"), x) ->
-      T.Tuple3.replace1  (Some x) t
-  | (("urn:oasis:names:tc:opendocument:xmlns:office:1.0", "value"), x) ->
-      T.Tuple3.replace2  (Some x) t
-  | (("urn:oasis:names:tc:opendocument:xmlns:office:1.0", "date-value"), x) ->
-      T.Tuple3.replace2  (Some x) t
-  | (("urn:oasis:names:tc:opendocument:xmlns:table:1.0", "number-columns-repeated"), x) ->
-      T.Tuple3.replace3  (Some x) t
-  | _ -> t
-  in List.fold_left _load (None, None, None) attrs
+(** Map for storing all the attributes *)
+module AttributesMap = Map.Make (struct
+  type t = string * string
+  let compare = Pervasives.compare
+end)
+
+let get_attr map key = begin
+  try Some (AttributesMap.find key map) with
+  Not_found -> None
+end
 
 let load_formula formula =
   let lineBuffer = Lexing.from_string formula in
-  Expression.Formula (
-    Expression.Expression (
-      Odf_ExpressionParser.value Odf_ExpressionLexer.read lineBuffer))
+  try
+    Expression.Formula (
+      Expression.Expression (
+        Odf_ExpressionParser.value Odf_ExpressionLexer.read lineBuffer))
+  with e ->
+    print_endline formula;
+    raise e
+
 
 let load_content content = begin function
   | "float" -> Expression.Basic (
@@ -38,38 +40,52 @@ let load_content content = begin function
         UTF8.from_utf8string content))
 end
 
+(** Load the content from a cell *)
 let load_cell sheet cell_num row_num changed (attrs, cell) = begin
 
-  let attributes = load_attrs attrs in
-  let repetition = match T.Tuple3.thd attributes with
+  (* Load all the attributes from the xml element *)
+  let add_attr map (key, value) = AttributesMap.add key value map in
+  let attributes = List.fold_left add_attr AttributesMap.empty attrs in
+
+  (* Check if the content is repeated *)
+  let repetition = match get_attr attributes NS.number_columns_repeat_attr with
+  | None -> 1
+  | Some x -> int_of_string x
+
+  (* cell width *)
+  and cell_width = match get_attr attributes NS.number_columns_spanned_attr with
   | None -> 1
   | Some x -> int_of_string x in
 
   let vtype =
     try List.assoc NS.ovalue_type_attr attrs
     with Not_found -> "" in
-  let expression, new_change = begin match attributes with
-  | Some x, _, _ -> load_formula x, true
-  | _, Some x, _ ->
+
+  let formula = get_attr attributes NS.formula_attr
+  and value   = get_attr attributes NS.value_attr in
+
+  let expression, update = begin match formula, value with
+  | Some x, _ -> load_formula x, true
+  | _, Some x ->
       (load_content x vtype) , true
   | _ ->
     begin try
           Xml.member "p" cell
        |> Xml.data_to_string
        |> fun x -> (load_content x vtype, true)
-    with Xml.Tag_not_found _ -> Expression.Basic ScTypes.Undefined, false
+    with Xml.Tag_not_found _ -> Expression.Undefined, false
     end
   end in
 
-  if new_change then (
+  if update then (
     for i = 1 to repetition do
-      incr cell_num;
+      cell_num := !cell_num + cell_width;
       sheet := snd @@ Sheet.Raw.add (!cell_num, !row_num) (Expression.load_expr expression) !sheet
     done
   ) else (
-    cell_num := !cell_num + repetition
+    cell_num := !cell_num + (repetition * cell_width )
   );
-  changed || new_change
+  changed || update
 end
 
 let load_row sheet row_num (attrs, row) = begin
@@ -119,13 +135,13 @@ let load file =
   Zip.copy_entry_to_file zip content tmp_file;
 
   let input = open_in_bin tmp_file in
-  Tools.try_finally (fun () ->
-    load_xml input
-  )( fun () ->
-    close_in input;
-    Unix.unlink tmp_file;
-    Zip.close_in zip
-  )
+  Tools.try_finally
+    (fun () -> load_xml input)
+    (fun () ->
+      close_in input;
+      Unix.unlink tmp_file;
+      Zip.close_in zip
+    )
 
 
 let write_type ovalue_type cvalue_type attrs output value = begin
@@ -157,7 +173,6 @@ let write_basic attrs output = begin function
   | ScTypes.Date d ->
       let value = Tools.Date.to_string d in
       write_date ((NS.date_value_attr, value)::attrs) output value
-  | _ -> ()
 end
 
 let write_formula output attrs f = begin function
@@ -180,11 +195,13 @@ let rec print_expr buffer = begin function
   | ScTypes.Value (ScTypes.Num (n, _))  ->
       UTF8.Buffer.add_string buffer @@ u(string_of_float @@ Num.float_of_num n)
   | ScTypes.Value (ScTypes.Str s)  ->
-      UTF8.Buffer.add_string buffer @@ u"\"";
-      UTF8.Buffer.add_string buffer s;
-      UTF8.Buffer.add_string buffer @@ u"\""
-  | ScTypes.Value (ScTypes.Bool b) -> UTF8.Buffer.add_string buffer @@ u(string_of_bool b)
-  | ScTypes.Value x -> ()
+      UTF8.Printf.bprintf buffer "\"%s\"" (UTF8.to_utf8string s)
+  | ScTypes.Value (ScTypes.Bool b) ->
+       u(string_of_bool b)
+    |> UTF8.Buffer.add_string buffer
+  | ScTypes.Value (ScTypes.Date d) ->
+        u(Tools.Date.to_string d)
+    |> UTF8.Buffer.add_string buffer
   | ScTypes.Ref r -> print_ref buffer r
   | ScTypes.Expression x ->
       UTF8.Buffer.add_char buffer '(';
@@ -194,6 +211,10 @@ let rec print_expr buffer = begin function
       begin match (UTF8.to_utf8string ident) with
       | "+" | "*" | "-" | "/" | "^" | "="
       | "<>" | "<=" | ">=" | "<" | ">" -> begin match params with
+        | v1::[] ->
+          UTF8.Printf.bprintf buffer "%s%a"
+          (UTF8.to_utf8string ident)
+          print_expr v1
         | v1::v2::[] ->
           UTF8.Printf.bprintf buffer "%a%s%a"
           print_expr v1
@@ -210,6 +231,7 @@ let rec print_expr buffer = begin function
 end
 
 let write_cell output value = begin function
+  | Expression.Undefined -> ()
   | Expression.Basic b -> write_basic [] output b
   | Expression.Formula (Expression.Expression f) ->
       let buffer = UTF8.Buffer.create 10 in
@@ -222,8 +244,9 @@ let write_cell output value = begin function
 end
 
 (** Jump to the wanted position *)
-let goto output (from_x, from_y) (to_x, to_y) = begin
+let goto output (from_x, from_y) (to_x, to_y) :unit = begin
 
+  (** Insert as many rows than required *)
   let insert_rows count = begin
     (* Close the previous openend rows *)
     Xmlm.output output `El_end;
@@ -240,6 +263,7 @@ let goto output (from_x, from_y) (to_x, to_y) = begin
     1
   end
 
+  (** Insert as many cells as required *)
   and insert_cells count = begin
     Xmlm.output output (
       `El_start (
@@ -255,11 +279,11 @@ let goto output (from_x, from_y) (to_x, to_y) = begin
     else
       from_x in
   let jump_cell = to_x - from_x' in
-  if jump_cell > 0 then insert_cells jump_cell;
-
-
+  if jump_cell > 0 then
+    insert_cells jump_cell
 end
 
+(** Write the cell content and return the updated position *)
 let f output cursor position (expr, value) = begin
 
   goto output cursor position;
@@ -271,7 +295,7 @@ let f output cursor position (expr, value) = begin
   Tools.Tuple2.map1 ((+) 1)  position
 end
 
-let save sheet file =
+let save sheet file = begin
   let tmp_file = Filename.temp_file "content" ".xml" in
   Unix.unlink tmp_file;
   let out_channel = open_out_bin tmp_file in
@@ -308,3 +332,4 @@ let save sheet file =
     Zip.close_out zip;
     Unix.unlink tmp_file
   )
+end
diff --git a/odf/odf_ExpressionLexer.mll b/odf/odf_ExpressionLexer.mll
index 28fce22..1db73c3 100755
--- a/odf/odf_ExpressionLexer.mll
+++ b/odf/odf_ExpressionLexer.mll
@@ -13,9 +13,13 @@ let newline = "\r\n" | '\n' | '\r'
 let space = ['\t' ' '] | newline
 
 let letters = ['A'-'Z' 'a'-'z']
-let identifier = letters (letters | digit | ['-' '_' '.'])* (letters | digit)+
 
-let text = letters | digit 
+(* Function identifier.
+   Valid identifiers are : 
+     ORG.OPENOFFICE.DAYSINMONTH
+   it cannot end with a digit.
+ *)
+let identifier = letters (letters | digit | ['-' '_' '.'])* letters+
 
 let cell = letters+ digit+
 
@@ -36,7 +40,7 @@ rule read = parse
   | '+'         { PLUS }
   | '-'         { MINUS }
   | '/'         { DIVIDE }
-  | '"'         { read_string (Buffer.create 17) lexbuf }
+  | '"'         { read_string (Buffer.create 16) lexbuf }
   | ';'         { SEMICOLON }
   | ':'         { COLON }
   | '['         { L_SQ_BRACKET }
@@ -47,6 +51,7 @@ rule read = parse
   | '.'         { DOT }
 
   | letters+ as _1   { LETTERS _1}
+  | identifier as _1 { IDENT _1}
 
   | '\000'      { EOF }
   | eof         { EOF }
diff --git a/odf/odf_ExpressionParser.mly b/odf/odf_ExpressionParser.mly
index 6c34c1d..9731699 100755
--- a/odf/odf_ExpressionParser.mly
+++ b/odf/odf_ExpressionParser.mly
@@ -13,6 +13,7 @@
 %token <string> STR
 
 %token <string> LETTERS
+%token <string> IDENT
 
 %token DOLLAR
 %token DOT
@@ -43,7 +44,8 @@ value:
 
 expr:
   | num                     {Value (Num ((snd $1), Some (u(fst $1))))}
-  | MINUS num               {Value (Num (Num.minus_num (snd $2), Some (u("-" ^(fst $2)) )))}
+  | MINUS expr              {Call (F.sub, [$2])}
+  | PLUS expr               {Call (F.add, [$2])}
 
 
   | L_SQ_BRACKET ref R_SQ_BRACKET {$2}
@@ -85,6 +87,7 @@ num:
   | NUM                     {$1}
 
 ident:
+  | IDENT                   { $1 }
   | text+                   { String.concat "" $1 }
 
 text:
diff --git a/odf/odf_ns.ml b/odf/odf_ns.ml
index c22ae7e..5a501da 100755
--- a/odf/odf_ns.ml
+++ b/odf/odf_ns.ml
@@ -52,7 +52,8 @@ let table_cell_node       = (table, "table-cell")
   let ovalue_type_attr    = (office, "value-type")
   let value_attr          = (office, "value")
   let formula_attr        = (table, "formula")
-  let date_value_attr           = (office, "date-value")
+  let date_value_attr     = (office, "date-value")
+  let number_columns_spanned_attr = (table, "number-columns-spanned")
 
 let text_node             = (text, "p")
 
diff --git a/scTypes.ml b/scTypes.ml
index 6ea9f35..869df8b 100755
--- a/scTypes.ml
+++ b/scTypes.ml
@@ -12,8 +12,6 @@ type types =
   | Num  of Num.num * (UTF8.t option)     (** A number *)
   | Str  of UTF8.t                        (** A string *)
   | Date of Num.num                       (** A date in julian day *)
-
-  | Undefined                             (** The content is not defined *)
   | Bool of bool                          (** A boolean *)
 
 type refs =
@@ -55,7 +53,6 @@ module Type = struct
   end
 
   and show buffer = begin function
-    | Undefined -> ()
     | Num (n,x)     ->
       begin match x with
       | Some value -> UTF8.Buffer.add_string buffer value
@@ -171,6 +168,10 @@ let rec show_expr buffer : expression -> unit = begin function
     begin match utf8ident with
     | "+" | "*" | "-" | "/" | "^" | "="
     | "<>" | "<=" | ">=" | "<" | ">" -> begin match params with
+      | v1::[] ->
+        UTF8.Printf.bprintf buffer "%s%a"
+        utf8ident
+        show_expr v1
       | v1::v2::[] ->
         UTF8.Printf.bprintf buffer "%a%s%a"
         show_expr v1
diff --git a/scTypes.mli b/scTypes.mli
index deef1a0..1d8fe54 100755
--- a/scTypes.mli
+++ b/scTypes.mli
@@ -10,8 +10,6 @@ type types =
   | Num  of Num.num * (UTF8.t option)     (** A number *)
   | Str  of UTF8.t                        (** A string *)
   | Date of Num.num                       (** A date in julian day *)
-
-  | Undefined                             (** The content is not defined *)
   | Bool of bool                          (** A boolean *)
 
 type refs =
diff --git a/screen.ml b/screen.ml
index d48381a..a8e2d0c 100755
--- a/screen.ml
+++ b/screen.ml
@@ -4,13 +4,13 @@ module Color = Curses.Color
 
 module T2 = Tools.Tuple2
 
+module Option = Tools.Option
+
 let cell_size = 10
 
 let u = UTF8.from_utf8string
 
-type t = Sheet.t
-
-type screen = {
+type t = {
   window: Curses.window;    (* the main window *)
   sheet: Curses.window;     (* the spreadsheet *)
   input: Curses.window;     (* the input window *)
@@ -52,15 +52,16 @@ end
 
 let status screen msg = begin
   let height, width = screen.size in
-  let encoded = UTF8.encode msg in
-  let status = Bytes.make (width -1) ' ' in
-  Bytes.blit encoded 0 status 0 (String.length encoded);
-  Curses.werase screen.status;
-  if not (
-    Curses.mvwaddstr screen.status 0 0 encoded
-    && Curses.wrefresh screen.status
-  ) then
+  UTF8.encode msg |> Option.iter (fun encoded ->
+    let status = Bytes.make (width -1) ' ' in
+    Bytes.blit encoded 0 status 0 (String.length encoded);
+    Curses.werase screen.status;
+    if not (
+      Curses.mvwaddstr screen.status 0 0 encoded
+      && Curses.wrefresh screen.status
+    ) then
     raise (Failure "Status update")
+  )
 end
 
 (** Draw the spreadsheet *)
@@ -99,10 +100,13 @@ let draw data screen = begin
       else
         Curses.wattrset screen.sheet (Attrs.color_pair 1 )
       end;
+
     ignore
     @@ Curses.mvwaddstr screen.sheet 0 (x * cell_size + screen.left_margin)
-    @@ Printf.sprintf "%-*s" cell_size (UTF8.encode @@ Cell.to_hname pos_x);
+    @@ Printf.sprintf "%-*s" cell_size (UTF8.raw_encode @@ Cell.to_hname pos_x);
+
     Curses.wattrset screen.sheet Attrs.normal;
+
     for y = 1 to (height-2) do
 
       let pos_y = y + (snd screen.start) - 1 in
@@ -118,22 +122,25 @@ let draw data screen = begin
           Curses.wattrset screen.sheet Attrs.normal;
       end;
 
+
+      (* Get the content from the cell *)
       let content = Sheet.Raw.get_value (pos_x, pos_y) data.Sheet.data
-               |> ScTypes.Result.show
-               |> UTF8.split ~sep:(u"\n") in
-
-      let value = UTF8.encode content
-      and length = UTF8.length content in
-      let strlength = String.length value in
-      let blank = cell_size - length in
-      let padding = if blank > 0
-        then String.make blank ' '
-        else "" in
-
-      ignore
-      @@ Curses.mvwaddnstr screen.sheet y (x * cell_size + screen.left_margin)
-         (Printf.sprintf "%s%s" value padding)
-         0 (blank + strlength)
+        |> Option.map (fun x -> UTF8.split ~sep:(u"\n") (ScTypes.Result.show x))
+        |> Option.default UTF8.empty in
+
+      (* If the content is defined, try to encode it and print it*)
+      UTF8.encode content |> Tools.Option.iter (fun value ->
+        let length = UTF8.length content in
+        let strlength = String.length value in
+        let blank = cell_size - length in
+        let padding = if blank > 0
+          then String.make blank ' '
+          else "" in
+        ignore
+        @@ Curses.mvwaddnstr screen.sheet y (x * cell_size + screen.left_margin)
+           (Printf.sprintf "%s%s" value padding)
+           0 (blank + strlength)
+      )
     done
   done;
   ignore @@ Curses.wrefresh screen.sheet;
@@ -190,20 +197,23 @@ let draw_input t screen = begin
   let expr = Sheet.Raw.get_expr (Selection.extract t.Sheet.selected) t.Sheet.data
           |> Expression.show in
 
-  (* Compute the difference between number of bytes in the string, and the
-     number of character printed : Printf.sprintf format use the bytes number
-     in the string, while Curses print the characters in the user encoding *)
   let result = Sheet.Raw.get_value (Selection.extract t.Sheet.selected) t.Sheet.data
-            |> ScTypes.Result.show in
-  let encoded_result = UTF8.encode result in
-  let result_length_delta = (UTF8.length result) - (String.length encoded_result) in
+            |> Option.map ScTypes.Result.show
+            |> Option.default UTF8.empty in
 
-  ignore (
-     encoded_result
-  |> Printf.sprintf "%-*s" (width - 11 - result_length_delta)
-  |> Curses.mvwaddstr screen.input 0 10
+  UTF8.encode result |> Option.iter (fun encoded_result ->
+    (* Compute the difference between number of bytes in the string, and the
+       number of character printed : Printf.sprintf format use the bytes number
+       in the string, while Curses print the characters in the user encoding *)
+    let result_length_delta = (UTF8.length result) - (String.length encoded_result) in
+
+    ignore (
+       encoded_result
+    |> Printf.sprintf "%-*s" (width - 11 - result_length_delta)
+    |> Curses.mvwaddstr screen.input 0 10
 
-  && Curses.wrefresh screen.input);
+    && Curses.wrefresh screen.input)
+  );
   status screen expr;
   screen
 end
@@ -248,8 +258,8 @@ let resize data t = begin
 end
 
 let editor ?position ?(prefix=UTF8.empty) ?(init=UTF8.empty) t = begin
-  let encodedPrefix = UTF8.encode prefix
-  and encodedInit = UTF8.encode init in
+  let encodedPrefix = UTF8.raw_encode prefix
+  and encodedInit = UTF8.raw_encode init in
   let with_refs, position = match position with
   | None -> false, (1, 1)
   | Some x -> true, x in
@@ -262,7 +272,7 @@ let editor ?position ?(prefix=UTF8.empty) ?(init=UTF8.empty) t = begin
   | [] -> ()
   | elems -> ( (* Rewrite each char after the cursor *)
     let y, x = Curses.getyx t.status in
-    List.iter (fun x -> ignore @@ Curses.waddstr t.status (UTF8.encode x)) elems;
+    List.iter (fun x -> ignore @@ Curses.waddstr t.status (UTF8.raw_encode x)) elems;
     ignore @@ Curses.wmove t.status y x )
   end
 
@@ -285,6 +295,10 @@ let editor ?position ?(prefix=UTF8.empty) ?(init=UTF8.empty) t = begin
   | "\027" -> (* Escape, cancel the modifications *)
     None
   | "\010" -> (* Enter, validate the input *)
+
+    (* We concatenate all the characters. This can create an invalid string in
+     * the current locale (if there are copy/paste, or other events).
+     *)
     Some (UTF8.implode @@ (UTF8.rev_implode before)::after)
 
   | "\001\004" -> (* Left *)
@@ -414,7 +428,7 @@ let editor ?position ?(prefix=UTF8.empty) ?(init=UTF8.empty) t = begin
   and insert_cell_name position name before after = begin
     let cell_name = Cell.to_string @@ (position, (false, false)) in
     ignore @@ delete_previous name;
-    ignore @@ Curses.waddstr t.status (UTF8.encode cell_name);
+    ignore @@ Curses.waddstr t.status (UTF8.raw_encode cell_name);
     rewrite_after after;
     ignore @@ Curses.wrefresh t.status;
     select_content position cell_name before after @@ read_key t
@@ -438,12 +452,8 @@ let search screen = begin
   end
 end
 
-(*
-let read_input position screen = begin
-  let result = editor ~position ~init:(u"=") screen in
-  begin match result with
-  | Some content -> content
-  | None -> UTF8.empty
-  end
-end
-*)
+let run f =
+  let window = init () in
+  Tools.try_finally
+    (fun () -> f window)
+    (fun () -> ignore @@ close window )
diff --git a/screen.mli b/screen.mli
index a6a33dc..b5f74b2 100755
--- a/screen.mli
+++ b/screen.mli
@@ -1,31 +1,29 @@
 (** Represent the {!module:Sheet} *)
 
-type screen
+type t
 
-(** Initialise thee screen *)
-val init: unit -> screen
-
-val close: screen -> unit
+(** Run the screen *)
+val run: (t -> 'a) -> 'a
 
 (** {2 Screen updates} *)
 
-val draw: Sheet.t -> screen -> screen
+val draw: Sheet.t -> t -> t
 
-val draw_input: Sheet.t -> screen -> screen
+val draw_input: Sheet.t -> t -> t
 
-val resize: Sheet.t -> screen -> screen 
+val resize: Sheet.t -> t -> t 
 
 (** Display a message in the status bar. *)
-val status: screen -> UTF8.t -> unit
+val status: t -> UTF8.t -> unit
 
 (** {2 User inputs} *)
 
 (** Wait for a keycode *)
-val read_key : screen -> string
+val read_key : t -> string
 (** The keycode is always NULL terminated *)
 
-val search: screen -> UTF8.t
+val search: t -> UTF8.t
 
-val get_cell: screen -> int * int -> (int * int) option
+val get_cell: t -> int * int -> (int * int) option
 
-val editor: ?position: int * int -> ?prefix:UTF8.t -> ?init:UTF8.t -> screen -> UTF8.t option
+val editor: ?position: int * int -> ?prefix:UTF8.t -> ?init:UTF8.t -> t -> UTF8.t option
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
diff --git a/sheet.mli b/sheet.mli
index 59a1fa7..d3c8151 100755
--- a/sheet.mli
+++ b/sheet.mli
@@ -17,13 +17,17 @@ module Raw: sig
   val add: cell -> Expression.t -> t -> Cell.Set.t * t
   
   val remove: cell -> t -> Cell.Set.t * t
-  
-  val get_value: cell -> t -> ScTypes.result
+
+  (** Get the value content. 
+      @return None if the cell is not defined
+   *)
+  val get_value: cell -> t -> ScTypes.result option
   
   val get_expr: cell -> t -> Expression.t
 
   val get_sink: cell -> t -> Cell.Set.t
   
+  (** Fold over all the defined values *)
   val fold: ('a -> cell -> (Expression.t * ScTypes.result ) -> 'a) -> 'a -> t -> 'a
 
 end
@@ -38,7 +42,7 @@ type t = {
 }
 
 type search = [
-  | `Pattern of ScTypes.result
+  | `Pattern of ScTypes.result option
   | `Next
   | `Previous
 ]
diff --git a/tests/expressionParser_test.ml b/tests/expressionParser_test.ml
index 7c16233..25d9d00 100755
--- a/tests/expressionParser_test.ml
+++ b/tests/expressionParser_test.ml
@@ -4,8 +4,8 @@ let u = UTF8.from_utf8string
 
 let _msg ~(expected:Expression.t) ~(result:Expression.t) =
     Printf.sprintf "Expected %s but got %s"
-    (UTF8.encode @@ Expression.show @@ Expression.load_expr expected)
-    (UTF8.encode @@ Expression.show @@ Expression.load_expr result)
+    (UTF8.raw_encode @@ Expression.show @@ Expression.load_expr expected)
+    (UTF8.raw_encode @@ Expression.show @@ Expression.load_expr result)
 
 let load_expr str =
   Expression.Formula (
diff --git a/tests/expression_test.ml b/tests/expression_test.ml
index d1ac2ba..3f00e67 100755
--- a/tests/expression_test.ml
+++ b/tests/expression_test.ml
@@ -9,14 +9,13 @@ let _msg ~expected ~result =
     | Expression.Basic ScTypes.Num _      -> "N"
     | Expression.Basic ScTypes.Str _      -> "S"
     | Expression.Basic ScTypes.Date _     -> "D"
-    | Expression.Basic ScTypes.Undefined  -> "U"
     | Expression.Basic ScTypes.Bool _     -> "B"
     | Expression.Formula _                -> "F" in
 
     Printf.sprintf "Expected %s:%s but got %s:%s"
-    (UTF8.encode @@ Expression.show expected)
+    (UTF8.raw_encode @@ Expression.show expected)
     (get_type expected)
-    (UTF8.encode @@ Expression.show result)
+    (UTF8.raw_encode @@ Expression.show result)
     (get_type result)
 
 let assert_equal expected result =
@@ -86,8 +85,8 @@ let test_sources ctx = begin
   let expected = Cell.Set.singleton (1, 1) in
 
   let msg = Printf.sprintf "Expected %s but got %s"
-    (UTF8.encode @@ Tools.String.print_buffer Cell.Set.printb expected)
-    (UTF8.encode @@ Tools.String.print_buffer Cell.Set.printb result) in
+    (UTF8.raw_encode @@ Tools.String.print_buffer Cell.Set.printb expected)
+    (UTF8.raw_encode @@ Tools.String.print_buffer Cell.Set.printb result) in
 
   OUnit2.assert_equal ~msg expected result
 
diff --git a/tests/odf/odf_ExpressionParser_test.ml b/tests/odf/odf_ExpressionParser_test.ml
new file mode 100755
index 0000000..2cdb3bb
--- /dev/null
+++ b/tests/odf/odf_ExpressionParser_test.ml
@@ -0,0 +1,74 @@
+open OUnit2
+
+let u = UTF8.from_utf8string
+
+let _msg ~(expected:ScTypes.expression) ~(result:ScTypes.expression) =
+    let b1 = UTF8.Buffer.create 16
+    and b2 = UTF8.Buffer.create 16 in
+    ScTypes.show_expr b1 expected;
+    ScTypes.show_expr b2 result;
+
+    Printf.sprintf "Expected \n\t%s but got \n\t%s"
+      (UTF8.raw_encode @@ UTF8.Buffer.contents b1)
+      (UTF8.raw_encode @@ UTF8.Buffer.contents b2)
+
+
+let test_formula ctx = begin
+
+  let test1 = "of:=CONCATENATE(SUM([.F16:.AJ16]);\"/\";8*NETWORKDAYS([.F6]; [.F6]+(ORG.OPENOFFICE.DAYSINMONTH([.F6])-1)))" in
+
+  let line = Lexing.from_string test1 in
+  let result = Odf_ExpressionParser.value Odf_ExpressionLexer.read line in
+
+  let expected = ScTypes.(
+
+    Call(u"CONCATENATE", [
+      Call (u"SUM", [
+        Ref (Range (((6, 16), (false, false)), (((36, 16), (false, false)))))]);
+      Value (Str (u"/"));
+      Call(u"*", [
+        Value (Num ((Num.num_of_int 8, Some (u"8"))));
+        Call(u"NETWORKDAYS", [
+          Ref (Cell ((6, 6), (false, false)));
+          Call(u"+", [
+            Ref (Cell ((6, 6), (false, false)));
+            Expression (
+              Call( u"-", [
+                Call(u"ORG.OPENOFFICE.DAYSINMONTH", [
+                  Ref (Cell ((6, 6), (false, false)))]);
+                Value (Num ((Num.num_of_int 1, Some (u"1"))));
+              ]))])])])])) in
+
+  assert_equal
+    ~msg:(_msg ~expected ~result)
+    expected
+    result
+
+end
+
+let test_formula2 ctx = begin
+  let value = "of:=+[.H51]*[.G52]" in
+  let line = Lexing.from_string value in
+  let result = Odf_ExpressionParser.value Odf_ExpressionLexer.read line in
+
+  let expected = ScTypes.(
+
+    Call (u"+", [
+      Call(u"*", [
+        Ref (Cell ((8, 51), (false, false)));
+        Ref (Cell ((7, 52), (false, false)))
+      ])])) in
+
+  assert_equal
+    ~msg:(_msg ~expected ~result)
+    expected
+    result
+
+end
+
+let tests = "odf_ExpressionParser_test">::: [
+
+  "test_formula"              >:: test_formula;
+  "test_formula2"             >:: test_formula2;
+
+ ]
diff --git a/tests/sheet_test.ml b/tests/sheet_test.ml
index de42730..1a1bef3 100755
--- a/tests/sheet_test.ml
+++ b/tests/sheet_test.ml
@@ -1,11 +1,20 @@
 open OUnit2
 
+module Option = Tools.Option
+
 let u = UTF8.from_utf8string
 
-let _msg ~expected ~result =
+let _msg ~expected ~result = begin
+
+  let get_string v = match v with
+  | None -> "Undefined"
+  | Some x -> UTF8.raw_encode @@ ScTypes.Result.show x
+  in
+
     Printf.sprintf "Expected %s but got %s"
-    (UTF8.encode @@ ScTypes.Result.show expected)
-    (UTF8.encode @@ ScTypes.Result.show result)
+    (get_string expected)
+    (get_string result)
+end
 
 (** Test a simple references between two cells *)
 let test_create_ref_1 ctx = begin
@@ -15,7 +24,7 @@ let test_create_ref_1 ctx = begin
        |> snd |> Sheet.Raw.add (0,0) @@ Expression.load @@ u"=C3"
        |> snd in
   let result = (Sheet.Raw.get_value (0, 0) s) in
-  let expected = (ScTypes.Result (ScTypes.Num (Num.num_of_int (-1), None))) in
+  let expected = Some (ScTypes.Result (ScTypes.Num (Num.num_of_int (-1), None))) in
 
   assert_equal
     ~msg:(_msg ~expected ~result)
@@ -33,7 +42,7 @@ let test_create_ref_2 ctx = begin
 
 
   let result = (Sheet.Raw.get_value (2, 2) s) in
-  let expected = ScTypes.Result (ScTypes.Num (Num.num_of_int 123, None)) in
+  let expected = Some (ScTypes.Result (ScTypes.Num (Num.num_of_int 123, None))) in
 
   assert_equal
     ~msg:(_msg ~expected ~result)
@@ -47,7 +56,7 @@ let test_create_direct_cycle ctx = begin
        |> Sheet.Raw.add (2,2) @@ Expression.load @@ u"=B2"
        |> snd in
   let result = (Sheet.Raw.get_value (2, 2) s) in
-  let expected = ScTypes.Error Errors.TypeError in
+  let expected = Some (ScTypes.Error Errors.TypeError) in
 
   assert_equal
     ~msg:(_msg ~expected ~result)
@@ -63,7 +72,7 @@ let test_create_indirect_cycle ctx = begin
        |> snd |> Sheet.Raw.add (0,0) @@ Expression.load @@ u"=A1"
        |> snd in
   let result = (Sheet.Raw.get_value (0, 0) s) in
-  let expected = ScTypes.Error Errors.TypeError in
+  let expected = Some (ScTypes.Error Errors.TypeError) in
 
   assert_equal
     ~msg:(_msg ~expected ~result)
@@ -80,7 +89,7 @@ let test_delete ctx = begin
        |> snd |> Sheet.Raw.remove (3,3)
        |> snd in
   let result = (Sheet.Raw.get_value (3, 3) s) in
-  let expected = ScTypes.Result ScTypes.Undefined in
+  let expected = None in
 
   assert_equal
     ~msg:(_msg ~expected ~result)
@@ -101,8 +110,8 @@ let test_update_succs1 ctx = begin
   let expected = Cell.Set.of_list [(1,1); (1, 2); (2,2)] in
 
   let msg = Printf.sprintf "Expected %s but got %s"
-    (UTF8.encode @@ Tools.String.print_buffer Cell.Set.printb expected)
-    (UTF8.encode @@ Tools.String.print_buffer Cell.Set.printb result) in
+    (UTF8.raw_encode @@ Tools.String.print_buffer Cell.Set.printb expected)
+    (UTF8.raw_encode @@ Tools.String.print_buffer Cell.Set.printb result) in
 
   assert_equal ~msg
     expected
diff --git a/tests/test.ml b/tests/test.ml
index 8a24cd5..b9672ab 100755
--- a/tests/test.ml
+++ b/tests/test.ml
@@ -5,6 +5,7 @@ let () =
     ExpressionParser_test.tests;
     Expression_test.tests;
     Sheet_test.tests;
+    Odf_ExpressionParser_test.tests;
   ]
   in OUnit2.run_test_tt_main tests
 
diff --git a/tools.ml b/tools.ml
index f4befa5..33185ec 100755
--- a/tools.ml
+++ b/tools.ml
@@ -5,6 +5,20 @@ module Option = struct
   let map f = function
   | Some x -> Some (f x)
   | None -> None
+
+  let iter f = function
+  | Some x -> f x
+  | None -> ()
+
+  let bind f = function
+  | None -> None
+  | Some x -> f x
+
+  let default v = function
+  | None -> v
+  | Some x -> x
+
+
 end
 
 module String = struct
@@ -125,22 +139,29 @@ module List = struct
     UTF8.Buffer.add_string buffer last
   end
 
+  let rec find_map f = begin function
+  | [] -> raise Not_found
+  | hd::tl -> begin match f hd with
+              | Some x -> x
+              | None -> find_map f tl
+              end
+  end
+
   let rec findOpt p = begin function
   | [] -> None
   | x::l ->
-      if p x then
-        Some(x)
-      else
-        findOpt p l
+    if p x then
+      Some(x)
+    else
+      findOpt p l
   end
 
-  and find2 p = begin function
+  and find_map2 p = begin function
   | [] -> raise Not_found
   | x::l ->
-      begin match findOpt p x with
-      | None -> find2 p l
-      | Some x -> x
-      end
+    begin try find_map p x with
+    Not_found -> find_map2 p l
+    end
   end
 
   (** Convert the list [l] as an array *)