diff --git a/src/grew_utils.ml b/src/grew_utils.ml
index 730b8f4348bbefd548ba77ecaaf35afb9843e141..a5c62f480b569322c8ea40dd2a7d52b6f2db6171 100644
--- a/src/grew_utils.ml
+++ b/src/grew_utils.ml
@@ -7,13 +7,48 @@ module StringMap = Map.Make (String)
 module IntSet = Set.Make (struct type t = int let compare = Pervasives.compare end)
 module IntMap = Map.Make (struct type t = int let compare = Pervasives.compare end)
 
+(* ================================================================================ *)
+module Loc = struct
+  type t = string * int
+
+  let to_string (file,line) = sprintf "(file: %s, line: %d)" (Filename.basename file) line
+
+  let opt_set_line line = function
+    | None -> None
+    | Some (file,_) -> Some (file, line)
+
+  let opt_to_string = function
+    | None -> ""
+    | Some x -> to_string x
+end (* module Loc *)
+
+(* ================================================================================ *)
+module Error = struct
+
+  exception Build of (string * Loc.t option)
+  exception Run of (string * Loc.t option)
+  exception Bug of (string * Loc.t option)
+
+  let build_ ?loc message =
+    Log.fmessage "[%s] %s" (match loc with None -> "?" | Some x -> Loc.to_string x) message;
+    raise (Build (message, loc))
+  let build ?loc = Printf.ksprintf (build_ ?loc)
+
+  let run_ ?loc message = raise (Run (message, loc))
+  let run ?loc = Printf.ksprintf (run_ ?loc)
+
+  let bug_ ?loc message = raise (Bug (message, loc))
+  let bug ?loc = Printf.ksprintf (bug_ ?loc)
+end (* module Error *)
 
 (* ================================================================================ *)
 module String_ = struct
 
   let to_float string =
     try float_of_string string
-    with _ -> float_of_string (Str.global_replace (Str.regexp "\\.") "," string)
+    with _ ->
+      try float_of_string (Str.global_replace (Str.regexp "\\.") "," string)
+      with _ -> Error.build "[String_.to_float] cannot convert '%s'" string
 
   let of_float float = Str.global_replace (Str.regexp ",") "." (sprintf "%g" float)
 
@@ -28,20 +63,6 @@ module Dot = struct
     ignore(Sys.command(sprintf "dot -Tpng -o %s %s " output_file temp_file_name))
 end (* module Dot *)
 
-(* ================================================================================ *)
-module Loc = struct
-  type t = string * int
-
-  let to_string (file,line) = sprintf "(file: %s, line: %d)" (Filename.basename file) line
-
-  let opt_set_line line = function
-    | None -> None
-    | Some (file,_) -> Some (file, line)
-
-  let opt_to_string = function
-    | None -> ""
-    | Some x -> to_string x
-end (* module Loc *)
 
 (* ================================================================================ *)
 module File = struct
@@ -536,24 +557,6 @@ module Massoc_gid = Massoc_make (Gid)
 (* ================================================================================ *)
 module Massoc_pid = Massoc_make (Pid)
 
-(* ================================================================================ *)
-module Error = struct
-
-  exception Build of (string * Loc.t option)
-  exception Run of (string * Loc.t option)
-  exception Bug of (string * Loc.t option)
-
-  let build_ ?loc message =
-    Log.fmessage "[%s] %s" (match loc with None -> "?" | Some x -> Loc.to_string x) message;
-    raise (Build (message, loc))
-  let build ?loc = Printf.ksprintf (build_ ?loc)
-
-  let run_ ?loc message = raise (Run (message, loc))
-  let run ?loc = Printf.ksprintf (run_ ?loc)
-
-  let bug_ ?loc message = raise (Bug (message, loc))
-  let bug ?loc = Printf.ksprintf (bug_ ?loc)
-end (* module Error *)
 
 (* ================================================================================ *)
 module Id = struct