anchor.diff:  (* ------------------------------------------------------------------------------- *)
   let intkey_to_key (a,b) = abytes(a),abytes(b)
   let key_to_intkey (a,b) = cbytes(a),cbytes(b)
  +
  +(* ------------------------------------------------------------------------------- *)
  +let intvalue_to_value (a,b) = abytes(a),b
  +let value_to_intvalue (a,b) = cbytes(a),b
   
   (* ------------------------------------------------------------------------------- *)
   let create (filename:string) =
  
positive.code: 
      let select (db : DB.db) =
          DB.get db key
              |> Option.map DB.deserialize<Value>
            
      let db = DB.opendb self.filename in
  
  
negative.code: (* ------------------------------------------------------------------------------- *)
  let insert self key v =
      let key = DB.serialize<IntKey> (key_to_intkey key) in
      let v   = DB.serialize<IntValue> (value_to_intvalue v) in
    
      let insert (db : DB.db) =
          match DB.get db key with
          | Some _ -> ()
          | None   -> DB.put db key v in
  
      let db = DB.opendb self.filename in
  
  