color_change t str     = case readMaybe str :: Maybe (Word8,Word8,Word8) of
                             Nothing -> error ("Parse error on line "
                                               ++ show (comln t)
                                               ++ ": invalid color: '" ++ str
                                               ++ "': use '(r,g,b)'")
                                        >> exitFailure >> nEW_TURTLE
                             Just c -> return t { color = c }

-- |News a new turtle on white image of size x y.
color_change t str     = case readMaybe str :: Maybe (Word8,Word8,Word8) of
                             Nothing -> error ("Parse error on line "
                                               ++ show (comln t)
                                               ++ ": invalid color: '" ++ str
                                               ++ "': use '(r,g,b)'")
                                        >> exitFailure >> nEW_TURTLE
                             Just c -> return t { color = c }

-- |News a new turtle on white image of size x y.
color_change t str     = case readMaybe str :: Maybe (Word8,Word8,Word8) of
                             Nothing -> error ("Parse error on line "
                                               ++ show (comln t)
                                               ++ ": invalid color: '" ++ str
                                               ++ "': use '(r,g,b)'")
                                        >> exitFailure >> nEW_TURTLE
                             Just c -> return t { color = c }

-- |News a new turtle on white image of size x y.