rnTurtle :: (Angle n -> Angle n)   -- ^ Transformation to apply on current orientation
           -> TurtleState n    -- ^ Turtle to turn
           -> TurtleState n    -- ^ Resulting turtle
turnTurtle f t@(TurtleState _ _ h _ _ _) = t { heading = f h  }


turnTurtle :: (Angle n -> Angle n)   -- ^ Transformation to apply on current orientation
           -> TurtleState n    -- ^ Turtle to turn
           -> TurtleState n
turnTurtle f t@(TurtleState _ _ h _ _ _) = t { heading = f h  }
turnTurtle f t@(TurtleState _ _ h _ _ _) = t { heading = f h  }