-- | @right z@ returns the zipper with the focus
-- shifted right one element; this can move the
-- cursor off the end.
right :: Zipper a -> Zipper a
right (Zip ls (a:rs)) = Zip (a:ls) rs
right :: Zipper a -> Zipper a
right (Zip ls (a:rs)) = Zip (a:ls) rs
right (Zip ls (a:rs)) = Zip (a:ls) rs