maybeRead :: Read a => String -> Maybe a
maybeRead str = case reads str of
                [(x, "")] -> Just x
                _         -> Nothing
maybeRead :: Read a => String -> Maybe a
maybeRead str = case reads str of
                [(x, "")] -> Just x
                _         -> Nothing
maybeRead str = case reads str of
                [(x, "")] -> Just x
                _         -> Nothing