greaterThan :: Int -> Int -> Validation
greaterThan m n | n > m     = OK
                | otherwise = ERR "number too small!"
greaterThan :: Int -> Int -> Validation
greaterThan m n | n > m     = OK
                | otherwise = ERR "number too small!"
greaterThan m n | n > m     = OK
                | otherwise = ERR "number too small!"