makeTagId tagId | null tagId = Left (ValidationError "tagId is empty") | otherwise = Right (TagId tagId) makeTag :: String -> String -> Int -> Either ValidationError Tag makeTag id gid order = do tagId <- makeTagId id groupId <- makeGroupId gid sortOrder <- makeSortOder order return (Tag tagId groupId sortOrder) )BTLFMM ྫ͑ϞφυʹɺೖΕࢠʹ ͳͬͨίʔυΛฏୱԽ͢Δޮ༻ ͕͋Δ