import Data.Foldable (foldMap)
import Data.Monoid (First(First, getFirst))
import Data.Maybe (fromMaybe)

data Fruit = Fruit { color :: String, weight :: Int }

theFruitIsRed :: Fruit -> Maybe String
theFruitIsRed (Fruit "red" _) = Nothing
theFruitIsRed _               = Just "Fruit not red"

theFruitIsNotTooHeavy :: Fruit -> Maybe String
theFruitIsNotTooHeavy (Fruit _ w)
    | w < 500   = Nothing
    | otherwise = Just "Too heavy"

checkRules :: Fruit -> Maybe String
checkRules = getFirst . foldMap (First .)
    [ theFruitIsRed
    , theFruitIsNotTooHeavy
    ]
    
main = mapM (putStrLn . fromMaybe "No problems!" . checkRules)
	[ Fruit "red" 1000
	, Fruit "red" 10
	, Fruit "blue" 600
	, Fruit "blue" 100
	]