data Person = Person { personName :: String
                     , personAge  :: Int
                     , personGender :: String
                     } deriving Show

defaultPerson = Person { personName   = "Unknown name"
                       , personAge    = 0
                       , personGender = "Unknown gender"
                       }

person = defaultPerson { personAge = 24 }

λ> person
Person {personName = "Unknown name", personAge = 24, personGender = "Unknown gender"}