Created
February 7, 2010 01:26
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import Data.Maybe | |
data Person = Person { name :: String | |
, partner :: Partner | |
} deriving Eq | |
-- パートナー | |
type Partner = Maybe Person | |
instance Show Person where | |
show (Person n Nothing) = n | |
show (Person n p) = n ++ "{" ++ (name $ fromJust p) ++ "}" | |
-- 誕生 | |
born n = Person n Nothing | |
-- 結婚 | |
marry p1 p2 = (p1 { partner = Just p2 }, p2 { partner = Just p1 }) | |
-- 離婚 | |
divorce (p1,p2) = (p1 { partner = Nothing }, p2 { partner = Nothing }) | |
main = do let tarou = born "Tarou" | |
hanako = born "Hanako" | |
m = marry tarou hanako | |
d = divorce m | |
print m -- (Tarou{Hanako},Hanako{Tarou}) | |
print d -- (Tarou,Hanako) |
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