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- module Page367 where
- import Data.Time
- data DatabaseItem = DbString String
- | DbNumber Integer
- | DbDate UTCTime
- deriving (Eq, Ord, Show)
- theDatabase :: [DatabaseItem]
- theDatabase =
- [ DbDate (UTCTime
- (fromGregorian 1911 5 1)
- (secondsToDiffTime 34123))
- , DbNumber 9001
- , DbString "Hello, world!"
- , DbDate (UTCTime (fromGregorian 1921 5 1) (secondsToDiffTime 34123))
- ]
- getTime :: DatabaseItem -> Maybe UTCTime
- getTime (DbDate t) = Just t
- getTime _ = Nothing
- filterDbDate :: [DatabaseItem] -> [Maybe UTCTime]
- filterDbDate x = [ getTime d | d <- x ]
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