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{- git-annex UUID type
-
- Copyright 2011 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU GPL version 3 or higher.
-}
{-# LANGUAGE TypeSynonymInstances, FlexibleInstances #-}
module Types.UUID where
import qualified Data.Map as M
import qualified Data.UUID as U
import Data.Maybe
-- A UUID is either an arbitrary opaque string, or UUID info may be missing.
data UUID = NoUUID | UUID String
deriving (Eq, Ord, Show, Read)
fromUUID :: UUID -> String
fromUUID (UUID u) = u
fromUUID NoUUID = ""
class ToUUID a where
toUUID :: a -> UUID
instance ToUUID UUID where
toUUID = id
instance ToUUID String where
toUUID [] = NoUUID
toUUID s = UUID s
isUUID :: String -> Bool
isUUID = isJust . U.fromString
type UUIDMap = M.Map UUID String
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