module Data.Vault.ST.LAZINESS ( -- * Vault Vault, Key, empty, newKey, lookup, insert, adjust, delete, union, -- * Locker Locker, lock, unlock, ) where import Data.Monoid (Monoid(..)) import Prelude hiding (lookup) import Control.Applicative hiding (empty) import Control.Monad.ST import Control.Monad.ST.Unsafe as STUnsafe import Data.Unique.Really {- The GHC-specific implementation uses unsafeCoerce for reasons of efficiency. See http://apfelmus.nfshost.com/blog/2011/09/04-vault.html for the second implementation that doesn't need to bypass the type checker. -} #if UseGHC #include "backends/GHC.hs" #else #include "backends/IORef.hs" #endif {----------------------------------------------------------------------------- Vault ------------------------------------------------------------------------------} instance Monoid (Vault s) where mempty = empty mappend = union -- | The empty vault. empty :: Vault s empty = Vault Map.empty -- | Create a new key for use with a vault. newKey :: ST s (Key s a) -- | Lookup the value of a key in the vault. lookup :: Key s a -> Vault s -> Maybe a -- | Insert a value for a given key. Overwrites any previous value. insert :: Key s a -> a -> Vault s -> Vault s -- | Adjust the value for a given key if it's present in the vault. adjust :: (a -> a) -> Key s a -> Vault s -> Vault s -- | Delete a key from the vault. delete :: Key s a -> Vault s -> Vault s -- | Merge two vaults (left-biased). union :: Vault s -> Vault s -> Vault s union (Vault m) (Vault m') = Vault $ Map.union m m' {----------------------------------------------------------------------------- Locker ------------------------------------------------------------------------------} -- | Put a single value into a 'Locker'. lock :: Key s a -> a -> Locker s -- | Retrieve the value from the 'Locker'. unlock :: Key s a -> Locker s -> Maybe a