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-{- |
- Implementation of fixed-size hash tables, with a type
- class for constructing hash values for structured types.
--}
-module Hash (
- -- * The @HashTable@ type
- HashTable,
-
- -- ** Operations on @HashTable@s
- new, insert, lookup,
-
- -- * The @Hash@ class
- Hash(..),
- ) where
-
-import Array
-
--- | A hash table with keys of type @key@ and values of type @val@.
--- The type @key@ should be an instance of 'Eq'.
-data HashTable key val = HashTable Int (Array Int [(key,val)])
-
--- | Builds a new hash table with a given size
-new :: (Eq key, Hash key) => Int -> IO (HashTable key val)
-
--- | Inserts a new element into the hash table
-insert :: (Eq key, Hash key) => key -> val -> IO ()
-
--- | Looks up a key in the hash table, returns @'Just' val@ if the key
--- was found, or 'Nothing' otherwise.
-lookup :: Hash key => key -> IO (Maybe val)
-
--- | A class of types which can be hashed.
-class Hash a where
- -- | hashes the value of type @a@ into an 'Int'
- hash :: a -> Int
-
-instance Hash Int where
- hash = id
-
-instance Hash Float where
- hash = trunc
-
-instance (Hash a, Hash b) => Hash (a,b) where
- hash (a,b) = hash a `xor` hash b
-