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authorKazu Yamamoto <kazu@iij.ad.jp>2013-02-01 11:59:24 +0900
committerKazu Yamamoto <kazu@iij.ad.jp>2013-02-01 11:59:24 +0900
commit8d4c94ca5a969a5ebbb791939fb0195dc672429e (patch)
tree560a944a7105cd715f9acba46790bd7e1a77f82f /html-test/src/Hash.hs
parent266a20afd2d27f28bbb62839ebc3f70bd83bfcce (diff)
parent3d25ea2929a9a9bd0768339b8ac5fd1b7c4670ad (diff)
Merge branch 'ghc-7.6' into ghc-7.6-merge-2
Conflicts: haddock.cabal src/Haddock/Interface/AttachInstances.hs src/Haddock/Interface/Create.hs src/Haddock/Interface/LexParseRn.hs src/Haddock/InterfaceFile.hs src/Haddock/Types.hs Only GHC HEAD can compile this. GHC 7.6.x cannot compile this. Some test fail.
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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 Data.Array
+import Prelude hiding (lookup)
+
+-- | 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)
+new = undefined
+
+-- | Inserts a new element into the hash table
+insert :: (Eq key, Hash key) => key -> val -> IO ()
+insert = undefined
+
+-- | 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)
+lookup = undefined
+
+-- | 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
+
+trunc = undefined
+xor = undefined