Safe Haskell | None |
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This module contains a `HashTable`

typeclass for the hash table
implementations in this package. This allows you to provide functions which
will work for any hash table implementation in this collection.

It is recommended to create a concrete type alias in your code when using this package, i.e.:

import qualified Data.HashTable.IO as H type HashTable k v = H.BasicHashTable k v foo :: IO (HashTable Int Int) foo = do ht <- H.new H.insert ht 1 1 return ht

or

import qualified Data.HashTable.ST.Cuckoo as C import qualified Data.HashTable.Class as H type HashTable s k v = C.HashTable s k v foo :: ST s (HashTable s k v) foo = do ht <- H.new H.insert ht 1 1 return ht

Firstly, this makes it easy to switch to a different hash table
implementation, and secondly, using a concrete type rather than leaving your
functions abstract in the `HashTable`

class should allow GHC to optimize
away the typeclass dictionaries.

Note that the functions in this typeclass are in the `ST`

monad; if you want
hash tables in `IO`

, use the convenience wrappers in Data.HashTable.IO.

- class HashTable h where
- new :: ST s (h s k v)
- newSized :: Int -> ST s (h s k v)
- insert :: (Eq k, Hashable k) => h s k v -> k -> v -> ST s ()
- delete :: (Eq k, Hashable k) => h s k v -> k -> ST s ()
- lookup :: (Eq k, Hashable k) => h s k v -> k -> ST s (Maybe v)
- foldM :: (a -> (k, v) -> ST s a) -> a -> h s k v -> ST s a
- mapM_ :: ((k, v) -> ST s b) -> h s k v -> ST s ()
- computeOverhead :: h s k v -> ST s Double

- fromList :: (HashTable h, Eq k, Hashable k) => [(k, v)] -> ST s (h s k v)
- toList :: HashTable h => h s k v -> ST s [(k, v)]

# Documentation

A typeclass for hash tables in the `ST`

monad. The operations on these
hash tables are typically both key- and value-strict.

Creates a new, default-sized hash table. *O(1)*.

newSized :: Int -> ST s (h s k v)Source

Creates a new hash table sized to hold `n`

elements. *O(n)*.

insert :: (Eq k, Hashable k) => h s k v -> k -> v -> ST s ()Source

Inserts a key/value mapping into a hash table, replacing any existing mapping for that key.

*O(n)* worst case, *O(1)* amortized.

delete :: (Eq k, Hashable k) => h s k v -> k -> ST s ()Source

Deletes a key-value mapping from a hash table. *O(n)* worst case,
*O(1)* amortized.

lookup :: (Eq k, Hashable k) => h s k v -> k -> ST s (Maybe v)Source

Looks up a key-value mapping in a hash table. *O(n)* worst case,
(*O(1)* for cuckoo hash), *O(1)* amortized.

foldM :: (a -> (k, v) -> ST s a) -> a -> h s k v -> ST s aSource

A strict fold over the key-value records of a hash table in the `ST`

monad. *O(n)*.

mapM_ :: ((k, v) -> ST s b) -> h s k v -> ST s ()Source

A side-effecting map over the key-value records of a hash
table. *O(n)*.

computeOverhead :: h s k v -> ST s DoubleSource

Computes the overhead (in words) per key-value mapping. Used for
debugging, etc; time complexity depends on the underlying hash table
implementation. *O(n)*.