Data.Cache.LRU

Implements an LRU cache.

This module provides a pure LRU cache based on a doubly-linked list through a Data.Map structure. This gives O(log n) operations on insert, lookup, delete, and pop, and O(n * log n) for toList.

The interface this module provides is opaque. If further control is desired, the Data.Cache.LRU.Internal module can be used.

Documentation

data LRU key val

Stores the information that makes up an LRU cache

Instances

Functor (LRU key)

(Eq key, Eq val) => Eq (LRU key val)

(Ord key, Show key, Show val) => Show (LRU key val)

newLRU

Arguments

:: Ord key

=> Maybe Integer

the optional maximum size of the LRU

-> LRU key val

Make an LRU. If a size limit is specified, the LRU is guaranteed to not grow above the specified number of entries.

fromList

Arguments

:: Ord key

=> Maybe Integer

the optional maximum size of the LRU

-> [(key, val)]

-> LRU key val

Build a new LRU from the given maximum size and list of contents, in order from most recently accessed to least recently accessed.

toList :: Ord key => LRU key val -> [(key, val)]

Retrieve a list view of an LRU. The items are returned in order from most recently accessed to least recently accessed.

maxSize :: LRU key val -> Maybe Integer

the maximum size of the LRU cache

insert :: Ord key => key -> val -> LRU key val -> LRU key val

Add an item to an LRU. If the key was already present in the LRU, the value is changed to the new value passed in. The item added is marked as the most recently accessed item in the LRU returned.

If this would cause the LRU to exceed its maximum size, the least recently used item is dropped from the cache.

lookup :: Ord key => key -> LRU key val -> (LRU key val, Maybe val)

Look up an item in an LRU. If it was present, it is marked as the most recently accesed in the returned LRU.

delete :: Ord key => key -> LRU key val -> (LRU key val, Maybe val)

Remove an item from an LRU. Returns the new LRU, and the value removed if the key was present.

pop :: Ord key => LRU key val -> (LRU key val, Maybe (key, val))

Removes the least-recently accessed element from the LRU. Returns the new LRU, and the key and value from the least-recently used element, if there was one.

size :: LRU key val -> Int

Returns the number of elements the LRU currently contains.