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GHC 9.10.3 · lts/ghc-9.10.x · c74966e · 2026-09-27

Modulelrucache-1.2.0.1Haskell98

Data.Cache.LRU.Internal

This module provides access to all the internals use by the LRU type. This can be used to create data structures that violate the invariants the public interface maintains. Be careful when using this module. The valid function can be used to check if an LRU structure satisfies the invariants the public interface maintains.

If this degree of control isn't needed, consider using Data.Cache.LRU instead.

  • 2 types
  • 15 values
  • Packagelrucache-1.2.0.1
  • Exports17
  • LanguageHaskell98
  • LicenceBSD-3-Clause
  • SourceInternal.hs
datadata LRU key val
#

Stores the information that makes up an LRU cache

Constructors

Instances6Functor, Foldable, Traversable, Eq, Data, Show
  • Functor (LRU key)Defined in lrucache-1.2.0.1 · Data.Cache.LRU.Internal
  • Ord key => Foldable (LRU key)Defined in lrucache-1.2.0.1 · Data.Cache.LRU.Internal
  • Ord key => Traversable (LRU key)Defined in lrucache-1.2.0.1 · Data.Cache.LRU.Internal
  • (Eq key, Eq val) => Eq (LRU key val)Defined in lrucache-1.2.0.1 · Data.Cache.LRU.Internal
  • (Data key, Data val, Ord key) => Data (LRU key val)Defined in lrucache-1.2.0.1 · Data.Cache.LRU.Internal
  • (Ord key, Show key, Show val) => Show (LRU key val)Defined in lrucache-1.2.0.1 · Data.Cache.LRU.Internal
datadata LinkedVal key val
#

The values stored in the Map of the LRU cache. They embed a doubly-linked list through the values of the Map.

Constructors

Instances5Functor, Foldable, Traversable, Eq, Data
valuenewLRU
  1. :: Ord key
  2. => Maybe Integer

    the optional maximum size of the LRU

  3. -> 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.

valuefromList
  1. :: Ord key
  2. => Maybe Integer

    the optional maximum size of the LRU

  3. -> [(key, val)]
  4. -> 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.

valuetoList :: 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.

valuepairs
  1. :: (Ord key, Applicative f, Contravariant f)
  2. => (key, val) -> f (key, val)
  3. -> LRU key val
  4. -> f (LRU key val)
#

Traverse the (key, value) pairs of the LRU, in a read-only way. This is a Fold in the sense used by the lens package. It must be read-only because alterations could break the underlying Map structure.

valuekeys
  1. :: (Ord key, Applicative f, Contravariant f)
  2. => key -> f key
  3. -> LRU key val
  4. -> f (LRU key val)
#

Traverse the keys of the LRU, in a read-only way. This is a Fold in the sense used by the lens package. It must be read-only because alterations could break the underlying Map structure.

valueinsert :: 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.

valuelookup :: 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.

valuedelete :: 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.

valuepop :: 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.

valuesize :: LRU key val -> Int
#

Returns the number of elements the LRU currently contains.

valuehit' :: Ord key => key -> LRU key val -> LRU key val
#

Internal function. The key passed in must be present in the LRU. Moves the item associated with that key to the most recently accessed position.

valuedelete'
  1. :: Ord key
  2. => key

    The key must be present in the provided LRU

  3. -> LRU key val

    This is the LRU to modify

  4. -> Map key (LinkedVal key val)

    this is the Map from the previous argument, but with the key already removed from it. This isn't consistent yet, as it still might contain LinkedVals with pointers to the removed key.

  5. -> LinkedVal key val

    This is the LinkedVal that corresponds to the key in the passed in LRU. It is absent from the passed in map.

  6. -> LRU key val
#

An internal function used by insert (when the cache is full) and delete. This function has strict requirements on its arguments in order to work properly.

As this is intended to be an internal function, the arguments were chosen to avoid repeated computation, rather than for simplicity of calling this function.

valueadjust' :: Ord k => (a -> a) -> k -> Map k a -> Map k a
#

Internal function. This is very similar to adjust, with two major differences. First, it's strict in the application of the function, which is a huge win when working with this structure.

Second, it requires that the key be present in order to work. If the key isn't present, undefined will be inserted into the Map, which will cause problems later.

valuevalid :: Ord key => LRU key val -> Bool
#

Internal function. This checks the four structural invariants of the LRU cache structure:

  1. The cache's size does not exceed the specified max size.

  2. The linked list through the nodes is consistent in both directions.

  3. The linked list contains the same number of nodes as the cache.

  4. Every key in the linked list is in the Map.