This module implements a least-recently-used structure. Conceptually, it's a list of values where the head of the list is the most recently used value. When a value is used, it's moved from its place in the list to the head of the list. The last element in the list is thus the least-recently-used value.

This structure is often used in caches to decide which values to evict when the cache becomes full.

This module uses a Map to implement the LRU efficiently and thus there's the requirement that the elements of the LRU be instances of Ord, which a more general (but slower) LRU implementation could avoid.

- data Ord a => LRU a
- empty :: Ord a => LRU a
- null :: Ord a => LRU a -> Bool
- size :: Ord a => LRU a -> Int
- hit :: Ord a => a -> LRU a -> LRU a
- delete :: Ord a => a -> LRU a -> LRU a
- toList :: Ord a => LRU a -> [a]
- member :: Ord a => a -> LRU a -> Bool
- pop :: Ord a => LRU a -> LRU a
- last :: (Ord a, Monad m) => LRU a -> m a

# Documentation

An LRU. Contains the head element, last element and the map from elements to their Items

hit :: Ord a => a -> LRU a -> LRU aSource

Insert a value into an LRU. If the value is already in the LRU, it's moved to the head of the list. O(log n)

toList :: Ord a => LRU a -> [a]Source

Returns a list of the members of the LRU in order, newest first. O(n(log n))

member :: Ord a => a -> LRU a -> BoolSource

Returns true iff the given element is in the LRU. O(log n)