Previous Up Next

Module CCCache

module CCCache: sig .. end

Caches

Particularly useful for memoization. See CCCache.with_cache and CCCache.with_cache_rec for more details.
Since 0.6

type 'a equal = 'a -> 'a -> bool

type 'a hash = 'a -> int

Value interface

Typical use case: one wants to memoize a function f : 'a -> 'b. Code sample:

   let f x =
    print_endline "call f";
    x + 1;;
   let f' = with_cache (lru 256) f;;
   f' 0;; (* prints *)
   f' 1;; (* prints *)
   f' 0;; (* doesn't print, returns cached value *)

type ('a, 'b) t

val clear : ('a, 'b) t -> unit

Clear the content of the cache

val with_cache : ('a, 'b) t -> ('a -> 'b) -> 'a -> 'b

with_cache c f behaves like f, but caches calls to f in the cache c. It always returns the same value as f x, if f x returns, or raise the same exception. However, f may not be called if x is in the cache.

val with_cache_rec : ('a, 'b) t -> (('a -> 'b) -> 'a -> 'b) -> 'a -> 'b

with_cache_rec c f is a function that first, applies f to some f' = fix f, such that recursive calls to f' are cached in c. It is similar to CCCache.with_cache but with a function that takes as first argument its own recursive version. Example (memoized Fibonacci function):

   let fib = with_cache_rec (lru 256)
     (fun fib' n -> match n with
       | 1 | 2 -> 1
       | _ -> fib' (n-1) + fib' (n-2)
     );;
   fib 70;;

val size : ('a, 'b) t -> int

Size of the cache (number of entries). At most linear in the number of entries.

val iter : ('a, 'b) t -> ('a -> 'b -> unit) -> unit

Iterate on cached values. Should yield size cache pairs.

val dummy : ('a, 'b) t

Dummy cache, never stores any value

val linear : ?eq:'a equal -> int -> ('a, 'b) t

Linear cache with the given size. It stores key/value pairs in an array and does linear search at every call, so it should only be used with small size.

eq : optional equality predicate for keys

val replacing : ?eq:'a equal -> ?hash:'a hash -> int -> ('a, 'b) t

Replacing cache of the given size. Equality and hash functions can be parametrized. It's a hash table that handles collisions by replacing the old value with the new (so a cache entry is evicted when another entry with the same hash (modulo size) is added). Never grows wider than the given size.

val lru : ?eq:'a equal -> ?hash:'a hash -> int -> ('a, 'b) t

LRU cache of the given size ("Least Recently Used": keys that have not been used recently are deleted first). Never grows wider than the given size.

val unbounded : ?eq:'a equal -> ?hash:'a hash -> int -> ('a, 'b) t

Unbounded cache, backed by a Hash table. Will grow forever unless CCCache.clear is called manually.