Module CCHash

Hash combinators

The API of this module is stable as per semantic versioning, like the rest of containers. However the exact implementation of hashing function can change and should not be relied on (i.e. hashing a value always returns the same integer within a run of a program, not across versions of OCaml and Containers).

Definitions

type hash = int

A hash value is a positive integer.

type 'a t = 'a -> hash

A hash function for values of type 'a.

val const : hash -> _ t

const h hashes any value into h. Use with caution!.

val const0 : _ t

Always return 0. Useful for ignoring elements. Example: Hash.(pair string const0) will map pairs ("a", 1) and ("a", 2) to the same hash, but not the same as ("b", 1).

since
1.5
val int : int t
val bool : bool t
val char : char t
val int32 : int32 t
val int64 : int64 t
val nativeint : nativeint t
val slice : string -> int -> int t

slice s i len state hashes the slice i, …, i+len-1 of s into state.

val bytes : bytes t

Hash a byte array.

since
3.5
val string : string t
val list : 'a t -> 'a list t
val array : 'a t -> 'a array t
val opt : 'a t -> 'a option t
val pair : 'a t -> 'b t -> ('a * 'b) t
val triple : 'a t -> 'b t -> 'c t -> ('a * 'b * 'c) t
val quad : 'a t -> 'b t -> 'c t -> 'd t -> ('a * 'b * 'c * 'd) t
val map : ('a -> 'b) -> 'b t -> 'a t

map f h is the hasher that takes x, and uses h to hash f x.

For example:

module Str_set = Set.Make(String)

let hash_str_set : Str_set.t CCHash.t = CCHash.(map Str_set.to_seq @@ seq string)
since
3.5
val if_ : bool -> 'a t -> 'a t -> 'a t

Decide which hash function to use depending on the boolean.

val poly : 'a t

poly x is Hashtbl.hash x. The regular polymorphic hash function.

val list_comm : 'a t -> 'a list t

Commutative version of list. Lists that are equal up to permutation will have the same hash.

since
1.0
val array_comm : 'a t -> 'a array t

Commutative version of array. Arrays that are equal up to permutation will have the same hash.

since
1.0

Base hash combinators

val combine : 'a t -> hash -> 'a -> hash
val combine2 : hash -> hash -> hash
val combine3 : hash -> hash -> hash -> hash
val combine4 : hash -> hash -> hash -> hash -> hash
val combine5 : hash -> hash -> hash -> hash -> hash -> hash
since
2.1
val combine6 : hash -> hash -> hash -> hash -> hash -> hash -> hash
since
2.1

Iterators

type 'a iter = ('a -> unit) -> unit
type 'a gen = unit -> 'a option
val seq : 'a t -> 'a Stdlib.Seq.t t
val iter : 'a t -> 'a iter t
val gen : 'a t -> 'a gen t