package containers

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Hash combinators

Definitions

type t = int

A hash value is a positive integer

type state

State required by the hash function.

  • since 0.16 the state is abstract, for more flexibility
type 'a hash_fun = 'a -> state -> state

Hash function for values of type 'a, merging a fingerprint of the value into the state of type t

Applying Hash

val init : state

Initial value

val finish : state -> int

Extract a usable hash value

val apply : 'a hash_fun -> 'a -> int

Apply a hash function to a value. apply f x is the same as finish (f x init)

Basic Combinators

Those combinators have been renamed in 0.13, so as to remove the trailing "_". They are now defined by the application of Make

val bool_ : bool hash_fun
val char_ : char hash_fun
val int_ : int hash_fun
  • deprecated

    use int

val string_ : string hash_fun
val int32_ : int32 hash_fun
val int64_ : int64 hash_fun
val nativeint_ : nativeint hash_fun
val list_ : 'a hash_fun -> 'a list hash_fun

Hash a list. Each element is hashed using f.

val array_ : 'a hash_fun -> 'a array hash_fun

Iterators

type 'a sequence = ('a -> unit) -> unit
type 'a gen = unit -> 'a option
type 'a klist = unit -> [ `Nil | `Cons of 'a * 'a klist ]

Generic Hashing

Parametrize over the state, and some primitives to hash basic types. This can for instance be used for cryptographic hashing or checksums such as MD5.

  • since 0.13
module type HASH = sig ... end
module type S = sig ... end
module Make (H : HASH) : S with type state = H.state
include S with type state := state and type 'a hash_fun := 'a hash_fun
include HASH with type state := state
val int : int -> state -> state
val bool : bool -> state -> state
val char : char -> state -> state
val int32 : int32 -> state -> state
val int64 : int64 -> state -> state
val nativeint : nativeint -> state -> state
val slice : string -> int -> int -> state -> state

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

val string : string hash_fun
val list : 'a hash_fun -> 'a list hash_fun
val array : 'a hash_fun -> 'a array hash_fun
val opt : 'a hash_fun -> 'a option hash_fun
val pair : 'a hash_fun -> 'b hash_fun -> ('a * 'b) hash_fun
val triple : 'a hash_fun -> 'b hash_fun -> 'c hash_fun -> ('a * 'b * 'c) hash_fun
val if_ : bool -> 'a hash_fun -> 'a hash_fun -> 'a hash_fun

Decide which hash function to use depending on the boolean

Iterators

val seq : 'a hash_fun -> 'a sequence hash_fun
val gen : 'a hash_fun -> 'a gen hash_fun
val klist : 'a hash_fun -> 'a klist hash_fun