Module `CCRandom`

Random Generators

Documentation for the standard Random module

include module type of sig ... end

val init : int -> unit
val full_init : int array -> unit
val self_init : unit -> unit
val bits : unit -> int
val int : int -> int
val int32 : Stdlib.Int32.t -> Stdlib.Int32.t
val nativeint : Stdlib.Nativeint.t -> Stdlib.Nativeint.t
val int64 : Stdlib.Int64.t -> Stdlib.Int64.t
val float : float -> float
val bool : unit -> bool

module State = Stdlib__random.State

val get_state : unit -> State.t
val set_state : State.t -> unit

type state = Stdlib.Random.State.t
type 'a t = state -> 'a: Random generator for values of type 'a.

type 'a random_gen = 'a t

val return : 'a -> 'a t: return x is the generator that always returns x. Example: let random_int = return 4 (* fair dice roll *).

val flat_map : ('a -> 'b t) -> 'a t -> 'b t: flat_map f g st is f (g st) st.

val (>>=) : 'a t -> ('a -> 'b t) -> 'b t: Monadic bind.

val map : ('a -> 'b) -> 'a t -> 'b t: map f g st is f (g st).

val (>|=) : 'a t -> ('a -> 'b) -> 'b t

val delay : (unit -> 'a t) -> 'a t

Delay evaluation. Useful for side-effectful generators that need some code to run for every call. Example:

let gensym = let r = ref 0 in fun () -> incr r; !r ;;

delay (fun () ->
  let name = gensym() in
  small_int >>= fun i -> return (name,i)
)

since: 0.4

val choose : 'a t list -> 'a option t: Choose a generator within the list.

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

Like choose but without option.

raises Invalid_argument: if the list is empty.

val choose_array : 'a t array -> 'a option t: Choose a generator within the array.

val choose_return : 'a list -> 'a t

Choose among the list.

raises Invalid_argument: if the list is empty.

val replicate : int -> 'a t -> 'a list t: replicate n g makes a list of n elements which are all generated randomly using g.

val sample_without_duplicates : cmp:('a -> 'a -> int) -> int -> 'a t -> 'a list t

sample_without_replacement n g makes a list of n elements which are all generated randomly using g with the added constraint that none of the generated random values are equal.

raises Invalid_argument: if n <= 0.

since: 2.4

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

Build random lists from lists of random generators.

since: 0.4

exception Pick_from_empty

since: 0.16

val pick_list : 'a list -> 'a t

Pick an element at random from the list.

raises Pick_from_empty: if the list is empty.

since: 0.16

val pick_array : 'a array -> 'a t

Pick an element at random from the array.

raises Pick_from_empty: if the array is empty.

since: 0.16

val small_int : int t: A small int (100).

val int : int -> int t: Random int within the given range.

val int_range : int -> int -> int t: Inclusive range.

val small_float : float t

A reasonably small float (100.0).

since: 0.6.1

val float : float -> float t

Random float within the given range.

since: 0.6.1

val float_range : float -> float -> float t

Inclusive range. float_range a b assumes a < b.

since: 0.6.1

val split : int -> (int * int) option t

Split a positive value n into n1,n2 where n = n1 + n2.

returns: None if the value is too small.

val split_list : int -> len:int -> int list option t

Split a value n into a list of values whose sum is n and whose length is length. The list is never empty and does not contain 0.

raises Invalid_argument: if len <= 1.

returns: None if the value is too small.

val retry : ?⁠max:int -> 'a option t -> 'a option t

retry g calls g until it returns some value, or until the maximum number of retries was reached. If g fails, then it counts for one iteration, and the generator retries.

parameter max:: maximum number of retries. Default 10.

val try_successively : 'a option t list -> 'a option t: try_successively l tries each generator of l, one after the other. If some generator succeeds its result is returned, else the next generator is tried.

val (<?>) : 'a option t -> 'a option t -> 'a option t: a <?> b is a choice operator. It first tries a, and returns its result if successful. If a fails, then b is returned.

val fix : ?⁠sub1:('a t -> 'a t) list -> ?⁠sub2:('a t -> 'a t -> 'a t) list -> ?⁠subn:(int t * ('a list t -> 'a t)) list -> base:'a t -> int t -> 'a t

Recursion combinators, for building recursive values. The integer generator is used to provide fuel. The sub_ generators should use their arguments only once!

parameter sub1: cases that recurse on one value.

parameter sub2: cases that use the recursive gen twice.

parameter subn: cases that use a list of recursive cases.

Applicative

val pure : 'a -> 'a t
val (<*>) : ('a -> 'b) t -> 'a t -> 'b t

Let operators on OCaml >= 4.08.0, nothing otherwise

since: 2.8

include CCShimsMkLet_.S with type 'a t_let := 'a t

type 'a t_let

val let+ : 'a t_let -> ('a -> 'b) -> 'b t_let
val and+ : 'a t_let -> 'b t_let -> ('a * 'b) t_let
val let* : 'a t_let -> ('a -> 'b t_let) -> 'b t_let
val and* : 'a t_let -> 'b t_let -> ('a * 'b) t_let

Run a generator

val run : ?⁠st:state -> 'a t -> 'a: Using a random state (possibly the one in argument) run a generator.