# Module Random

    module Random: sig .. end

Pseudo-random number generators (PRNG).

## Basic functions

    val init : int -> unit

Initialize the generator, using the argument as a seed. The same seed will always yield the same sequence of numbers.

    val full_init : int array -> unit

Same as `Random.init` but takes more data as seed.

    val self_init : unit -> unit

Initialize the generator with a random seed chosen in a system-dependent way. If `/dev/urandom` is available on the host machine, it is used to provide a highly random initial seed. Otherwise, a less random seed is computed from system parameters (current time, process IDs).

    val bits : unit -> int

Return 30 random bits in a nonnegative integer.

- Before 3.12.0 used a different algorithm (affects all the following functions)

    val int : int -> int

`Random.int bound` returns a random integer between 0 (inclusive) and `bound` (exclusive). `bound` must be greater than 0 and less than 230.

    val full_int : int -> int

`Random.full_int bound` returns a random integer between 0 (inclusive) and `bound` (exclusive). `bound` may be any positive integer.

If `bound` is less than 230, `Random.full_int bound` is equal to `Random.int` `bound`. If `bound` is greater than 230 (on 64-bit systems or non-standard environments, such as JavaScript), `Random.full_int` returns a value, where `Random.int` raises `Invalid_argument`.

- Since 4.13.0

    val int32 : Int32.t -> Int32.t

`Random.int32 bound` returns a random integer between 0 (inclusive) and `bound` (exclusive). `bound` must be greater than 0.

    val nativeint : Nativeint.t -> Nativeint.t

`Random.nativeint bound` returns a random integer between 0 (inclusive) and `bound` (exclusive). `bound` must be greater than 0.

    val int64 : Int64.t -> Int64.t

`Random.int64 bound` returns a random integer between 0 (inclusive) and `bound` (exclusive). `bound` must be greater than 0.

    val float : float -> float

`Random.float bound` returns a random floating-point number between 0 and `bound` (inclusive). If `bound` is negative, the result is negative or zero. If `bound` is 0, the result is 0.

    val bool : unit -> bool

`Random.bool ()` returns `true` or `false` with probability 0.5 each.

## Advanced functions

The functions from module `Random.State` manipulate the current state of the random generator explicitly. This allows using one or several deterministic PRNGs, even in a multi-threaded program, without interference from other parts of the program.

    module State: sig .. end

    val get_state : unit -> State.t

Return the current state of the generator used by the basic functions.

    val set_state : State.t -> unit

Set the state of the generator used by the basic functions.