Module Random

module Random: sig .. end

Pseudo-random number generators (PRNG).

Basic functions

let init: int => unit;

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

let full_init: array(int) => unit;

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

let 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).

let bits: unit => int;

Return 30 random bits in a nonnegative integer.
Before 3.12.0 used a different algorithm (affects all the following functions)

let 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.

let int32: Int32.t => Int32.t;

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

let nativeint: Nativeint.t => Nativeint.t;

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

let int64: Int64.t => Int64.t;

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

let 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.

let bool: unit => bool;

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

Advanced functions

The functions from module 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

let get_state: unit => State.t;

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

let set_state: State.t => unit;

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