`Stdlib.Random`

Pseudo-random number generators (PRNG).

With multiple domains, each domain has its own generator that evolves independently of the generators of other domains. When a domain is created, its generator is initialized by splitting the state of the generator associated with the parent domain.

In contrast, all threads within a domain share the same domain-local generator. Independent generators can be created with the `Random.split`

function and used with the functions from the `Random.State`

module.

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

Same as `Random.init`

but takes more data as seed.

Initialize the domain-local 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, domain-local state).

`Random.int bound`

returns a random integer between 0 (inclusive) and `bound`

(exclusive). `bound`

must be greater than 0 and less than 2^{30}.

`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 2^{30}, `Random.full_int bound`

is equal to `Random.int`

` bound`

. If `bound`

is greater than 2^{30} (on 64-bit systems or non-standard environments, such as JavaScript), `Random.full_int`

returns a value, where `Random.int`

raises `Stdlib.Invalid_argument`

.

`Random.int32 bound`

returns a random integer between 0 (inclusive) and `bound`

(exclusive). `bound`

must be greater than 0.

`Random.int64 bound`

returns a random integer between 0 (inclusive) and `bound`

(exclusive). `bound`

must be greater than 0.

`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 bits32 : unit -> Int32.t`

`Random.bits32 ()`

returns 32 random bits as an integer between `Int32.min_int`

and `Int32.max_int`

.

`val bits64 : unit -> Int64.t`

`Random.bits64 ()`

returns 64 random bits as an integer between `Int64.min_int`

and `Int64.max_int`

.

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`

`val get_state : unit -> State.t`

`get_state()`

returns a fresh copy of the current state of the domain-local generator (which is used by the basic functions).

`val set_state : State.t -> unit`

`set_state s`

updates the current state of the domain-local generator (which is used by the basic functions) by copying the state `s`

into it.