Module Random = Core_kernel.Core_random

Signature

Pseudo-random number generators (PRNG).

Basic functions

Note that all of these "basic" functions mutate a global random state.

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 : ?allow_in_tests:bool -> unit -> unit

Initialize the generator with a more-or-less random seed chosen in a system-dependent way. By default, self_init is disallowed in inline tests, as it's often used for no good reason and it just creates non deterministic failures for everyone. Passing ~allow_in_tests:true removes this restriction in case you legitimately want non-deterministic values, like in Filename.temp_dir.

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.

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 (inclusive) and bound (exclusive). 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

module State : sig .. end

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

val get_state : unit -> [

| `Consider_using_Random_State_default

]

OCaml's Random.get_state makes a copy of the default state, which is almost certainly not what you want. State.default, which is the actual default state, is probably what you want.

val set_state : State.t -> unit

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