# Module `Base.Random`

Pseudo-random number generation.

This is a wrapper of the standard library's `Random`

library, though it does not share state with that library.

###### 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 : ?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 nondeterministic failures for everyone. Passing`~allow_in_tests:true`

removes this restriction in case you legitimately want nondeterministic 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 -> int32`

`Random.int32 bound`

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

(exclusive).`bound`

must be greater than 0.

`val nativeint : nativeint -> nativeint`

`Random.nativeint bound`

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

(exclusive).`bound`

must be greater than 0.

`val int64 : int64 -> int64`

`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 int_incl : int -> int -> int`

Produces a random value between the given inclusive bounds. Raises if bounds are given in decreasing order.

`val int32_incl : int32 -> int32 -> int32`

`val nativeint_incl : nativeint -> nativeint -> nativeint`

`val int64_incl : int64 -> int64 -> int64`

`val float_range : float -> float -> float`

Produces a value between the given bounds (inclusive and exclusive, respectively). Raises if bounds are given in decreasing order.

`val char : unit -> char`

Return a uniformly-chosen

`char`

.

`val ascii : unit -> char`

Return a uniformly-chosen

`char`

in the ASCII range.

###### Advanced functions

`module State : sig ... end`

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.

`val set_state : State.t -> unit`

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