.TH "Random" 3o 2023-09-18 OCamldoc "OCaml library"
.SH NAME
Random \- Pseudo-random number generators (PRNG).
.SH Module
Module   Random
.SH Documentation
.sp
Module
.BI "Random"
 : 
.B sig end

.sp
Pseudo\-random number generators (PRNG)\&.

.sp

.sp
.sp

.PP
.SS Basic functions

.PP

.I val init 
: 
.B int -> unit
.sp
Initialize the generator, using the argument as a seed\&.
The same seed will always yield the same sequence of numbers\&.

.sp

.I val full_init 
: 
.B int array -> unit
.sp
Same as 
.ft B
Random\&.init
.ft R
but takes more data as seed\&.

.sp

.I val self_init 
: 
.B unit -> unit
.sp
Initialize the generator with a random seed chosen
in a system\-dependent way\&.  If 
.ft B
/dev/urandom
.ft R
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)\&.

.sp

.I val bits 
: 
.B unit -> int
.sp
Return 30 random bits in a nonnegative integer\&.

.sp
.B "Before3.12.0"
used a different algorithm (affects all the following
functions)


.sp

.I val int 
: 
.B int -> int
.sp

.ft B
Random\&.int bound
.ft R
returns a random integer between 0 (inclusive)
and 
.ft B
bound
.ft R
(exclusive)\&.  
.ft B
bound
.ft R
must be greater than 0 and less
than 2^30\&.

.sp

.I val full_int 
: 
.B int -> int
.sp

.ft B
Random\&.full_int bound
.ft R
returns a random integer between 0 (inclusive)
and 
.ft B
bound
.ft R
(exclusive)\&. 
.ft B
bound
.ft R
may be any positive integer\&.
.sp
If 
.ft B
bound
.ft R
is less than 2^30, 
.ft B
Random\&.full_int bound
.ft R
is equal to
.ft B
Random\&.int
.ft R
.ft B
bound
.ft R
\&. If 
.ft B
bound
.ft R
is greater than 2^30 (on 64\-bit systems
or non\-standard environments, such as JavaScript), 
.ft B
Random\&.full_int
.ft R
returns a value, where 
.ft B
Random\&.int
.ft R
raises 
.ft B
Invalid_argument
.ft R
\&.

.sp
.B "Since"
4.13.0

.sp

.I val int32 
: 
.B Int32.t -> Int32.t
.sp

.ft B
Random\&.int32 bound
.ft R
returns a random integer between 0 (inclusive)
and 
.ft B
bound
.ft R
(exclusive)\&.  
.ft B
bound
.ft R
must be greater than 0\&.

.sp

.I val nativeint 
: 
.B Nativeint.t -> Nativeint.t
.sp

.ft B
Random\&.nativeint bound
.ft R
returns a random integer between 0 (inclusive)
and 
.ft B
bound
.ft R
(exclusive)\&.  
.ft B
bound
.ft R
must be greater than 0\&.

.sp

.I val int64 
: 
.B Int64.t -> Int64.t
.sp

.ft B
Random\&.int64 bound
.ft R
returns a random integer between 0 (inclusive)
and 
.ft B
bound
.ft R
(exclusive)\&.  
.ft B
bound
.ft R
must be greater than 0\&.

.sp

.I val float 
: 
.B float -> float
.sp

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

.sp

.I val bool 
: 
.B unit -> bool
.sp

.ft B
Random\&.bool ()
.ft R
returns 
.ft B
true
.ft R
or 
.ft B
false
.ft R
with probability 0\&.5 each\&.

.sp

.I val bits32 
: 
.B unit -> Int32.t
.sp

.ft B
Random\&.bits32 ()
.ft R
returns 32 random bits as an integer between
.ft B
Int32\&.min_int
.ft R
and 
.ft B
Int32\&.max_int
.ft R
\&.

.sp
.B "Since"
4.14.0

.sp

.I val bits64 
: 
.B unit -> Int64.t
.sp

.ft B
Random\&.bits64 ()
.ft R
returns 64 random bits as an integer between
.ft B
Int64\&.min_int
.ft R
and 
.ft B
Int64\&.max_int
.ft R
\&.

.sp
.B "Since"
4.14.0

.sp

.I val nativebits 
: 
.B unit -> Nativeint.t
.sp

.ft B
Random\&.nativebits ()
.ft R
returns 32 or 64 random bits (depending on
the bit width of the platform) as an integer between
.ft B
Nativeint\&.min_int
.ft R
and 
.ft B
Nativeint\&.max_int
.ft R
\&.

.sp
.B "Since"
4.14.0

.sp

.PP
.SS Advanced functions

.PP

.PP
The functions from module 
.ft B
Random\&.State
.ft R
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\&.
.PP
.I module State : 
.B sig end

.sp

.sp

.I val get_state 
: 
.B unit -> State.t
.sp
Return the current state of the generator used by the basic functions\&.

.sp

.I val set_state 
: 
.B State.t -> unit
.sp
Set the state of the generator used by the basic functions\&.

.sp