Chicken » Module (chicken random)

## Module (chicken random)

This module provides access to entropy (as provided by the operating system) and a pseudo random number generator.

On UNIX systems entropy is by default obtained from `/dev/urandom`. On Linux, the `getrandom(2)` system call is used instead, if available. On OpenBSD it is `arc4random_buf(3)`, on Windows `RtlGenRandom`.

The pseudo random number generator is an implementation of the WELL algorithm.

#### set-pseudo-random-seed!

set-pseudo-random-seed! SEED #!optional SIZEprocedure

  Set seed for the PRNG from the at most SIZE bytes of SEED. which should be a byte vector or a string containing random data. If SIZE is not given, it defaults to the size of SEED. If SIZE (or the size of SEED) is below the required size of the random state used by the PRNG, then it will necessarily be initialized in a less random manner as possible.

#### pseudo-random-integer

pseudo-random-integer RANGEprocedure

  Returns a uniformly distributed pseudo random integer between 0 and `RANGE-1`, which may be a big integer.

#### pseudo-random-real

pseudo-random-realprocedure

  Returns a uniformly distributed pseudo-random inexact number between 0 and 1.

#### random-bytes

random-bytes #!optional BUF SIZEprocedure

  Returns random bytes from the available entropy source. If BUF is given, it should be a string or byte vector which will be filled with up to SIZE random bytes. SIZE defaults to the size of the BUF argument. If no arguments are given, `random-bytes` returns a freshly allocated byte vector of sufficient size to be used as a seed for `set-pseudo-random-seed!`.

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