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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! 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 RANGEprocedure

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



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


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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