11.8 srfi.27 - Sources of Random Bits ¶

Module: srfi.27 ¶

This module provides SRFI-27 pseudo random generator interface, using Mersenne Twister algorithm (see math.mt-random - Mersenne Twister Random number generator) as the backbone.

The random sources provided in this module is thread safe; multiple thread can use the same random source without breaking its internal state.

Function: random-integer n ¶

[SRFI-27]{srfi.27} Returns a random exact integer between [0, n-1], inclusive, using the default random source. To set a random seed for this procedure, use random-source-randomize! or random-source-pseudo-randomize! on default-random-source.

Function: random-real ¶

[SRFI-27]{srfi.27} Returns a random real number between (0, 1), exclusive, using the default random source. To set a random seed for this procedure, use random-source-randomize! or random-source-pseudo-randomize! on default-random-source.

Variable: default-random-source ¶

[SRFI-27]{srfi.27} Keeps the default random source that is used by random-integer and random-real.

Function: make-random-source ¶

[SRFI-27]{srfi.27} Creates and returns a new random source. In the current Gauche implementation, it is just a <mersenne-twister> object. It may be changed in the future implementation.

Function: random-source? obj ¶

[SRFI-27]{srfi.27} Returns #t if obj is a random source object.

Function: random-source-state-ref s ¶

Function: random-source-state-set! s state ¶

[SRFI-27]{srfi.27} Gets and sets the "snapshot" of the state of the random source s. State is an opaque object whose content depends on the backbone generator.

Function: random-source-randomize! s ¶

[SRFI-27]{srfi.27} Makes an effort to set the state of the random source s to a truly random state. The current implementation uses the current time and the process ID to set the random seed.

Function: random-source-pseudo-randomize! s i j ¶

[SRFI-27]{srfi.27} Changes the state of the random source s into the initial state of the (i, j)-th independent random source, where i and j are non-negative integers. This procedure can be used to reuse a random source s as large number of independent random source, indexed by two non-negative integers. Note that this procedure is entirely deterministic.

Function: random-source-make-integers s ¶

[SRFI-27]{srfi.27} Returns a procedure, that takes one integer argument n and returns a random integer between 0 and n-1 inclusive for every invocation, from the random source s.

Function: random-source-make-reals s :optional unit ¶

[SRFI-27]{srfi.27} Returns a procedure, that takes no argument and returns a random real between 0 and 1 exclusive for every invocation, from the random source s. If unit is given, the random real the returned procedure generates will be quantized by the given unit, where 0 < unit < 1.