For Gauche 0.9.5


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11.9 srfi-27 - Sources of Random Bits

Module: srfi-27

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

Function: random-integer n

[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] 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] Keeps the default random source that is used by random-integer and random-real.

Function: make-random-source

[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] Returns #t if obj is a random source object.

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

[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] 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] 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] 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] 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.


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