Spaces:
Sleeping
Sleeping
| ;;; srfi-27.scm --- Sources of Random Bits | |
| ;; Copyright (C) 2010 Free Software Foundation, Inc. | |
| ;; This library is free software; you can redistribute it and/or | |
| ;; modify it under the terms of the GNU Lesser General Public | |
| ;; License as published by the Free Software Foundation; either | |
| ;; version 3 of the License, or (at your option) any later version. | |
| ;; This library is distributed in the hope that it will be useful, | |
| ;; but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| ;; Lesser General Public License for more details. | |
| ;; You should have received a copy of the GNU Lesser General Public | |
| ;; License along with this library. If not, see | |
| ;; <http://www.gnu.org/licenses/>. | |
| ;;; Commentary: | |
| ;; This module is fully documented in the Guile Reference Manual. | |
| ;;; Code: | |
| (define-module (srfi srfi-27) | |
| #:export (random-integer | |
| random-real | |
| default-random-source | |
| make-random-source | |
| random-source? | |
| random-source-state-ref | |
| random-source-state-set! | |
| random-source-randomize! | |
| random-source-pseudo-randomize! | |
| random-source-make-integers | |
| random-source-make-reals) | |
| #:use-module (srfi srfi-9)) | |
| (cond-expand-provide (current-module) '(srfi-27)) | |
| (define-record-type :random-source | |
| (%make-random-source state) | |
| random-source? | |
| (state random-source-state set-random-source-state!)) | |
| (define (make-random-source) | |
| (%make-random-source (seed->random-state 0))) | |
| (define (random-source-state-ref s) | |
| (random-state->datum (random-source-state s))) | |
| (define (random-source-state-set! s state) | |
| (set-random-source-state! s (datum->random-state state))) | |
| (define (random-source-randomize! s) | |
| (let ((time (gettimeofday))) | |
| (set-random-source-state! s (seed->random-state | |
| (+ (* (car time) 1e6) (cdr time)))))) | |
| (define (random-source-pseudo-randomize! s i j) | |
| (set-random-source-state! s (seed->random-state (i+j->seed i j)))) | |
| (define (i+j->seed i j) | |
| (logior (ash (spread i 2) 1) | |
| (spread j 2))) | |
| (define (spread n amount) | |
| (let loop ((result 0) (n n) (shift 0)) | |
| (if (zero? n) | |
| result | |
| (loop (logior result | |
| (ash (logand n 1) shift)) | |
| (ash n -1) | |
| (+ shift amount))))) | |
| (define (random-source-make-integers s) | |
| (lambda (n) | |
| (random n (random-source-state s)))) | |
| (define random-source-make-reals | |
| (case-lambda | |
| ((s) | |
| (lambda () | |
| (let loop () | |
| (let ((x (random:uniform (random-source-state s)))) | |
| (if (zero? x) | |
| (loop) | |
| x))))) | |
| ((s unit) | |
| (or (and (real? unit) (< 0 unit 1)) | |
| (error "unit must be real between 0 and 1" unit)) | |
| (random-source-make-reals s)))) | |
| (define default-random-source (make-random-source)) | |
| (define random-integer (random-source-make-integers default-random-source)) | |
| (define random-real (random-source-make-reals default-random-source)) | |