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authorBryan Newbold <bnewbold@robocracy.org>2017-02-20 00:05:28 -0800
committerBryan Newbold <bnewbold@robocracy.org>2017-02-20 00:05:28 -0800
commitbd9733926076885e3417b74de76e4c9c7bc56254 (patch)
tree2c99dced547d48407ad44cb0e45e31bb4d02ce43 /random.scm
parentfa3f23105ddcf07c5900de47f19af43d1db1b597 (diff)
downloadslib-bd9733926076885e3417b74de76e4c9c7bc56254.tar.gz
slib-bd9733926076885e3417b74de76e4c9c7bc56254.zip
Import Upstream version 2c7upstream/2c7
Diffstat (limited to 'random.scm')
-rw-r--r--random.scm167
1 files changed, 105 insertions, 62 deletions
diff --git a/random.scm b/random.scm
index d22388e..dc4c3fb 100644
--- a/random.scm
+++ b/random.scm
@@ -1,5 +1,5 @@
;;;; "random.scm" Pseudo-Random number generator for scheme.
-;;; Copyright (C) 1991, 1993 Aubrey Jaffer.
+;;; Copyright (C) 1991, 1993, 1998, 1999 Aubrey Jaffer.
;
;Permission to copy this software, to redistribute it, and to use it
;for any purpose is granted, subject to the following restrictions and
@@ -20,77 +20,120 @@
(require 'byte)
(require 'logical)
-(define (make-rng seed)
- (define mutex #f)
- (define idx 0)
- (define idy 0)
- (define sta (make-bytes 256))
- ; initialize state
- (do ((idx #xff (+ -1 idx)))
- ((negative? idx))
- (byte-set! sta idx idx))
-
- (if (number? seed)
- (set! seed (number->string seed)))
-
- ; merge seed into state
- (do ((idx 0 (+ 1 idx))
- (kdx 0 (modulo (+ 1 kdx) seed-len))
- (seed-len (bytes-length seed)))
- ((>= idx 256) (set! idy 0))
- (let ((swp (byte-ref sta idx)))
- (set! idy (logand #xff (+ idy (byte-ref seed kdx) swp)))
- (byte-set! sta idx (byte-ref sta idy))
- (byte-set! sta idy swp)))
- ; spew
- (lambda ()
- (if mutex (slib:error "random state called reentrantly"))
- (set! mutex #t)
- (set! idx (logand #xff (+ 1 idx)))
- (let ((xtm (byte-ref sta idx)))
- (set! idy (logand #xff (+ idy xtm)))
- (let ((ytm (byte-ref sta idy)))
- (byte-set! sta idy xtm)
- (byte-set! sta idx ytm)
- (let ((ans (byte-ref sta (logand #xff (+ ytm xtm)))))
- (set! mutex #f)
- ans)))))
-
-(define *random-state*
- (make-rng "http://swissnet.ai.mit.edu/~jaffer/SLIB.html"))
-
;;; random:chunk returns an integer in the range of 0 to 255.
-(define (random:chunk v) (v))
+(define (random:chunk sta)
+ (cond ((positive? (byte-ref sta 258))
+ (byte-set! sta 258 0)
+ (slib:error "random state called reentrantly")))
+ (byte-set! sta 258 1)
+ (let* ((idx (logand #xff (+ 1 (byte-ref sta 256))))
+ (xtm (byte-ref sta idx))
+ (idy (logand #xff (+ (byte-ref sta 257) xtm))))
+ (byte-set! sta 256 idx)
+ (byte-set! sta 257 idy)
+ (let ((ytm (byte-ref sta idy)))
+ (byte-set! sta idy xtm)
+ (byte-set! sta idx ytm)
+ (let ((ans (byte-ref sta (logand #xff (+ ytm xtm)))))
+ (byte-set! sta 258 0)
+ ans))))
+
-(define (random:random modu . args)
+;;@args n
+;;@args n state
+;;Accepts a positive integer or real @1 and returns a number of the
+;;same type between zero (inclusive) and @1 (exclusive). The values
+;;returned by @0 are uniformly distributed from 0 to @1.
+;;
+;;The optional argument @var{state} must be of the type returned by
+;;@code{(seed->random-state)} or @code{(make-random-state)}. It defaults
+;;to the value of the variable @code{*random-state*}. This object is used
+;;to maintain the state of the pseudo-random-number generator and is
+;;altered as a side effect of calls to @code{random}.
+(define (random modu . args)
(let ((state (if (null? args) *random-state* (car args))))
(if (exact? modu)
- (let ((bitlen (integer-length (+ -1 modu))))
- (do ((bln bitlen (+ -8 bln))
- (rbs 0 (+ (ash rbs 8) (random:chunk state))))
- ((<= bln 7)
- (modulo
- (if (zero? bln) rbs
- (+ (ash rbs bln)
- (logand (bit-field (random:chunk state) 0 bln))))
- modu))))
+ (letrec ((bitlen (integer-length (+ -1 modu)))
+ (rnd (lambda ()
+ (do ((bln bitlen (+ -8 bln))
+ (rbs 0 (+ (ash rbs 8) (random:chunk state))))
+ ((<= bln 7)
+ (set! rbs (+ (ash rbs bln)
+ (bit-field (random:chunk state) 0 bln)))
+ (and (< rbs modu) rbs))))))
+ (do ((ans (rnd) (rnd))) (ans ans)))
+ (* (random:uniform1 state) modu))))
- (* (random:uniform state) modu))))
+(define random:random random)
;;;random:uniform is in randinex.scm. It is needed only if inexact is
;;;supported.
+
+;;@defvar *random-state*
+;;Holds a data structure that encodes the internal state of the
+;;random-number generator that @code{random} uses by default. The nature
+;;of this data structure is implementation-dependent. It may be printed
+;;out and successfully read back in, but may or may not function correctly
+;;as a random-number state object in another implementation.
+;;@end defvar
+
+
+;;@args state
+;;Returns a new copy of argument @1.
+;;
+;;@args
+;;Returns a new copy of @code{*random-state*}.
+(define (copy-random-state . sta)
+ (copy-string (if (null? sta) *random-state* (car sta))))
+
+
+;;@body
+;;Returns a new object of type suitable for use as the value of the
+;;variable @code{*random-state*} or as a second argument to @code{random}.
+;;The number or string @1 is used to initialize the state. If
+;;@0 is called twice with arguments which are
+;;@code{equal?}, then the returned data structures will be @code{equal?}.
+;;Calling @0 with unequal arguments will nearly
+;;always return unequal states.
+(define (seed->random-state seed)
+ (define sta (make-bytes (+ 3 256) 0))
+ (if (number? seed) (set! seed (number->string seed)))
+ ; initialize state
+ (do ((idx #xff (+ -1 idx)))
+ ((negative? idx))
+ (byte-set! sta idx idx))
+ ; merge seed into state
+ (do ((i 0 (+ 1 i))
+ (j 0 (modulo (+ 1 j) seed-len))
+ (seed-len (bytes-length seed))
+ (k 0))
+ ((>= i 256))
+ (let ((swp (byte-ref sta i)))
+ (set! k (logand #xff (+ k (byte-ref seed j) swp)))
+ (byte-set! sta i (byte-ref sta k))
+ (byte-set! sta k swp)))
+ sta)
+
+
+;;@args
+;;@args obj
+;;Returns a new object of type suitable for use as the value of the
+;;variable @code{*random-state*} or as a second argument to @code{random}.
+;;If the optional argument @var{obj} is given, it should be a printable
+;;Scheme object; the first 50 characters of its printed representation
+;;will be used as the seed. Otherwise the value of @code{*random-state*}
+;;is used as the seed.
(define (make-random-state . args)
- (let ((seed (if (null? args)
- (do ((bts (make-bytes 10))
- (idx 0 (+ 1 idx)))
- ((>= idx 10) bts)
- (byte-set! bts idx (random:random 256)))
- (let ()
- (require 'object->string)
- (object->limited-string (car args) 20)))))
- (make-rng seed)))
+ (let ((seed (if (null? args) *random-state* (car args))))
+ (cond ((string? seed))
+ ((number? seed) (set! seed (number->string seed)))
+ (else (let ()
+ (require 'object->string)
+ (set! seed (object->limited-string seed 50)))))
+ (seed->random-state seed)))
-(define random random:random)
+(define *random-state*
+ (make-random-state "http://swissnet.ai.mit.edu/~jaffer/SLIB.html"))
(provide 'random) ;to prevent loops
(if (provided? 'inexact) (require 'random-inexact))