diff options
Diffstat (limited to 'randinex.scm')
| -rw-r--r-- | randinex.scm | 28 |
1 files changed, 15 insertions, 13 deletions
diff --git a/randinex.scm b/randinex.scm index 8a0afd1..19b9d81 100644 --- a/randinex.scm +++ b/randinex.scm @@ -1,9 +1,9 @@ ;;;"randinex.scm" Pseudo-Random inexact real numbers for scheme. -;;; Copyright (C) 1991, 1993, 1999 Aubrey Jaffer. +;;; Copyright (C) 1991, 1993, 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 -;understandings. +;Permission to copy this software, to modify it, to redistribute it, +;to distribute modified versions, and to use it for any purpose is +;granted, subject to the following restrictions and understandings. ; ;1. Any copy made of this software must include this copyright notice ;in full. @@ -70,6 +70,8 @@ ;;; 1-exp(-r^2/2). This latter means that u=exp(-r^2/2) is uniformly ;;; distributed on [0,1], so r=sqrt(-2 log u) can be used to generate r. +(define *2pi (* 8 (atan 1))) + ;;@args vect ;;@args vect state ;;Fills @1 with inexact real random numbers which are independent @@ -82,7 +84,7 @@ (set! sum2 (+ sum2 (* x x)))))) (do ((n (- (vector-length vect) 1) (- n 2))) ((negative? n) sum2) - (let ((t (* 6.28318530717958 (random:uniform1 state))) + (let ((t (* *2pi (random:uniform1 state))) (r (sqrt (* -2 (log (random:uniform1 state)))))) (do! n (* r (cos t))) (if (positive? n) (do! (- n 1) (* r (sin t))))))))) @@ -94,10 +96,9 @@ ;;@args vect ;;@args vect state ;;Fills @1 with inexact real random numbers the sum of whose -;;squares is less than 1.0. Thinking of @1 as coordinates in -;;space of dimension @var{n} = @code{(vector-length @1)}, the -;;coordinates are uniformly distributed within the unit @var{n}-shere. -;;The sum of the squares of the numbers is returned. +;;squares is equal to 1.0. Thinking of @1 as coordinates in space +;;of dimension n = @code{(vector-length @1)}, the coordinates are +;;uniformly distributed over the surface of the unit n-shere. (define (random:hollow-sphere! vect . args) (let ((ms (sqrt (apply random:normal-vector! vect args)))) (do ((n (- (vector-length vect) 1) (- n 1))) @@ -113,13 +114,14 @@ ;;@args vect ;;@args vect state ;;Fills @1 with inexact real random numbers the sum of whose -;;squares is equal to 1.0. Thinking of @1 as coordinates in space -;;of dimension n = @code{(vector-length @1)}, the coordinates are -;;uniformly distributed over the surface of the unit n-shere. +;;squares is less than 1.0. Thinking of @1 as coordinates in +;;space of dimension @var{n} = @code{(vector-length @1)}, the +;;coordinates are uniformly distributed within the unit @var{n}-shere. +;;The sum of the squares of the numbers is returned. (define (random:solid-sphere! vect . args) (apply random:hollow-sphere! vect args) (let ((r (expt (random:uniform1 (if (null? args) *random-state* (car args))) (/ (vector-length vect))))) (do ((n (- (vector-length vect) 1) (- n 1))) - ((negative? n)) + ((negative? n) r) (vector-set! vect n (* r (vector-ref vect n)))))) |