mdw@git.distorted.org.uk Git - ssr/blob - StraySrc/Libraries/Sapphire/sh/rand

   1 ;
   2 ; rand.sh
   3 ;
   4 ; Generating random numbers
   5 ;
   6 ; © 1994-1998 Straylight
   7 ;
   8
   9 ;----- Licensing note -------------------------------------------------------
  10 ;
  11 ; This file is part of Straylight's Sapphire library.
  12 ;
  13 ; Sapphire is free software; you can redistribute it and/or modify
  14 ; it under the terms of the GNU General Public License as published by
  15 ; the Free Software Foundation; either version 2, or (at your option)
  16 ; any later version.
  17 ;
  18 ; Sapphire is distributed in the hope that it will be useful,
  19 ; but WITHOUT ANY WARRANTY; without even the implied warranty of
  20 ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21 ; GNU General Public License for more details.
  22 ;
  23 ; You should have received a copy of the GNU General Public License
  24 ; along with Sapphire.  If not, write to the Free Software Foundation,
  25 ; 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  26
  27 ;----- Overview -------------------------------------------------------------
  28 ;
  29 ; Functions provided:
  30 ;
  31 ;  rand
  32 ;  rand_setSeed
  33 ;  rnd
  34 ;  rand_init
  35
  36                 [       :LNOT::DEF:rand__dfn
  37                 GBLL    rand__dfn
  38
  39 ; --- rand ---
  40 ;
  41 ; On entry:     --
  42 ;
  43 ; On exit:      R0 == a pseudorandom number between 0 and &7FFFFFFF
  44 ;
  45 ; Use:          Returns a pseudorandom number.  The algorithm used is the
  46 ;               additive generator found in Knuth.  The table is generated
  47 ;               from the current monotonic time using a linear congruential
  48 ;               generator.  Randomness is fairly good, and it's very quick.
  49
  50                 IMPORT  rand
  51
  52 ; --- rand_setSeed ---
  53 ;
  54 ; On entry:     R0 == a pseudorandom seed
  55 ;
  56 ; On exit:      --
  57 ;
  58 ; Use:          Sets up the random number generator (rand) to the given start
  59 ;               position.  The table of values is initialised from the seed
  60 ;               in a psuedorandom manner, using a linear congruential
  61 ;               generator.
  62
  63                 IMPORT  rand_setSeed
  64
  65 ; --- rnd ---
  66 ;
  67 ; On entry:     R0 == start value (inclusive)
  68 ;               R1 == end value (inclusive)
  69 ;
  70 ; On exit:      R0 == random number between the boundaries given
  71 ;
  72 ; Use:          Returns a random integer between the boundaries given.
  73 ;               The distribution is slightly skewed towards lower numbers,
  74 ;               but there's not a lot I can do about this, folks.
  75
  76                 IMPORT  rnd
  77
  78 ; --- rand_init ---
  79 ;
  80 ; On entry:     --
  81 ;
  82 ; On exit:      --
  83 ;
  84 ; Use:          Initialise the random number table.
  85
  86                 IMPORT  rand_init
  87
  88                 ]
  89
  90 ;----- That's all, folks ----------------------------------------------------
  91
  92                 END