random.idel

来自「idel虚拟机源码」· IDEL 代码 · 共 36 行

\ Minimal Standard Random Number Generator
\ Park & Miller, CACM 31(10), Oct 1988, 32 bit integer version.
\ better constants, as proposed by Park.
\ Adapted from the Scheme version by Ozan Yigit modified by Jonathan Kleid.

#define Q 44488
#define A 48271
#define R 3399
#define M 0x7fffffff

ints: seed   1   ;ints

\ The argument must be in the range [1..M-1], apparently.
def 1 0 srand   seed ! ;

def 0 1 rand
  seed @ Q /mod
  { quot rem --
    A rem *  R quot * - 
    { test --
      0 test < if  test  else  test M +  then } } 
  { result --
    result seed !  result } ;

def 1 1 random
  { n --
    M n /mod { q slop -- slop n random-loop } } ;

def 2 1 random-loop
  rand { slop n r --
         slop r < if
           r n /mod { q rem -- rem }
         else
           slop n random-loop 
         then } ;