/* Fluctuating R250 U[0,1)                                               */
/* (C) Copyright 2005 Yosuke Amijima. All Rights Reserved.               */
/* Notice: Initial seed of this version is based on rndu for simplicity. */
new; cls;
nb=100;        /* +-nb of band width (if nb=0, original) */
nn=10000;                      /* Up to 10000 in Light version of GAUSS */
x=r250f(nb,nn);
library pgraph;
graphset;
call hist(x,29);



proc r250f(nb,nn);
   local a,c,m,q,r,x,i,high,low,t;
   a=16807; c=0; m=2^31-1;
   q=127773; r=2836;
   x=zeros(nn,1);
/* seed */
   x[1]=floor(rndu(1,1)*(m-1))+1;                    /* integer between 1 and m-1 */
/* R250 */
   i=1;
   do while i<=nn-1;
      high=x[i]/q;
      low=x[i]%q;
      t=a*low-r*high;
      if t>=0;
         x[i+1]=t;
      else;
         x[i+1]=t+m;
      endif;
      i=i+1;
   endo;
/* add fluctuating factor */
   x=x-nb+floor((2*nb+1)*rndu(nn,1));
   x=mod(x,m);
   x=x/m;         /* If you want to avoid 0's, replace this line by x=(x+1)/(m+1); */
   retp(x);
endp;

proc mod(x,m);
   retp( (x.>=0).*(x%m)+(x.<0).*((x+m.*ceil(abs(x)/m))%m) );
endp;