/* Copyright (C) 2016 - IIT Bombay - FOSSEE

 This file must be used under the terms of the CeCILL.
 This source file is licensed as described in the file COPYING, which
 you should have received as part of this distribution.  The terms
 are also available at
 http://www.cecill.info/licences/Licence_CeCILL_V2-en.txt
 Author: Mushir
 Organization: FOSSEE, IIT Bombay
 Email: toolbox@scilab.in
*/

#include "rand.h"
#include <stdio.h>

double i16rands(void)  
{

int m=1;
const int itwo=2;
static int m2=0,halfm=0,ia=0,ic=0,mic=0,iy=0;
static double s=0.0;
if(m2==0)
{
  /*if first entry,compute machine integer word length*/
  while(m>m2)
   {
      m2=m;
      m=itwo*m2;
   }
   halfm = m2;
   /* compute multiplier and increment for linear congruential methos */
   ia = 8*(int)(halfm*atan(1.0)/8.0) + 5;
   ic = 2*(int)(halfm*(0.5-sqrt(3.0)/6.0)) +1;
   mic = (m2 - ic) + m2;
  /* s is the scale factor for converting to floating point*/
  s = 0.5/halfm;

}

/* compute next random number */
 iy = iy*ia;
/* the following statement is for computers which do not allow interger overflow on addition*/
if(iy > mic) iy = (iy - m2) - m2;
 iy = iy + ic;

 /* the following statement is for computers where the word length for addition is greater than for multiplication */
 if(iy/2 > m2) iy = (iy - m2) - m2;
 /* the following statement is for computers where integer overflow affects the sign bit */
 if(iy < 0) iy = (iy + m2) + m2;
 return (double)iy*s;





}