#include <stdio.h>
#include <stdlib.h>
#include <iostream.h>
#include "krand.h"

#include <time.h>

#define MBIG  1000000000L
#define MSEED 161803398L
#define FAC   (1.0 / MBIG)

static int inext;
static int inextp;
static long ma[56];
                                 
double knuth_random(void) {
  long mj;
  if (++inext == 56) inext = 1;
  if (++inextp == 56)	inextp = 1;
  mj = ma[inext] - ma[inextp];
  if (mj < 0)	mj += MBIG;
  ma[inext] = mj;
  return mj * FAC;
}

long seed_random(long seed) {
  long mj, mk;
  register int i, k;

  if (seed < 0) {
  	time_t tp;
    seed = time(&tp);
  }

  if (seed >= MBIG) {
	  cerr<<"Seed value too big (> "<<MBIG<<") in knuth_srand().";
	  exit(1);
  }

  ma[55] = mj = seed;
  mk = 1;

  for (i = 1; i <= 54; i++) {
    register int ii = (21 * i) % 55;
	  ma[ii] = mk;
	  mk = mj - mk;
	  if (mk < 0) mk += MBIG;
    mj = ma[ii];
  }

  for (k = 0; k < 4; k++) {
    for (i = 1; i <= 55; i++) {
	    ma[i] -= ma[1 + (i + 30) % 55];
	    if (ma[i] < 0) ma[i] += MBIG;
    }
  }

  inext = 0;
  inextp = 31;

  return seed;
}

int krandom(int max) {
  int retval = (int)(knuth_random() * max);
  if (retval < 0 || retval >= max) {
    cout<<"ERROR: random num generator out of bounds!"<<endl;
    exit(-1);
  }
  return retval;
}


/*
//for testing
void main(void) {
  seed_random(100);
  for (int i = 0; i < 24; i++) cout<<i<<" "<<knuth_random()<<" "<<krandom(100)<<endl;
  cin.get();
  seed_random(200);
  for (i = 0; i < 24; i++) cout<<i<<" "<<knuth_random()<<" "<<krandom(100)<<endl;
  cin.get();
  seed_random(100);
  for (i = 0; i < 24; i++) cout<<i<<" "<<knuth_random()<<" "<<krandom(100)<<endl;
  cin.get();
}
*/