//////////////////////////////////////////////////////////////////////
// random number generator
// uses table set up by rand.c
extern long randomtab[], *randomjay, *randomkay;

////////////////////////////////////////
// (31 bit integer) random number
inline long irand() {
    if (++randomjay >= &randomtab[98]) randomjay -= 98;
    if ((randomkay = randomjay + 27) >= &randomtab[98]) randomkay -= 98;
    return(*randomjay ^= *randomkay);
}

// some useful constants:
// const float two31 =   65536. * 32768.;
//   const float two31m1 = 65536. * 32768. - 1.;
#define two31m1 2147483647.

////////////////////////////////////////
// (floating) random on the interval [0, 1]
inline float rand01() {
  return(irand() / two31m1);
}

////////////////////////////////////////
// (floating) random on the interval [-1, 1]
inline float rand11() {
  return(rand01() * 2. - 1.);
}