static int indexOfMaxEntryInDoubleArray(double[] a) {
  if (empty(a)) ret -1;
  int bestIndex = 0;
  double bestValue = a[0];
  int n = l(a);
  for (int i = 1; i < n; i++) {
    double x = a[i];
    if (x > bestValue) {
      bestIndex = i;
      bestValue = x;
    }
  }
  ret bestIndex;
}