static L<Int> cyclicLocalMinima(float[] l) {
  int n = l(l);
  new L<Int> minima;
  if (allSame(l)) ret minima;
  int i = 0;
  while (i < n && l[mod(i+1, n)] >= l[i]) ++i;
  // found the first downslope at start -> start+1
  int start = i, flatSince = i;
  do {
    i = mod(i+1, n);
    float diff = l[mod(i+1, n)]-l[i];
    if (diff < 0) flatSince = i;
    else if (diff > 0) {
      if (flatSince >= 0) {
        int middle = mod(flatSince+mod(i-flatSince, n)/2, n);
        minima.add(middle);
        flatSince = -1;
      }
    }
  } while (i != start);
  ret minima;
}