static L<Int> localMaximaIncludingPlateaus(double[] l) {
  ret localMaximaIncludingPlateaus(l, 0, l(l));
}

static L<Int> localMaximaIncludingPlateaus(double[] l, int from, int to) {
  new L<Int> out;
  int n = l(l);
  for (int i = from; i < to; i++)
    if ((i == from || l[i] >= l[i-1])
      && (i == to-1 || l[i] >= l[i+1]))
      out.add(i);
  ret out;
}

Began life as a copy of #1025236