static L<Int> localMaxima(L<Double> l) {
  ret localMaxima(toDoubleArray(l));
}

static L<Int> localMaxima(double[] l) {
  new L<Int> out;
  int n = l(l);
  for i to n:
    if ((i == 0 || l[i] > l[i-1])
      && (i == n-1 || l[i] > l[i+1]))
      out.add(i);
  ret out;
}