macro mapToDoubleArray_body {
  int n = l(l);
  double[] a = new[n];
  Iterator<A> it = iterator(l);
  for i to n:
    a[i] = f.get(it.next());
  ret a;
}

static <A> double[] mapToDoubleArray(Cl<A> l, IF1<A, Double> f) {
  mapToDoubleArray_body
}

static double[] mapToDoubleArray(double[] l, IF1_DoubleToDouble f) {
  int n = l(l);
  double[] a = new[n];
  for i to n:
    a[i] = f.get(l[i]);
  ret a;
}


/*static <A> double[] mapToDoubleArray(Cl<A> l, IF1_ObjectToDouble<A> f) {
  mapToDoubleArray_body
}*/