static O[] spliceObjectArray(O[] a, int from, int to, O[] b) {
  int lA = l(a), lB = l(b);
  O[] newArray = new[lA-(to-from)+lB];
  copyArray(a, 0, newArray, 0, from);
  copyArray(b, 0, newArray, from, lB);
  copyArray(a, to, newArray, from+lB, lA-from);
  ret newArray;
}