// syntax 1: replace all occurrences of x in l with y
static <A> L<A> replaceSublist(L<A> l, L<A> x, L<A> y) {
  if (x == null) ret l;
  
  int i = 0;
  while (true) {
    i = indexOfSubList(l, x, i);
    if (i < 0) break;
    
    replaceSublist(l, i, i+l(x), y);
    i += l(y);
  }
  ret l;
}

// syntax 2: splice l at fromIndex-toIndex and replace middle part with y
static <A> L<A> replaceSublist(L<A> l, int fromIndex, int toIndex, L<A> y) {
  int n = y.size(), toIndex_new = fromIndex+n;
  if (toIndex_new < toIndex) {
    removeSubList(l, toIndex_new, toIndex);
    copyListPart(y, 0, l, fromIndex, n);
  } else {
    copyListPart(y, 0, l, fromIndex, toIndex-fromIndex);
    if (toIndex_new > toIndex)
      l.addAll(toIndex, subList(y, toIndex-fromIndex));
  }
  ret l;
}

ifclass IntRange
static <A> L<A> replaceSublist(L<A> l, IntRange r, L<A> y) {
  ret replaceSublist(l, r.start, r.end, y);
}
endif