static int numberOfXYZVars(S s) {
  int m = 0;
  for (S t : javaTokC(s)) m = max(m, xyzVarToIndex(t));
  ret m;
}

static int numberOfXYZVars(L<S> tok) {
  int m = 0;
  for (int i = 1; i < l(tok); i += 2)
    m = max(m, xyzVarToIndex(tok.get(i)));
  ret m;
}