// Return value is index of ")"
static int tok_findEndOfForExpression(L<S> tok, int i) {
  int level = 1;
  
  while (i < l(tok)) {
    S t = tok.get(i);
    if (eq(t, "(")) ++level;
    else if (eq(t, ")"))
      if (--level == 0) ret i;
    i += 2;
  }
  ret i;
}