// i must point at the (possibly imaginary) closing bracket
// index returned is index of opening bracket
static int findBeginningOfBlock(LS cnc, int i) {
  int j = i-2, level = 1;
  while (j > 0) {
    if (eq(cnc.get(j), "}")) ++level;
    else if (eq(cnc.get(j), "{")) --level;
    if (level == 0)
      ret j;
    j -= 2;
  }
  ret -1;
}