code: func ReadBigNum(r *bufio.Reader) Value {
  	ReadWhitespace(r)
  	if !ReadBigNumStart(r) {
  		return nil
  	}
  	result := ReadDataUntil(r, untilFixed('#'))
  	if !ReadBigNumEnd(r) {
  		return nil
  	}
  	return NewBigNum(string(result))
  }
docs: // ReadBigNum will read a bignum from the given reader and return it