        # File lib/ferret/number_tools.rb, line 35
    35:   def to_s_lex
    36:     if (self >= 0)
    37:       num_str = self.to_s
    38:       len_str = LEN_STR_TEMPLATE % num_str.size
    39:       return len_str + num_str
    40:     else
    41:       num = self * -1
    42:       num_str = num.to_s
    43:       num_len = num_str.size
    44:       len_str = LEN_STR_TEMPLATE % (NEG_LEN_MASK - num_len)
    45:       num = (10 ** num_str.size) - num
    46:       return "-#{len_str}%0#{num_len}d" % num
    47:     end
    48:   end