class RDoc::RubyLex

def identify_number
  @lex_state = EXPR_END
  num = ''
  if peek(0) == "0" && peek(1) !~ /[.eE]/
    num << getc
    case peek(0)
    when /[xX]/
      ch = getc
      match = /[0-9a-fA-F_]/
    when /[bB]/
      ch = getc
      match = /[01_]/
    when /[oO]/
      ch = getc
      match = /[0-7_]/
    when /[dD]/
      ch = getc
      match = /[0-9_]/
    when /[0-7]/
      match = /[0-7_]/
    when /[89]/
      raise RDoc::Error, "Illegal octal digit"
    else
      return Token(TkINTEGER, num)
    end
    num << ch if ch
    len0 = true
    non_digit = false
    while ch = getc
      num << ch
      if match =~ ch
        if ch == "_"
          if non_digit
            raise RDoc::Error, "trailing `#{ch}' in number"
          else
            non_digit = ch
          end
        else
          non_digit = false
          len0 = false
        end
      else
        ungetc
        num[-1, 1] = ''
        if len0
          raise RDoc::Error, "numeric literal without digits"
        end
        if non_digit
          raise RDoc::Error, "trailing `#{non_digit}' in number"
        end
        break
      end
    end
    return Token(TkINTEGER, num)
  end
  type = TkINTEGER
  allow_point = true
  allow_e = true
  non_digit = false
  while ch = getc
    num << ch
    case ch
    when /[0-9]/
      non_digit = false
    when "_"
      non_digit = ch
    when allow_point && "."
      if non_digit
        raise RDoc::Error, "trailing `#{non_digit}' in number"
      end
      type = TkFLOAT
      if peek(0) !~ /[0-9]/
        type = TkINTEGER
        ungetc
        num[-1, 1] = ''
        break
      end
      allow_point = false
    when allow_e && "e", allow_e && "E"
      if non_digit
        raise RDoc::Error, "trailing `#{non_digit}' in number"
      end
      type = TkFLOAT
      if peek(0) =~ /[+-]/
        num << getc
      end
      allow_e = false
      allow_point = false
      non_digit = ch
    else
      if non_digit
        raise RDoc::Error, "trailing `#{non_digit}' in number"
      end
      ungetc
      num[-1, 1] = ''
      break
    end
  end
  Token(type, num)
end