Method nextToken

src/sys/expressionparser.cxx:619–757

}

char ExpressionParser::LexInfo::nextToken() {
  while (isspace(static_cast<unsigned char>(LastChar))) {
    LastChar = static_cast<signed char>(ss.get());
  }

  if (!ss.good()) {
    curtok = 0;
    return 0;
  }

  // Handle numbers
  if (isdigit(static_cast<unsigned char>(LastChar))
      || (LastChar == '.')) { // Number: [0-9.]+
    bool gotdecimal = false, gotexponent = false;
    std::string NumStr;

    while (true) {
      if (LastChar == '.') {
        if (gotdecimal || gotexponent) {
          throw ParseException("Unexpected '.' in number expression");
        }
        gotdecimal = true;
      } else if ((LastChar == 'E') || (LastChar == 'e')) {
        if (gotexponent) {
          throw ParseException(
              "ExpressionParser error: Unexpected extra 'e' in number expression");
        }
        gotexponent = true;
        // Next character should be a '+' or '-' or digit
        NumStr += 'e';
        LastChar = static_cast<signed char>(ss.get());
        if ((LastChar != '+') && (LastChar != '-')
            && !isdigit(static_cast<unsigned char>(LastChar))) {
          throw ParseException(
              "ExpressionParser error: Expecting '+', '-' or number after 'e'");
        }
      } else if (!isdigit(static_cast<unsigned char>(LastChar))) {
        break;
      }

      NumStr += LastChar;
      LastChar = static_cast<signed char>(ss.get());
    }

    curval = std::stod(NumStr);
    curtok = -1;
    return curtok;
  }

  // Symbols can contain anything else which is not reserved
  if ((LastChar == '`') || (reserved_chars.find(LastChar) == std::string::npos)) {

    // Special case: If the last token returned was a number
    // then insert a multiplication ("*")
    if (curtok == -1) {
      curtok = '*';
      return curtok;
    }