Function num_from_string

src/utils/folder_reader.cpp:35–50

using boost::algorithm::starts_with;

int num_from_string(const std::string& query_str) {
  if (query_str.empty()) {
    return 0;
  }
  const char* pattern = "\\d+";
  boost::regex re(pattern);
  boost::match_results<std::string::const_iterator> what;
  auto start = query_str.begin();
  auto end = query_str.end();
  int found_num = 0;
  while (boost::regex_search(start, end, what, re)) {
    start = what[0].second;
    found_num = std::stoi(what[0].str());
  }
  return found_num;
}

bool numeric_string_compare(const std::string& s1, const std::string& s2) {
  return num_from_string(s1) < num_from_string(s2);