C++ 文本查询程序设计（12.3.1）

C.md

class QueryResult {
friend std::ostream& print(std:ostream&, const QueryResult&);
public:
  QueryResult(std::string s,
              std::shared_ptr<std::set<line_no>> p,
              std::shared_ptr<std::vector<std::string>> f
            ): sought(s), lines(p), file(f) {}
private:
   std::string sought;
   std::shared_ptr<std::set<line_no>> lines;
   std::shared_ptr<std::vector<std::string>> file;
}

QueryResult TextQuery::query(const string &sought) const
{
  static shared_ptr<set<line_no>> nodata(new set<line_no>);
  auto loc = wm.find(sought);
  if (loc == wm.end()) 
    return QueryResult(sought, nodata, file)
  else
    return QueryResult(sought, loc->second, file);
}

ostream &print(ostream & os, cosnt QueryResult &qr)
{
  os << qr.sought << " occurs " << qr.lines->size() << " "
     << make_plural(qr.lines->size(), "time", "s") << endl;
  for (auto num: *qr.lines)
    os << "\t(line )" << num + 1 << ") "
       << *(qr.file->begin() + num) << endl;
  return os;
}