C++11: Dynamic Memory

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

class QueryResult;

class TextQuery {
public:
        using line_no = std::vector<std::string>::size_type;
        TextQuery(std::ifstream&);
        QueryResult query(const std::string &);
private:
        std::shared_ptr<std::vector<std::string>> file;
        std::map<std::string, std::shared_ptr<std::set>> wm;
};

std::ostream& print(std::ostream &, const QueryResult &);

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

void runQueries(std::ifstream &is)
{
        TextQuery tq(is);
        while (true) {
                std::cout << "enter word to look for, or q to quit: ";
                std::string s;
                if (!(std::cin >> s) || s == "q") break;
                print(std::cout, tq.query(s)) << std::endl;
        }
}

int main()
{
        std::ifstream is("data.dat");
        runQueries(is);
        return 0;
}

TextQuery::TextQuery(std::ifstream &is) : file(new std::vector<std::string>)
{
        std::string text;
        while (std::getline(is, text)) {
                file->push_back(text);
                int n = file->size() - 1;
                std::istringstream line(text);
                std::string word;
                while (line >> word) {
                        auto &lines = wm[word];
                        if (!lines) {
                                lines.reset(new std::set);
                        }
                        lines->insert(n);
                }
        }
}

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


std::string make_plural(std::size_t ctr, const std::string &word, const std::string &ending)
{
        return (ctr > 0) ? word + ending : word;
}

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

/* clang++ xx.cpp -std=c++11
** Apple LLVM version 7.0.2 (clang-700.1.81)
** Target: x86_64-apple-darwin15.2.0
** Thread model: posix
*/
// C++ primer 5th: Using the Library: A Text-Query Program(p484)