c++ primer 10.6

 #include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <set>
#include <map>
#include <vector>
using namespace::std;
class TextQuery
{
public:
typedef std::vector<std::string>::size_type line_no;
void read_file(std::ifstream &file)
{
     store_file(file);
     build_map();    
}
std::set<line_no> run_query(const std::string &) const;
std::string text_line(line_no) const;
private:
void store_file(std::ifstream &);
void build_map(); 
std::vector<std::string> text_of_line;
std::map<std::string,std::set<line_no> > word_map;   
};
void TextQuery::store_file(std::ifstream &is)
{
     string textline;
     while(getline(is,textline))
     text_of_line.push_back(textline);
}
void TextQuery::build_map()
{
     for(line_no linenum=0;linenum!=text_of_line.size();++linenum)
     {
     istringstream line(text_of_line[linenum]);
     string word;
     while(line>>word)
     word_map[word].insert(linenum);
          }
}
set<TextQuery::line_no>
TextQuery::run_query(const string &query_word) const
{
map<string, set<line_no> >::const_iterator loc=word_map.find(query_word);
if (loc==word_map.end())
return set<line_no> ();
else return loc->second;
}
string TextQuery::text_line(line_no line) const
{
if(line<text_of_line.size())
return text_of_line[line];
else cerr<<"OUT OF RANGE!"<<endl;
}
void print_results(const set<TextQuery::line_no> &locs, const string sought,const TextQuery &tq)
{
     typedef set<TextQuery::line_no> linenums;
     linenums::size_type size=locs.size();
     cout<<"/n"<<sought<<" occurs "<<size<<" times:"<<endl;
     linenums::iterator it=locs.begin();
     for(;it!=locs.end();++it)
     cout<<"/t(line "<<(*it)+1<<")"<<tq.text_line(*it)<<endl;
}
int main()
{  
    string fname("D://1.txt");
    ifstream file(fname.c_str());
    if(!file)
    {
    cerr<<"CAN NOT OPEN FILE!"<<endl;
    return -1;
    }
    TextQuery tq;
    tq.read_file(file);
    while(true)
    {
    cout<<"Please input the word to find out, or q to quit:"<<endl;
    string s;
    cin>>s;
    if(!cin||s=="q") break;
    set<TextQuery::line_no> locs=tq.run_query(s);
    print_results(locs,s,tq);
    }
    system("pause");
    return 0;  
    }