C++详解Primer文本查询程序的实现-C/C++开发

这个程序还是比较复杂的，把这句话作为文章的开头可以看出它的真实性.....这篇文章主要介绍了文本查询程序的实现，下面我们一起来看看

15.9的文本查询程序是对12.3节的文本查询程序的扩展，而使用的主要知识也是15章的核心：继承和多态，即面向对象程序设计。

恩，这一节看的过程中，会有很多不理解。特别是在没有把整个程序都看完之前，会有很多疑惑，而看完之后，再思考思考，回头再看本节的前面所写的程序介绍，会有一些感悟。更加清楚这个程序的原理。

TextQuery.h

#ifndef QUERY_TEXTQUERY_H
#define QUERY_TEXTQUERY_H
#include<iostream>
#include<vector>
#include<string>
#include<memory>
#include<map>
#include<set>
#include<cstdio>
#include<cstdlib>
#include<sstream>
#include<algorithm>
#include<fstream>
#include<stack>
using namespace std;
class QueryResult;
// ??????????????????????
class TextQuery
{
public:
    using line_no = vector<string>::size_type;
    TextQuery(ifstream&); // ?????????????????????????????в????????
    QueryResult query(const string&) const;  // ???????string???????string???в????
private:
    shared_ptr<vector<string>> file;  // ???????
    map<string, shared_ptr<set<line_no>>> wm;  // ???????????????????????к?set??
};
inline TextQuery::TextQuery(ifstream &is): file(new vector<string>) {
    string text;
    while (getline(is, text)) {   // ??????е?????
        file->push_back(text);    // ????????е????
        int n = file->size() - 1;  // ???浱????к???????·?????????????shared_ptr<set<line_no>> ?????????к?
        istringstream line(text);
        string word;
        while(line >> word){
            auto &lines = wm[word];  // lines?????shared_ptr
            if(!lines)   // ??????±??????????map?д????????word?????word????????shared_ptr??????shared_ptr???????nullptr;
                lines.reset(new set<line_no>);
            lines->insert(n);
        }
    }
}
class QueryResult{
    friend ostream& print(ostream& os, const QueryResult& qr);
public:
    QueryResult(string s, shared_ptr<set<TextQuery::line_no>> p, shared_ptr<vector<string>> f)
            : sought(s), lines(p), file(f) {}
    auto begin()const {return lines->begin();}
    auto end()const{return lines->end();}
    shared_ptr<vector<string>> get_file()const {return file;}
private:
    string sought; // ????????
    shared_ptr<set<TextQuery::line_no>> lines;  // ??????к?
    shared_ptr<vector<string>> file;  // ???????
};
inline QueryResult TextQuery::query(const string& s)const {
    static shared_ptr<set<line_no>> nodata(new set<line_no>()); // ?????????????к?set??shared_ptr
    auto loc = wm.find(s);
    if(loc == wm.cend())
        return QueryResult(s, nodata, file);
    else
        return QueryResult(s, loc->second, file);
}
inline ostream& print(ostream& os, const QueryResult& qr)
{
    os<<qr.sought<<" occurs "<<qr.lines->size()<<" "<<((qr.lines->size()>1)?"times":"time")<<endl;
    for(const auto& num: *(qr.lines)){
        os << "\t(lines "<<num+1<<") "<<(*(qr.file))[num]<<endl;
    }
    return os;
}
inline void runQueries(ifstream& infile)
{
    // infile?????ifstream??????????????????
    TextQuery  tq(infile);
    // ????????????????????????????????????????????
    while(true)
    {
        cout<<"enter word to look for, or q to quit: "<<endl;
        string s;
        // ?????????????s=='q'?????
        if(!(cin>>s) || s == "q")  break;
        print(cout, tq.query(s)) << endl;
    }
}
inline void independent_word_query(ifstream& ifile){
    vector<string> file;
    map<string,set<int>> word_map;
    string text;
    while(getline(ifile, text)){
        file.push_back(text);
        int n = (int)file.size()-1;  // ???push_back?????е??±?
        istringstream line(text);   // ???string text???????????
        string word;
        while(line >> word){
            word_map[word].insert(n);
        }
    }
    while(true){
        cout << "Enter word to look for, or q to quit: "<<endl;
        string s;
        if(!(cin>>s) || s=="q")  break;
        const auto& lines = word_map.find(s); // ?????????????????????pair<string,set<int>>
        cout<<s<<" occurs "<<(*lines).second.size()<<(lines->second.size()>1?" times":" time")<<endl;
        for(const auto& i:lines->second){
            cout<<"\t(lines "<<i+1<<") "<<file[i]<<endl;
        }
    }
}
#endif

Query.h

#ifndef QUERY_QUERY_H
#define QUERY_QUERY_H
#include"TextQuery.h"
class Query_base
{
    friend class Query;
protected:
    using line_no = TextQuery::line_no;   // �����������eval������ʹ�ã�������Ϊprotected��
    virtual ~Query_base() = default;
private:
    // eval���������뵱ǰQueryƥ���QueryResult
    virtual QueryResult eval(const TextQuery&) const = 0;
    // rep��ʾ��ѯ��һ��string
    virtual string rep() const = 0;
};
class Query
{
    friend Query operator|(const Query&, const Query&);
    friend Query operator&(const Query&, const Query&);
    friend Query operator~(const Query&);
public:
    Query(const string&);    // ����һ���µ�WordQuery
public:
    QueryResult eval(const TextQuery& t)const { return q->eval(t); }
    string rep()const { return q->rep(); }
private:
    Query(shared_ptr<Query_base> query) :q(query){}
    shared_ptr<Query_base> q;
};
//ostream& operator<<(ostream& os, const Query& q)
//{
//    // Query::repͨ������Query_baseָ���rep�����������
//    return os<<q.rep();
/