面向对象编程

--再谈文本查询示例[续/习题]

//P522 习题15.41
//1 in TextQuery.h
#ifndef TEXTQUERY_H_INCLUDED
#define TEXTQUERY_H_INCLUDED

#include <iostream>
#include <fstream>
#include <sstream>
#include <vector>
#include <set>
#include <map>
#include <string>
#include <stdexcept>

using namespace std;

class TextQuery
{
public:
    typedef std::vector<std::string>::size_type line_no;
    typedef string::size_type str_size;

    void read_file(std::ifstream &is)
    {
        store_file(is);
        build_map();
    }

    std::set<line_no> run_query(const std::string &) const;
    std::string text_line(line_no) const;

    line_no size() const;

private:
    void store_file(std::ifstream &);
    void build_map();

    std::vector<std::string> line_of_text;
    std::map< std::string,std::set<line_no> > word_map;
};

#endif // TEXTQUERY_H_INCLUDED

//2 in TextQuery.cpp
#include "TextQuery.h"

void TextQuery::store_file(ifstream &is)
{
    string textline;
    while (getline(is,textline))
    {
        line_of_text.push_back(textline);
    }
}

void TextQuery::build_map()
{
    for (line_no line_num = 0;
            line_num != line_of_text.size();
            ++line_num)
    {
        istringstream line(line_of_text[line_num]);
        string word;

        while (line >> word)
        {
            word_map[word].insert(line_num);
        }
    }
}

set<TextQuery::line_no>
TextQuery::run_query(const std::string &query_word) const
{
    map<string,set<line_no> >::const_iterator loc =
        word_map.find(query_word);

    if (loc == word_map.end())
    {
        return set<TextQuery::line_no>();
    }
    else
    {
        return loc -> second;
    }
}

string TextQuery::text_line(line_no line) const
{
    if (line < line_of_text.size())
    {
        return line_of_text[line];
    }
    throw out_of_range("line number out of range");
}

TextQuery::str_size TextQuery::size() const
{
    return line_of_text.size();
}

//3 in Query.h
#ifndef QUERY_H_INCLUDED
#define QUERY_H_INCLUDED

#include "TextQuery.h"
#include <iostream>
#include <fstream>
#include <string>
#include <set>
#include <algorithm>

using namespace std;

class Query_base
{
    friend class Query;

protected:
    typedef TextQuery::line_no line_no;
    virtual ~Query_base() {}

private:
    virtual set<line_no> eval(const TextQuery &) const = 0;
    virtual ostream &display(ostream & = cout) const = 0;
};

class Query
{
    friend Query operator~(const Query &);
    friend Query operator|(const Query &,const Query &);
    friend Query operator&(const Query &,const Query &);

public:
    Query(const string &);

    Query(const Query &c):p(c.p),use(c.use)
    {
        ++ *use;
    }
    ~Query()
    {
        decr_use();
    }
    Query &operator=(const Query &);

    set<TextQuery::line_no>
    eval(const TextQuery &t) const
    {
        return p -> eval(t);
    }

    ostream &display(ostream &os) const
    {
        return p -> display(os);
    }

private:
    Query(Query_base *query):
        p(query),use(new std::size_t(1)) {}

    Query_base *p;
    std::size_t *use;

    void decr_use()
    {
        if ( -- *use == 0 )
        {
            delete p;
            delete use;
        }
    }
};

inline Query &
Query::operator=(const Query &rhs)
{
    ++ * rhs.use;
    decr_use();

    p = rhs.p;
    use = rhs.use;

    return *this;
}

inline ostream &
operator<<(ostream &os,const Query &q)
{
    return q.display(os);
}

class WordQuery : public Query_base
{
    friend class Query;

    WordQuery(const string &s):query_word(s) {}

    set<line_no> eval(const TextQuery &t) const
    {
        return t.run_query(query_word);
    }
    ostream &display(ostream &os) const
    {
        return os << query_word;
    }

    string query_word;
};

inline Query::Query(const string &s):
    p(new WordQuery(s)),use(new std::size_t(1)) {}

class NotQuery : public Query_base
{
    friend Query operator~(const Query &);
    NotQuery(Query q):query(q) {}

    set<line_no> eval(const TextQuery &) const;

    ostream &display(ostream &os) const
    {
        return os << "~(" << query << ")";
    }

    const Query query;
};

class BinaryQuery : public Query_base
{
protected:
    BinaryQuery(Query left,Query right,string op):
        lhs(left),rhs(right),oper(op) {}

    ostream &display(ostream &os) const
    {
        return os << "(" << lhs << " " << oper << " "
               << rhs << ")";
    }

    const Query lhs,rhs;
    const string oper;
};

class AndQuery : public BinaryQuery
{
    friend Query operator&(const Query &,const Query &);

    AndQuery(Query left,Query right):
        BinaryQuery(left,right,"&"){}

    set<line_no> eval(const TextQuery &) const;
};

class OrQuery : public BinaryQuery
{
    friend Query operator|(const Query &,const Query &);

    OrQuery(Query left,Query right):
        BinaryQuery(left,right,"|"){}

    set<line_no> eval(const TextQuery &) const;
};

inline Query
operator&(const Query &lhs,const Query &rhs)
{
    return new AndQuery(lhs,rhs);
}

inline Query
operator|(const Query &lhs,const Query &rhs)
{
    return new OrQuery(lhs,rhs);
}

inline Query
operator~(const Query &oper)
{
    return new NotQuery(oper);
}

#endif // QUERY_H_INCLUDED

//4 in Query.cpp
#include "Query.h"

set<TextQuery::line_no>
OrQuery::eval(const TextQuery &file) const
{
    set<line_no> left = lhs.eval(file),
                 ret_lines = rhs.eval(file);

    ret_lines.insert(left.begin(),left.end());

    return ret_lines;
}

set<TextQuery::line_no>
AndQuery::eval(const TextQuery &file) const
{
    set<line_no> left = lhs.eval(file),
    right = rhs.eval(file);

    set<line_no> ret_lines;
    set_intersection(left.begin(),left.end(),
                     right.begin(),right.end(),
                     inserter(ret_lines,ret_lines.begin()));

    return ret_lines;
}

set<TextQuery::line_no>
NotQuery::eval(const TextQuery &file) const
{
    set<line_no> hav_val = query.eval(file);
    set<line_no> ret_val;

    for (line_no n = 0; n != file.size(); ++n)
    {
        if (hav_val.find(n) == hav_val.end())
        {
            ret_val.insert(n);
        }
    }

    return ret_val;
}

//5 in main.cpp
//测试数据与前面相同
#include <iostream>
#include <algorithm>
#include "TextQuery.h"
#include "Query.h"

using namespace std;

int main()
{
    ifstream inFile("input");

    TextQuery file;
    file.read_file(inFile);

    Query q = Query("fiery") & Query("bird") | Query("wind");

    cout << "Executed Query for :" << q << endl;

    typedef set<TextQuery::line_no> line_nums;

    const line_nums &locs = q.eval(file);

    cout << "match occurs " << locs.size()
         << " times" << endl;

    line_nums::const_iterator it = locs.begin();
    for (; it != locs.end(); ++it)
    {
        cout << "\t(line " << (*it) + 1 << ") "
             << file.text_line(*it) << endl;
    }
}

运行示例：