chap14 c++

输出操作符

//output operator redefined
ostream& operator<<（ostream& out, const Sales_item& s)
{
   //line break(\n) not allowed, tab(\t) used instead
    out << s.isbn << "\t" << s.units_sold << "\t" 
          << s.revenue << "\t" << s.avg_prive();   
}

 输入操作符

//redefine of input operator
istream&  operator>> (istream& in, Sales_item& si)
{
    in >> si.isbn >> si.units_sold;
    //check that the inputs succeed
    if(in)
        s.revenue = s.units_sold * price;
    else
        s = Sales_item();    //input failed:rest object to default state
    return in;
}

 vector  and  >> operator

class CheckoutRecord{
    friend istream& operator>> (istream& in, CheckoutRecord cc);
public:
    
private:
    double bookId;
    string title;
    string dateBorrowed;            //Date uncertain, use string instead.
    pair<string,string> borrower;
    vector<pair<string,string>* > waitList;
};
//redefine >> for CheckoutRecord
istream& operator>> (istream& in, CheckoutRecord cc)
{
    in >>  cc.bookId >> cc.title >> cc.dateBorrowed 
        >> cc.borrower.first >> cc.borrower.second;
    //check that the input succeed
    if(!in)
    {
        cc = CheckoutRecord();    //input failed: reset object to default state
        return in;
    }    
    //clear vector context before input.        // copy in answer; I can not see the necessary.
    cc.waitList.clear();        
    while(in)
    {
        pair<string,string>* pt = new pair<string,string>; 
                                        //pointer type members in vector , should be built dynamically.
        in >> pt->first >> pt->second;
        if(!in)        return in;            //wrong input will break the loop.
        cc.waitList.push_back(pt);
    }
    return in;
}

 vector, assign opeator

    //clear vector context
    waitList.clear();
    for( vector< pair<string,string>* >::const_iterator beg = other.waitList.begin(); beg != other.waitList.end(); ++beg)
    {
        //as point type, need to alocate space to the pointer
        pair<string,string>* p = new pair<string,string>;
        *p = **beg;            //deep copy, to avoid memory access, copy the value context, instead of the pointer
        waitList.push_back( p );
    }
    return *this;