7.1.2

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7.2

#ifndef CP5_ex7_02_h#define CP5_ex7_02_h#include <string>struct Sales_data {    std::string isbn() const { return bookNo; };    Sales_data& combine(const Sales_data&);    std::string bookNo;    unsigned units_sold = 0;    double revenue = 0.0;};Sales_data& Sales_data::combine(const Sales_data& rhs){    units_sold += rhs.units_sold;    revenue += rhs.revenue;    return *this;}#endif

7.3

#include "ex7_02.h"#include <iostream>using std::cin; using std::cout; using std::endl;int main(){    Sales_data total;    if (cin >> total.bookNo >> total.units_sold >> total.revenue)    {        Sales_data trans;        while (cin >> trans.bookNo >> trans.units_sold >> trans.revenue) {            if (total.isbn() == trans.isbn())                total.combine(trans);            else {                cout << total.bookNo << " " << total.units_sold << " " << total.revenue << endl;                total = trans;            }        }        cout << total.bookNo << " " << total.units_sold << " " << total.revenue << endl;    }    else    {        std::cerr << "No data?!" << std::endl;        return -1;    }    return 0;}

7.4

#include <string>class Person {    std::string name;    std::string address;};

7.5

#include <string>class Person {    std::string name;    std::string address;public:    std::string & get_name() const  { return name; }    std::string & get_addr() const  { return address; }};

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