7.1.4

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7.11

#include <string>#include <iostream>class Sales_data {public:    Sales_data() = default;    Sales_data(const std::string &s):bookNo(s) { }    Sales_data(const std::string &s, unsigned n, double p):bookNo(s), units_sold(n), revenue(n*p){ }    Sales_data(std::istream &is);    std::string isbn() const { return bookNo; };    Sales_data& combine(const Sales_data&);private:    std::string bookNo;    unsigned units_sold = 0;    double revenue = 0.0;};// nonmember functionsstd::istream &read(std::istream &is, Sales_data &item){    double price = 0;    is >> item.bookNo >> item.units_sold >> price;    item.revenue = price * item.units_sold;    return is;}std::ostream &print(std::ostream &os, const Sales_data &item){    os << item.isbn() << " " << item.units_sold << " " << item.revenue;    return os;}Sales_data add(const Sales_data &lhs, const Sales_data &rhs){    Sales_data sum = lhs;    sum.combine(rhs);    return sum;}   // member functions.Sales_data::Sales_data(std::istream &is){    read(is, *this);}Sales_data& Sales_data::combine(const Sales_data& rhs){    units_sold += rhs.units_sold;    revenue += rhs.revenue;    return *this;}

7.12

#include <string>#include <iostream>struct Sales_data;std::istream &read(std::istream&, Sales_data&);class Sales_data {public:    Sales_data() = default;    Sales_data(const std::string &s):bookNo(s) { }    Sales_data(const std::string &s, unsigned n, double p):bookNo(s), units_sold(n), revenue(n*p){ }    Sales_data(std::istream &is) { read(is, *this); }    std::string isbn() const { return bookNo; };    Sales_data& combine(const Sales_data&);private:    std::string bookNo;    unsigned units_sold = 0;    double revenue = 0.0;};// member functions.Sales_data& Sales_data::combine(const Sales_data& rhs){    units_sold += rhs.units_sold;    revenue += rhs.revenue;    return *this;}// nonmember functionsstd::istream &read(std::istream &is, Sales_data &item){    double price = 0;    is >> item.bookNo >> item.units_sold >> price;    item.revenue = price * item.units_sold;    return is;}std::ostream &print(std::ostream &os, const Sales_data &item){    os << item.isbn() << " " << item.units_sold << " " << item.revenue;    return os;}Sales_data add(const Sales_data &lhs, const Sales_data &rhs){    Sales_data sum = lhs;    sum.combine(rhs);    return sum;}

7.13

int main(){    Sales_data total(std::cin);    if (!total.isbn().empty())    {        std::istream &is = std::cin;        while (is) {            Sales_data trans(is);            if (total.isbn() == trans.isbn())                total.combine(trans);            else {                print(std::cout, total) << std::endl;                total = trans;            }        }        print(std::cout, total) << std::endl;    }    else    {        std::cerr << "No data?!" << std::endl;        return -1;    }    return 0;}

7.14

Sales_data() : units_sold(0) , revenue(0){ }

7.15

#include <string>#include <iostream>class Person {public:    Person() = default;    Person(const std::string sname, const std::string saddr):name(sname), address(saddr){ }    Person(std::istream &is){ read(is, *this); }    std::string getName() const { return name; }    std::string getAddress() const { return address; } private:    std::string name;    std::string address;};std::istream &read(std::istream &is, Person &person){    is >> person.name >> person.address;    return is;}std::ostream &print(std::ostream &os, const Person &person){    os << person.name << " " << person.address;    return os;}

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