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#include <iostream>
/*
*
* 7.48
*
*
*/
struct SalesData;
SalesData add(const SalesData&, const SalesData&);
std::ostream &print(std::ostream&, const SalesData&);
std::istream &read(std::istream&, SalesData&);
struct SalesData {
SalesData() = default;
explicit SalesData(const std::string &s): BookNo(s) { } //constructor, bookNo only
SalesData(const std::string &s, unsigned n, double p): // constructor, both bookno, UnitsSold and Revenue
BookNo(s), UnitsSold(n), Revenue(p*n) { }
explicit SalesData(std::istream &sdcin) { read(sdcin, *this); }; // Constructor, but read from istream
std::string isbn() const { return BookNo; } // member function
SalesData &combine(const SalesData&); // member function, defined elsewhere
inline double avg_price() const; // member function, defined elsewhere
std::string BookNo; // data member
unsigned int UnitsSold = 0; // data member
double Revenue = 0.0; // data member
};
inline double SalesData::avg_price() const {
if (UnitsSold)
return Revenue / UnitsSold;
else
return 0;
}
SalesData& SalesData::combine(const SalesData &rhs) {
UnitsSold += rhs.UnitsSold;
Revenue += rhs.Revenue;
return *this;
}
std::istream &read(std::istream &is, SalesData &item) { // Not member function
double price = 0;
is >> item.BookNo >> item.UnitsSold >> price;
item.Revenue = price * item.UnitsSold;
return is;
}
std::ostream &print(std::ostream &os, const SalesData &item) { // Not member function
os << item.isbn() << " " << item.UnitsSold << " "
<< item.Revenue << " " << item.avg_price();
return os;
}
SalesData add(const SalesData sd1, const SalesData sd2) { // Not member function
SalesData sdsum = sd1;
sdsum.combine(sd2);
return sdsum;
}
int main () {
// Seems like the same thing happens for explicit and non-explicit
std::string null_isbn("9-999-99999-9");
SalesData i1(null_isbn);
SalesData i2("9-999-99999-9");
print(std::cout, i1) << "\n";
print(std::cout, i2) << std::endl;
return 0;
}
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