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#include <iostream>
/*
*
* 7.49
*
*
*/
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;
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) { }
SalesData(std::istream &sdcin) { read(sdcin, *this); }; // Constructor, but read from istream
std::string isbn() const { return BookNo; } // member function
//-------
SalesData &combine(SalesData);
//SalesData &combine(SalesData&);
//SalesData &combine(const SalesData&) const; Does not compile
//-------
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(SalesData rhs) {
UnitsSold += rhs.UnitsSold;
Revenue += rhs.Revenue;
return *this;
}
/*
SalesData& SalesData::combine(SalesData &rhs) {
UnitsSold += rhs.UnitsSold;
Revenue += rhs.Revenue;
return *this;
}
*/
/*
SalesData& SalesData::combine(const SalesData &rhs) const {
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 () {
/*
For each of the three following declarations of combine, explain what
happens if we call i.combine(s), where i is a Sales_data and s is a string:
(a) SalesData &combine(Sales_data); It does not combine as expected, i'm not sure.
(b) Sales_data &combine(Sales_data&); // does not compile
(c) Sales_data &combine(const Sales_data&) const; // does not compile
*/
std::string s = "7.49";
SalesData i("",0,0);
i.combine(SalesData(s));
print(std::cout, i);
return 0;
}
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