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Exer14_45_Sales_data.h
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Exer14_45_Sales_data.h
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#ifndef SALES_DATA_H
#define SALES_DATA_H
#include <iostream>
#include <string>
class Sales_data {
// friend
// overloaded output operator required by exercise 14.6
friend std::ostream &operator<<(std::ostream&, const Sales_data&);
// overloaded input operator required by exercise 14.9
friend std::istream &operator>>(std::istream&, Sales_data&);
// overloaded addition operator required by exercise 14.13
friend Sales_data operator+(const Sales_data&, const Sales_data&);
// overloaded equality on page 561
friend bool operator==(const Sales_data&, const Sales_data&);
friend bool operator!=(const Sales_data&, const Sales_data&);
// overloaded addition operator required by exercise 14.20
friend Sales_data operator+(const Sales_data&, const Sales_data&);
public:
// constructor
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(p*n) {}
explicit Sales_data(std::istream &is) { is >> *this; }
// member
std::string isbn() const { return bookNo; }
// overloaded compound-assignment operator required by exercise 14.20
Sales_data& operator+=(const Sales_data&);
// conversion operator required by exercise 14.45
operator std::string() const { return bookNo; }
operator double() const { return revenue; }
private:
std::string bookNo;
unsigned units_sold = 0;
double revenue = 0.0;
double avg_price() const;
};
// member functions definition
// assumes both objects refer to the same book
Sales_data& Sales_data::operator+=(const Sales_data& rhs)
{
// create temporary object, calls copy constructor, then calls copy-assignment operator.
*this = *this + rhs;
return *this;
}
// define avg_price as inline, required by exercise 7.26
inline double Sales_data::avg_price() const
{
if(units_sold != 0)
return revenue / units_sold;
else
return revenue;
}
// overloaded output operator
std::ostream& operator<<(std::ostream& os, const Sales_data& item)
{
os << item.bookNo << " "
<< item.units_sold << " "
<< item.revenue << " "
<< item.avg_price();
return os;
}
// overloaded input operator
std::istream& operator>>(std::istream &is, Sales_data& item)
{
double price = 0;
is >> item.bookNo >> item.units_sold >> price;
if(is) // check if input invalid
item.revenue = item.units_sold * price;
else
item = Sales_data(); // input failed:given the object default state
return is;
}
bool operator==(const Sales_data &lhs, const Sales_data &rhs)
{
return lhs.bookNo == rhs.bookNo &&
lhs.units_sold == rhs.units_sold &&
lhs.revenue == rhs.revenue;
}
bool operator!=(const Sales_data &lhs, const Sales_data &rhs)
{
return !(lhs == rhs);
}
// assumes both objects refer to the same book
Sales_data operator+(const Sales_data &lhs, const Sales_data &rhs)
{
Sales_data sum = lhs;
sum.units_sold = sum.units_sold + rhs.units_sold;
sum.revenue = sum.revenue + rhs.revenue;
return sum;
}
#endif
// Note: compared this with Sales_data.h, we can find that we have to create
// temporary objects when adding. For built-in type, this might not be a problem.
// But for members of class type, this might cause performance problem.