1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114
|
#ifndef SALESITEM_H #define SALESITEM_H
// Definition of Sales_item class and related functions goes here
#include <iostream> #include <string>
class Sales_item { friend bool operator==(const Sales_item&, const Sales_item&); // other members as before public: // added constructors to initialize from a string or an istream Sales_item(const std::string &book): isbn(book), units_sold(0), revenue(0.0) { } Sales_item(std::istream &is) { is >> *this; } friend std::istream& operator>>(std::istream&, Sales_item&); friend std::ostream& operator<<(std::ostream&, const Sales_item&); public: // operations on Sales_item objects // member binary operator: left-hand operand bound to implicit this pointer Sales_item& operator+=(const Sales_item&); // other members as before public: // operations on Sales_item objects double avg_price() const; bool same_isbn(const Sales_item &rhs) const { return isbn == rhs.isbn; } // default constructor needed to initialize members of built-in type Sales_item(): units_sold(0), revenue(0.0) { } // private members as before private: std::string isbn; unsigned units_sold; double revenue;
};
// nonmember binary operator: must declare a parameter for each operand Sales_item operator+(const Sales_item&, const Sales_item&);
inline bool operator==(const Sales_item &lhs, const Sales_item &rhs) { // must be made a friend of Sales_item return lhs.units_sold == rhs.units_sold && lhs.revenue == rhs.revenue && lhs.same_isbn(rhs); }
inline bool operator!=(const Sales_item &lhs, const Sales_item &rhs) { return !(lhs == rhs); // != defined in terms of operator== }
using std::istream; using std::ostream;
// assumes that both objects refer to the same isbn inline Sales_item& Sales_item::operator+=(const Sales_item& rhs) { units_sold += rhs.units_sold; revenue += rhs.revenue; return *this; }
// assumes that both objects refer to the same isbn inline Sales_item operator+(const Sales_item& lhs, const Sales_item& rhs) { Sales_item ret(lhs); // copy lhs into a local object that we'll return ret += rhs; // add in the contents of rhs return ret; // return ret by value }
inline istream& operator>>(istream& in, Sales_item& s) { double price; in >> s.isbn >> s.units_sold >> price; // check that the inputs succeeded if (in) s.revenue = s.units_sold * price; else s = Sales_item(); // input failed: reset object to default state return in; }
inline ostream& operator<<(ostream& out, const Sales_item& s) { out << s.isbn << "t" << s.units_sold << "t" << s.revenue << "t" << s.avg_price(); return out; }
inline double Sales_item::avg_price() const { if (units_sold) return revenue/units_sold; else return 0; }
#endif
|
近期评论