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- /* This file defines the Sales_item class used in chapter 1.
- * The code used in this file will be explained in
- * Chapter 7 (Classes) and Chapter 14 (Overloaded Operators)
- * Readers shouldn't try to understand the code in this file
- * until they have read those chapters.
- */
- #ifndef SALESITEM_H
- // we're here only if SALESITEM_H has not yet been defined
- #define SALESITEM_H
- #include "Version_test.h"
- // Definition of Sales_item class and related functions goes here
- #include <iostream>
- #include <string>
- class Sales_item {
- // these declarations are explained section 7.2.1, p. 270
- // and in chapter 14, pages 557, 558, 561
- friend std::istream& operator>>(std::istream&, Sales_item&);
- friend std::ostream& operator<<(std::ostream&, const Sales_item&);
- friend bool operator<(const Sales_item&, const Sales_item&);
- friend bool
- operator==(const Sales_item&, const Sales_item&);
- public:
- #if defined(IN_CLASS_INITS) && defined(DEFAULT_FCNS)
- Sales_item() = default;
- #else
- Sales_item(): units_sold(0), revenue(0.0) { }
- #endif
- Sales_item(const std::string &book):
- bookNo(book), units_sold(0), revenue(0.0) { }
- Sales_item(std::istream &is) { is >> *this; }
- public:
- // operations on Sales_item objects
- // member binary operator: left-hand operand bound to implicit this pointer
- Sales_item& operator+=(const Sales_item&);
- // operations on Sales_item objects
- std::string isbn() const { return bookNo; }
- double avg_price() const;
- // private members as before
- private:
- std::string bookNo; // implicitly initialized to the empty string
- #ifdef IN_CLASS_INITS
- unsigned units_sold = 0;
- double revenue = 0.0;
- #else
- unsigned units_sold;
- double revenue;
- #endif
- };
- // used in chapter 10
- inline
- bool compareIsbn(const Sales_item &lhs, const Sales_item &rhs)
- { return lhs.isbn() == rhs.isbn(); }
- // 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.isbn() == rhs.isbn();
- }
- inline bool
- operator!=(const Sales_item &lhs, const Sales_item &rhs)
- {
- return !(lhs == rhs); // != defined in terms of operator==
- }
- // assumes that both objects refer to the same ISBN
- 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
- 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
- }
- std::istream&
- operator>>(std::istream& in, Sales_item& s)
- {
- double price;
- in >> s.bookNo >> 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;
- }
- std::ostream&
- operator<<(std::ostream& out, const Sales_item& s)
- {
- out << s.isbn() << " " << s.units_sold << " "
- << s.revenue << " " << s.avg_price();
- return out;
- }
- double Sales_item::avg_price() const
- {
- if (units_sold)
- return revenue/units_sold;
- else
- return 0;
- }
- #endif
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