/* * This file contains code from "C++ Primer, Fifth Edition", by Stanley B. * Lippman, Josee Lajoie, and Barbara E. Moo, and is covered under the * copyright and warranty notices given in that book: * * "Copyright (c) 2013 by Objectwrite, Inc., Josee Lajoie, and Barbara E. Moo." * * * "The authors and publisher have taken care in the preparation of this book, * but make no expressed or implied warranty of any kind and assume no * responsibility for errors or omissions. No liability is assumed for * incidental or consequential damages in connection with or arising out of the * use of the information or programs contained herein." * * Permission is granted for this code to be used for educational purposes in * association with the book, given proper citation if and when posted or * reproduced.Any commercial use of this code requires the explicit written * permission of the publisher, Addison-Wesley Professional, a division of * Pearson Education, Inc. Send your request for permission, stating clearly * what code you would like to use, and in what specific way, to the following * address: * * Pearson Education, Inc. * Rights and Permissions Department * One Lake Street * Upper Saddle River, NJ 07458 * Fax: (201) 236-3290 */
/* 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
// Definition of Sales_item class and related functions goes here #include<iostream> #include<string>
classSales_item { // these declarations are explained section 7.2.1, p. 270 // and in chapter 14, pages 557, 558, 561 friendstd::istream& operator>>(std::istream&, Sales_item&); friendstd::ostream& operator<<(std::ostream&, const Sales_item&); friendbooloperator<(const Sales_item&, const Sales_item&); friendbool operator==(const Sales_item&, const Sales_item&); public: // constructors are explained in section 7.1.4, pages 262 - 265 // default constructor needed to initialize members of built-in type Sales_item() = default; Sales_item(conststd::string &book): bookNo(book) { } 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::stringisbn()const{ return bookNo; } doubleavg_price()const; // private members as before private: std::string bookNo; // implicitly initialized to the empty string unsigned units_sold = 0; // explicitly initialized double revenue = 0.0; };
// used in chapter 10 inline boolcompareIsbn(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&);
inlinebool 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(); }
inlinebool 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; }