Bookstore program is "c ++ primer" an important example involves most of the important points, but the code disperse inconvenience in reading, are summarized below in accordance with the order of the chapters
Sales_item.h
#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: // constructors are explained in section 7.1.4, pages 262 - 265 // default constructor needed to initialize members of built-in type #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; // explicitly initialized 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
- Sales_item defined class, which involves knowledge of operator overloading, etc. in the following sections will involve
item_io.cpp
#include <iostream> #include "Sales_item.h" int main() { Sales_item book; // read ISBN, number of copies sold, and sales price std::cin >> book; // write ISBN, number of copies sold, total revenue, and average price std::cout << book << std::endl; return 0; }
- Realized from the standard input data into a Sales_item object, then the object's content is written back to the standard output
add_item.cpp
#include <iostream> #include "Sales_item.h" int main() { Sales_item item1, item2; std::cin >> item1 >> item2; //read a pair of transactions std::cout << item1 + item2 << std::endl; //print their sum return 0; }
- To achieve the two objects are added Sales_item
add_item2.cpp
#include <iostream> #include "Sales_item.h" int main() { Sales_item item1, item2; std::cin >> item1 >> item2; // first check that item1 and item2 represent the same book if (item1.isbn() == item2.isbn()) { std::cout << item1 + item2 << std::endl; return 0; // indicate success } else { std::cerr << "Data must refer to same ISBN" << std::endl; return -1; // indicate failure } }
- Achieved Sales_item first determine whether two objects have the same ISBN, we then adding
avg_price.cpp
#include <iostream> #include "Sales_item.h" int main() { Sales_item total; // // read the first transaction and ensure that there are data to process if (std::cin >> total) { Sales_item trans; // variable to hold the running sum // read and process the remaining transactions while (std::cin >> trans) { // if we're still processing the same book if (total.isbn() == trans.isbn()) total += trans; // update the running total else { // print results for the previous book std::cout << total << std::endl; total = trans; // total now refers to the next book } } std::cout << total << std::endl; // print the last transaction } else { // no input! warn the user std::cerr << "No data?!" << std::endl; return -1; // indicate failure } return 0; }
- Implements a file read from the record sales, book sales reports generated for each display the number of copies sold, the average price, and sales total (assuming all the records for each ISBN ISBN together saved in a file)
- ISBN merge all data is stored for each variable total, each record stored by the variable trans read, and if the total point to the same trans ISBN total value is updated, otherwise the value of total printing, and resets it to just read trans