Блог

Я использую электронную книгу Primer c , и я дошел до главы, в которой я должен создать программу, которая вводит названия 2 книг, цену и количество проданных и выводит сумму прибыли / среднюю цену продажи. Мне поручено вставить код, который они мне дали, в новый класс внутри проекта, а затем использовать его с моим основным классом, я не смог скомпилировать код, компилятор (как codeblocks, так и VS express) показывает ошибку, когда я это делаю.

(Обратите внимание, что это было до того, как я начал писать какой-либо собственный код, так что, вероятно, это проблема в том, как я создал класс или компилятор) (Чтобы создать класс, я нажал File> New class — назвал его Sales_item и закончил, чем он спросил меня, хочу ли я связатьэто связано с проектом, над которым я работаю {пустой проект только с пустым основным методом} Я нажал да и вставил код)

 /*
 * 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>

class Sales_item {
// these declarations are explained section 7.2.1, p. 270 
// and in chapter 14, pages 557, 558, 561
friend std::istreamamp; operator>>(std::istreamamp;, Sales_itemamp;);
friend std::ostreamamp; operator<<(std::ostreamamp;, const Sales_itemamp;);
friend bool operator<(const Sales_itemamp;, const Sales_itemamp;);
friend bool 
operator==(const Sales_itemamp;, const Sales_itemamp;);
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(const std::string amp;book): bookNo(book) { }
    Sales_item(std::istream amp;is) { is >> *this; }
public:
    // operations on Sales_item objects
    // member binary operator: left-hand operand bound to implicit this pointer
    Sales_itemamp; operator =(const Sales_itemamp;);

    // 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
    unsigned units_sold = 0; // explicitly initialized
    double revenue = 0.0;
};

// used in chapter 10
inline
bool compareIsbn(const Sales_item amp;lhs, const Sales_item amp;rhs) 
{ return lhs.isbn() == rhs.isbn(); }

// nonmember binary operator: must declare a parameter for each operand
Sales_item operator (const Sales_itemamp;, const Sales_itemamp;);

inline bool 
operator==(const Sales_item amp;lhs, const Sales_item amp;rhs)
{
    // must be made a friend of Sales_item
    return lhs.units_sold == rhs.units_sold amp;amp;
           lhs.revenue == rhs.revenue amp;amp;
           lhs.isbn() == rhs.isbn();
}

inline bool 
operator!=(const Sales_item amp;lhs, const Sales_item amp;rhs)
{
    return !(lhs == rhs); // != defined in terms of operator==
}

// assumes that both objects refer to the same ISBN
Sales_itemamp; Sales_item::operator =(const Sales_itemamp; 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_itemamp; lhs, const Sales_itemamp; 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::istreamamp; 
operator>>(std::istreamamp; in, Sales_itemamp; 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::ostreamamp; 
operator<<(std::ostreamamp; out, const Sales_itemamp; 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
  

И это ошибка —

 ||=== Build: Debug in Sales_item (compiler: GNU GCC Compiler) ===|
includeSales_item.h|56|warning: defaulted and deleted functions only available with -std=c  11 or -std=gnu  11|
includeSales_item.h|70|warning: non-static data member initializers only available with -std=c  11 or -std=gnu  11|
includeSales_item.h|71|warning: non-static data member initializers only available with -std=c  11 or -std=gnu  11|
includeSales_item.h|45|error: constructor required before non-static data member for 'Sales_item::units_sold' has been parsed|
includeSales_item.h|45|error: constructor required before non-static data member for 'Sales_item::revenue' has been parsed|
C:UsersTomerDesktopC  CodeSales_itemsrcSales_item.cpp|3|error: definition of explicitly-defaulted 'Sales_item::Sales_item()'|
includeSales_item.h|56|error: 'Sales_item::Sales_item()' explicitly defaulted here|
C:UsersTomerDesktopC  CodeSales_itemsrcSales_item.cpp|8|error: definition of implicitly-declared 'Sales_item::~Sales_item()'|
||=== Build failed: 5 error(s), 3 warning(s) (0 minute(s), 0 second(s)) ===|
  

Извините за плохой английский.

Возможно, вам следует настроить свой компилятор или IDE для поддержки c 11, потому что в коде используются некоторые новые ключевые слова. Я тестирую его, и он хорошо работает с c 11.