14.3

最新推荐文章于 2025-12-27 12:23:29 发布

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本文展示了C++中运算符重载的实现方法，包括加法、减法等运算符的重载，并提供了书籍类的具体实现案例。通过这些示例，读者可以了解如何在自定义类中使用运算符重载。

14.13

Sales_data& Sales_data::operator+=(const Sales_data &rhs)
{
    units_sold += rhs.units_sold;
    revenue += rhs.revenue;
    return *this;
}


Sales_data& Sales_data::operator-=(const Sales_data &rhs)
{
    units_sold -= rhs.units_sold;
    revenue -= rhs.revenue;
    return *this;
}

std::istream& operator>>(std::istream &is, Sales_data &item)
{
    double price = 0.0;
    is >> item.bookNo >> item.units_sold >> price;
    if (is)
        item.revenue = price * item.units_sold;
    else
        item = Sales_data();
    return is;
}

std::ostream& operator<<(std::ostream &os, const Sales_data &item)
{
    os << item.isbn() << " " << item.units_sold << " " << item.revenue << " " << item.avg_price();
    return os;
}

Sales_data operator+(const Sales_data &lhs, const Sales_data &rhs)
{
    Sales_data sum = lhs;
    sum += rhs;
    return sum;
}

Sales_data operator-(const Sales_data &lhs, const Sales_data &rhs)
{
    Sales_data sum = lhs;
    sum -= rhs;
    return sum;
}

14.14

http://stackoverflow.com/questions/21071167/why-is-it-more-efficient-to-define-operator-to-call-operator-rather-than-the

14.15

#include <iostream>
#include <string>

class Book {
    friend std::istream& operator>>(std::istream&, Book&);
    friend std::ostream& operator<<(std::ostream&, const Book&);
    friend bool operator==(const Book&, const Book&);
    friend bool operator!=(const Book&, const Book&);
    friend bool operator<(const Book&, const Book&);
    friend bool operator>(const Book&, const Book&);
    friend Book operator+(const Book&, const Book&);

public:
    Book() = default;
    Book(unsigned no, std::string name, std::string author, std::string pubdate, unsigned number):no_(no), name_(name), author_(author), pubdate_(pubdate), number_(number) { }
    Book(std::istream &in) { in >> *this; }

    Book& operator+=(const Book&);

private:
    unsigned no_;
    std::string name_;
    std::string author_;
    std::string pubdate_;
    unsigned number_;
};

std::istream& operator>>(std::istream&, Book&);
std::ostream& operator<<(std::ostream&, const Book&);
bool operator==(const Book&, const Book&);

std::istream& operator>>(std::istream &in, Book &book)
{
    in >> book.no_ >> book.name_ >> book.author_ >> book.pubdate_ >> book.number_;
    return in;
}

std::ostream& operator<<(std::ostream &out, const Book &book)
{
    out << book.no_ << " " << book.name_ << " " << book.author_ << " " << book.pubdate_ << " " << book.number_ << std::endl;
    return out;
}

bool operator==(const Book &lhs, const Book &rhs)
{
    return lhs.no_ == rhs.no_;
}

bool operator!=(const Book &lhs, const Book &rhs)
{
    return !(lhs == rhs);
}

bool operator<(const Book &lhs, const Book &rhs)
{
    return lhs.no_ < rhs.no_;
}

bool operator>(const Book &lhs, const Book &rhs)
{
    return rhs < lhs;
}

Book& Book::operator+=(const Book &rhs)
{
    if (rhs == *this)
        this->number_ += rhs.number_;

    return *this;
}

Book operator+(const Book &lhs, const Book &rhs)
{
    Book book = lhs;
    book += rhs;
    return book;
}