不允许使用友元函数，改写习题15-3程序。 #include using namespace std; //代码修改----- class Car{ public: Car(int j){size=j;} friend int Leisure(int time, Car& aobj, Boat& bobj); protected: int size; }; class Boat{ public: Boat(int j){size=j;} friend int Leisure(int time, Car& aobj, Boat& bobj); protected: int size; }; //------------------------ int Leisure(int time, Car& aobj, Boat& bobj){ return time * aobj.Get() * bobj.Get(); } int main(){ Car c1(2); Boat b1(3); int time =4; cout <<Leisure(time,c1,b1); }

习题15-3程序是一个使用了友元函数的程序，题目要求我们禁止使用友元函数，并对程序进行修改。具体修改方法视程序实际情况而定，但应该是通过其他方式实现程序原有的功能，并且不使用友元函数。例如，可以使用类的public成员函数来操作私有数据，或者使用全局函数但不使用友元函数等。

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2.定义了Money类请补充完代码 #include <iostream> using namespace std; class Money { int Yuan, Jiao; // 元、角 public: Money(int y = 0, int j = 0) Money(double d) Money operator++(); //①用成员函数实现前置++ Money operator++(int); //②用成员函数实现后置++ friend Money operator--(Money &m); //③用友元函数实现前置-- friend Money operator--(Money &m, int); //④用友元函数实现后置-- operator double(); friend ostream & operator<<(ostream & out,Money & m); int main(void) { Money m(15, 3), m1, m2, m3, m4; cout<<"m:"<<m;//m.Show("m"); m1 = ++m; cout << "m1=++m;\n"<<"m1:"<<m1<<"m:"<<m; m2 = m++; cout << "m2=m++;\n"<<"m2:"<<m2<<"m:"<<m; m3 = --m; cout << "m3=--m;\n"<<"m3:"<<m3<<"m:"<<m; m4 = m--; cout << "m4=m--;\n"<<"m4:"<<m4<<"m:"<<m; Money m5 = m4 + 8.5; //A行 cout<<"m5= m4 + 8.5\nm5:"<<m5; return 0; }

下面是补充完整的Money类代码：

#include <iostream>
using namespace std;

class Money {
    int Yuan, Jiao; // 元、角
public:
    Money(int y = 0, int j = 0) : Yuan(y), Jiao(j) {}
    Money(double d) {
        Yuan = static_cast<int>(d);
        Jiao = static_cast<int>((d - Yuan) * 10 + 0.5);
    }
    Money operator++();                    //①用成员函数实现前置++
    Money operator++(int);                 //②用成员函数实现后置++
    friend Money operator--(Money &m);     //③用友元函数实现前置--
    friend Money operator--(Money &m, int);//④用友元函数实现后置--
    operator double() { return Yuan + Jiao / 10.0; }
    friend ostream & operator<<(ostream & out,Money & m);
    Money operator+(double x) {
        Money temp(*this);
        temp.Yuan += static_cast<int>(x);
        temp.Jiao += static_cast<int>((x - static_cast<int>(x)) * 10 + 0.5);
        return temp;
    }
};

Money Money::operator++() {
    Jiao++;
    if(Jiao == 10) {
        Jiao = 0;
        Yuan++;
    }
    return *this;
}

Money Money::operator++(int) {
    Money temp(*this);
    Jiao++;
    if(Jiao == 10) {
        Jiao = 0;
        Yuan++;
    }
    return temp;
}

Money operator--(Money &m) {
    m.Jiao--;
    if(m.Jiao == -1) {
        m.Jiao = 9;
        m.Yuan--;
    }
    return m;
}

Money operator--(Money &m, int) {
    Money temp(m);
    m.Jiao--;
    if(m.Jiao == -1) {
        m.Jiao = 9;
        m.Yuan--;
    }
    return temp;
}

ostream & operator<<(ostream & out, Money & m) {
    out << m.Yuan << "." << m.Jiao << "元";
    return out;
}

int main(void) {
    Money m(15, 3), m1, m2, m3, m4;
    cout << "m:" << m << endl;
    m1 = ++m;
    cout << "m1=++m;\n" << "m1:" << m1 << "m:" << m << endl;
    m2 = m++;
    cout << "m2=m++;\n" << "m2:" << m2 << "m:" << m << endl;
    m3 = --m;
    cout << "m3=--m;\n" << "m3:" << m3 << "m:" << m << endl;
    m4 = m--;
    cout << "m4=m--;\n" << "m4:" << m4 << "m:" << m << endl;
    Money m5 = m4 + 8.5;               //A行
    cout << "m5= m4 + 8.5\nm5:" << m5 << endl;
    return 0;
}

Money类中的主要成员函数和友元函数功能如下：

- Money(int y = 0, int j = 0)：构造函数，初始化元和角；
- Money(double d)：构造函数，根据浮点数d初始化元和角；
- Money operator++()：前置++，使元和角都加1；
- Money operator++(int)：后置++，使元和角都加1，但返回原对象的副本；
- friend Money operator--(Money &m)：前置--，使元和角都减1；
- friend Money operator--(Money &m, int)：后置--，使元和角都减1，但返回原对象的副本；
- operator double()：类型转换运算符，将对象转换为浮点数；
- friend ostream & operator<<(ostream & out,Money & m)：输出运算符，输出对象的元和角；
- Money operator+(double x)：重载+运算符，将Money对象和浮点数相加，返回结果Money对象。

在main函数中，先创建一个Money对象m(15, 3)，然后依次调用前置++、后置++、前置--、后置--和重载+运算符，最后将结果输出。

填写下方空白处代码，通过重载运算符使得Counter类型可以以x为值参与整数加法运算 ​#include<bits/stdc++.h> using namespace std; class Counter { public: Counter(int d){x=d;} int getx() const{return x;} private: int x; }; //------------------code here---------------------------- //------------------------------------------------------------- int main() { int a,y; cin>>a>>y; Counter x(a); cout<<x+y<<' '<<y+x; }

#include<bits/stdc++.h>
using namespace std;
class Counter
{
public:
    Counter(int d){x=d;}
    int getx() const{return x;}

    Counter operator+(int y)
    {
        return Counter(x+y);
    }

    friend Counter operator+(int y, const Counter& c)
    {
        return Counter(c.x+y);
    }

private:
    int x;
};
//-------------------------------------------------------------
int main()
{
    int a,y;
    cin>>a>>y;
    Counter x(a);
    cout<<x+y<<' '<<y+x;
}

在代码中，我们为Counter类重载了加法运算符。我们使用成员函数的方式重载了`Counter operator+(int y)`，使得可以将整数与Counter对象相加。同时，我们也使用友元函数的方式重载了`friend Counter operator+(int y, const Counter& c)`，使得可以将Counter对象与整数相加。这样，就可以实现Counter类型以x为值参与整数加法运算。