燕山大学-面向对象程序设计实验-实验7 多态性：函数与运算符重载-实验报告

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实验七多态性—函数与运算符重载

💎7.1 实验目的

1．理解动态联编和动态联编的概念；

2．理解掌握成员函数方式运算符重载；

3．理解掌握友元函数方式运算符重载；

4．理解掌握++、--、=运算符的重载。

💎7.2 实验内容

7.2.1程序阅读

💎1．理解下面的程序，并在VC++6.0下运行查看结果，回答程序后面的问题。

#include "iostream"

class CComplex

{

public:

       CComplex()

       {

              real = 0;

              imag = 0;

       }

       CComplex(int x,int y)

       {

              real = x;

              imag = y;

       }

      

       int real;

       int imag;

      

       CComplex operator + (CComplex obj1)-----------------------------------------------①

       {

              CComplex obj2(real + obj1.real, imag + obj1.imag);

              return obj2;

       }

};

void main()

{

       CComplex obj1(100,30);

       CComplex obj2(20, 30);

       CComplex obj;

       obj = obj1+obj2; ------------------------------------------------------------------②

       cout << obj.real <<endl;

       cout << obj.imag << endl;

}

问题一：①处的运算符重载，为什么该函数的返回值要设计成CComplex类型？

答：①处重载加法运算符，两个CComplex型数据相加后，仍然为CComplex型，相加不改变数据类型，故仍返回CComplex类型。

问题二：②处的运算符重载函数调用就相当于“obj=operator+(obj1,obj2);”，但是为什么CComplex类中的运算符重载函数只设计了一个参数？

答：运算符重载是一个成员函数，本身就可以获取到自身，而自身就相当于obj1，故只需要再设计一个参数给obj2即可。

💎2．理解下面的程序，并在VC++6.0下运行查看结果，回答程序后面的问题。

#include "iostream"

class CComplex

{

public:

       CComplex()

       {

              real = 0.0;

              imag = 0.0;

       }

       CComplex(float x, float y)

       {

              real = x;

              imag = y;

       }

       CComplex operator + (CComplex &obj1, CComplex &obj2)

       {

              CComplex obj3(obj1.real + obj2.real, obj1.imag + obj2.imag);

              return obj3;

       }

       CComplex &operator++(CComplex &obj)

       {

              obj.real += 1;

              obj.imag +=1;

              return obj;

       }

       void print()

       {

              cout<<real<<"+"<<imag<<"i"<<endl;

       }

private:

       float real;

       float imag;

};

CComplex &operator--(CComplex &x)

{

       x.real -= 1;

       x.imag -= 1;

       return x;

}

void main()

{

       CComplex obj1(2.1,3.2);

       CComplex obj2(3.6,2.5);

       cout<<"obj1=";

       obj1.print();

       cout<<"obj2=";

       obj2.print();

       CComplex obj3 = obj1 + obj2;

       cout<<"befor++, obj3=";

       obj3.print();

       ++obj3;

       cout<<"after++, obj3=";

       obj3.print();

       --obj3;

       cout<<"after--, obj3=";

       obj3.print();

       CComplex obj4 = ++obj3;

       cout<<"obj4=";

       obj4.print();

}

问题一：以上程序中的三个运算符重载都有错误，试改正过来，并分析该程序的输出结果。

答：修改后代码如下

#include <iostream>
 
using namespace std;
 
 
 
class CComplex{
 
    public:
 
        CComplex(){
 
            real = 0.0;
 
            imag = 0.0;
 
        }
 
        CComplex(float x, float y){
 
            real = x;
 
            imag = y;
 
        }
 
        CComplex operator + (CComplex &obj2){//重载加法运算符只需要额外加一个参数
 
            CComplex obj3(real + obj2.real,imag + obj2.imag);
 
            return obj3;
 
        }
 
        CComplex& operator++(){//重载++运算符括号里为空 
 
            real += 1;
 
            imag +=1;
 
            return *this;
 
        }
 
        CComplex& operator--(){//作为成员函数，放在类内
 
            real -= 1;
 
            imag -= 1;
 
            return *this;
 
        }
 
        void print(){
 
            cout<<real<<"+"<<imag<<"i"<<endl;
 
        }
 
    private:
 
        float real;
 
        float imag;
 
};
 
 
 
int main(){
 
    CComplex obj1(2.1,3.2);
 
    CComplex obj2(3.6,2.5);
 
    cout<<"obj1=";
 
    obj1.print();
 
    cout<<"obj2=";
 
    obj2.print();
 
    CComplex obj3 = obj1 + obj2;
 
    cout<<"befor++, obj3=";
 
    obj3.print();
 
    ++obj3;
 
    cout<<"after++, obj3=";
 
    obj3.print();
 
    --obj3;
 
    cout<<"after--, obj3=";
 
    obj3.print();
 
    CComplex obj4 = ++obj3;
 
    cout<<"obj4=";
 
    obj4.print();
 
    return 0;
 
}

分析：
初始状态，构造obj1=2.1+3.2i，obj2=3.6+2.5i，正常输出
运行obj3=obj1+obj2，重载+运算符，实部real和虚部imag分别相加，输出obj3=5.7+5.7i
运行++obj3，重载前置++运算符，实部real和虚部imag分别自增，输出obj3=6.7+6.7i
运行—obj3，重载前置—运算符，实部real和虚部imag分别自减，输出obj3=5.7+5.7i
运行obj4=++obj3，即先令++obj3，obj3=6.7+6.7i，随后令obj4=obj3=6.7+6.7i，正常输出obj4

💎7.2.2 程序设计

1．把7.2.1中第一道题的程序改造成采取友元函数重载方式来实现“+”运算符，并采取友元函数重载方式增加前置和后置“++”以及“--”运算符重载，并设计主函数来验证重载运算符的用法。

答：

#include <iostream>
 
using namespace std;
 
 
 
class CComplex{
 
    public:
 
        CComplex(){
 
            real = 0;
 
            imag = 0;
 
        }
 
        CComplex(int x,int y){
 
            real = x;
 
            imag = y;
 
        }
 
       
 
        int real;
 
        int imag;
 
       
 
        friend CComplex operator + (CComplex& obj1,CComplex& obj2);
 
        friend CComplex &operator++(CComplex &obj);
 
        friend CComplex &operator--(CComplex &obj);
 
        friend CComplex &operator++(CComplex &obj,int);
 
        friend CComplex &operator--(CComplex &obj,int);
 
};
 
 
 
CComplex operator + (CComplex& obj1,CComplex& obj2){
 
    CComplex obj3(obj1.real + obj2.real, obj1.imag + obj2.imag);
 
    return obj3;
 
}
 
 
 
CComplex &operator++(CComplex &obj){
 
    obj.real += 1;
 
    obj.imag += 1;
 
    return obj;
 
}
 
 
 
CComplex &operator--(CComplex &obj){
 
    obj.real -= 1;
 
    obj.imag -= 1;
 
    return obj;
 
}
 
 
 
CComplex &operator++(CComplex &obj,int){
 
    CComplex tmp=obj;
 
    obj.real += 1;
 
    obj.imag += 1;
 
    return tmp;
 
}
 
 
 
CComplex &operator--(CComplex &obj,int){
 
    CComplex tmp=obj;
 
    obj.real -= 1;
 
    obj.imag -= 1;
 
    return tmp;
 
}
 
 
 
int main(){
 
    CComplex obj1(2,3);
 
    CComplex obj2(3,2);
 
    cout<<"obj1="<<obj1.real<<"+"<<obj1.imag<<"i"<<endl;
 
    cout<<"obj2="<<obj2.real<<"+"<<obj2.imag<<"i"<<endl;
 
    CComplex obj3 = obj1 + obj2;
 
    cout<<"obj3=obj1+obj2=";
 
    cout<<obj3.real<<"+"<<obj3.imag<<"i"<<endl;
 
    ++obj3;
 
    cout<<"前置++,";
 
    cout<<"obj3="<<obj3.real<<"+"<<obj3.imag<<"i"<<endl;
 
    --obj3;
 
    cout<<"前置--,";
 
    cout<<"obj3="<<obj3.real<<"+"<<obj3.imag<<"i"<<endl;
 
    CComplex obj4 = ++obj3;
 
    cout<<"obj4=++obj3="<<obj4.real<<"+"<<obj4.imag<<"i"<<endl;
 
   
 
    obj3++;
 
    cout<<"后置++,";
 
    cout<<"obj3="<<obj3.real<<"+"<<obj3.imag<<"i"<<endl;
 
    obj3--;
 
    cout<<"后置--,";
 
    cout<<"obj3="<<obj3.real<<"+"<<obj3.imag<<"i"<<endl;
 
    obj4 = obj3++;
 
    cout<<"obj4=obj3++="<<obj4.real<<"+"<<obj4.imag<<"i"<<endl;
 
   
 
    return 0;
 
}

💎7.3思考题

１．定义CPoint类，有两个成员变量：横坐标（x）和纵坐标（y），对CPoint类重载“++”（自增运算符）、“--”（自减运算符），实现对坐标值的改变。（每个函数均采用友元禾成员函数实现）

答：

（友元函数实现）
 
#include<iostream>
 
using namespace std;
 
 
 
class CPoint{
 
    private:
 
        double x;
 
        double y;
 
    public:
 
        CPoint(double x,double y):x(x),y(y)
 
        {
 
        }
 
        void print(){
 
            cout<<"坐标为("<<x<<","<<y<<")"<<endl;
 
        }
 
        friend CPoint &operator++(CPoint &obj);
 
        friend CPoint &operator--(CPoint &obj);
 
        friend CPoint &operator++(CPoint &obj,int);
 
        friend CPoint &operator--(CPoint &obj,int);
 
 
 
};
 
 
 
CPoint &operator++(CPoint &obj){
 
    obj.x += 1;
 
    obj.y += 1;
 
    return obj;
 
}
 
 
 
CPoint &operator--(CPoint &obj){
 
    obj.x -= 1;
 
    obj.y -= 1;
 
    return obj;
 
}
 
 
 
CPoint &operator++(CPoint &obj,int){
 
    CPoint tmp=obj;
 
    obj.x += 1;
 
    obj.y += 1;
 
    return tmp;
 
}
 
 
 
CPoint &operator--(CPoint &obj,int){
 
    CPoint tmp=obj;
 
    obj.x -= 1;
 
    obj.y -= 1;
 
    return tmp;
 
}
 
 
 
int main(){
 
    CPoint a(2.5,5.2);
 
    a.print();
 
 
 
    cout<<"a++";
 
    (a++).print();
 
    cout<<"++后a";
 
    a.print();
 
   
 
    cout<<"a--";
 
    (a--).print();
 
    cout<<"--后a";
 
    a.print();
 
   
 
    cout<<"++a";
 
    (++a).print();
 
    cout<<"++后a";
 
    a.print();
 
   
 
    cout<<"--a";
 
    (--a).print();
 
    cout<<"--后a";
 
    a.print();
 
   
 
    return 0;
 
}