C++之重写运算符练习

#include<iostream>
#include<string>
using namespace std;

class MyString{
private:
    char* cp;
public:
    MyString(char*);
    ~MyString();
    MyString(MyString&ms);
    MyString& operator +(MyString&);
    MyString&operator=(MyString&);
    MyString&operator+=(MyString&);
    char operator[](int i);
    char* getP();

};
MyString::MyString(char*cp=NULL):cp(cp){
}
MyString::~MyString(){}
MyString::MyString(MyString&ms){//深复制
    int len = strlen(ms.cp);//先确定原来字符串长度
    char*tempcp = new char[len+1];//开辟足够的空间
    strcpy(tempcp,ms.cp);//复制相同的内容
    cp = tempcp;//初始化对象的指针
}

MyString& MyString:: operator +(MyString&ms){
    int len = strlen(cp) + strlen(ms.cp);
    char *tempcp = new char[len+1];
    strcpy(tempcp,cp);
    strcat(tempcp,ms.cp);
    
    return *(new MyString(tempcp));//不改变两边对象的内容，返回一个新的对象
}
MyString&MyString::operator=(MyString&ms){
    if (cp == NULL || strlen(cp) < strlen(ms.cp)){
        if (cp){
            delete[] cp;//释放原来的小空间
        }
        cp = new char[(strlen(ms.cp) + 1)];//开辟足够的空间
    }
    cp=strcpy(cp, ms.cp);//复制内容
    return *this;
}
MyString& MyString::operator+=(MyString&ms){

    char*tempcp = cp;//暂存cp,因为要重新开辟空间//如果直接使strcat空间不够会出错
    cp = new char[strlen(cp)+strlen(ms.cp)+1];
    strcpy(cp,tempcp);
    strcat(cp,ms.cp);
    
    return *this;
}
char MyString::operator[](int i){
    return cp[i];
}
char*MyString::getP(){//用于主函数中查看对象内容
    return cp;
}
int main(){
    MyString ms1("hello"),ms2("world");
    cout << "+result:" << (ms1 + ms2).getP() << endl;
    ms1 += ms2;
    cout << "+=result:" << ms1.getP() << endl;
    ms1 = ms2;
    cout << "=result:" << ms1.getP() << endl;
    cout << "[]result:" << ms1[0] << endl;

}

#include<iostream>

using namespace std;

class Point{
public:
    Point& operator ++();
    Point operator ++(int);
    Point&operator --();
    Point operator --(int);
    Point(){ _x = _y = 0; }
    int x(){ return _x; }
    int y(){ return _y; }
private:
    int _x, _y;
};
Point& Point::operator ++(){
    _x++;
    _y++;
    return *this;
}
Point Point::operator ++(int){
    Point temp = *this;
    ++*this;
    return temp;
}

Point& Point::operator --(){
    _x--;
    _y--;
    return *this;
}
Point Point::operator --(int){
    Point temp = *this;
    --*this;
    return temp;
}

void main(){
    Point A;
    cout << "A的值为" << A.x() << "," << A.y() << endl;
    A++;
    cout << "A的值为" << A.x() << "," << A.y() << endl;
    ++A;
    cout << "A的值为" << A.x() << "," << A.y() << endl;
    A--;
    cout << "A的值为" << A.x() << "," << A.y() << endl;
    --A;
    cout << "A的值为" << A.x() << "," << A.y() << endl;
    

}

//使用全局函数重载

#include<iostream>
using namespace std;

class Point{
private:
    int x;
    int y;
public:
    Point(int x, int y):x(x),y(y){}
    friend Point& operator+(Point&one,Point& two);
    int getX(){ return x; }
    int getY(){ return y; }
};

Point& operator+(Point&one, Point& two){
    int x = one.x + two.x;
    int y = one.y + two.y;
    return *new Point(x,y);
}

int main(){
    Point p1(1,1),p2(2,2);
    Point& result = p1 + p2;
    cout << result.getX() << ":" << result.getY();
    return 0;
}