C++运算符重载实例

本文用C++写两个自定义类的例子，主要练习一下运算符重载。

point类

#include <stdio.h>
#include <iostream>
using namespace std;
class point
{
        public:
                point(int xx, int yy):x(xx), y(yy) {}
                point& operator=(point &a)
                {
                        printf("operator=\n");
                        x = a.x;
                        y = a.y;
                        return *this;
                }
                point operator+(point &a)
                {
                        printf("operator+\n");
                        return point(x+a.x, y+a.y);
                }
                point operator-(point &a)
                {
                        printf("operator-\n");
                        return point(x-a.x, y-a.x);
                }
                point& operator++()
                {
                        printf("operator前++\n");
                        x++;
                        y++;
                        return *this;
                }
                point operator++(int)
                {
                        printf("operator后++\n");
                        point a = *this;
                        x++;
                        y++;
                        return a;
                }
                point& operator--()
                {
                        printf("operator前--\n");
                        x--;
                        y--;
                        return *this;
                }
                point operator--(int)
                {
                        printf("operator后--\n");
                        point a = *this;
                        x--;
                        y--;
                        return a;
                }
                bool operator==(point &a)
                {
                        printf("operator==\n");
                        return x==a.x && y==a.y;
                }
                void show()
                {
                        printf("x=%d,y=%d\n", x, y);
                }
        private:
                int x;
                int y;
};
int main()
{
        point a(3, 4);
        point b(5, 5);
        point c = a + b;
        c.show();
        point d = c;
        d.show();
        ++a;
        a++;
        d = a;
        return 0;
}

String类

#include <iostream>
#include <string.h>
using namespace std;
class String
{
        public:
                String(const char *str = NULL);
                String(const String &other);
                ~String();
                String& operator=(const String &other);
        private:
                char *m_data;
};
String::~String()
{
        cout<<"析构函数"<<endl;
        delete [] m_data;
}
String::String(const char *str)
{
        cout<<"普通构造函数"<<endl;
        if (str == NULL) {
                m_data = new char[1];
                *m_data = 0;
        } else {
                int length = strlen(str);
                m_data = new char[length+1];
                strcpy(m_data, str);
        }
}
String::String(const String &other)
{
        cout<<"拷贝构造函数"<<endl;
        int length = strlen(other.m_data);
        m_data = new char[length+1];
        strcpy(m_data, other.m_data);
}
String& String::operator=(const String &other)
{
        cout<<"赋值函数"<<endl;
        if (this == &other)
                return *this;
        delete [] m_data;
        int length = strlen(other.m_data);
        m_data = new char[length+1];
        strcpy(m_data, other.m_data);
        return *this;
}
int main()
{
        String s1("hello");
        String s2(s1);
        String s3 = s2;
        s3 = s1;
        return 0;
}