运算符重载相关代码

<span style="font-family:Courier New;">#include <iostream>
#include <stdlib.h>
#include <string.h>

using namespace std;

class mystring
{
public:
char *s;
public:
mystring()
{
s = new char[1024];
cout << "mystring" << endl;
}
mystring(const mystring &it)//深拷贝
{
cout << "copy mystring" << endl;
s = new char[1024];
memset(s, 0, 1024);
strcpy(s, it.s);
}

~mystring()
{
cout << "~mystring" << endl;
delete []s;
}

mystring operator =(const mystring &it)//重载了一个=号操作符
{
cout << "= operator" << endl;
memset(s, 0, 1024);
strcpy(s, it.s);
return *this;
}

mystring operator =(const char *str)//重载了一个=号操作符
{
memset(s, 0, 1024);
strcpy(s, str);
return *this;
}

mystring operator =(int i)//重载了一个=号操作符
{
memset(s, 0, 1024);
sprintf(s, "%d", i);
return *this;
}

mystring operator + (const mystring &it)//重载了一个+号操作符
{
strcat(s, it.s);
return *this;
}

mystring operator + (const char *str)//重载了一个+号操作符
{
strcat(s, str);
return *this;
}

void operator +=(const char *str)//
{
strcat(this->s, str);
}

mystring operator + (int i)//重载了一个+号操作符,一元操作符重载
{
char temp[100] = {0};
sprintf(temp, "%d", i);
strcat(s, temp);
return *this;
}
void operator <<(const char *str)//把<<操作符定义为赋值
{
strcpy(s, str);
}

void operator >>(char *str)//把<<操作符定义为赋值
{
strcpy(str, s);
}

mystring operator ++(int)//重载++操作符的函数int参数是固定
{
int len = strlen(s);
for(int i = 0;i < len; i++)
{
s[i]++;//让s的第一个成员char + 1,就是将s[0]对应字符的ASCII码 + 1
}
return *this;
}

void * operator new(size_t size)//如果重载的new，那么必须重载delete
{
//参数size就是sizeof(mystring)的大小.
cout << "size = " << size << endl;
mystring *p = (mystring *)malloc(size);
return p;
}

void * operator new[](size_t size)//如果重载的new，那么必须重载delete
{
//参数size就是sizeof(mystring)的大小 * new[x] + 4个字节.
cout << "size = " << size << endl;
//mystring *p = (mystring *)malloc(size);
return NULL;
}

void operator delete[](void *obj)
{
free((mystring *)obj);
obj = NULL;
}

void operator delete(void *obj)
{
free((mystring *)obj);//不能直接free一个void *；
obj = NULL;//防止野指针
}

bool operator ==(const mystring &it)
{
if (strcmp(s, it.s) == 0)//如果this->s和it的s相同,就返回true
{
return true;
}else
return false;
}

bool operator ==(const char *str)
{
if (strcmp(s, str) == 0)//如果this->s和it的s相同,就返回true
{
return true;
}else
return false;
}

//如果返回的是char，代表的是一个右值，右值是不能直接赋值的，
//如果返回的是char的引用，那么[]就可以当左值使用了
char &operator[](int index)
{
return s[index];
}

void operator ()(const char *str)//重载函数调用操作符
{
strcpy(s, str);
}

void operator ()(int i)
{
sprintf(s, "%d", i);
}

operator int()
{
return atoi(s);
}

friend mystring operator +(const char *str, const mystring &it);

};

bool operator ==(const char *str, const mystring &it)
{
if (strcmp(str, it.s) == 0)
{
return true;
}else
return false;
}

//操作符重载，有一个最基本条件，就是一定有一个一元是一个自定义的C++类
//如果两个都是基本数据类型操作符重载是非法的

mystring operator +(const char *str, const mystring &it)
{
mystring str1;
char buf[1024] = {0};
sprintf(buf, "%s%s", str, it.s);
strcpy(str1.s, buf);
return str1;
}

mystring operator ++(mystring &it)
{
int len = strlen(it.s);
for(int i = 0;i < len; i++)
{
it.s[i]++;//让s的第一个成员char + 1,就是将s[0]对应字符的ASCII码 + 1
}
return it;
}

mystring operator +(int i, const mystring &it)
{
mystring str1;
char buf[1024] = {0};
sprintf(buf, "%d%s", i, it.s);
strcpy(str1.s, buf);
return str1;
}

class Demo
{
public:
Demo()
{

}
};

void test(int i)
{
cout << i << endl;
}

int main()
{
//    mystring str;
//    str << "123";

//    test(str);//导致C++编译器自动的配备int（）操作符

mystring *p = new mystring;
delete p;

//    mystring *p = (mystring *)malloc(sizeof(mystring));
//    free(p);

return 0;
}

int main04()
{
mystring str1;
str1 << "hello";
mystring str2;
str2 << "hello";

if ("hello" == str1)
{
cout << "true" << endl;
}else
{
cout << "fasle" << endl;
}

str1[2] = 'a';

//str1("aaaaaaaa");
str1(10);

cout << str1.s << endl;

return 0;

}

int main03()
{
cout << "mystring size =" << sizeof(mystring) << endl;
mystring str1;
str1 =  "hello";
mystring str2;
str2 = " world";
mystring str3;
//str3 = str1 + str2;//对C++编译器来讲，不能识别两个类+是什么含义
//str3 = str1 + "aaaaaaaaaaaa";
//str3 = str1 + 100;
//str3 = "AAAAA" + str1;
str3 = 100 + str1;
str3 += "BBBBBB";
str3 << "CCCCC";
char buf[1024] = {0};
str3 >> buf;
str2 = str3++;
str2 = ++str3;

mystring *pstr = new mystring;
delete pstr;

cout << str3.s << endl;
return 0;
}

int main01()
{
mystring str1;
strcpy(str1.s, "hello world");
mystring str2;
str2 = str1;//这个过程不是拷贝构造的过程，只是=号操作
//str2.operator =(str1);//和直接写=号是一摸一样的

cout << str2.s << endl;

str2 = "test";//C++编译器不能理解把一个字符串赋给一个类是什么含义

mystring str3;

str3 = str2 = 100;
//str3 = str2.operator =(100);//上一条语句的等效语法

cout << str2.s << endl;

return 0;
}

</span>