运算符重载
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#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;}
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