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关于运算符重载的各种应用，具体看代码注释
MyString.h
#pragma once#includeusing namespace std;//c中没有字符串，字符串类(c风格的字符串)//空串 ""class MyString{ friend ostream& operator<<(ostream &out,MyString &s); //这里是函数运算符重载，之所以用全局而不是用成员函数，是因为第一个操作数无法通过this指针隐士传递，第一个操作数其类型是ostream friend istream& operator>>(istream& in,MyString &s);public: MyString(int len = 0); MyString(const char* p); MyString(const MyString& s); ~MyString();public: //重载=号运算符 MyString& operator=(const char* p); //第一个操作数通过this指针隐式传递 MyString& operator=(const MyString& s); char& operator[](int index);public: //重载 == !== bool operator==(const char *p) const; bool operator==(const MyString &s) const; bool operator!=(const char *p) const; bool operator!=(const MyString& s) const;public: int operator<(const char *p); int operator>(const char *p); int operator<(const MyString &s); int operator>(const MyString& s); //把类的指针露出来public: char* c_str() { return m_p; } const char* c_str2() { return m_p; } int length() { return m_len; }private: int m_len; char* m_p;};
MyString.cpp
#define _CRT_SECURE_NO_WARNINGS#include "MyString.h"ostream& operator<<(ostream& out, MyString& s){ out << s.m_p; return out;}istream& operator>>(istream& in, MyString& s){ cin >> s.m_p; return in;}MyString::MyString(int len){ if (len == 0) { m_len = 0; m_p = new char[m_len+1]; strcpy(m_p, ""); } else { m_len = len; m_p = new char[m_len + 1]; memset(m_p,0,m_len); }}MyString::MyString(const char *p){ if (p == NULL) { m_len = 0; m_p = new char[m_len + 1]; strcpy(m_p, ""); } else { m_len = strlen(p); m_p = new char[m_len + 1]; strcpy(m_p,p); }}//拷贝构造函数MyString::MyString(const MyString& s){ m_len = s.m_len; m_p = new char[m_len+1]; strcpy(m_p,s.m_p);}MyString::~MyString(){ if(m_p!=NULL) { delete[] m_p; m_p = NULL; m_len = 0; }} s4="s2222"MyString& MyString::operator=(const char* p){ //旧内存释放掉 if (m_p != NULL) { delete[] m_p; m_p = NULL; m_len = 0; } if (p == NULL) { m_len = 0; m_p = new char[m_len+1]; strcpy(m_p,""); } else { m_len = strlen(p); m_p = new char[m_len + 1]; strcpy(m_p,p); } return *this;}//s4=s2MyString& MyString::operator=(const MyString& s){ //把旧的内存释放掉 if (m_p != NULL) { delete[] m_p; m_p = NULL; m_len = 0; } if (s == NULL) { m_len = 0; m_p = new char[m_len + 1]; strcpy(m_p,""); } else { m_len = s.m_len; m_p = new char[m_len + 1]; strcpy(m_p, s.m_p); } return *this;} char& MyString::operator[](int index) //注意这里，第一个操作数通过this指针隐式传递，{ return m_p[index];}//if (s2=="s2222222")bool MyString::operator==(const char* p) const{ if (p == NULL) { if (m_len == 0) { return true; } else { return false; } } else { if (m_len == strlen(p)) { return !strcmp(m_p,p); } else { return false; } }}bool MyString::operator!=(const char* p) const{ return !(*this == p);}bool MyString::operator==(const MyString& s) const{ if (m_len != s.m_len) { return false; } return !strcmp(m_p,s.m_p);}bool MyString::operator!=(const MyString& s) const{ return !(*this == s);}//if (s3 < "bbbb")int MyString::operator<(const char* p){ return strcmp(this->m_p, p);}int MyString::operator>(const char* p){ return strcmp(p, this->m_p);}int MyString::operator<(const MyString& s){ return strcmp(this->m_p, s.m_p);}int MyString::operator>(const MyString& s){ return strcmp(s.m_p, m_p);} 测试类：
#define _CRT_SECURE_NO_WARNINGS#includeusing namespace std;#include "MyString.h"void main01(){ MyString s1; MyString s2("s2"); MyString s2_2 = NULL; MyString s3 = s2; MyString s4 = "s4444444444"; //测试运算符重载 和 重载[] //= s4 = s2; s4 = "s2222"; s4[1] = '4'; printf("%c", s4[1]); cout << s4 << endl; //ostream& operator<<(ostream &out, MyString &s) //char& operator[] (int index) //MyString& operator=(const char *p); //MyString& operator=(const MyString &s); cout << "hello..." << endl; system("pause"); return;}void main02(){ MyString s1; MyString s2("s2"); MyString s3 = s2; if (s2 == "aa") { printf("相等"); } else { printf("不相等"); } if (s3 == s2) { printf("相等"); } else { printf("不相等"); }}void main03(){ MyString s1; MyString s2("s2"); MyString s3 = s2; s3 = "aaa"; int tag = (s3 < "bbbb"); if (tag < 0) { printf("s3 小于 bbbb"); } else { printf("s3 大于 bbbb"); } MyString s4 = "aaaaffff"; strcpy(s4.c_str(), "aa111"); //MFC cout << s4 << endl;}void main011(){ MyString s1(128); cout << "\n请输入字符串(回车结束)"; cin >> s1; cout << s1; system("pause");}void main(){ MyString s1(128); cout << "\n请输入字符串(回车结束)"; cin >> s1; cout << s1 << endl; system("pause");}
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