运算符重载之数组实例的应用

╰+哭是因爲堅強的太久メ 2023-07-08 15:29 23阅读 0赞

关于运算符重载的各种应用，具体看代码注释

MyString.h

#pragma once
    #include<iostream>
    using 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=s2
    MyString& 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
    #include <iostream>
    using 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");
    
    }