C++-DAY(4)-(有元、运算符重载.........)

自己定义myString将能进行重载的运算符全部重载

main.c

#include <iostream>
#include <cstring>

using namespace std;

class myString
{
private:
    char *str;   //记录C风格的字符串
    int size;    //记录字符串的实际长度

public:
    //无参构造
    myString():size(10)
    {
        str = new char[size];  //构造出一个长度为10的字符串
        strcpy(str,"");
    }

    //有参构造
    myString(const char *s)
    {
        size = strlen(s);
        str = new char[size + 1];
        strcpy(str, s);
    }

    //拷贝构造函数
    myString(myString &other):str(new char(*(other.str)))
    {
        size = other.size;
        str = new char[size + 1];
        strcpy(str, other.str);
    }

    //析构函数
    ~myString()
    {
        delete str;
    };

    //判空函数
    bool empty()
    {
        if(strlen(str) == 0)
        {
            return false;
        }
        else
        {
            return true;
        }
    }

    //size函数
    int mysize()
    {
        return size;
    }

    //c_str函数
    char *c_str()
    {
        return str;
    }

    //at函数
    char &at(int pos)
    {
        return str[pos];
    }

    myString &operator = (const myString &other)
    {
        if(this != &other)
        {
            delete []str;
            this -> size = other.size;
            this -> str = new char[size + 1];
            strcpy(this -> str, (other.str));
        }

        return *this;
    }

//=========================================================================
//算数运算符重载

    //“+” 运算
    const myString operator + (const myString &R)const
    {
        myString temp;
        temp.size = this -> size + R.size;
        temp.str = new char[size + 1];
        strcpy(temp.str, this -> str);
        strcat(temp.str, R.str);

        return temp;
    }

    //中括号[]
    char &operator[](int index)
    {
        if(index <= 0 || index >= this -> size)
        return this -> str[index];
    }

    //“==”恒等于
    bool operator == (const myString &R)const
    {
        if(strcmp(this -> str, R.str) == 0)
        {
            return true;
        }
        else
        {
            return false;
        }
    }

    //“>”大于
    bool operator > (const myString &R)const
    {
       if(strcmp(this -> str, R.str) > 0)
       {
           return true;
       }
       else
       {
           return false;
       }
    }

    //“<”小于
    bool operator < (const myString &R)const
    {
        if(strcmp(this -> str, R.str) < 0)
        {
            return true;
        }
        else
        {
            return false;
        }
    }

    //将<<运算符重载函数设置成有元
    friend ostream &operator << (ostream &L, const myString &O);

    //将<<运算符重载函数设置成有元
    friend istream &operator >> (istream &L, const myString &O);


};

//全局函数“<<”
ostream &operator << (ostream &L, const myString &O)
{
    L << O.str << endl;
    return L;
}

//全局函数“>>”
istream &operator >> (istream &L, const myString &O)
{
    L >> O.str;

    cout << O.str << endl;
    return L;
}

int main()
{
   cout << "===================================================" << endl;
   cout << "有参类型" << endl;
   //有参类型
   char s[50] = "";
   cout << "请输入一个字符串：";
   gets(s);
   myString str(s);
   cout << "str = " << str.c_str() << endl;
   cout << "===================================================" << endl;
   cout << endl;
   cout << endl;


   cout << "===================================================" << endl;
   cout << "拷贝构造函数" << endl;
   //拷贝构造函数
   myString str1(str);
   cout << "str1 = " << str1.c_str() << endl;
   cout << "===================================================" << endl;
   cout << endl;
   cout << endl;


   cout << "===================================================" << endl;
   cout << "size函数" << endl;
   //size
   cout << "str_size = " << str.mysize() << endl;
   cout << "===================================================" << endl;
   cout << endl;
   cout << endl;


   cout << "===================================================" << endl;
   cout << "empty判空函数" << endl;
   //empty
   cout << "str_empty = " << str.empty() << endl;
   cout << "===================================================" << endl;
   cout << endl;
   cout << endl;


//   //at函数
//   int n;
//   cout << "请输入要查找字符串的第几位：";
//   cin >> n;
//   int size = strlen(s);
//   if(n < 0 || n > size)
//   {
//       cout << "访问越界" << endl;
//   }
//   cout << "str_at[" << n << "] = " << str.at(n) << endl;


   cout << "===================================================" << endl;
   cout << "构造拷贝赋值函数" << endl;
   //构造拷贝赋值函数
   myString str2(str);
   cout << "str2 = " << str2.c_str() << endl;
   cout << "===================================================" << endl;
   cout << endl;
   cout << endl;


   cout << "===================================================" << endl;
   cout << "“+” 运算" << endl;
   //“+” 运算
   myString str3;
   str3 = str + "  word";
   cout << "str3 = " << str3.c_str() << endl;
   cout << "===================================================" << endl;
   cout << endl;
   cout << endl;

   cout << "===================================================" << endl;
   cout << "“[]”中括号" << endl;
   //“[]”中括号
   str[0] = 'H';
   cout << "str = " << str.c_str() << endl;
   cout << "===================================================" << endl;
   cout << endl;
   cout << endl;


   cout << "===================================================" << endl;
   cout << "“==”恒等于" << endl;
   //“==”恒等于
   if(str == str1)
   {
       cout << "true" << endl;
   }
   else
   {
       cout << "false" << endl;
   }
   cout << "===================================================" << endl;
   cout << endl;
   cout << endl;


   cout << "===================================================" << endl;
   cout << "“>”大于" << endl;
   //“>”大于
   if(str > str1)
   {
       cout << "true" << endl;
   }
   else
   {
       cout << "false" << endl;
   }
   cout << "===================================================" << endl;
   cout << endl;
   cout << endl;


   cout << "===================================================" << endl;
   cout << "“<”小于" << endl;
   //“<”小于
   if(str < str1)
   {
       cout << "true" << endl;
   }
   else
   {
       cout << "false" << endl;
   }
   cout << "===================================================" << endl;
   cout << endl;
   cout << endl;


   cout << "===================================================" << endl;
   cout << "“<<” 输出函数" << endl;
   //“<<” 输出函数
   cout << str;
   cout << "===================================================" << endl;
   cout << endl;
   cout << endl;


   cout << "===================================================" << endl;
   cout << "“>>” 输入函数" << endl;
   //“>>” 输入函数
   cin >> "hello";
   cout << "===================================================" << endl;
   cout << endl;
   cout << endl;

    return 0;
}

结果：