手写C++中string类(编译时多态：运算符重载)

Mystring.h

#ifndef _MYSTRING_H_
#define _MYSTRING_H_
#include<iostream>
using namespace std;
class Mystring
{
    private:
        int m_length;
        char *String;
    public:
        Mystring();
        Mystring(char *s);
        Mystring(const Mystring &s);
        Mystring(int a,char ch);
        friend ostream &operator <<(ostream &out,const Mystring &s);
        friend istream &operator >>(istream &in,Mystring &s);
        char operator [](int index);
        Mystring operator = (const Mystring &s);
        Mystring operator = (char *s);
        Mystring operator + (const Mystring &s);
        Mystring operator +(char *s);
        Mystring operator += (const Mystring &s);
        Mystring operator +=(char *s);
        bool operator ==(const Mystring &s);
        bool operator ==(char *s);
        bool operator !=(const Mystring &s);
        bool operator !=(char *s);
        bool operator >(const Mystring &s);
        bool operator >(char *s);
        bool operator <(const Mystring &s);
        bool operator <(char *s);
        bool operator >=(const Mystring &s);
        bool operator >=(char *s);
        bool operator <=(const Mystring &s);
        bool operator <=(char *s);

        ~Mystring();
};
#endif#ifndef _MYSTRING_H_
#define _MYSTRING_