重载双目运算符

#include<iostream.h>#include<string.h>//using namespace std;class String{public:String(){p=NULL;}//定义默认构造函数String(char *str);//构造函数重载friend bool operator>(String &string1,String &string2);friend bool operator<(String &string1,String &string2);friend bool operator==(String &string1,String &string2);void display();private:char *p;//char型指针，指向字符串};String::String(char *str){p=str;}void String::display(){cout<<p;}bool operator>(String &string1,String &string2){  if(strcmp(string1.p ,string2.p )>0)  {  return true;  }  else     return false;}bool operator<(String &string1,String &string2){if(strcmp(string1.p ,string2.p )<0)return true;elsereturn false;}bool operator==(String &string1,String &string2){  if(strcmp(string1.p ,string2.p )==0)return true;elsereturn false;}void compare(String &string1,String &string2){if(operator>(string1,string2)==1){string1.display();cout<<">";string2.display();}elseif(operator<(string1,string2)==1){          string1.display();cout<<"<";string2.display();}elseif(operator==(string1,string2)==1){              string1.display();       cout<<"=";      string2.display();}cout<<endl;}int main(){String string1("hello"),string2("book"),string3("hello"),string4("computer");    compare(string1,string2);compare(string2,string4);compare(string1,string3);return 0;}