c10-4-3.cpp

这我们老师对是面向对象程序设计（清华大学出版社）一书制作的PPT

#include <iostream>
#include <string>
using namespace std;
class String
 {public:
   String(){p=NULL;}
   String(char *str);
   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;
 };
 
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;
   else
    return false;
  }

bool operator==(String &string1,String &string2)
  {if(strcmp(string1.p,string2.p)==0)
    return true;
   else
    return false;
  }

int main()
{String string1("Hello"),string2("Book"),string3("Computer");
 cout<<(string1>string2)<<endl;
 cout<<(string1<string3)<<endl;
 cout<<(string1==string2)<<endl;
 return 0;
}