几个典型操作符重载例子

//* char operator [] (int i);
 const operator [] (int i) const;

//*     String & operator = (const String &);
 String & operator = (const char *);

//*     friend bool operator < (const String & st,const String & st2);

//*     friend bool operator > (const String & st,const String & st2);

//* friend bool operator == (const String & st,const String & st2);

//*     friend std::ostream & operator << (std::ostream & os,const String & st);

//* friend std::istream & operator >> (std::istream & is,String & st);

///////////////////////////////////////
///////////main.cpp////////////////////
#include <iostream>
#include "strngbad.h"
const int ArSize=10;
const int MaxLen=81;

int main()
{
 using std::cout;
 using std::cin;
 using std::endl;
 String name;
 cout<<"hi,what'your name?\n>>";
 cin>>name;
   
 cout<<name<<",please enter up to "<<ArSize<<" short saying  <empty line to quit>:\n";
 String sayings[ArSize];
 char temp[MaxLen];
 int i;
 for (i=0;i<ArSize;i++)
 {
  cout<<i+1<<": ";
  cin.get(temp,MaxLen);
  while (cin&&cin.get()!='\n')
   continue;
  if(!cin||temp[0]=='\0')
   break;
  else
   sayings[i]=temp;
 }
 int total=i;

 cout<<"here are your sayings:\n";
 for (i=0;i<total;i++)
  cout<<sayings[i][0]<<": "<<sayings[i]<<endl;

 int shortest=0;
 int first=0;
 for (i=1;i<total;i++)
 {
  if(sayings[i].length()<sayings[shortest].length())
   shortest=i;
  if(sayings[i]<sayings[first])
   first=i;
 }

 cout<<"short: "<<sayings[shortest]<<endl;
 cout<<"first: "<<sayings[first]<<endl;
 cout<<String::howmany()<<endl;
 return 0;
}

/////////////////////////////////////////
/////////////////strngbad.h//////////////
#include <iostream>
#ifndef STRNGBAD_H_
#define STRNGBAD_H_

class String
{
private:
 char * str;
 int len;
 static int num_strings;
//  static const int CinLim=80;
    enum {CinLim=80};
public:
 String(const char * s);
 String();
 String(const String &);
 ~String();
 int length()const {return len;}

    String & operator = (const String &);
 String & operator = (const char *);
 char  & operator [] (int i);
 const char & operator [] (int i) const;

    friend bool operator < (const String & st,const String & st2);
 friend bool operator > (const String & st,const String & st2);
 friend bool operator == (const String & st,const String & st2);
 friend std::ostream & operator << (std::ostream & os,const String & st);
 friend std::istream & operator >> (std::istream & is,String & st);

 static int howmany();
};

#endif

 

///////////////////////////////////////////////////////////
//////////////////////////strngbad.cpp/////////////////////
#include <cstring>
#include "strngbad.h"
using std::cout;
using std::cin;

int String::num_strings=0;

String::String(const char * s)
{
 len=strlen(s);
 str=new char [len+1];
 strcpy(str,s);
 num_strings++;
}

String::String()
{
 len=4;
 str=new char [1];
 str[0]='\0';
 num_strings++;
}

String::String(const String & st)
{
 len=st.len;
 str=new char [len+1];
 strcpy(str,st.str);
 num_strings++;
}

String::~String()
{
 --num_strings;
 delete [] str;
}

String & String::operator = (const String & st)
{
 if (this==&st)
  return *this;
 delete [] str;
 len=st.len;
 str=new char [len+1];
 strcpy(str,st.str);
 return *this;
}

String & String::operator = (const char * st)
{
 delete [] str;
 len=strlen(st);
 str=new char [len+1];
 strcpy(str,st);
 return *this;
}

char & String::operator [] (int i)
{
 return str[i];
}

const char & String::operator [] (int i) const
{
 return str[i];
}

bool operator < (const String & st,const String & st2)
{
 return (strcmp(st.str,st2.str)<0);
}

bool operator > (const String & st,const String & st2)
{
 return st2.str<st.str;
}

bool operator == (const String & st,const String & st2)
{
 return (strcmp(st.str,st2.str)==0);
}

std::ostream & operator << (std::ostream & os,const String & st)
{
 os<<st.str;
 return os;
}

std::istream & operator >> (std::istream & is,String & st)
{
 char temp[String::CinLim];
//    char temp[CinLim];
 is.get(temp,String::CinLim);
 if(is)
  st=temp;
 while (is&&is.get()!='\n')
  continue;
 return is;
}

int String::howmany()
{
 return num_strings;
}















/////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////
////////////////////////////////用指针实现///////////////

////////////////////////////////////////////////////////
////////////////main.cpp////////////////////////////////
#include <iostream>
#include <cstdlib>
#include <ctime>
#include "string1.h"
const int ArSize=10;
const int MaxLen=81;
int main()
{
 using std::cout;
 using std::cin;
 using std::endl;
 String name;
 cout<<"hi,what'your name?\n>>";
 cin>>name;
   
 cout<<name<<",please enter up to "<<ArSize<<" short saying  <empty line to quit>:\n";
 String sayings[ArSize];
 char temp[MaxLen];
 int i;
 for (i=0;i<ArSize;i++)
 {
  cout<<i+1<<": ";
  cin.get(temp,MaxLen);
  while (cin&&cin.get()!='\n')
   continue;
  if(!cin||temp[0]=='\0')
   break;
  else
   sayings[i]=temp;
 }
 int total=i;
    if (total>0)
 {
     cout<<"here are your sayings:\n";
     for (i=0;i<total;i++)
   cout<<sayings[i]<<"\n";

  String * shortest=& sayings[0];
  String * first=& sayings[0];
  for (i=1;i<total;i++)
  {
   if (sayings[i].length()<shortest->length())
    shortest=&sayings[i];
   if (sayings[i]<*first)
    first=&sayings[i];
  }
  cout<<"shortest saying: \n"<<*shortest<<endl;
  cout<<"first alphabetically: \n"<<*first<<endl;

  srand(int(time(0)));
  int choice =rand()%total;

  String * favorite=new String (sayings[choice]);
  cout<<"my favorite saying: \n"<<*favorite<<endl;
  delete favorite;
 }
 else
  cout<<"no much to say,eh?\n";
 cout<<"bye.\n";

 return 0;
}