Thread: Operator Overloading...

Hey guys I have this problem where I'm trying to use the "++" operator with objects. I'm new to classes and I don't know exactly where I can find the problem so I'm posting my whole code...

Code:

#include<iomanip.h>


 class Date
 {
 private:
   int month;
   int day;
   int year;
 public:
   Date(int=1,int=1,int=2001);
   Date(long);
   Date(const Date&);
   Date operator++(int);
   void setdate(int, int, int);
   void showdate();
 };


Date::Date(int mm, int dd, int yyyy)
{
  month=mm;
  day=dd;
  year=yyyy;
}


Date::Date(long yyyymmdd)
{ 
  year=int(yyyymmdd/10000);
  month=int((yyyymmdd-year*10000)/100);
  day=int(yyyymmdd-year*10000-month*100);
}





Date::Date(const Date& olddate)
{ 
  month=olddate.month;
  day=olddate.day;
  year=olddate.year;
}

Date Date::operator++(int day)
{
 day=day+1;
 
} 


void Date::setdate(int mm, int dd, int yyyy)
{ 
  month =mm;
  day=dd;
  year=yyyy;
 
  return;
}




void Date::showdate()
{ 
  cout<<setfill('0');
  cout<<setw(2)<<month<<'/'
      <<setw(2)<<day<<'/'
      <<setw(2)<<year<<" ";
}


 main()
{ int i;
 Date d1,d2(03,21,2002);
 Date d3(d1);
 Date d4=d2;
 Date d5(20020507L);
 
 cout<<"Date 1="; d1.showdate();  cout<<"Date 2=";d2.showdate();
 cout<<"Date 3="; d3.showdate();  cout<<"Date 4=";d4.showdate();
 cout<<"Date 5="; d5.showdate();  cout<<endl;
 
 ++d1;/* d2=d2+30; d3++; i=d2-d4; d5=d1;
 
  cout<<"Date 1="<<d1.showdate(); cout<<"Date 2="<<d2.showdate();
  cout<<"Date 3="<<d3.showdate(); cout<<"Date 4="<<d4.showdate();
  cout<<"Date 5="<<d5.showdate(); cout<<endl;
  cout<<"i="<<i<<endl;

  d1--; --d3; d5=20020507L;
 
  if(d1==d3)
    cout<<"Date 1 and Date 3 are equal\n";
  else 
    cout<<"Date 1 and Date 3 are not equal\n";
  
  if(d2>d4)
    cout<<"Date 2 is greater than Date 4\n";
  else
    cout<<"Date 2 is not greater than Date 4\n";
  
  cout<<"Date 1="<<d1.showdate(); cout<<"Date 2="<<d2.showdate();
  cout<<"Date 3="<<d3.showdate(); cout<<"Date 4="<<d4.showdate();
  cout<<"Date 5="<<d5.showdate(); cout<<endl;
 */
 return 0;
}

The compiler gives me these errors:

lb05fa02.C: In function `int main()':
lb05fa02.C:91: no match for `++Date &'
lb05fa02.C:53: candidates are: class Date Date::operator ++(int) line 53 only has an opening brace. The function header is on 52.

Any help is greatly appreciated

I didn't look through the entire code but I do see one problem with your overloaded operator.

Code:

Date Date::operator++(int day)
{
 day=day+1;

}

This is what you have. You clearly say you will return a Date object but yet you have no return statement. Try writing the code like this.

Code:

Date Date::operator++(int day)
{
  day = day + 1; // or ++day;
  return *this;
}

That should work.

Your postfix increment is faulty in several ways.

>Date Date::operator++(int day)
The return value should be const so that you can avoid confusing syntax like

d1++++;

Also, don't name the parameter, that is only there to tell the compiler that you are overloading the postfix operator and not the prefix operator. You also need to return a value. The correct working of the postfix increment operator is to save the old value, increment the current value and then return the old value as a constant:

Code:

const Date Date::operator++ ( int )
{
  const Date old = *this; // Save the old Date

  ++day; // Increment the day

  return old; // return the old Date
}

>++d1;
Here you try to use the prefix increment operator yet you've only implemented the postfix, so this won't work. Change it to

d1++;

And that problem will be fixed.

-Prelude