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:
You will find them in Red

lb05fa02.C: In function `int main()':
lb05fa02.C:91: no match for `++Date &'
lb05fa02.C:53: candidates are: class Date Date::operator ++(int)there's nothing except an opening brace on line 53. This function starts on line 52.

Any help is appreciated!!

you're trying to pre-increment. I don't believe you can override that.

way to post this thing twice :rolleyes:

Didn't mean to post it twice. i tried several times to submit post and I got this screen that said something about it not going through...and that an email has been sent to technical staff. sorry 'bout that.

Try this :

Code:

---

Date& Date:operator++(Date& date)
{
    day = day+1;
    return *this;
}

---

dog, that's preincrement? cool I should have known there was a way.

No Luck.. the compiler says that the argument has to be of type int. I can't figure out why though

>> No Luck.. the compiler says that the argument has to be of type int. I can't figure out why thoughNo Luck.. the compiler says that the argument has to be of type int. I can't figure out why though

Try changing the declaration of the function in the class as well, not just the definition.

Code:

---

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

---

I tried that Dog.. still comes up with that error. :(

Code:

---

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

---

Change the declaration accordingly.

If I remember correctly, the int in this case doesn't technically mean integer, its just a way for the compiler to know you mean post-increment instead of pre-increment. This has something to do with the creators of all this loved to reuse commands instead of creating new ones. Try writing:

Code:

---

Date& operator++(int);  // defined within the class
 
Date& Date::operator++(int)  // outside the class
{
        day = day + 1;
        return *this;
}

---

If you wanted to to the pre-increment, then just do the same thing but without the int and leave the parenthesis blank. If this still gets an error, try making the function void instead of returning Date.

I'm pretty sure this should work, although can't test it until I get to my computer at home!

PJYelton, you are correct.

Quote:

---

you're trying to pre-increment. I don't believe you can override that.

---

Originally, no.
But now it is possible, the two functions are.

Code:

---

Type& operator ++();      //prefix  ++x
Type  operator ++(int);  //postfix x++

---

Note that the int argument is just syntactic and is not to be used.

Thanks a lot guys... I learned a lot from those comments. I appreciate it... Til next time