Overloading operators

Overloading the plus operator

Distance Distance:: operator + (Distance rhs)
{
Distance temp;
temp.feet = feet + rhs.feet;
temp.inches = inches + rhs.inches;
if (temp.inches >=12)
{ temp.inches -=12;
temp.feet++;
}
return temp;
}

Overloading the > operator

Overloading the += operator

Overload the << and >> operators

• This lets you input and output object like basic types

• We would like to be able to say:
cout << d1; or
cin >> d2
instead of call functions to do the I/O

The ostream class

• When we overload the << operator, we must return a reference to an object of type ostream

• If we overload << for the Distance class, it looks like this:

ostream& operator << (ostream& s, Distance& d)
{ s << d.feet << " feet " << d.inches << " inches ";
return s }

• The problem with this is that it must directly access Distance data members, but is not part of the Distance class

– So in the header, we declare it a friend function.

• This enables us to say cout << d1;

Friends

• To do this, you use the keyword friend with the prototype of the function to be declared a friend

• This goes in the header, within the class declaration

• Example:

– friend ostream& operator << (ostream& s,
Distance& d);

• Both classes and functions can be declared friends to a class

The istream class

• When we overload the >> operator, we must return a reference to an object of type istream

• Overloading the >> operator for the Distance class
istream& operator >> (istream& s, Distance& d)
{ cout << " \nEnter feet: " ; s >> d.feet;
cout << " Enter inches: "; s >> d.inches;
return s;
}

• This function must also be declare a friend to the Distance class