This is the declaration for the class, the program should take the input a number of no more than 25 numbers. Then the data will be stored in a vector of short int of size 25. Each digit is represented by a single short Int. I have problems Implementing the operator+ function. Can I get any help? Thanks!

#include <iostream>
#include <string>
#include <vector>
using namespace std;

const int MAX_DIGITS = 25;

class CHugeInt
{
public:
CHugeInt( void );
// Postcondition: integer is zero
CHugeInt( int num );
// Postcondition: integer is equal to num
CHugeInt( const string& num );
// Precondition: num contains a valid integer no more than MAX_DIGITS long
// Postcondition: integer is equal to the number represented by num

CHugeInt operator+( const CHugeInt& rInteger ) const;
// Postcondition: the sum of this integer and rInteger has been computed
// and returned
bool operator==( const CHugeInt& rInteger ) const;
// Postcondition: true has been returned if this integer is equal to
// rInteger; otherwise false has been returned
bool operator<( const CHugeInt& rInteger ) const;
// Postcondition: true has been returned if this integer is less than
// rInteger; otherwise false has been returned

friend ostream& operator<<( ostream& outStream, const CHugeInt& hugeInt );
// Postcondition: integer has been printed on screen
friend istream& operator>>( istream& inStream, CHugeInt& hugeInt );
// Postcondition: integer has been read from keyboard

private:
vector< short > m_integer;
};