Thread: Counting evens via pointer

Hi Guys

I am trying one of exercises in my book and its asked me to create
an array, pass it to a function and count the number of even numbers
via a pointer.

It compiles but my result is a garbage value? I dont get why as I
have technically assign the value which is a pointer in main to zero.
And I am sure I have dereferenced it correctly.

Code:

// function prototype
void totalEven ( int[], const int, int* );

// main function - driver //////////////////////////////////////////////////////
//
int main ( void )
{
	const int ARRAY_SIZE = 12;
	int total = 0;

	int data[ ARRAY_SIZE ] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 };

	totalEven ( data, ARRAY_SIZE, &total );
	
	std::cin.get(); // freeze console output window
   
        return 0; // retu#rn value from int main
}

// function to count total even numbers
// in the passed array
void totalEven ( int dat[], const int SIZE, int *pNum )
{
	for ( int k = 0; k < SIZE; k += 2 )
	{
		*( pNum )++;
	}

	std::cout << "Total even numbers: " << *pNum
	       << std::endl;
}

I think you want (*pnum)++.

Your current code is just moving away from total by doing pnum++ - the star to dereference it is just causing the compiler to read the location [which it probably optimizes out anyways].

If you step through the compiler, you should see the pnum increment by 4 each time you find an even number, rather than the total value (*pnum) increment by 1.

--
Mats

Thanks matsp. Its working now.