Bad code in book?

Ok. I'm reading "Programming Roleplaying Games with DirectX" and at the beginning of the book, there's a C++ primer. The code on function overloading seems like nonsense to me.

Prototypes/Definitions:

Code:

long AddNumbers ( long Num1, long Num2 );
long AddNumbers ( long * NumArray, long NumOfNums );

long AddNumbers ( long Num1, long Num2 )
{
     return ( Num1 + Num2 );
}

long AddNumbers ( long * NumArray, long NumOfNums )
{
     long Result, i;

     Result = 0;

     while ( NumOfNums-- )
          Result += NumArray [i];     // Hmm? i was not initialized!

     return Result;
}

In main:

Code:

long Array [5] = { 10, 20, 30, 40, 50 };

Result = AddNumbers ( 10, 20 );
Result = AddNumbers ( Array, 5 );     // Hmm? Shouldn't it be passing an address?

Is this bad code? Or am I seeing wrong?

Also, how could I fix this to pass the entire array? Would I be passing the address of Array?

Originally Posted by Darklighter

In main:

Code:

long Array [5] = { 10, 20, 30, 40, 50 };

Result = AddNumbers ( 10, 20 );
Result = AddNumbers ( Array, 5 );     // Hmm? Shouldn't it be passing an address?

An array name used in an expression becomes the address of the first element.

The code is correct. An array name generally decays into a pointer to the first element.

Code:

int array[3] = {12,13,14};
std::cout << *array << std::endl;

When i'm using the name array alone it is decaying into a pointer to int, pointing to the first element of the array. The * (dereference operator) is getting the value of array. The output of the code will be 12.

Your code is taking advantage of that property of arrays. By passing the name of the array only it is actually passing a pointer to the first element of the array. It is passing a pointer to long. And your function is expecting exactly a pointer to long.

Alright, this explains part of it.

But according to the book, Result should give 150 when passing the array, so shouldn't the function take the whole array and not a pointer to the first element, since it should add up all the elements of the array?

Also, what is i's purpose anyways?

Code:

long AddNumbers ( long * NumArray, long NumOfNums )
{
     long Result, i;

     Result = 0;

     while ( NumOfNums-- )
          Result += NumArray [i];     // Hmm? i was not initialized!

     return Result;
}

You're correct. 'i' needs to be initialized before the loop, and incremented during the loop.

Ah, it all makes sense now! Thanks a lot!

>An array name generally decays into a pointer to the first element.
Why are you people so mean to pointers? They didn't do anything to you.

Originally Posted by Prelude

>An array name generally decays into a pointer to the first element.
Why are you people so mean to pointers? They didn't do anything to you.

C'mon. Everyone should know it's not nice to point.