Thread: Pointer Syntax

I've got a card dealing program and I want to convert all the array syntax into pointer syntax. Whereas in array syntax I would just use the element's subscript (i.e. arr[3] ) in pointer syntax I need to use the address of the first element and add to it the number of bytes of memory I want to move over (i.e. *(arr+3) ). I know this is the long way around but I need a way to do this for a multi-dimensional array.




How can I turn this into pointer syntax?

wDeck[row][column]

Here's some good reading for you to get started with...

Array[X + (Y * MaxX)]

X = column
Y = row
MaxX = Maximum number of columns available

Thank You Magos! I knew that formula existed I just couldn't figure it out. Again thanks!

Originally posted by Magos
Array[X + (Y * MaxX)]

X = column
Y = row
MaxX = Maximum number of columns available

/me winces

did you try compiling this? didn't think so. used with his array wDeck[row][column], this yields a pointer to an integer (NOT an integer) that is out-of-bounds (i.e. not in your memory area). the real answer is here.

and if you're curious, i wasn't 100% sure about my answer either, so i tried compiling it and guess what? it worked.

edit: btw i don't expect anyone to try a test compile before they answer every question, but if you're not quite sure wth you are doing, then, yeah.

Originally posted by Magos
What?

What? It doesn't work! That's what.

edit: apparently the person who asked this question wrote two threads about it (not a good idea), and i'm interchanging information between the two threads. the reason your way doesnt work here is because of the way he's using the array.

Originally posted by monkey_C
OK, wDeck was originally declared in main() as

int deck [4] [13] = {0};

and was passed into the function containing my problematic line as

const int wDeck[][13]

but I still don't see how that's affecting my code. I think I've just been staring at the same line for too long.

check out http://cboard.cprogramming.com/showt...threadid=24797 for the whole dealie. because he's passing it as a two dimensional array, trying to access it as a one dimensional array wont work unless you something like
(&wDeck[0][0])[X + (Y * MaxX)]

or pass a *int in the first place, or do something like hammer outlined. but this is all very redundant and useless. monkeyc, care to elaborate why it must be this way?

Try this:

Code:

myType  wDeck[50][50];    //for arguments sake
myType* temp;

temp = (wDeck + (y * MaxX + x)); //MaxX is a constant

y is the first subscript and x is the second.

so to access element wDeck[1][10]; which is the 61st element, y would be 50, which gives us 50, plus x which is 10, gives us 60,
added to wDeck reveals the 61st element.

I haven't tried it but it look's sound to me.