How to safely check arrays bounds

Question

Hi, I am making game of life in 2D array. I need to determine when all adjacent cells are empty so I just test all of them. It works well unless the cell being checked is the boundary. Then of course testing X+1 throws an exception as the index is out of the array boundaries. Can I handle this somehow instead of handling the exception? Thanks

Answer 1

Yes, before accessing the element at index i + 1, check whether i + 1 is strictly inferior to array.Length.

Answer 2

use:

GetLength(0)
GetLength(1)

to get the width and height of the array.

There is also a neat performance trick the runtime uses for it's own bounds checks: casting to unsigned int to make the two checks into one. But of course this costs readability, so only use it if it's really performance critical.

(i>=0)&&(i<length)
becomes
(uint)i<length

Answer 3

If you want speed you'll have to threat the edge-cells differently and process the rest with a

 for(int x = 1; x < Size-1; x++)  // these all have x-1 and x+1 neighbours