I am trying to pass a reference to a two-dimensional array to a function in C++. I know the size of both dimensions at compile time. Here is what I have right now:
const int board_width = 80; const int board_height = 80; void do_something(int[board_width][board_height]& array); //function prototype
But this doesn't work. I get this error from g++:
error: expected ‘,’ or ‘...’ before ‘*’ token
What does this error mean, and how can I fix it?
If you know the size at compile time, this will do it:
//function prototype void do_something(int (&array)[board_width][board_height]);
Doing it with
void do_something(int array[board_width][board_height]);
Will actually pass a pointer to the first sub-array of the two dimensional array ("board_width" is completely ignored, as with the degenerate case of having only one dimension when you have
int array accepting a pointer), which is probably not what you want (because you explicitly asked for a reference). Thus, doing it with the reference, using sizeof on the parameter
sizeof array will yield
sizeof(int[board_width][board_height]) (as if you would do it on the argument itself) while doing it with the second method (declaring the parameter as array, thus making the compiler transform it to a pointer) will yield
sizeof(int(*)[board_height]), thus merely the sizeof of a pointer.