Thread: class vars checked b4 object needs them?

Take this code for example

Code:

#define upleft  buffer[a-1][b-1]
#define upcent  buffer[a-1][b]
#define upright buffer[a-1][b+1]
#define left    buffer[a][b-1]
#define right   buffer[a][b+1]
#define loleft  buffer[a+1][b-1]
#define locent  buffer[a+1][b]
#define loright buffer[a+1][b+1]

class intertia
{
public:
	double a,b;
	intertia() {a=b=0;}
	void calculate()
	{
		a++;
		if(upleft==1) {b-=.3;}
		if(upright==1) {b+=.3;}
		if(left==1) {b-=.3;}
		if(right==1) {b+=.3;}
		if(loleft==1) {b-=.3;}
		if(loright==1) {b+=.3;}
	}
};

int main()
{
	int buffer[70][70];
	memset(buffer,0,sizeof(buffer));
	intertia inert[70][70];

//...

The compiler complains that it doesn't know the identifier 'buffer'. Yet, the function that calls 'buffer' is not even called. Why would it complain if it doesn't need to use it yet? Buffer is declared by the time any object is constructed...

I suppose the answer to my question is that yes, the class checks to see if it knows variables before any object is even constructed. But could anyone reassure me on that fact? Why is it implemented this way, making the code above have errors?

Thanks a lot for the help