I'm using: Windows 10, C++, Visual Studio 2013.
I'm looking for a way to access my 2D-array with negative numbers, for example I know this works with a 1D-array:
int myarray[35];
#define a (myarray + 50)
a[-45] = 0; //accesses myarray[5]
but can't figure out how to make it work with a 2D-array:
int foo[32][32]
#define bar (foo + 50)(foo + 50)
// The above does not work
You could use the same approach with 2D arrays as defines may have arguments:
int a[100][100];
#define b(x,y) a[x + 50][y + 50]
a[0][0] = 123;
cout << b(-50, -50) << endl; // prints 123
I personally would not like using this define-driven method as this limits the operations you could perform on your array (for example, you can't write b(1) to mean one specific row a[51] or have to define another macro for it).
To improve readability and maintainability, consider writing your own class, based on std::vector:
template<typename T>
class ShiftedVector {
private:
int shift;
std::vector<T> storage;
public:
T& operator[] (int idx) {
return storage[idx + shift];
}
// Definitions of other useful operations
}
ShiftedVector<ShiftedVector<int>> x; // Usage
a[-5]you've done an out of bounds request.(??--5)[array- -!! array] = 123;.