Question

I actually have 2 questions about the same idea:

I want to create a TruthMatrix class, How can i:

1. allocate a dynamic nXn matrix of bools, is the only way of doing it is as following?:

class TruthMatrix {

        bool **mat;
    public:
        TruthMatrix(int n) {
            mat=new bool*[n];
            for (int i=0;i<n;i++) {
                mat[i]=new bool[n];
            }
        }
    };

1. override the [][] operator for quick access to the matrix elements such in mat[i][j]

Thanks!

Answer 1

1. No, it’s not the only way. You could simulate a matrix with one large array, and you could use STL containers to ease memory management (for one). (Or use dynamic_bitset or similar).

2. It’s probably not worth it. It’s common for matrix classes to be subscripted with operator() because it’s much easier to implement. To do it with several square brackets (akin to arrays of arrays) you need a suitable proxy object to return from your operator[] (do note that there’s no such thing as operator[][]).

Example:

class TruthMatrix {
    /* ... */
    bool& operator()(int row, int column); // usage: matrixobj(1, 2)
};
// or
class TruthMatrix {
     /* ... */
     class Proxy {
         /* ... */
         bool& operator[](int column);
     };
     Proxy operator[](int row); // usage: matrixobj[1][2]
 };