c++ out of range exception

Question

I'm creating a function which iterates through a grid of points and returns the indices of all adjacent points. For the edge of the grid, there are adjacent points which do not exist, so I have created a few try blocks to handle these cases. Here is the code:

try {
            all_below[j] = Mesh.matrix[r[i]][c[i] - j];
        }
        catch (const std::out_of_range& oor) {
            below = NAN;
            below_k = NAN;
        }

But whenever I try to run the program, the catch statement doesn't catch the exception and the program crashes (because Mesh.matrix is out of range). What am I doing wrong?

Edit:

matrix is a 2D vector of int.

Answer 1

If all_below and Mesh.matrix are arrays then arrays do not throw any exception if you are using an index outside the available range.

And as noted @Mooing Duck the subscript operator of vectors also does not throw an exception. It is member function at() that throws an exception.

Answer 2

std::vector does not throw exceptions on out-of-bounds access using vector's operator [ ]. If you want an exception to be thrown, then use the vector::at() function instead of [ ].

Answer 3

vector<int> vec;
vec.push_back(1);
vec.push_back(2);

try
{
    cout << vec.at(2) << endl;
}
catch (const out_of_range& e)
{
    cerr << e.what() << endl;
}