When implementing operator[] how should I include bounds checking?

Question

First of all I apologize for the long lead up to such a simplistic question.

I am implementing a class which serves as a very long 1 dimensional index on a space fil

Answer 1

Your solution would be nice if you were providing access to the points of an elliptic shape. But it will lead to very nasty bugs if you use it for arbitrary geometric functions, because you knowingly provide a false value.