C++: Namespaces — How to use in header and source files correctly?

Question

Consider a pair of two source files: an interface declaration file (*.h or *.hpp) and its implementation file (*.cpp).

Let the

Answer 1

From a code readability standpoint, it is probably better in my opinion to use the #2 method for this reason:

You can be using multiple namespaces at a time, and any object or function written below that line can belong to any of those namespaces (barring naming conflicts). Wrapping the whole file in a namespace block is more explicit, and allows you to declare new functions and variables that belong to that namespace within the .cpp file as well