C++: Why member function has priority over global function

Question

Why in the next program the member function foo has priority over the global foo although the global one match the type?

#include 
using name         


        

Answer 1

You could think of it as increasing "specialisation" as you move from the global namespace through any nested namespaces around your class, nested classes etc. down to the member functions involved. If you say "foo" in this inner context, a more "specialised" foo can be expected to be more relevant to the caller. Further, if the global one was used preferentially, then someone adding symbols to a less "specialised" scope could break a class that defined a same-named symbol, undoing a lot of the benefits of namespaces and identifier scoping. The basic idea is that your class has a lot of freedom to use meaningful but concise identifiers - which may well be used by other code in your application - but it's only when a meaning for that identifier isn't available in the most local scope that it starts looking further and further afield.