Why is no qualification necessary?

Question

OK, I\'ll just post the complete program even though it has extraneous stuff and the code in question is the dead code…

#include 
#include         


        

Answer 1

Another observation is that ios_base::openmode works, but ios::openmode does not:

class InFStream
    : public std::ifstream
{
    // ...
    ios::openmode m1;       // error: ios does not name a type
    ios_base::openmode m2;  // ok
}

I think a1ex07 has found the crux of the matter: here again, ios_base is the name of a class, while ios is merely a typedef.

And the difference is that the name of a class is a member of that class (9/2), and so can be looked up as the name of the type in InFStream (3.4.1/7 item 1) as it is a member of a base class of InFStream. But some typedef merely alongside the base class off in some other namespace can't be seen.

[Standard section numbers from C++98.]