Re: namespace trouble

"Victor Bazarov" <>
Wed, 31 May 2006 11:14:17 -0400
Bruno de Oliveira Schneider wrote:

Victor Bazarov wrote:

If you try referring to 'Transform' inside 'VART::BoundingBox' class,
which 'Transform' would that be? Is that obvious? I am not saying
that you *can't* do that. I am saying that you *shouldn't*.

It seems pretty obvious to me :) Since method names are pointers to

The names are names. Take a look

   struct Blah { operator int() { return 42;} };
   int Blah() { return 73; }

If it were allowed (or accepted), what would this be

   int i = Blah();

? Is that a call to the function Blah or is that an instantiation of
a temporary of type Blah and conversion to int? What value should 'i'

Names become "pointers to code" only if they are used in particular way.
If the compiler cannot distinguish between them, it will complain. Even
if the compiler *can* tell one from the other, are you sure that *you*
know which one it picks? Are you sure everybody else can tell?

they couldn't be where a class/type is expected. However, if you
say its not obvious to the compiler, I'll take it. The method has been
renamed. :)

The point here is not that the compiler can't tell, it's that *you* or
anybody else reading the code can't.

You could prefix it with '::' (meaning in the global namespace).

How do I do that? I tried:
=== begin code ===
namespace VART
   class Transform;
   class BoundingBox {
       friend std::ostream& ::operator<<(std::ostream& output, const
BoundingBox& box);
=== end code ===
But g++ gives me:
error: 'std::ostream& operator<<(std::ostream&, const
VART::BoundingBox&)' should have been declared inside '::'

So, the compiler tells you that you're referring to a function that
has not been declared. So declare it.

I don't get it. The declaration is the problem. I'll be referring to
it in the implementation. If that is not a declaration, then what is

It's a "friend declaration". If you're referring to a qualified name in
a friend declaration, it must be declared prior to that. Add a "normal"
declaration of that function to the global namespace.

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