John Harrison wrote:
[color=blue]
> "glen stark" <mail@nospam.glenstark.org> wrote in message
> news:416beaa3$1@pfaff2.ethz.ch...
>[color=green]
>>Hi.
>>
>>I had an interesting experience with a brand x compiler recently. I had
>>class defined within a namespace, and in that class I declared the "<<"
>>operator as a friend to that class. Then, in the cpp code I implemented
>>the operator overloading within a "using namespace" context, only to get
>>access errers. To get it to work I had to put a namespaceName:: in
>>front of the operator keyword...
>>
>>for your edification, here is a sample code:
>>================
>>HEADER FILE
>>
>>#include <string>
>>#include <ostream>
>>
>>namespace voxel{
>>class PrivateClass{
>>public:
>> PrivateClass():info("hiya"){};
>> friend std::ostream& operator<<(std::ostream&, const PrivateClass&);
>>private:
>> std::string info;
>>};
>>}
>>===================
>>CPP FILE
>>
>>#include "stdafx.h"
>>#include "PrivateClass.h"
>>using namespace voxel;
>>std::ostream& voxel::operator<<(std::ostream& os, const PrivateClass& pc)
>>{
>> os<<pc.info;
>> return os;
>>}
>>
>>int main(int argc, char* argv[])
>>{
>>
>> PrivateClass pc;
>> std::cout<<pc;
>> return 0;
>>
>>}
>>
>>
>>=====end of code
>>
>>So my question is: is this a compiler bug, or is this a loophole in the
>>standard somehow?[/color]
>
>
> Neither, its your understanding of C++ that is wrong.
>
>[color=green]
>>If it's a compiler bug, does the standard imply that
>>it should behave as i would think, or what? I would very much like any
>>clarification you can offer me.[/color]
>
>
> You seem to be assuming that writing 'using namespace voxel;' should put
> subsequent definitions in the voxel namespace but that is not the case (if
> it were the case then you would have put main in the voxel namespace). Or
> maybe you are thinking that the compiler should somehow make a connection
> between the operator<< in your source file and the operator<< in your header
> file, but as far as the compiler is concerned they are just similar
> functions in different namespaces.
>
> 'Using namespace ...' affects how names are looked up, it does not affect
> which namespace names are defined in. The only way to do that is this
>
> namespace voxel
> {
> std::ostream& operator<<(std::ostream& os, const PrivateClass& pc)
> {
> ...
> }
> }
>
> or this
>
> std::ostream& voxel::operator<<(std::ostream& os, const PrivateClass&
> pc)
> {
> ...
> }
>
> john
>
>[/color]
Thanks, that clears it up.
Glen
