From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2006-05-04 11:37:51
Ho Jan,
Jan Stetka(e)k dio:
> Yes I understand that I can't use shmem::map and std::map if they are
> both on the global namespace. I've looked at the implementation of the
> std::map header from the STL implementation that is included in vc++ 7.2
> and that doesn't forward declare std::list in <map>. This is a design
> issue rather than a bug. Why forward declare shmem::list by including it
> in map.hpp when it isn't used?
All classes in Shmem include shmem_fwd.hpp or container_fwd.hpp where
Shmem defines default arguments (for example default Less, or Allocator
template parameter). That's why you get the predeclaration of list
including map. Another alternative would be to declare a *_fwd.hpp for
each class defined in Shmem, but you would get a lot of extra headers,
and I would have a lot of work to maintain.
Even if I don't include list predeclaration with map, I'm free to use
any Shmem container in any Shmem class (for example, I can implement a
pooled allocator using a list container), so it's likely that a Shmem
class include will include more Shmem classes (predeclarations, or full
declarations). I don't consider it a design error, but a design choice.
What I see dangerous is pushing two namespaces, std, and shmem to the
same context because they have similar classes. An alternative would be
to rename shmem classes like "vector" to "shmem_vector", .... But
weren't namespaces born to allow that?
Regards,
Ion