reference type of output_iterator_wrapper

[Douglas Gregor]

On Apr 17, 2006, at 3:59 PM, Howard Hinnant wrote:
> Fwiw I suggested the standard do something like this in Berlin and  
> got met with pretty strong opposition (give a non-void  
> iterator_traits to output iterators).

I obviously missed that part of the discussion.

> The standard currently says that value_type and difference_type  
> should be void for output iterators (24.3.1/1).  I think it's a bad  
> rule, and apparently I'm not alone.  But there's an up hill battle  
> in the LWG here.  Packaging it with concepts might help.

Well, the right thing to do with value_type and difference_type for  
output iterators is to say nothing at all about them. void is  
blatantly wrong, because:

	- if it's an output iterator, difference_type must be void
	- if it's a forward iterator, difference_type must be a signed  
integral type
	- every forward iterator is an output iterator
	- but void isn't a signed integral type

Anyway, we'll clean this up with concepts.

	Doug