RE: [boost] Re: [iterator_facade] postfix ++/--

From: Glen Knowles (gknowles_at_[hidden])
Date: 2004-07-13 14:50:42

> From: David Abrahams
> 
> iterator_facade now has to choose between *r++ = o being 
> valid and being a conforming TR1 input iterator (which 
> requires *r++ is of type T -- we have since declared that a 
> defect and *r++ need only be convertible to T).  It makes 
> that choice by looking at the CategoryOrTraversal parameter: 
> iff it's convertible to std::output_iterator_tag, *r++ = o 
> will be valid.
> 
> I am thinking it might be more appropriate to detect that *r 
> is a proxy, and only make *r++ = o valid in that case.  Can 
> anyone think of a reason that a non-writable iterator 
> implementation would need to return a proxy from its operator*?

I may be confused as what qualifies as a proxy, but there is the
vector<bool> case. OTOH, if you're talking about needing to reach back into
the container its probably fine. I can imagine a caching scheme that returns
a week_ptr and goes back to the container to recreate it if its gone, but I
don't think I'd want to do it. :)

Glen