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