On Wed, Jun 15, 2005 at 12:01:27PM -0400, David Abrahams wrote:
Jonathan Wakely <cow@compsoc.man.ac.uk> writes:
On Wed, Jun 15, 2005 at 10:24:10AM +0200, Thorsten Ottosen wrote:
"David Abrahams" <dave@boost-consulting.com> wrote in message news:uk6kws88y.fsf@boost-consulting.com...
| If someone would clearly and succinctly spell out the question, I'd be | happy to.
should one be able to add, subtract, and compare mutable random access iterators with random access const_iterators provided they point to the same container?
It's not required for any iterator in general (you can't convert all output iterators to input iterators, for instance ostream_iterator cannot be converted to a read-only iterator type).
But the container requirements require that X::iterator be convertible to X::const_iterator, and then all those operations work by using that conversion.
That's incorrect. For example, if the operations are templated no implicit conversion will take place.
That's true, thanks, Dave. Reading it back I've also realised that the last sentence of mine that you quote is ambiguous. I didn't mean to suggest that the container requirements require that those operations use the conversion. The requirement is that X::iterator is convertible to X::const_iterator. The operations _could_ work by using that conversion, but aren't required to. jon -- "I was born not knowing and have had only a little time to change that here and there." - Feynman