Boost C++ Libraries: Ticket #1887: [doc] input_iterator_archetype is not a valid InputIterator

status changed

Dave Abrahams — Thu, 01 May 2008 19:42:49 GMT

status new → assigned

Dave Abrahams — Sat, 28 Nov 2009 17:35:04 GMT

There may be a problem, but it's not quite what you said. Table 72 quite clearly says that the type of *r++ is T, the iterator's value_type.

owner, status changed

Dave Abrahams — Sat, 28 Nov 2009 17:45:23 GMT

owner changed from Dave Abrahams to Eric Niebler
status assigned → new

Well, there's probably a bug in the C++03 standard here. What it actually says, if you read carefully enough, is that *a is required to be convertible to T—where a is any value of type X, the iterator type)—but *r++ is required to be exactly T, where r is of type X&. I'm guessing the strictly correct thing to do in the archetype is something like this:

   T operator*();
   reference operator*() const;

Your thoughts?

attachment set

Eric Niebler — Tue, 20 Sep 2011 19:13:25 GMT

attachment → creating_concepts.patch

owner changed

Eric Niebler — Tue, 20 Sep 2011 19:15:01 GMT

owner changed from Eric Niebler to Dave Abrahams

The bug in the standard has been fixed in C++11. Both *a and *i++ are merely required to convert something convertible to T. So the input_iterator_archetype is correct, and only the docs are wrong. I've attached a patch.