Phil Endecott wrote:
I've done some more experiments, and it seems to work with std::pair<const KEY, value&> if i write (*iter).second rather than iter->second.
Looking at the iterator_facade source, operator-> calls operator* and passes the result to operator_arrow_result::make(). This takes its address and, because std::pair<const KEY,VALUE&> is not a reference, it tries to convert it to operator_arrow_proxy<...>. This fails because std::pair<const KEY,VALUE&> is not convertible to std::pair<KEY,VALUE>.
I think I just want operator-> to return a pointer to my reference type, but the operator_arrow_result stuff is trying to do something more complicated. In what case is the operator_arrow_proxy useful? Is there some way to get what I want using iterator_facade? <snip> BTW I have been testing with an oldish version of Boost, but I've looked at the source in svn and it doesn't seem to have changed much.
Cheers, Phil.
(Also looking at the code) operator_array_proxy should be probably be instantiated with the Reference, not ValueType...??? Would that be correct? I.e., operator_array_proxy should wrap a reference (which is not a real C++ reference), not a value... You *could* just overload operator-> in the derived class to do something else (in this case, I would say try using a proxy that wraps a reference). Also, just to be clear, the operator_array_proxy stuff in iterator_facade fails not because std::pair< const KEY, VALUE& > isn't convertible to std::pair< KEY, VALUE >, but because their pointers aren't convertible. At least that's what I'm seeing... Seems like I stumbled on this in the past and rather than figure out what was wrong, I just redefined operator-> in the derived class to work... - Jeff