Joao Abecasis wrote:
Fernando Cacciola wrote:
Maybe boost::reference_wrapper can be used internally to wrap reference types and solve this issue.
How?
I was suggesting the use of reference_wrapper to avoid singling out reference types everywhere in the code. The new assignment operators might just work.
Ha, well, optional<> uses make_reference_content<> (from variant<>) so I don't even need to distinguish between reference and non-reference types except were explicitely needed. In fact, the new assignment operators "just work" in this case with no need of special dispatching code.
Anyway, I haven't tested any of this so...
I suggest you document how users may workaround this issue in their code using boost::reference_wrapper/ref/cref. Here's a small snippet you can use. #include <boost/optional.hpp> #include <boost/none.hpp> #include <boost/ref.hpp>
int main() { int a = 32; int b = 1279;
boost::reference_wrapper<int> ra(a);
boost::optional<boost::reference_wrapper<int> > orw1, // default constructor orw2(boost::none), // none_t constructor orw3(ra), // value constructor orw4(boost::ref(a)); // make reference
boost::optional<int &> ori1(orw1), ori2(orw2), ori3(orw3.get());
orw1 = boost::ref(b); }
Best regards,
Nice :-) I can at least tell users how to get the "old" semantics if they really need it. Thank you! Fernando Cacciola