In fact boost::optional examples use default constructor in this case - at least all examples I've seen, see http://www.boost.org/doc/libs/1_58_0/libs/optional/

In fact boost::optional examples use default constructor in this case - at least all examples I've seen, see http://www.boost.org/doc/libs/1_58_0/libs/optional/doc/html/boost_optional/examples.html http://www.boost.org/doc/libs/1_58_0/libs/optional/doc/html/...