For people using boost, this feature has been available for some time: http://www.boost.org/doc/libs/1_60_0/libs/optional/doc/html/index.html http://www.boost.o

For people using boost, this feature has been available for some time: http://www.boost.org/doc/libs/1_60_0/libs/optional/doc/html/index.html http://www.boost.org/doc/libs/1_60_0/libs/optional/doc/html/...