[Boost-users] standard way to specify undefined values

hi, i have a userdefined type "foobar". it has a special value that means "undefined". is there a standard way to specify which value is undefined? i do not want to use boost::optional here, as foobar itself can be "undefined". you know: class foobar { static const foobar undefined(blablabla); int a,b,c; } but is this "standard"? cya erik -- Erik Thiele