"Joe Gottman" <[EMAIL PROTECTED]> escribió en el mensaje news:[EMAIL PROTECTED] > It would be nice if boost::optional<T> had operator< defined whenever > operator< was defined for T. This would allow us to use optional<T> as the > key of an associative container. I suggest the following semantics: > > bool operator<(optional<T> const &x, optional<T> const &y); > > Returns: If y is uninitialized, false. If y is initialized and x is > uninitialized, true. If x and y are both initialized, (*x < *y). > > > > This results in a strict weak ordering with uninitialized optional<T> > objects being sorted first. > > I don't see any problem introducing this with the given semantic as long as the choice is well documented and a rationale for it is included.
I like the semantic you are proposing, it looks right to me: 'nothing' is always less than 'something' but never less then 'nothing'. I'll try to find some other background on this sort of ordering to see other possible semantics (if any), and if there are any subtelties with this one. If it still looks OK after that, I'll add it. Thank you. Fernando Cacciola _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
