----- Original Message ----- From: "Peter Dimov" <[EMAIL PROTECTED]> To: "Boost mailing list" <[EMAIL PROTECTED]> Sent: Wednesday, December 11, 2002 2:22 PM Subject: Re: [boost] Formal review: Optional library
> From: "Fernando Cacciola" <[EMAIL PROTECTED]> > [...] > > Conclusion: I will adopt William's reset, leaving operator*() return > > a reference to the optional value *only* if it is initialized > > (independently of whether opt is const or not). > > > > Therefore, the proxy is not needed. And so value() isn't needed either. > > > > (B) > > Since most reviewers wanted it, I will add a safe_bool idiom, which will > > allow > > conditional expressions like: > > > > if ( opt ) > > if ( opt == 0 ) > > if ( opt != 0 ) > > Can you please update the documentation to reflect the changes? I want to > vote on the revised version. ;-) > Yes, but first look at my last post where I show the new interface entirely. If that is more or less OK I'll update the documentation in order to continue with the review. > > However, I'm still unconvinced that uninitialized optionals should compare > > false, > > and even though, you can always compare optional values (via operator*), > so > > I see no benefit in defining relational operators directly (thus these > > operators > > will be poisoned) > > I think that the proposed comparisons make a lot of sense. > Just to make sure I understand what you're saying: Do you agree about having comparisons undefined for optionals directly and only defined for optional values (i.e. *opt1==*opt2)? > > You should consider providing operator<<(std::ostream&, optional), too. > Interesting... The idea is that if the optional is uninitialized, it outputs something like "[NULL]", else forwards to T::operator <<(), right? I agree it is usefull, but I'm not sure if it should be provided by the library itself. A user can define a sort of to_string() with whatever output he wants for uninitialized. Fernando Cacciola _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
