Re: [boost] New Library Proposal: dual_state

From: Jost, Andrew (Andrew_Jost_at_[hidden])
Date: 2005-07-11 08:45:37

> -----Original Message-----
> From: boost-bounces_at_[hidden] 
> [mailto:boost-bounces_at_[hidden]] On Behalf Of David Abrahams
> Sent: Monday, July 11, 2005 8:50 PM
> To: boost_at_[hidden]
> Subject: Re: [boost] New Library Proposal: dual_state
> 
> "Jost, Andrew" <Andrew_Jost_at_[hidden]> writes:
> 
> >  > -----Original Message-----
> >> From: boost-bounces_at_[hidden]
> >> [mailto:boost-bounces_at_[hidden]] On Behalf Of David Abrahams
> >> Sent: Sunday, July 10, 2005 10:23 PM
> >> To: boost_at_[hidden]
> >> Subject: Re: [boost] New Library Proposal: dual_state
> >> 
> >> Eelis van der Weegen <gmane_at_[hidden]> writes:
> >> 
> >> > So, in conclusion, the motivation for your dual_state is
> >> very valid,
> >> > but personally I think Boost.Optional is a more 
> appropriate design.
> >> 
> >> IMO the "guaranteed object delivery" feature makes for a useful 
> >> specialization of the Boost.Optional design.  However, it would be 
> >> nice to have both; it's not an alternative to Boost.Optional.
> >
> > I agree.  These are two separate ideas, each with its own utility.
> >
> >> 
> >> There's a lot of resonance with the Boost.Parameter 
> library in here.
> >
> > Where can I find information on Boost.Parameter?
> 
> In the CVS at libs/parameter (new docs in progress at
> libs/parameter/doc) and boost/parameter.  An earlier version 
> of the tutorial docs are at 
> http://cvs.sourceforge.net/viewcvs.py/*checkout*/boost-sandbox
> /boost-sandbox/libs/utility/doc/named_params.html#tutorial

Thanks, I found it.  What a great idea!

> 
> > One additional thought occurred to me.  How does 
> Boost.Optional handle 
> > cases where object construction fails?  I'm not sure how many 
> > approaches exist to the problem of failed constructors, but I think 
> > most programmers agree that constructors should rarely (if ever) be 
> > allowed to throw an exception.
> 
> No, that's approximately 180 degrees away from correct.  
> Bjarne Stroustrup used to recommend it, and it appears that a 
> few people still think it makes sense, but in fact throwing 
> from constructors is a very good idea because it allows us to 
> establish simple class invariants.
> 

Based on several replies, my perception was obviouly outdated.

> --
> Dave Abrahams
> Boost Consulting
> www.boost-consulting.com
> 
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