Re: [boost] [variant2] documentation request

Subject: Re: [boost] [variant2] documentation request
From: Peter Dimov (lists_at_[hidden])
Date: 2019-03-03 15:17:16

degski wrote:
> On Sun, 3 Mar 2019 at 14:39, Peter Dimov via Boost <boost_at_[hidden]> 
> wrote:
>
> > The behavior of emplace varies depending on a number of things:
> >
> > - whether all types are trivially destructible
> > - whether the variant is single- or double-buffered
> > - whether the type we're constructing is nothrow constructible from the 
> > arguments
> > - whether all contained types are trivially move constructible and move 
> > assignable
> > - and finally, whether, in the single buffered case, we have a monostate 
> > type
>
> Do I need to remember all of the above to correctly use variant2 (and not 
> run into trouble)?

No. The high-level behavior is the same - emplace<i>(args...) replaces the 
currently held value with Ti(args...), and on exception, the variant holds 
"a valid but unspecified value".