Re: [boost] [variant] Please vote for behavior

Subject: Re: [boost] [variant] Please vote for behavior
From: Markus Klein (markus-klein_at_[hidden])
Date: 2013-01-29 16:34:20

On Fri, Jan 25, 2013 at 10:21 AM, Dave Abrahams <dave_at_[hidden]> wrote:

> Yes.  IIUC the question here is whether the invariant of variant [;-)] 
> shall be weakened to accommodate efficient move semantics, thereby 
> breaking some code, or not, at some cost (the specific costs to be 
> incurred by various strategies presently under discussion).

I'm new to this list, so I won't be offended if you correct me on any rookie
mistakes.
Concerning the invariant of variant:
Why not provide a specialization of boost::optional for variant, which
supports move
Semantics? Users who don't want their invariant harmed, can use
boost::variant as is.
Users who need to squeeze out performance could use an optional<variant> and
would
be explicitly aware of the new null state they introduced for this.

Markus
www.clean-cpp.org