Re: [boost] variant2 never empty guarantees (was: Re: Outcome/expected/etc/etc/etc)

Subject: Re: [boost] variant2 never empty guarantees (was: Re: Outcome/expected/etc/etc/etc)
From: Peter Dimov (lists_at_[hidden])
Date: 2017-06-14 16:21:49

Andrzej Krzemienski wrote:

> If you are not doing double buffering, how can you guarantee that 
> `emplace` is strong? You move the original to the side?

I could do that, but I construct on the side instead and move it into place. 
This is another instance where people may disagree because emplace should as 
a principle always construct in-place. But realistically, construct on the 
side + move is never inferior to move original to the side, construct 
in-place, optionally move original back if constructor throws.