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Subject: Re: [boost] Boost.Convert. Take 2.
From: Vladimir Batov (vb.mail.247_at_[hidden])
Date: 2014-02-21 04:31:13

> Andrzej Krzemienski <akrzemi1 <at>> writes:
> ...
> If you added MoveConstructible requirement (I am not saying you should, I
> am just exploring the possibility), you would be probably saying "It also
> works with non-CopyConstructible but MoveConstructible types, but in that
> case there is a limited number of ways Boost.Convert's interface can be
> used." The above example would not work, but the following one should:
> convert<std::string>::from(12345, cnv).value_or("bummer");
> That is, you do not care that a temporary's internal value is moved from.
> But this may not be implementable in C++03. I guess we do not know how to
> emulate rvalue references for *this. However, the following should be easy
> to implement:
> convert<std::string>::from(12345, cnv).value();
> For some background, move semantics obtained a nice language support in
> C++11, but it is also available in C++03 for some extent. This is why we
> have Boost.Move. I will try to add move semantics to Boost.Optional, so
> that you can use it.

RE: convert<>::from().value();

This one is fine as it returns a const reference (unless it throws. So, no
additional requirements whatsoever... right?

RE: MoveConstructible

I do think that your clarifications should be in the docs and Rob's
std::move() deployment in the code. Still, I feel that this sort of detailed
explanations/clarifications/implementation could wait... until we decide if
we want to proceed any further with "convert"... I just do not want our
effort wasted. I hope you understand my hesitation.


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