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Subject: Re: [boost] [variant] Maintainer
From: Larry Evans (cppljevans_at_[hidden])
Date: 2015-07-14 09:01:45

On 06/28/2015 03:38 AM, Vicente J. Botet Escriba wrote:
> Le 27/06/15 21:32, Agustín K-ballo Bergé a écrit :
>> On 6/27/2015 12:38 PM, Vicente J. Botet Escriba wrote:
>>> I would accept Eggs.Variant without even a review (or with a minimal
>>> review) as an experimental library as part of Boost.Variant after some
>>> minimal adaptation to fit in Boost of course.
> I know that your variant is possibly empty and the C++ standard proposal
> is never-empty, and this makes them different from the user point of
> view. Bjarne S. and Anthony W. are pushing towards a possible empty
> variant, we don't know yet what the std::experimental::variant will be
> and less yet what std::variant will be in C++17.
> boost::variant combined with boost::blanc gives this kind of possibly
> empty variant, but IMHO this is a quite different type.
> template <class ...Ts>
> using optional_variant = boost::variant<boost::blanc, Ts...>; // +/-
> I suggest to name them as
> variant<Ts...> : never-empty

What about variant<>, or is that disallowed?
If it is disallowed, then tuple<> should, I guess, also be disallowed.
FWIW, there was some discussion of the meaning of
variant<> and tuple<> in the haskellforall page:

IOW, maybe:
  variant<> is somewhat like the Zero
  tuple<> is somewhat like the One
in that haskellforall page.

Just thought it interesting, but I've no idea
if Zero or One would be useful in c++.
Anyone have any ideas about how they would be useful?

> optionals<Ts...> : possibly empty
> I believe that the usage of these classes is quite different.

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