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Subject: Re: [std-proposals] explicit class
From: Andrew Tomazos (andrewtomazos_at_[hidden])
Date: 2019-11-11 16:36:42


What are some examples of classes that you would mark explicit? How would
you make the design decision of whether to mark a class as explicit or
not? Or would you recommend marking all of your classes explicit?

On Tue, Nov 12, 2019 at 5:47 AM Steve Weinrich via Std-Proposals <
std-proposals_at_[hidden]> wrote:

> This is an idea that has been roaming around my head for some 20 years!
>
>
>
> As we know, there is a list of some 15 (or so) operations (construction,
> assignment, copy, move, conversion, etc.) that the simple statement: "class
> T {};" defines.
>
>
>
> If one wishes some control over this behavior, one has to be knowledgeable
> in all that the compiler provides. In non-C++ terms, one has to say
> (modern use: =delete), "I don't want that, I don't want this, etc." The
> compiler provides no aid for this!
>
>
>
> My notion is to reverse this via "explicit class T {};". While I am sure
> there are some details that would need to be debated, this would eliminate
> (most) everything that the compiler defines for you. Thus, if you wanted
> something, you would have to define it or use " = default" (yes, I am aware
> that would require extending "= default" to more items - seems OK to me).
> The obvious advantage is that the compiler now provides some help, in that
> using something that is not defined will yield a compiler error.
>
>
>
> Does anyone know if this has been proposed before? If not, what do you
> think?
>
>
>
> Thanks in advance!
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>



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