Re: [boost] [variant2] Review of Variant2 started today : April 1 - April 10

Subject: Re: [boost] [variant2] Review of Variant2 started today : April 1 - April 10
From: Robert Ramey (ramey_at_[hidden])
Date: 2019-04-02 14:39:40

On 4/2/19 6:43 AM, Peter Dimov via Boost wrote:
>> Andrey Semashev wrote:
>> > Also, IMHO, it's better to have libraries more focused and fine 
>> grained. > Why not have `expected` as a separate library?
>>
>> expected<T, E...> is basically a variant, with a slightly different 
>> interface.
> 
> To expand on that a bit... to implement expected<T, E...> you need an 
> underlying variant. You can either implement your own ad-hoc one, which 
> is a duplication of work; or you could use an existing variant, but then 
> you inherit its properties and have to reflect those in the 
> specification of `expected`. For instance, if the variant can be 
> valueless, you need to figure out what to do in `expected` when it gets 
> into that state.
> 
> For those reasons, it makes most sense to develop `variant` and 
> `expected` in parallel, as parts of the same library.

I'm thinking more of variant.  Then expected, etc become "use cases" 
rather than first class library types.

Robert Ramey
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