Re: [boost] [optional] Safe optional

Subject: Re: [boost] [optional] Safe optional
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2014-11-18 04:36:45

On Tue, Nov 18, 2014 at 12:23 PM, Andrzej Krzemienski
<akrzemi1_at_[hidden]> wrote:
> 2014-11-18 8:00 GMT+01:00 Andrey Semashev <andrey.semashev_at_[hidden]>:
>>
>> So, basically, the proposal is to add visitation API, am I correct?
>
>
> And to remove operator* and get() and value() and get_pointer() - anything
> that could cause UB. And remove implicit conversion from T
>
>> In
>> that case why not add it to the regular optional?
>>
>> IMHO, in order to introduce an alternative component, there should be
>> significant and incompatible design and interface differences between
>> the two. So far I don't see the need for such differences.
>>
>
> As explained above: serious backwards incompatibility. Unacceptable by
> many, including myself.

I see. In this case I agree in that the original optional should
remain the same. However, I don't see much point in such a restricted
subset of the current optional. Just imagining myself using
functions/lambdas instead of get() and similar code makes me dizzy.

IMO, visitation API could be useful for generic code (i.e. which
already uses boost::visit or similar facility and is as such
compatible with boost::variant). It's not a direct replacement for
extraction API (i.e. getters), it's just too cumbersome. I had
realized this when I was working on Boost.Log and ended up with both
interfaces to attribute values - each has its strong and weak sides
and is more useful than the other in some cases.