Re: [optional] Feedback on the range interface for Boost.Optional

From: Andrzej Krzemienski (akrzemi1_at_[hidden])
Date: 2024-10-05 15:09:09

sob., 5 paź 2024 o 17:02 Steve Downey <sdowney_at_[hidden]> napisał(a):

>
>
> On Sat, Oct 5, 2024, 10:42 Andrzej Krzemienski <akrzemi1_at_[hidden]> wrote:
>
>>
>>
>> czw., 3 paź 2024 o 00:51 Vinnie Falco <vinnie.falco_at_[hidden]>
>> napisał(a):
>>
>>> On Mon, Sep 16, 2024 at 8:32 AM Steve Downey via Boost <
>>> boost_at_[hidden]> wrote:
>>>
>>>> ...
>>>
>>>
>>> For what it is worth, I rather like p3168r2 over the alternative. The
>>> design of ranges seems such that it anticipates an open set of library and
>>> user-defined adaptors, and long pipelines containing many small
>>> transformations to achieve a desired result. The `views::maybe` and
>>> `views::nullable` adaptors look very much like in the spirit of the ranges
>>> design: small, focused algorithms to achieve a specific well-defined
>>> purpose.
>>>
>>> p3168r2 claims that this:
>>>
>>>     // Compute eye colors of 'people'.
>>>     vector<string> eye_colors = people
>>>       | views::transform(&Person::eye_color)
>>>       | views::transform(views::nullable)
>>>       | views::join
>>>       | ranges::to<set>()
>>>       | ranges::to<vector>();
>>>
>>> is worse than this:
>>>
>>>     // Compute eye colors of 'people'.
>>>     vector<string> eye_colors = people
>>>       | views::transform(&Person::eye_color)
>>>       // no extra wrapping necessary
>>>       | views::join
>>>       | ranges::to<set>()
>>>       | ranges::to<vector>();
>>>
>>> I prefer the first one, since the transformation is explicit. p3168r2
>>> suggests that the new syntax is "dramatically more straightforward" which
>>> seems exaggerated to me. It is in fact less straightforward, as now the
>>> reader is expected to know about std::optional's expanded role as a range.
>>>
>>> I'm all for simplicity, but when you choose C++ you are opting in to a
>>> certain minimum level of complexity. views::maybe and views::nullable seem
>>> like just the right level of complexity for C++. A rangeful std::optional
>>> does not do much for me.
>>>
>>
>> Ok, I now have a paper to revert the range interface from Optional:
>> https://isocpp.org/files/papers/D3415R0.html
>>
>> Regards,
>> &rzej;
>>
> I think when you say
> Whether [P2988R7]
> <https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p2988r7.pdf> should
> be added instead, we have no strong opinion.
>
> You mean P1255, view maybe?  P2988 is optional<T&>
>

Indeed. Thank you!

>
> Are you going to be at Wroclaw?
>
Yes.

Regards,
&rzej;