Re: Adding optional<T&> find like method to associative containers in boost.

From: Neil Groves (neilgroves_at_[hidden])
Date: 2024-12-17 16:00:31

On Tue, 17 Dec 2024 at 15:51, Vinnie Falco via Boost <boost_at_[hidden]>
wrote:

> On Tue, Dec 17, 2024 at 7:21 AM Andrey Semashev via Boost <
> boost_at_[hidden]> wrote:
>
> > I don't see why it should be limited to unordered containers.
> >
>
> I meant associative, not just unordered. The choices are:
>
>
It doesn't even need to be limited to containers. I think it generalizes to
ranges. Isn't the free function along the lines of auto find_or(Rng&& rng,
Key&& key, Default&& default) ? This works for all containers that allow
the default to be something other than nullopt, which is very useful in
many contexts. Where there are associative containers it can delegate to
the optimal container implementation, but it can fall back to the general
logic of std::ranges::find. A production version would, I assume, have the
projection and other usual range idioms.

> 1. Add a member function to uncountably many existing and future
> associative containers by adding a member function
>
> 2. Write a single, separate free function template which works for all
> existing and future associative containers
>

The free function is clearly the objectively superior solution. This is
fact and is preferred over opinions no matter the authority.

The member function approach is objectively inferior, and has no
compensatory advantage.

>
> If we include all associative containers instead of just the unordered
> ones, the case for a free function is even stronger as the free function
> will work with more types. And the member function would require
> considerably more work (since there are even more containers which have to
> change).
>
> Thanks
>

Neil Groves