Re: [boost] Should boost have ofind(_if), that returns boost::optional<T&>?

Why not return a pointer/nullptr instead? pfind_if Den sön 3 apr. 2022 21:46Marshall Clow via Boost skrev:

On Mar 22, 2022, at 2:09 PM, Ivan Matek via Boost wrote:

...

Hi, I have been thinking for this for a long time so I wanted to get the feedback from others.

As you probably know better than me there is a bit of a drama https://brevzin.github.io/c++/2021/12/13/optional-ref-ptr/when it

comes

...

to std::optional and from what I see it will not be in C++23 for sure. I believe this gives an opportunity to boost to provide something nice for the users.

Now the issues are the following: AFAIK boost only has old ranges and iterator based algorithms, ideally we would just have something like std:: ranges and add the ofind/ofind_if to those, but AFAIK those do not exist. So I think best thing would be to add it to boost::algorithm < https://github.com/boostorg/algorithm/tree/develop/include/boost/algorithm

. There are further questions like, should boost containers like map/unordered_map gain similar functionality, but I think deciding if we want the general algorithm is the first step.

Another option I can think of is that those algorithms return something like a 0 or 1 element view(so you could access the optional value with range based for loop). This seems weird to me, so I would prefer boost::optional.

There is s a short example on godbolt https://godbolt.org/z/W9K3na9Gc, but don't look at implementation too much, it was just something I hacked quickly, I am mostly interested in in feedback on if functionality would be nice addition to boost.

Personally, I’m not really that enthusiastic about this interface. However, if someone wants to make a PR for boost.Algorithm, I will certainly review it.

— Marshall

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