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[std-proposals] Fwd: Chaining of the -> operator for std::optional< std::list<T>::iterator >

From: Frederick Virchanza Gotham <cauldwell.thomas_at_[hidden]>
Date: Thu, 25 May 2023 14:32:23 +0100
I will reply to people in series below:

Marcin Jaczewski wrote:
> No, standard should not allow this, reason is simple
> you hide multiple indirections that some could be `nullptr` or empty:
> ```
> std::optional< std::optional<std::string>* > p { nullptr };
> if (p) p->size(); // 2x UB and even if check look correct
> (***p).size(); //easy to see that you need 3 checks

In my code I check that the std::optional object contains a value, and
if it does then the logic of my code is that the iterator is always

But anyway maybe we could have a new operator such as '->>' which
stops when it encounters a nullptr. For example if you do:

    (***p).size(); // undefined behaviour
    p->>size(); // nothing happens

Giuseppe D'Angelo wrote:
> If it's the former, if you actually use any container that yields
> forward iterators, you can just use a value-initialized iterator object
> as "null iterator" https://eel.is/c++draft/forward.iterators#2 . Just
> static_assert that your iterator models forward_iterator.
> If it's the latter, then there's nothing to worry about because
> std::list never invalidates its end() iterator.

I want the code to be generic so that the container can be changed
later. I might end up using

Received on 2023-05-25 13:32:35