pt., 21 mar 2025 o 04:20 Jason McKesson via Std-Proposals
<std-proposals_at_[hidden]> napisał(a):
>
> On Thu, Mar 20, 2025 at 12:16 PM Marcin Jaczewski via Std-Proposals
> <std-proposals_at_[hidden]> wrote:
> >
> > Right now the only type that undergoes decaying is C array (aside of
> > refs or bit fields).
> > Some consider this "bad feature" but for me this is more is "bad
> > implementation" of "good feature".
> >
> > I think that many user defined types could benefit from this functionality.
> >
> > Proxy objects:
> > ```
> > std::vector<bool> ff = { false, false };
> > for (auto b : ff)
> > {
> > b = true;
> > }
> > assert(ff[0] == true);
> > ```
>
> I'm confused by this one. Because... it already "works"; it does what
> you seem to want.
>
> The problem is that it *shouldn't*.
>
> The result of doing `operator*` on a `vector<bool>` is not a `bool&`;
> it is a proxy object that acts like a reference to a bool. But since
> we're using `auto` which does not deduce references, `auto b` will
> deduce it as the actual proxy object type. So it's an "object", but
> that object acts like a reference. You can assign a bool to it, and it
> will modify the vector accordingly.
>
> Had this been a `vector<int>`, it wouldn't "work". Which is *actually*
> the behavior we want, because that's how it works for iteration over
> any non-proxy range. If you want to modify the elements of a container
> via ranged-based for, then you should use `auto&&`. If you use values
> instead of references, you should not expect them to work.
>
> And I'm uncomfortable with the idea of trying to allow it to invisibly "work".


I show this as "problem" too, you use `auto` and it updates the vector.
In any other type it would not do that.
All these examples were problems not solutions.


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