On Tuesday, March 4th, 2025 at 9:44 AM, Arthur O'Dwyer via Std-Proposals <std-proposals_at_[hidden]> wrote:

> On Tue, Mar 4, 2025 at 10:01 AM Avi Kivity via Std-Proposals <std-proposals_at_[hidden]> wrote:
>

> > C++ has a literal range type: std::initializer_list. However, its elements are const and so initializing a container from the elements involves a copy.
> >

>

> [...] A suitable proposal in this area should be able to compile
> std::vector<std::unique_ptr<int>> v = { std::make_unique<int>(1), std::make_unique<int>(2) };
> right out of the box. If we aren't enabling people to write that, then we aren't really helping them.


If someone is designing their own container,
a simple rvalue reference to array is usually
enough

   template<size_t N>
vector(T (&&arr)[N]);

    // use
  vector v1({2, 4});
  vector v2({std::make_unique<int>(1), std::make_unique<int>(2)});


https://godbolt.org/z/4fbYc37n6


>

> People can already write: https://godbolt.org/z/4WT1YGxeb
> std::vector<std::unique_ptr<int>> w(
> std::from_range,
> std::array{
> std::make_unique<int>(1),
> std::make_unique<int>(2),
> } | std::views::as_rvalue
> );
> so, anything that requires this general level of ceremony around it isn't worth the bother of standardizing. Simply replacing `std::array{...} | rv::as_rvalue` with `std::ranges::literal{...}` doesn't rise to the occasion.
>

> –Arthur


For standard containers, since the `from_range_t` tag
is already there, we could add an extra `T(&&)[N]` overload
to simplify this down to

    std::vector w( std::from_range,
        {
            std::make_unique<int>(1),
            std::make_unique<int>(2),
        }
    );

--
Zhihao Yuan, ID lichray
The best way to predict the future is to invent it.
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