On Tue, Mar 4, 2025 at 10:01 AM Avi Kivity via Std-Proposals <std-proposals@lists.isocpp.org> 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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