On Tue, 16 Jan 2024 at 14:39, Patrick Palka wrote:
>
> Tested on x86_64-pc-linux-gnu, does this look OK for trunk/13?
Oh! I thought this went in as part of the original cartesian_product
commit. I would have asked you to do it at the same time otherwise,
sorry.
Yes, OK for trunk and gcc-13, thanks.
>
> -- >8 --
>
> This paper changes the identity element of views::cartesian_product to
> be a single empty tuple instead of an empty range.
>
> libstdc++-v3/ChangeLog:
>
> * include/std/ranges (views::_CartesianProduct::operator()):
> Adjust identity case as per P2540R1.
> * testsuite/std/ranges/cartesian_product/1.cc (test01):
> Adjust expected result of the identity case.
> ---
> libstdc++-v3/include/std/ranges | 2 +-
> libstdc++-v3/testsuite/std/ranges/cartesian_product/1.cc | 6 +++---
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
> index 3135e6f0c08..7ef835f486a 100644
> --- a/libstdc++-v3/include/std/ranges
> +++ b/libstdc++-v3/include/std/ranges
> @@ -8748,7 +8748,7 @@ namespace views::__adaptor
> operator() [[nodiscard]] (_Ts&&... __ts) const
> {
> if constexpr (sizeof...(_Ts) == 0)
> - return views::empty<tuple<>>;
> + return views::single(tuple{});
> else
> return
> cartesian_product_view<all_t<_Ts>...>(std::forward<_Ts>(__ts)...);
> }
> diff --git a/libstdc++-v3/testsuite/std/ranges/cartesian_product/1.cc
> b/libstdc++-v3/testsuite/std/ranges/cartesian_product/1.cc
> index f69f965c0ce..7281cd8a2f4 100644
> --- a/libstdc++-v3/testsuite/std/ranges/cartesian_product/1.cc
> +++ b/libstdc++-v3/testsuite/std/ranges/cartesian_product/1.cc
> @@ -24,9 +24,9 @@ test01()
> int w[] = {9};
>
> auto v0 = views::cartesian_product();
> - VERIFY( ranges::end(v0) - ranges::begin(v0) == 0 );
> - VERIFY( ranges::size(v0) == 0 );
> - VERIFY( ranges::empty(v0) );
> + VERIFY( ranges::end(v0) - ranges::begin(v0) == 1 );
> + VERIFY( ranges::size(v0) == 1 );
> + VERIFY( !ranges::empty(v0) );
>
> auto v1 = views::cartesian_product(x);
> VERIFY( ranges::end(v1) - ranges::begin(v1) == 3 );
> --
> 2.43.0.334.gd4dbce1db5
>
