On Tue, 16 Jan 2024, Jonathan Wakely wrote:
> 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.
Thanks, and sorry for letting this slip through the cracks. I made
sure to include relevant LWG issue resolutions as part of the original
commit, but I managed to miss this paper.
>
>
> >
> > -- >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
> >
>
>
