Re: [PATCH 1/2] libstdc++: Implement LWG 3523 changes to ranges::iota_view

[Jonathan Wakely <jwakely@redhat.com>]

On Tue, 19 Oct 2021 at 13:18, Patrick Palka via Libstdc++
<libstdc++@gcc.gnu.org> wrote:
>
> libstdc++-v3/ChangeLog:
>
>         * include/std/ranges (iota_view::_Iterator): Befriend iota_view.
>         (iota_view::_Sentinel): Likewise.
>         (iota_view::iota_view): Add three overloads each taking an
>         iterator/sentinel pair as per LWG 3523.
>         * testsuite/std/ranges/iota/iota_view.cc (test06): New test.

OK for trunk and gcc-11 (after some soak time), thanks.


> ---
>  libstdc++-v3/include/std/ranges               | 21 +++++++++++++++++++
>  .../testsuite/std/ranges/iota/iota_view.cc    | 21 +++++++++++++++++++
>  2 files changed, 42 insertions(+)
>
> diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
> index b8de400dfbb..85f232d8fb9 100644
> --- a/libstdc++-v3/include/std/ranges
> +++ b/libstdc++-v3/include/std/ranges
> @@ -532,6 +532,7 @@ namespace ranges
>        private:
>         _Winc _M_value = _Winc();
>
> +       friend iota_view;
>          friend _Sentinel;
>        };
>
> @@ -568,6 +569,8 @@ namespace ranges
>         operator-(const _Sentinel& __x, const _Iterator& __y)
>           requires sized_sentinel_for<_Bound, _Winc>
>         { return __x._M_distance_from(__y); }
> +
> +       friend iota_view;
>        };
>
>        _Winc _M_value = _Winc();
> @@ -590,6 +593,24 @@ namespace ranges
>           __glibcxx_assert( bool(__value <= __bound) );
>        }
>
> +      constexpr
> +      iota_view(_Iterator __first, _Iterator __last)
> +       requires same_as<_Winc, _Bound>
> +       : iota_view(__first._M_value, __last._M_value)
> +      { }
> +
> +      constexpr
> +      iota_view(_Iterator __first, unreachable_sentinel_t __last)
> +       requires same_as<_Bound, unreachable_sentinel_t>
> +       : iota_view(__first._M_value, __last)
> +      { }
> +
> +      constexpr
> +      iota_view(_Iterator __first, _Sentinel __last)
> +       requires (!same_as<_Winc, _Bound>) && (!same_as<_Bound, unreachable_sentinel_t>)
> +       : iota_view(__first._M_value, __last._M_bound)
> +      { }
> +
>        constexpr _Iterator
>        begin() const { return _Iterator{_M_value}; }
>
> diff --git a/libstdc++-v3/testsuite/std/ranges/iota/iota_view.cc b/libstdc++-v3/testsuite/std/ranges/iota/iota_view.cc
> index 362ef1f7f78..5bebe4be693 100644
> --- a/libstdc++-v3/testsuite/std/ranges/iota/iota_view.cc
> +++ b/libstdc++-v3/testsuite/std/ranges/iota/iota_view.cc
> @@ -18,6 +18,7 @@
>  // { dg-options "-std=gnu++2a" }
>  // { dg-do run { target c++2a } }
>
> +#include <algorithm>
>  #include <ranges>
>  #include <testsuite_hooks.h>
>
> @@ -90,6 +91,25 @@ test05()
>    VERIFY( r.begin() - r.end() == -3 );
>  }
>
> +void
> +test06()
> +{
> +  // Verify LWG 3523 changes.
> +  auto v1 = std::views::iota(0, 5);
> +  auto w1 = decltype(v1)(v1.begin(), v1.end());
> +  VERIFY( std::ranges::equal(v1, w1) );
> +
> +  auto v2 = std::views::iota(0);
> +  auto w2 = decltype(v2)(v2.begin(), v2.end());
> +  static_assert(std::same_as<decltype(w2.end()), std::unreachable_sentinel_t>);
> +  VERIFY( *w2.begin() == 0 );
> +
> +  auto v3 = std::views::iota(0, 5l);
> +  auto w3 = decltype(v3)(v3.begin(), v3.end());
> +  static_assert(!std::ranges::common_range<decltype(w3)>);
> +  VERIFY( std::ranges::equal(v3, w3) );
> +}
> +
>  int
>  main()
>  {
> @@ -98,4 +118,5 @@ main()
>    test03();
>    test04();
>    test05();
> +  test06();
>  }
> --
> 2.33.1.637.gf443b226ca
>