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From: Jonathan Wakely <jwakely.gcc@gmail.com>
To: Patrick Palka <ppalka@redhat.com>
Cc: gcc-patches@gcc.gnu.org, libstdc++@gcc.gnu.org
Subject: Re: [PATCH] libstdc++: Implement P2770R0 changes to join_view / join_with_view
Date: Wed, 16 Aug 2023 18:28:31 +0100	[thread overview]
Message-ID: <CAH6eHdTyDjG5SRH_6Sqit4mmZfk+UOXj2iok67=subiffDWheg@mail.gmail.com> (raw)
In-Reply-To: <CAMOnLZbNSZD8kyw28_LqCZ0Chw6rpFah1EbBBFCnTuDyGEUhbA@mail.gmail.com>

On Wed, 16 Aug 2023 at 17:05, Patrick Palka via Libstdc++
<libstdc++@gcc.gnu.org> wrote:
>
> On Mon, Apr 17, 2023 at 9:39 AM Patrick Palka <ppalka@redhat.com> wrote:
> >
> > This C++23 paper fixes a bug in these views when adapting a certain kind
> > of non-forward range, and we treat it as a DR against C++20.
> >
> > Tested on x86_64-pc-linux-gnu, does this look OK for GCC 13?  This
> > is an ABI change for join_view so it'd be unsuitable for backporting
> > later I think :(
>
> Ping, does this look OK for trunk?

Looks like I completely missed this one, sorry.

OK for trunk.


>
> >
> > libstdc++-v3/ChangeLog:
> >
> >         * include/bits/regex.h (regex_iterator::iterator_concept):
> >         Define for C++20 as per P2770R0.
> >         (regex_token_iterator::iterator_concept): Likewise.
> >         * include/std/ranges (__detail::__as_lvalue): Define.
> >         (join_view::_Iterator): Befriend join_view.
> >         (join_view::_Iterator::_M_satisfy): Use _M_get_outer
> >         instead of _M_outer.
> >         (join_view::_Iterator::_M_get_outer): Define.
> >         (join_view::_Iterator::_Iterator): Split constructor taking
> >         _Parent argument into two as per P2770R0.  Remove constraint on
> >         default constructor.
> >         (join_view::_Iterator::_M_outer): Make this data member present
> >         only when the underlying range is forward.
> >         (join_view::_Iterator::operator++): Use _M_get_outer instead of
> >         _M_outer.
> >         (join_view::_Iterator::operator--): Use __as_lvalue helper.
> >         (join_view::_Iterator::operator==): Adjust constraints as per
> >         P2770R0.
> >         (join_view::_Sentinel::__equal): Use _M_get_outer instead of
> >         _M_outer.
> >         (join_view::_M_outer): New data member when the underlying range
> >         is non-forward.
> >         (join_view::begin): Adjust definition as per P2770R0.
> >         (join_view::end): Likewise.
> >         (join_with_view::_M_outer_it): New data member when the
> >         underlying range is non-forward.
> >         (join_with_view::begin): Adjust definition as per P2770R0.
> >         (join_with_view::end): Likewise.
> >         (join_with_view::_Iterator::_M_outer_it): Make this data member
> >         present only when the underlying range is forward.
> >         (join_with_view::_Iterator::_M_get_outer): Define.
> >         (join_with_view::_Iterator::_Iterator): Split constructor
> >         taking _Parent argument into two as per P2770R0.  Remove
> >         constraint on default constructor.
> >         (join_with_view::_Iterator::_M_update_inner): Adjust definition
> >         as per P2770R0.
> >         (join_with_view::_Iterator::_M_get_inner): Likewise.
> >         (join_with_view::_Iterator::_M_satisfy): Adjust calls to
> >         _M_get_inner.  Use _M_get_outer instead of _M_outer_it.
> >         (join_with_view::_Iterator::operator==): Adjust constraints
> >         as per P2770R0.
> >         (join_with_view::_Sentinel::operator==): Use _M_get_outer
> >         instead of _M_outer_it.
> >         * testsuite/std/ranges/adaptors/p2770r0.cc: New test.
> > ---
> >  libstdc++-v3/include/bits/regex.h             |   6 +
> >  libstdc++-v3/include/std/ranges               | 190 +++++++++++++-----
> >  .../testsuite/std/ranges/adaptors/p2770r0.cc  | 110 ++++++++++
> >  3 files changed, 257 insertions(+), 49 deletions(-)
> >  create mode 100644 libstdc++-v3/testsuite/std/ranges/adaptors/p2770r0.cc
> >
> > diff --git a/libstdc++-v3/include/bits/regex.h b/libstdc++-v3/include/bits/regex.h
> > index 26ac6a21c31..2d306868721 100644
> > --- a/libstdc++-v3/include/bits/regex.h
> > +++ b/libstdc++-v3/include/bits/regex.h
> > @@ -2740,6 +2740,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
> >        typedef const value_type*                  pointer;
> >        typedef const value_type&                  reference;
> >        typedef std::forward_iterator_tag          iterator_category;
> > +#if __cplusplus > 201703L
> > +      typedef std::input_iterator_tag    iterator_concept;
> > +#endif
> >
> >        /**
> >         * @brief Provides a singular iterator, useful for indicating
> > @@ -2869,6 +2872,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
> >        typedef const value_type*                        pointer;
> >        typedef const value_type&                        reference;
> >        typedef std::forward_iterator_tag                iterator_category;
> > +#if __cplusplus > 201703L
> > +      typedef std::input_iterator_tag          iterator_concept;
> > +#endif
> >
> >      public:
> >        /**
> > diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
> > index 283d757faa4..ddcf50cc93e 100644
> > --- a/libstdc++-v3/include/std/ranges
> > +++ b/libstdc++-v3/include/std/ranges
> > @@ -2705,6 +2705,14 @@ namespace views::__adaptor
> >      inline constexpr _DropWhile drop_while;
> >    } // namespace views
> >
> > +  namespace __detail
> > +  {
> > +    template<typename _Tp>
> > +      constexpr _Tp&
> > +      __as_lvalue(_Tp&& __t)
> > +      { return static_cast<_Tp&>(__t); }
> > +  } // namespace __detail
> > +
> >    template<input_range _Vp>
> >      requires view<_Vp> && input_range<range_reference_t<_Vp>>
> >      class join_view : public view_interface<join_view<_Vp>>
> > @@ -2767,6 +2775,8 @@ namespace views::__adaptor
> >           using _Parent = __detail::__maybe_const_t<_Const, join_view>;
> >           using _Base = join_view::_Base<_Const>;
> >
> > +         friend join_view;
> > +
> >           static constexpr bool _S_ref_is_glvalue
> >             = join_view::_S_ref_is_glvalue<_Const>;
> >
> > @@ -2780,9 +2790,10 @@ namespace views::__adaptor
> >                 return _M_parent->_M_inner._M_emplace_deref(__x);
> >             };
> >
> > -           for (; _M_outer != ranges::end(_M_parent->_M_base); ++_M_outer)
> > +           _Outer_iter& __outer = _M_get_outer();
> > +           for (; __outer != ranges::end(_M_parent->_M_base); ++__outer)
> >               {
> > -               auto&& __inner = __update_inner(_M_outer);
> > +               auto&& __inner = __update_inner(__outer);
> >                 _M_inner = ranges::begin(__inner);
> >                 if (_M_inner != ranges::end(__inner))
> >                   return;
> > @@ -2811,7 +2822,36 @@ namespace views::__adaptor
> >           using _Outer_iter = join_view::_Outer_iter<_Const>;
> >           using _Inner_iter = join_view::_Inner_iter<_Const>;
> >
> > -         _Outer_iter _M_outer = _Outer_iter();
> > +         constexpr _Outer_iter&
> > +         _M_get_outer()
> > +         {
> > +           if constexpr (forward_range<_Base>)
> > +             return _M_outer;
> > +           else
> > +             return *_M_parent->_M_outer;
> > +         }
> > +
> > +         constexpr const _Outer_iter&
> > +         _M_get_outer() const
> > +         {
> > +           if constexpr (forward_range<_Base>)
> > +             return _M_outer;
> > +           else
> > +             return *_M_parent->_M_outer;
> > +         }
> > +
> > +         constexpr
> > +         _Iterator(_Parent* __parent, _Outer_iter __outer) requires forward_range<_Base>
> > +           : _M_outer(std::move(__outer)), _M_parent(__parent)
> > +         { _M_satisfy(); }
> > +
> > +         constexpr explicit
> > +         _Iterator(_Parent* __parent) requires (!forward_range<_Base>)
> > +           : _M_parent(__parent)
> > +         { _M_satisfy(); }
> > +
> > +         [[no_unique_address]]
> > +           __detail::__maybe_present_t<forward_range<_Base>, _Outer_iter> _M_outer;
> >           optional<_Inner_iter> _M_inner;
> >           _Parent* _M_parent = nullptr;
> >
> > @@ -2823,13 +2863,7 @@ namespace views::__adaptor
> >             = common_type_t<range_difference_t<_Base>,
> >                             range_difference_t<range_reference_t<_Base>>>;
> >
> > -         _Iterator() requires default_initializable<_Outer_iter> = default;
> > -
> > -         constexpr
> > -         _Iterator(_Parent* __parent, _Outer_iter __outer)
> > -           : _M_outer(std::move(__outer)),
> > -             _M_parent(__parent)
> > -         { _M_satisfy(); }
> > +         _Iterator() = default;
> >
> >           constexpr
> >           _Iterator(_Iterator<!_Const> __i)
> > @@ -2857,13 +2891,13 @@ namespace views::__adaptor
> >           {
> >             auto&& __inner_range = [this] () -> auto&& {
> >               if constexpr (_S_ref_is_glvalue)
> > -               return *_M_outer;
> > +               return *_M_get_outer();
> >               else
> >                 return *_M_parent->_M_inner;
> >             }();
> >             if (++*_M_inner == ranges::end(__inner_range))
> >               {
> > -               ++_M_outer;
> > +               ++_M_get_outer();
> >                 _M_satisfy();
> >               }
> >             return *this;
> > @@ -2890,9 +2924,9 @@ namespace views::__adaptor
> >               && common_range<range_reference_t<_Base>>
> >           {
> >             if (_M_outer == ranges::end(_M_parent->_M_base))
> > -             _M_inner = ranges::end(*--_M_outer);
> > -           while (*_M_inner == ranges::begin(*_M_outer))
> > -             *_M_inner = ranges::end(*--_M_outer);
> > +             _M_inner = ranges::end(__detail::__as_lvalue(*--_M_outer));
> > +           while (*_M_inner == ranges::begin(__detail::__as_lvalue(*_M_outer)))
> > +             *_M_inner = ranges::end(__detail::__as_lvalue(*--_M_outer));
> >             --*_M_inner;
> >             return *this;
> >           }
> > @@ -2911,7 +2945,7 @@ namespace views::__adaptor
> >           friend constexpr bool
> >           operator==(const _Iterator& __x, const _Iterator& __y)
> >             requires _S_ref_is_glvalue
> > -             && equality_comparable<_Outer_iter>
> > +             && forward_range<_Base>
> >               && equality_comparable<_Inner_iter>
> >           {
> >             return (__x._M_outer == __y._M_outer
> > @@ -2943,7 +2977,7 @@ namespace views::__adaptor
> >           template<bool _Const2>
> >             constexpr bool
> >             __equal(const _Iterator<_Const2>& __i) const
> > -           { return __i._M_outer == _M_end; }
> > +           { return __i._M_get_outer() == _M_end; }
> >
> >           sentinel_t<_Base> _M_end = sentinel_t<_Base>();
> >
> > @@ -2972,6 +3006,9 @@ namespace views::__adaptor
> >         };
> >
> >        _Vp _M_base = _Vp();
> > +      [[no_unique_address]]
> > +       __detail::__maybe_present_t<!forward_range<_Vp>,
> > +         __detail::__non_propagating_cache<iterator_t<_Vp>>> _M_outer;
> >        [[no_unique_address]]
> >         __detail::__non_propagating_cache<remove_cv_t<_InnerRange>> _M_inner;
> >
> > @@ -2994,16 +3031,25 @@ namespace views::__adaptor
> >        constexpr auto
> >        begin()
> >        {
> > -       constexpr bool __use_const
> > -         = (__detail::__simple_view<_Vp>
> > -            && is_reference_v<range_reference_t<_Vp>>);
> > -       return _Iterator<__use_const>{this, ranges::begin(_M_base)};
> > +       if constexpr (forward_range<_Vp>)
> > +         {
> > +           constexpr bool __use_const
> > +             = (__detail::__simple_view<_Vp>
> > +                && is_reference_v<range_reference_t<_Vp>>);
> > +           return _Iterator<__use_const>{this, ranges::begin(_M_base)};
> > +         }
> > +       else
> > +         {
> > +           _M_outer = ranges::begin(_M_base);
> > +           return _Iterator<false>{this};
> > +         }
> >        }
> >
> >        constexpr auto
> >        begin() const
> > -       requires input_range<const _Vp>
> > +       requires forward_range<const _Vp>
> >           && is_reference_v<range_reference_t<const _Vp>>
> > +         && input_range<range_reference_t<const _Vp>>
> >        {
> >         return _Iterator<true>{this, ranges::begin(_M_base)};
> >        }
> > @@ -3022,11 +3068,11 @@ namespace views::__adaptor
> >
> >        constexpr auto
> >        end() const
> > -       requires input_range<const _Vp>
> > +       requires forward_range<const _Vp>
> >           && is_reference_v<range_reference_t<const _Vp>>
> > +         && input_range<range_reference_t<const _Vp>>
> >        {
> > -       if constexpr (forward_range<const _Vp>
> > -                     && is_reference_v<range_reference_t<const _Vp>>
> > +       if constexpr (is_reference_v<range_reference_t<const _Vp>>
> >                       && forward_range<range_reference_t<const _Vp>>
> >                       && common_range<const _Vp>
> >                       && common_range<range_reference_t<const _Vp>>)
> > @@ -6948,6 +6994,9 @@ namespace views::__adaptor
> >      using _InnerRange = range_reference_t<_Vp>;
> >
> >      _Vp _M_base = _Vp();
> > +    [[no_unique_address]]
> > +      __detail::__maybe_present_t<!forward_range<_Vp>,
> > +       __detail::__non_propagating_cache<iterator_t<_Vp>>> _M_outer_it;
> >      __detail::__non_propagating_cache<remove_cv_t<_InnerRange>> _M_inner;
> >      _Pattern _M_pattern = _Pattern();
> >
> > @@ -7035,16 +7084,25 @@ namespace views::__adaptor
> >      constexpr auto
> >      begin()
> >      {
> > -      constexpr bool __use_const = is_reference_v<_InnerRange>
> > -       && __detail::__simple_view<_Vp> && __detail::__simple_view<_Pattern>;
> > -      return _Iterator<__use_const>{*this, ranges::begin(_M_base)};
> > +      if constexpr (forward_range<_Vp>)
> > +       {
> > +         constexpr bool __use_const = is_reference_v<_InnerRange>
> > +           && __detail::__simple_view<_Vp> && __detail::__simple_view<_Pattern>;
> > +         return _Iterator<__use_const>{*this, ranges::begin(_M_base)};
> > +       }
> > +      else
> > +       {
> > +         _M_outer_it = ranges::begin(_M_base);
> > +         return _Iterator<false>{*this};
> > +       }
> >      }
> >
> >      constexpr auto
> >      begin() const
> > -      requires input_range<const _Vp>
> > +      requires forward_range<const _Vp>
> >         && forward_range<const _Pattern>
> >         && is_reference_v<range_reference_t<const _Vp>>
> > +       && input_range<range_reference_t<const _Vp>>
> >      { return _Iterator<true>{*this, ranges::begin(_M_base)}; }
> >
> >      constexpr auto
> > @@ -7062,13 +7120,13 @@ namespace views::__adaptor
> >
> >      constexpr auto
> >      end() const
> > -      requires input_range<const _Vp>
> > +      requires forward_range<const _Vp>
> >         && forward_range<const _Pattern>
> >         && is_reference_v<range_reference_t<const _Vp>>
> > +       && input_range<range_reference_t<const _Vp>>
> >      {
> >        using _InnerConstRange = range_reference_t<const _Vp>;
> > -      if constexpr (forward_range<const _Vp>
> > -                   && forward_range<_InnerConstRange>
> > +      if constexpr (forward_range<_InnerConstRange>
> >                     && common_range<const _Vp>
> >                     && common_range<_InnerConstRange>)
> >          return _Iterator<true>{*this, ranges::end(_M_base)};
> > @@ -7105,35 +7163,69 @@ namespace views::__adaptor
> >      static constexpr bool _S_ref_is_glvalue = join_with_view::_S_ref_is_glvalue<_Const>;
> >
> >      _Parent* _M_parent = nullptr;
> > -    _OuterIter _M_outer_it = _OuterIter();
> > +    [[no_unique_address]]
> > +      __detail::__maybe_present_t<forward_range<_Base>, _OuterIter> _M_outer_it;
> >      variant<_PatternIter, _InnerIter> _M_inner_it;
> >
> > +    constexpr _OuterIter&
> > +    _M_get_outer()
> > +    {
> > +      if constexpr (forward_range<_Base>)
> > +       return _M_outer_it;
> > +      else
> > +       return *_M_parent->_M_outer_it;
> > +    }
> > +
> > +    constexpr const _OuterIter&
> > +    _M_get_outer() const
> > +    {
> > +      if constexpr (forward_range<_Base>)
> > +       return _M_outer_it;
> > +      else
> > +       return *_M_parent->_M_outer_it;
> > +    }
> > +
> >      constexpr
> > -    _Iterator(_Parent& __parent, iterator_t<_Base> __outer)
> > +    _Iterator(_Parent& __parent, _OuterIter __outer)
> > +      requires forward_range<_Base>
> >      : _M_parent(std::__addressof(__parent)), _M_outer_it(std::move(__outer))
> >      {
> > -      if (_M_outer_it != ranges::end(_M_parent->_M_base))
> > +      if (_M_get_outer() != ranges::end(_M_parent->_M_base))
> > +       {
> > +         auto&& __inner = _M_update_inner();
> > +         _M_inner_it.template emplace<1>(ranges::begin(__inner));
> > +         _M_satisfy();
> > +       }
> > +    }
> > +
> > +    constexpr
> > +    _Iterator(_Parent& __parent)
> > +      requires (!forward_range<_Base>)
> > +    : _M_parent(std::__addressof(__parent))
> > +    {
> > +      if (_M_get_outer() != ranges::end(_M_parent->_M_base))
> >         {
> > -         auto&& __inner = _M_update_inner(_M_outer_it);
> > +         auto&& __inner = _M_update_inner();
> >           _M_inner_it.template emplace<1>(ranges::begin(__inner));
> >           _M_satisfy();
> >         }
> >      }
> >
> > -    constexpr auto&&
> > -    _M_update_inner(const _OuterIter& __x)
> > +    constexpr auto&
> > +    _M_update_inner()
> >      {
> > +      _OuterIter& __outer = _M_get_outer();
> >        if constexpr (_S_ref_is_glvalue)
> > -       return *__x;
> > +       return __detail::__as_lvalue(*__outer);
> >        else
> > -       return _M_parent->_M_inner._M_emplace_deref(__x);
> > +       return _M_parent->_M_inner._M_emplace_deref(__outer);
> >      }
> >
> > -    constexpr auto&&
> > -    _M_get_inner(const _OuterIter& __x)
> > +    constexpr auto&
> > +    _M_get_inner()
> >      {
> >        if constexpr (_S_ref_is_glvalue)
> > -       return *__x;
> > +       return __detail::__as_lvalue(*_M_get_outer());
> >        else
> >         return *_M_parent->_M_inner;
> >      }
> > @@ -7148,16 +7240,16 @@ namespace views::__adaptor
> >               if (std::get<0>(_M_inner_it) != ranges::end(_M_parent->_M_pattern))
> >                 break;
> >
> > -             auto&& __inner = _M_update_inner(_M_outer_it);
> > +             auto&& __inner = _M_update_inner();
> >               _M_inner_it.template emplace<1>(ranges::begin(__inner));
> >             }
> >           else
> >             {
> > -             auto&& __inner = _M_get_inner(_M_outer_it);
> > +             auto&& __inner = _M_get_inner();
> >               if (std::get<1>(_M_inner_it) != ranges::end(__inner))
> >                 break;
> >
> > -             if (++_M_outer_it == ranges::end(_M_parent->_M_base))
> > +             if (++_M_get_outer() == ranges::end(_M_parent->_M_base))
> >                 {
> >                   if constexpr (_S_ref_is_glvalue)
> >                     _M_inner_it.template emplace<0>();
> > @@ -7196,7 +7288,7 @@ namespace views::__adaptor
> >                                           iter_difference_t<_InnerIter>,
> >                                           iter_difference_t<_PatternIter>>;
> >
> > -    _Iterator() requires default_initializable<_OuterIter> = default;
> > +    _Iterator() = default;
> >
> >      constexpr
> >      _Iterator(_Iterator<!_Const> __i)
> > @@ -7306,7 +7398,7 @@ namespace views::__adaptor
> >      friend constexpr bool
> >      operator==(const _Iterator& __x, const _Iterator& __y)
> >        requires _S_ref_is_glvalue
> > -       && equality_comparable<_OuterIter> && equality_comparable<_InnerIter>
> > +       && forward_range<_Base> && equality_comparable<_InnerIter>
> >      { return __x._M_outer_it == __y._M_outer_it && __x._M_inner_it ==__y._M_inner_it; }
> >
> >      friend constexpr common_reference_t<iter_rvalue_reference_t<_InnerIter>,
> > @@ -7373,7 +7465,7 @@ namespace views::__adaptor
> >                             iterator_t<__detail::__maybe_const_t<_OtherConst, _Vp>>>
> >      friend constexpr bool
> >      operator==(const _Iterator<_OtherConst>& __x, const _Sentinel& __y)
> > -    { return __x._M_outer_it == __y._M_end; }
> > +    { return __x._M_get_outer() == __y._M_end; }
> >    };
> >
> >    namespace views
> > diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/p2770r0.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/p2770r0.cc
> > new file mode 100644
> > index 00000000000..15d71b2faa9
> > --- /dev/null
> > +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/p2770r0.cc
> > @@ -0,0 +1,110 @@
> > +// { dg-options "-std=gnu++20" }
> > +// { dg-do run { target c++20 } }
> > +
> > +#include <ranges>
> > +#include <algorithm>
> > +#include <regex>
> > +#include <string_view>
> > +#include <testsuite_hooks.h>
> > +
> > +namespace ranges = std::ranges;
> > +namespace views = std::views;
> > +
> > +void
> > +test01()
> > +{
> > +  // Test case from LWG 3698
> > +  char const text[] = "Hello";
> > +  std::regex regex{"[a-z]"};
> > +
> > +  auto lower
> > +    = ranges::subrange(std::cregex_iterator(ranges::begin(text),
> > +                                           ranges::end(text),
> > +                                           regex),
> > +                      std::cregex_iterator{})
> > +    | views::join
> > +    | views::transform([](auto const& sm) {
> > +      return std::string_view(sm.first, sm.second);
> > +    });
> > +
> > +  VERIFY( ranges::equal(lower, (std::string_view[]){"e", "l", "l", "o"}));
> > +}
> > +
> > +void
> > +test02()
> > +{
> > +#if __cpp_lib_ranges_join_with
> > +  // Analogous test case from LWG 3698 for join_with_view
> > +  char const text[] = "Hello";
> > +  std::regex regex{"[a-z]"};
> > +
> > +  auto lower
> > +    = ranges::subrange(std::cregex_iterator(ranges::begin(text),
> > +                                           ranges::end(text),
> > +                                           regex),
> > +                      std::cregex_iterator{})
> > +    | views::join_with(views::empty<std::sub_match<const char*>>)
> > +    | views::transform([](auto const& sm) {
> > +      return std::string_view(sm.first, sm.second);
> > +    });
> > +
> > +  VERIFY( ranges::equal(lower, (std::string_view[]){"e", "l", "l", "o"}));
> > +#endif
> > +}
> > +
> > +void
> > +test03()
> > +{
> > +  // Test case from LWG 3700
> > +  auto r = views::iota(0, 5) | views::split(1);
> > +  auto s = views::single(r);
> > +  auto j = s | views::join;
> > +  auto f = j.front();
> > +}
> > +
> > +void
> > +test04()
> > +{
> > +#if __cpp_lib_ranges_join_with
> > +  // Analogous test case from LWG 3700 for join_with_view
> > +  auto r = views::iota(0, 5) | views::split(1);
> > +  auto s = views::single(r);
> > +  auto j = s | views::join_with(views::empty<ranges::range_value_t<decltype(r)>>);
> > +  auto f = j.front();
> > +#endif
> > +}
> > +
> > +void
> > +test05()
> > +{
> > +  // Test case from LWG 3791
> > +  std::vector<std::vector<int>> v = {{1}};
> > +  auto r = v
> > +    | views::transform([](auto& x) -> auto&& { return std::move(x); })
> > +    | views::join;
> > +  auto e = --r.end();
> > +}
> > +
> > +void
> > +test06()
> > +{
> > +#if __cpp_lib_ranges_join_with
> > +  // Analogous test case from LWG 3791 for join_with_view
> > +  std::vector<std::vector<int>> v = {{1}};
> > +  auto r = v
> > +    | views::transform([](auto& x) -> auto&& { return std::move(x); })
> > +    | views::join_with(views::empty<int>);
> > +  auto e = --r.end();
> > +#endif
> > +}
> > +
> > +int
> > +main()
> > +{
> > +  test01();
> > +  test02();
> > +  test03();
> > +  test04();
> > +  test05();
> > +  test06();
> > +}
> > --
> > 2.40.0.335.g9857273be0
> >
>

      reply	other threads:[~2023-08-16 17:28 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-04-17 13:39 Patrick Palka
2023-08-16 16:04 ` Patrick Palka
2023-08-16 17:28   ` Jonathan Wakely [this message]

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