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From: Patrick Palka <ppalka@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r13-3389] libstdc++: Implement remaining P2474R2 changes to views::take/drop Date: Wed, 19 Oct 2022 19:43:39 +0000 (GMT) [thread overview] Message-ID: <20221019194339.E7BAB3858D3C@sourceware.org> (raw) https://gcc.gnu.org/g:fb4db9bc1c567eaf850e997853d084d0832dd4c1 commit r13-3389-gfb4db9bc1c567eaf850e997853d084d0832dd4c1 Author: Patrick Palka <ppalka@redhat.com> Date: Wed Oct 19 15:43:13 2022 -0400 libstdc++: Implement remaining P2474R2 changes to views::take/drop libstdc++-v3/ChangeLog: * include/std/ranges (views::__detail::__is_repeat_view): Define and later define a partial specialization. (views::__detail::__take_of_repeat_view): Declare and later define. (views::__detail::__drop_of_repeat_view): Likewise. (views::_Take::operator()): Return a repeat_view if the argument is a repeat_view as per P2474R2. (views::_Drop::operator()): Likewise. (repeat_view): Befriend __take/drop_of_repeat_view. * testsuite/std/ranges/repeat/1.cc (test04): New test. Diff: --- libstdc++-v3/include/std/ranges | 56 +++++++++++++++++++++++++++ libstdc++-v3/testsuite/std/ranges/repeat/1.cc | 33 ++++++++++++++++ 2 files changed, 89 insertions(+) diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges index b29264931cc..a55e9e7f760 100644 --- a/libstdc++-v3/include/std/ranges +++ b/libstdc++-v3/include/std/ranges @@ -2257,6 +2257,13 @@ namespace views::__adaptor template<typename _Winc, typename _Bound> inline constexpr bool __is_iota_view<iota_view<_Winc, _Bound>> = true; + template<typename _Range> + inline constexpr bool __is_repeat_view = false; + + template<typename _Range> + constexpr auto + __take_of_repeat_view(_Range&&, range_difference_t<_Range>); // defined later + template<typename _Range, typename _Dp> concept __can_take_view = requires { take_view(std::declval<_Range>(), std::declval<_Dp>()); }; @@ -2291,6 +2298,8 @@ namespace views::__adaptor else return iota_view(*__begin, *__end); } + else if constexpr (__detail::__is_repeat_view<_Tp>) + return __detail::__take_of_repeat_view(std::forward<_Range>(__r), __n); else return take_view(std::forward<_Range>(__r), __n); } @@ -2527,6 +2536,10 @@ namespace views::__adaptor { namespace __detail { + template<typename _Range> + constexpr auto + __drop_of_repeat_view(_Range&&, range_difference_t<_Range>); // defined later + template<typename _Range, typename _Dp> concept __can_drop_view = requires { drop_view(std::declval<_Range>(), std::declval<_Dp>()); }; @@ -2568,6 +2581,8 @@ namespace views::__adaptor else return _Tp(__begin, __end); } + else if constexpr (__detail::__is_repeat_view<_Tp>) + return __detail::__drop_of_repeat_view(std::forward<_Range>(__r), __n); else return drop_view(std::forward<_Range>(__r), __n); } @@ -7367,6 +7382,14 @@ namespace views::__adaptor struct _Iterator; + template<typename _Range> + friend constexpr auto + views::__detail::__take_of_repeat_view(_Range&&, range_difference_t<_Range>); + + template<typename _Range> + friend constexpr auto + views::__detail::__drop_of_repeat_view(_Range&&, range_difference_t<_Range>); + public: repeat_view() requires default_initializable<_Tp> = default; @@ -7540,6 +7563,9 @@ namespace views::__adaptor { namespace __detail { + template<typename _Tp, typename _Bound> + inline constexpr bool __is_repeat_view<repeat_view<_Tp, _Bound>> = true; + template<typename _Tp> concept __can_repeat_view = requires { repeat_view(std::declval<_Tp>()); }; @@ -7565,6 +7591,36 @@ namespace views::__adaptor }; inline constexpr _Repeat repeat; + + namespace __detail + { + template<typename _Range> + constexpr auto + __take_of_repeat_view(_Range&& __r, range_difference_t<_Range> __n) + { + using _Tp = remove_cvref_t<_Range>; + static_assert(__is_repeat_view<_Tp>); + if constexpr (sized_range<_Tp>) + return views::repeat(*__r._M_value, std::min(ranges::distance(__r), __n)); + else + return views::repeat(*__r._M_value, __n); + } + + template<typename _Range> + constexpr auto + __drop_of_repeat_view(_Range&& __r, range_difference_t<_Range> __n) + { + using _Tp = remove_cvref_t<_Range>; + static_assert(__is_repeat_view<_Tp>); + if constexpr (sized_range<_Tp>) + { + auto __sz = ranges::distance(__r); + return views::repeat(*__r._M_value, __sz - std::min(__sz, __n)); + } + else + return __r; + } + } } template<input_range _Vp> diff --git a/libstdc++-v3/testsuite/std/ranges/repeat/1.cc b/libstdc++-v3/testsuite/std/ranges/repeat/1.cc index 3698ed12c14..f9817c99600 100644 --- a/libstdc++-v3/testsuite/std/ranges/repeat/1.cc +++ b/libstdc++-v3/testsuite/std/ranges/repeat/1.cc @@ -84,10 +84,43 @@ test03() return true; } +constexpr bool +test04() +{ + // Verify P2474R2 changes to views::take/drop. + auto r = views::repeat(42); + + auto rt = r | views::take(10); + static_assert(views::__detail::__is_repeat_view<decltype(rt)>); + VERIFY( ranges::equal(rt, views::repeat(42, 10)) ); + + auto rd = r | views::drop(10); + static_assert(std::same_as<decltype(rd), decltype(r)>); + + auto br = views::repeat(42, 37); + + auto brt = br | views::take(10); + static_assert(std::same_as<decltype(brt), decltype(br)>); + VERIFY( ranges::equal(brt, views::repeat(42, 10)) ); + + auto brt100 = br | views::take(100); + VERIFY( ranges::equal(brt100, br) ); + + auto brd = br | views::drop(10); + static_assert(std::same_as<decltype(brd), decltype(br)>); + VERIFY( ranges::equal(brd, views::repeat(42, 27)) ); + + auto brd100 = br | views::drop(100); + VERIFY( ranges::empty(brd100) ); + + return true; +} + int main() { static_assert(test01()); static_assert(test02()); static_assert(test03()); + static_assert(test04()); }
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