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From: Patrick Palka <ppalka@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r12-4614] libstdc++: Implement P1739R4 changes to views::take/drop/counted Date: Thu, 21 Oct 2021 15:57:52 +0000 (GMT) [thread overview] Message-ID: <20211021155752.25CB73858405@sourceware.org> (raw) https://gcc.gnu.org/g:9626e44713ac4bd3c8a04ae7e62a77fae7b771e0 commit r12-4614-g9626e44713ac4bd3c8a04ae7e62a77fae7b771e0 Author: Patrick Palka <ppalka@redhat.com> Date: Thu Oct 21 11:55:16 2021 -0400 libstdc++: Implement P1739R4 changes to views::take/drop/counted This implements P1739R4 along with the resolution for LWG 3407 which corrects the paper's wording. libstdc++-v3/ChangeLog: * include/bits/ranges_util.h (views::_Drop): Forward declare. (subrange): Befriend views::_Drop. (subrange::_S_store_size): Declare constexpr instead of just const, remove obsolete comment. * include/std/ranges (views::__detail::__is_empty_view): Define. (views::__detail::__is_basic_string_view): Likewise. (views::__detail::__is_subrange): Likewise. (views::__detail::__is_iota_view): Likewise. (views::__detail::__can_take_view): Rename template parm _Tp to _Dp. (views::_Take): Rename template parm _Tp to _Dp, make it non-deducible and fix it to range_difference_t<_Range>. Implement P1739R4 and LWG 3407 changes. (views::__detail::__can_drop_view): Rename template parm _Tp to _Dp. (views::_Drop): As with views::_Take. (views::_Counted): Implement P1739R4 changes. * include/std/span (__detail::__is_std_span): Rename to ... (__detail::__is_span): ... this and turn it into a variable template. (__detail::__is_std_array): Turn it into a variable template. (span::span): Adjust uses of __is_std_span and __is_std_array accordingly. * testsuite/std/ranges/adaptors/p1739.cc: New test. Diff: --- libstdc++-v3/include/bits/ranges_util.h | 7 +- libstdc++-v3/include/std/ranges | 107 ++++++++++++++++++--- libstdc++-v3/include/std/span | 12 +-- .../testsuite/std/ranges/adaptors/p1739.cc | 88 +++++++++++++++++ 4 files changed, 193 insertions(+), 21 deletions(-) diff --git a/libstdc++-v3/include/bits/ranges_util.h b/libstdc++-v3/include/bits/ranges_util.h index a52b8fc8f54..060e665d8db 100644 --- a/libstdc++-v3/include/bits/ranges_util.h +++ b/libstdc++-v3/include/bits/ranges_util.h @@ -216,6 +216,8 @@ namespace ranges } // namespace __detail + namespace views { struct _Drop; } // defined in <ranges> + enum class subrange_kind : bool { unsized, sized }; /// The ranges::subrange class template @@ -226,10 +228,11 @@ namespace ranges class subrange : public view_interface<subrange<_It, _Sent, _Kind>> { private: - // XXX: gcc complains when using constexpr here - static const bool _S_store_size + static constexpr bool _S_store_size = _Kind == subrange_kind::sized && !sized_sentinel_for<_Sent, _It>; + friend struct views::_Drop; // Needs to inspect _S_store_size. + _It _M_begin = _It(); [[no_unique_address]] _Sent _M_end = _Sent(); diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges index 30ba0606869..d6bb78c09f9 100644 --- a/libstdc++-v3/include/std/ranges +++ b/libstdc++-v3/include/std/ranges @@ -42,6 +42,7 @@ #include <initializer_list> #include <iterator> #include <optional> +#include <span> #include <tuple> #include <bits/ranges_util.h> #include <bits/refwrap.h> @@ -2125,19 +2126,67 @@ namespace views::__adaptor { namespace __detail { - template<typename _Range, typename _Tp> + template<typename _Range> + inline constexpr bool __is_empty_view = false; + + template<typename _Tp> + inline constexpr bool __is_empty_view<empty_view<_Tp>> = true; + + template<typename _Range> + inline constexpr bool __is_basic_string_view = false; + + template<typename _CharT, typename _Traits> + inline constexpr bool __is_basic_string_view<basic_string_view<_CharT, _Traits>> + = true; + + template<typename _Range> + inline constexpr bool __is_subrange = false; + + template<typename _Iter, typename _Sent, subrange_kind _Kind> + inline constexpr bool __is_subrange<subrange<_Iter, _Sent, _Kind>> = true; + + template<typename _Range> + inline constexpr bool __is_iota_view = false; + + template<typename _Winc, typename _Bound> + inline constexpr bool __is_iota_view<iota_view<_Winc, _Bound>> = true; + + template<typename _Range, typename _Dp> concept __can_take_view - = requires { take_view(std::declval<_Range>(), std::declval<_Tp>()); }; + = requires { take_view(std::declval<_Range>(), std::declval<_Dp>()); }; } // namespace __detail struct _Take : __adaptor::_RangeAdaptor<_Take> { - template<viewable_range _Range, typename _Tp> - requires __detail::__can_take_view<_Range, _Tp> + template<viewable_range _Range, typename _Dp = range_difference_t<_Range>> + requires __detail::__can_take_view<_Range, _Dp> constexpr auto - operator() [[nodiscard]] (_Range&& __r, _Tp&& __n) const + operator() [[nodiscard]] (_Range&& __r, type_identity_t<_Dp> __n) const { - return take_view(std::forward<_Range>(__r), std::forward<_Tp>(__n)); + using _Tp = remove_cvref_t<_Range>; + if constexpr (__detail::__is_empty_view<_Tp>) + return _Tp(); + else if constexpr (random_access_range<_Tp> + && sized_range<_Tp> + && (std::__detail::__is_span<_Tp> + || __detail::__is_basic_string_view<_Tp> + || __detail::__is_subrange<_Tp> + || __detail::__is_iota_view<_Tp>)) + { + __n = std::min<_Dp>(ranges::distance(__r), __n); + auto __begin = ranges::begin(__r); + auto __end = __begin + __n; + if constexpr (std::__detail::__is_span<_Tp>) + return span<typename _Tp::element_type>(__begin, __end); + else if constexpr (__detail::__is_basic_string_view<_Tp>) + return _Tp(__begin, __end); + else if constexpr (__detail::__is_subrange<_Tp>) + return subrange<iterator_t<_Tp>>(__begin, __end); + else + return iota_view(*__begin, *__end); + } + else + return take_view(std::forward<_Range>(__r), __n); } using _RangeAdaptor<_Take>::operator(); @@ -2372,19 +2421,49 @@ namespace views::__adaptor { namespace __detail { - template<typename _Range, typename _Tp> + template<typename _Range, typename _Dp> concept __can_drop_view - = requires { drop_view(std::declval<_Range>(), std::declval<_Tp>()); }; + = requires { drop_view(std::declval<_Range>(), std::declval<_Dp>()); }; } // namespace __detail struct _Drop : __adaptor::_RangeAdaptor<_Drop> { - template<viewable_range _Range, typename _Tp> - requires __detail::__can_drop_view<_Range, _Tp> + template<viewable_range _Range, typename _Dp = range_difference_t<_Range>> + requires __detail::__can_drop_view<_Range, _Dp> constexpr auto - operator() [[nodiscard]] (_Range&& __r, _Tp&& __n) const + operator() [[nodiscard]] (_Range&& __r, type_identity_t<_Dp> __n) const { - return drop_view(std::forward<_Range>(__r), std::forward<_Tp>(__n)); + using _Tp = remove_cvref_t<_Range>; + if constexpr (__detail::__is_empty_view<_Tp>) + return _Tp(); + else if constexpr (random_access_range<_Tp> + && sized_range<_Tp> + && (std::__detail::__is_span<_Tp> + || __detail::__is_basic_string_view<_Tp> + || __detail::__is_iota_view<_Tp> + || __detail::__is_subrange<_Tp>)) + { + __n = std::min<_Dp>(ranges::distance(__r), __n); + auto __begin = ranges::begin(__r) + __n; + auto __end = ranges::end(__r); + if constexpr (std::__detail::__is_span<_Tp>) + return span<typename _Tp::element_type>(__begin, __end); + else if constexpr (__detail::__is_subrange<_Tp>) + { + if constexpr (_Tp::_S_store_size) + { + using ranges::__detail::__to_unsigned_like; + auto __m = ranges::distance(__r) - __n; + return _Tp(__begin, __end, __to_unsigned_like(__m)); + } + else + return _Tp(__begin, __end); + } + else + return _Tp(__begin, __end); + } + else + return drop_view(std::forward<_Range>(__r), __n); } using _RangeAdaptor<_Drop>::operator(); @@ -3519,7 +3598,9 @@ namespace views::__adaptor constexpr auto operator() [[nodiscard]] (_Iter __i, iter_difference_t<_Iter> __n) const { - if constexpr (random_access_iterator<_Iter>) + if constexpr (contiguous_iterator<_Iter>) + return span(std::__to_address(__i), __n); + else if constexpr (random_access_iterator<_Iter>) return subrange(__i, __i + __n); else return subrange(counted_iterator(std::move(__i), __n), diff --git a/libstdc++-v3/include/std/span b/libstdc++-v3/include/std/span index af0d24b29f2..61824dee845 100644 --- a/libstdc++-v3/include/std/span +++ b/libstdc++-v3/include/std/span @@ -58,16 +58,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION namespace __detail { template<typename _Tp> - struct __is_std_span : false_type { }; + inline constexpr bool __is_span = false; template<typename _Tp, size_t _Num> - struct __is_std_span<span<_Tp, _Num>> : true_type { }; + inline constexpr bool __is_span<span<_Tp, _Num>> = true; template<typename _Tp> - struct __is_std_array : false_type { }; + inline constexpr bool __is_std_array = false; template<typename _Tp, size_t _Num> - struct __is_std_array<std::array<_Tp, _Num>> : true_type { }; + inline constexpr bool __is_std_array<std::array<_Tp, _Num>> = true; template<size_t _Extent> class __extent_storage @@ -203,8 +203,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template<typename _Range> requires ranges::contiguous_range<_Range> && ranges::sized_range<_Range> && (ranges::borrowed_range<_Range> || is_const_v<element_type>) - && (!__detail::__is_std_span<remove_cvref_t<_Range>>::value) - && (!__detail::__is_std_array<remove_cvref_t<_Range>>::value) + && (!__detail::__is_span<remove_cvref_t<_Range>>) + && (!__detail::__is_std_array<remove_cvref_t<_Range>>) && (!is_array_v<remove_cvref_t<_Range>>) && __is_compatible_ref<ranges::range_reference_t<_Range>>::value constexpr explicit(extent != dynamic_extent) diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/p1739.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/p1739.cc new file mode 100644 index 00000000000..3e51aa01796 --- /dev/null +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/p1739.cc @@ -0,0 +1,88 @@ +// { dg-options "-std=gnu++20" } +// { dg-do run { target c++20 } } + +#include <algorithm> +#include <ranges> +#include <testsuite_hooks.h> + +// Verify P1739R4 (and LWG 3407) changes to views::take/drop/counted. + +namespace ranges = std::ranges; +namespace views = ranges::views; + +void +test01() +{ + ranges::empty_view<int> v; + using ty = decltype(v); + using ty = decltype(views::take(v, 42)); + using ty = decltype(views::drop(v, 42)); +} + +void +test02() +{ + int x[] = {1,2,3,4,5}; + std::span r(x, x+5); + using ty = decltype(r); + + std::same_as<ty> auto v1 = views::take(r, 2); + VERIFY( ranges::equal(v1, (int[]){1,2}) ); + + std::same_as<ty> auto v2 = views::drop(r, 3); + VERIFY( ranges::equal(v2, (int[]){4,5}) ); + + std::same_as<ty> auto v3 = views::counted(r.begin(), 4); + VERIFY( ranges::equal(v3, (int[]){1,2,3,4}) ); +} + +void +test03() +{ + using namespace std::literals; + std::string_view r = "hello world"sv; + using ty = decltype(r); + + std::same_as<ty> auto v1 = views::take(r, 5); + VERIFY( ranges::equal(v1, "hello"sv) ); + + std::same_as<ty> auto v2 = views::drop(r, 6); + VERIFY( ranges::equal(v2, "world"sv) ); +} + +void +test04() +{ + int x[] = {1,2,3,4,5}; + ranges::subrange r(x, x+5); + using ty = decltype(r); + + std::same_as<ty> auto v1 = views::take(r, 2); + VERIFY( ranges::equal(v1, (int[]){1,2}) ); + + std::same_as<ty> auto v2 = views::drop(r, 1); + VERIFY( ranges::equal(v2, (int[]){2,3,4,5}) ); +} + +void +test05() +{ + auto r1 = views::iota(1, 6); + using ty1 = decltype(r1); + + std::same_as<ty1> auto v1 = views::take(r1, 2); + VERIFY( ranges::equal(v1, (int[]){1,2}) ); + + std::same_as<ty1> auto v2 = views::drop(r1, 3); + VERIFY( ranges::equal(v2, (int[]){4,5}) ); +} + +int +main() +{ + test01(); + test02(); + test03(); + test04(); + test05(); +}
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