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[69.125.73.58]) by smtp.gmail.com with ESMTPSA id t190sm7977867qkb.1.2021.10.19.05.17.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Oct 2021 05:17:46 -0700 (PDT) To: gcc-patches@gcc.gnu.org Subject: [PATCH 2/2] libstdc++: Implement P1739R4 changes to views::take/drop/counted Date: Tue, 19 Oct 2021 08:17:04 -0400 Message-Id: <20211019121704.1510908-2-ppalka@redhat.com> X-Mailer: git-send-email 2.33.1.637.gf443b226ca In-Reply-To: <20211019121704.1510908-1-ppalka@redhat.com> References: <20211019121704.1510908-1-ppalka@redhat.com> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-15.7 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Patrick Palka via Gcc-patches From: Patrick Palka Reply-To: Patrick Palka Cc: libstdc++@gcc.gnu.org Errors-To: gcc-patches-bounces+patchwork=sourceware.org@gcc.gnu.org Sender: "Gcc-patches" This implements P1739R4 along with the resolution for LWG 3407 which corrects the paper's wording. Tested on x86_64-pc-linux-gnu, does this look OK for trunk? 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 its type 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. --- libstdc++-v3/include/bits/ranges_util.h | 7 +- libstdc++-v3/include/std/ranges | 106 +++++++++++++++--- libstdc++-v3/include/std/span | 12 +- .../testsuite/std/ranges/adaptors/p1739.cc | 88 +++++++++++++++ 4 files changed, 192 insertions(+), 21 deletions(-) create mode 100644 libstdc++-v3/testsuite/std/ranges/adaptors/p1739.cc diff --git a/libstdc++-v3/include/bits/ranges_util.h b/libstdc++-v3/include/bits/ranges_util.h index 7e7b958d274..1afa66d298c 100644 --- a/libstdc++-v3/include/bits/ranges_util.h +++ b/libstdc++-v3/include/bits/ranges_util.h @@ -211,6 +211,8 @@ namespace ranges } // namespace __detail + namespace views { struct _Drop; } + enum class subrange_kind : bool { unsized, sized }; /// The ranges::subrange class template @@ -221,8 +223,9 @@ namespace ranges class subrange : public view_interface> { private: - // XXX: gcc complains when using constexpr here - static const bool _S_store_size + friend struct views::_Drop; // Needs to inspect _S_store_size. + + static constexpr bool _S_store_size = _Kind == subrange_kind::sized && !sized_sentinel_for<_Sent, _It>; _It _M_begin = _It(); diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges index 85f232d8fb9..64396027c1b 100644 --- a/libstdc++-v3/include/std/ranges +++ b/libstdc++-v3/include/std/ranges @@ -42,6 +42,7 @@ #include #include #include +#include #include #include #include @@ -2147,19 +2148,66 @@ namespace views::__adaptor { namespace __detail { - template + template + constexpr bool __is_empty_view = false; + + template + constexpr bool __is_empty_view> = true; + + template + constexpr bool __is_basic_string_view = false; + + template + constexpr bool __is_basic_string_view> = true; + + template + constexpr bool __is_subrange = false; + + template + constexpr bool __is_subrange> = true; + + template + constexpr bool __is_iota_view = false; + + template + constexpr bool __is_iota_view> = true; + + template 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 - requires __detail::__can_take_view<_Range, _Tp> + template> + 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(__begin, __end); + else if constexpr (__detail::__is_basic_string_view<_Tp>) + return _Tp(__begin, __end); + else if constexpr (__detail::__is_subrange<_Tp>) + return subrange>(__begin, __end); + else + return iota_view(*__begin, *__end); + } + else + return take_view(std::forward<_Range>(__r), __n); } using _RangeAdaptor<_Take>::operator(); @@ -2394,19 +2442,49 @@ namespace views::__adaptor { namespace __detail { - template + template 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 - requires __detail::__can_drop_view<_Range, _Tp> + template> + 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(__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(); @@ -3536,7 +3614,9 @@ 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..ba75a497310 100644 --- a/libstdc++-v3/include/std/span +++ b/libstdc++-v3/include/std/span @@ -58,16 +58,16 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION namespace __detail { template - struct __is_std_span : false_type { }; + constexpr bool __is_span = false; template - struct __is_std_span> : true_type { }; + constexpr bool __is_span> = true; template - struct __is_std_array : false_type { }; + constexpr bool __is_std_array = false; template - struct __is_std_array> : true_type { }; + constexpr bool __is_std_array> = true; template class __extent_storage @@ -203,8 +203,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION template requires ranges::contiguous_range<_Range> && ranges::sized_range<_Range> && (ranges::borrowed_range<_Range> || is_const_v) - && (!__detail::__is_std_span>::value) - && (!__detail::__is_std_array>::value) + && (!__detail::__is_span>) + && (!__detail::__is_std_array>) && (!is_array_v>) && __is_compatible_ref>::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..243b8a03583 --- /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 +#include +#include + +// Verify P1739R4 (and LWG 3407) changes views::take/drop/counted. + +namespace ranges = std::ranges; +namespace views = ranges::views; + +void +test01() +{ + ranges::empty_view 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 auto v1 = views::take(r, 2); + VERIFY( ranges::equal(v1, (int[]){1,2}) ); + + std::same_as auto v2 = views::drop(r, 3); + VERIFY( ranges::equal(v2, (int[]){4,5}) ); + + std::same_as 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 auto v1 = views::take(r, 5); + VERIFY( ranges::equal(v1, "hello"sv) ); + + std::same_as 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 auto v1 = views::take(r, 2); + VERIFY( ranges::equal(v1, (int[]){1,2}) ); + + std::same_as 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 auto v1 = views::take(r1, 2); + VERIFY( ranges::equal(v1, (int[]){1,2}) ); + + std::same_as auto v2 = views::drop(r1, 3); + VERIFY( ranges::equal(v2, (int[]){4,5}) ); +} + +int +main() +{ + test01(); + test02(); + test03(); + test04(); + test05(); +}