[libc++][ranges]implement `std::views::take_while`
Differential Revision: https://reviews.llvm.org/D134952
NOKEYCHECK=True
GitOrigin-RevId: a2c6a1193f41e40840a7ead6c1c0540d3062c13a
diff --git a/include/CMakeLists.txt b/include/CMakeLists.txt
index b9b657b..93d7c2b 100644
--- a/include/CMakeLists.txt
+++ b/include/CMakeLists.txt
@@ -495,6 +495,7 @@
__ranges/size.h
__ranges/subrange.h
__ranges/take_view.h
+ __ranges/take_while_view.h
__ranges/transform_view.h
__ranges/view_interface.h
__ranges/views.h
diff --git a/include/__ranges/take_while_view.h b/include/__ranges/take_while_view.h
new file mode 100644
index 0000000..77d7390
--- /dev/null
+++ b/include/__ranges/take_while_view.h
@@ -0,0 +1,177 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___RANGES_TAKE_WHILE_VIEW_H
+#define _LIBCPP___RANGES_TAKE_WHILE_VIEW_H
+
+#include <__concepts/constructible.h>
+#include <__concepts/convertible_to.h>
+#include <__config>
+#include <__functional/bind_back.h>
+#include <__functional/invoke.h>
+#include <__iterator/concepts.h>
+#include <__memory/addressof.h>
+#include <__ranges/access.h>
+#include <__ranges/all.h>
+#include <__ranges/concepts.h>
+#include <__ranges/copyable_box.h>
+#include <__ranges/range_adaptor.h>
+#include <__ranges/view_interface.h>
+#include <__type_traits/decay.h>
+#include <__type_traits/is_nothrow_constructible.h>
+#include <__type_traits/is_object.h>
+#include <__type_traits/maybe_const.h>
+#include <__utility/forward.h>
+#include <__utility/in_place.h>
+#include <__utility/move.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 20
+
+namespace ranges {
+
+// The spec uses the unnamed requirement inside the `begin` and `end` member functions:
+// constexpr auto begin() const
+// requires range<const V> && indirect_unary_predicate<const Pred, iterator_t<const V>>
+// However, due to a clang-14 and clang-15 bug, the above produces a hard error when `const V` is not a range.
+// The workaround is to create a named concept and use the concept instead.
+// As of take_while_view is implemented, the clang-trunk has already fixed the bug.
+// It is OK to remove the workaround once our CI no longer uses clang-14, clang-15 based compilers,
+// because we don't actually expect a lot of vendors to ship a new libc++ with an old clang.
+template <class _View, class _Pred>
+concept __take_while_const_is_range =
+ range<const _View> && indirect_unary_predicate<const _Pred, iterator_t<const _View>>;
+
+template <view _View, class _Pred>
+ requires input_range<_View> && is_object_v<_Pred> && indirect_unary_predicate<const _Pred, iterator_t<_View>>
+class take_while_view : public view_interface<take_while_view<_View, _Pred>> {
+ template <bool>
+ class __sentinel;
+
+ _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
+ _LIBCPP_NO_UNIQUE_ADDRESS __copyable_box<_Pred> __pred_;
+
+public:
+ _LIBCPP_HIDE_FROM_ABI take_while_view()
+ requires default_initializable<_View> && default_initializable<_Pred>
+ = default;
+
+ _LIBCPP_HIDE_FROM_ABI constexpr take_while_view(_View __base, _Pred __pred)
+ : __base_(std::move(__base)), __pred_(std::in_place, std::move(__pred)) {}
+
+ _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
+ requires copy_constructible<_View>
+ {
+ return __base_;
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr const _Pred& pred() const { return *__pred_; }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto begin()
+ requires(!__simple_view<_View>)
+ {
+ return ranges::begin(__base_);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
+ requires __take_while_const_is_range<_View, _Pred>
+ {
+ return ranges::begin(__base_);
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto end()
+ requires(!__simple_view<_View>)
+ {
+ return __sentinel</*_Const=*/false>(ranges::end(__base_), std::addressof(*__pred_));
+ }
+
+ _LIBCPP_HIDE_FROM_ABI constexpr auto end() const
+ requires __take_while_const_is_range<_View, _Pred>
+ {
+ return __sentinel</*_Const=*/true>(ranges::end(__base_), std::addressof(*__pred_));
+ }
+};
+
+template <class _Range, class _Pred>
+take_while_view(_Range&&, _Pred) -> take_while_view<views::all_t<_Range>, _Pred>;
+
+template <view _View, class _Pred>
+ requires input_range<_View> && is_object_v<_Pred> && indirect_unary_predicate<const _Pred, iterator_t<_View>>
+template <bool _Const>
+class take_while_view<_View, _Pred>::__sentinel {
+ using _Base = __maybe_const<_Const, _View>;
+
+ sentinel_t<_Base> __end_ = sentinel_t<_Base>();
+ const _Pred* __pred_ = nullptr;
+
+ friend class __sentinel<!_Const>;
+
+public:
+ _LIBCPP_HIDE_FROM_ABI __sentinel() = default;
+
+ _LIBCPP_HIDE_FROM_ABI constexpr explicit __sentinel(sentinel_t<_Base> __end, const _Pred* __pred)
+ : __end_(std::move(__end)), __pred_(__pred) {}
+
+ _LIBCPP_HIDE_FROM_ABI constexpr __sentinel(__sentinel<!_Const> __s)
+ requires _Const && convertible_to<sentinel_t<_View>, sentinel_t<_Base>>
+ : __end_(std::move(__s.__end_)), __pred_(__s.__pred_) {}
+
+ _LIBCPP_HIDE_FROM_ABI constexpr sentinel_t<_Base> base() const { return __end_; }
+
+ _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const iterator_t<_Base>& __x, const __sentinel& __y) {
+ return __x == __y.__end_ || !std::invoke(*__y.__pred_, *__x);
+ }
+
+ template <bool _OtherConst = !_Const>
+ requires sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
+ _LIBCPP_HIDE_FROM_ABI friend constexpr bool
+ operator==(const iterator_t<__maybe_const<_OtherConst, _View>>& __x, const __sentinel& __y) {
+ return __x == __y.__end_ || !std::invoke(*__y.__pred_, *__x);
+ }
+};
+
+namespace views {
+namespace __take_while {
+
+struct __fn {
+ template <class _Range, class _Pred>
+ [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Pred&& __pred) const
+ noexcept(noexcept(/**/ take_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))))
+ -> decltype(/*--*/ take_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))) {
+ return /*-------------*/ take_while_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred));
+ }
+
+ template <class _Pred>
+ requires constructible_from<decay_t<_Pred>, _Pred>
+ [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Pred&& __pred) const
+ noexcept(is_nothrow_constructible_v<decay_t<_Pred>, _Pred>) {
+ return __range_adaptor_closure_t(std::__bind_back(*this, std::forward<_Pred>(__pred)));
+ }
+};
+
+} // namespace __take_while
+
+inline namespace __cpo {
+inline constexpr auto take_while = __take_while::__fn{};
+} // namespace __cpo
+} // namespace views
+} // namespace ranges
+
+#endif // _LIBCPP_STD_VER >= 20
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___RANGES_TAKE_WHILE_VIEW_H
diff --git a/include/module.modulemap.in b/include/module.modulemap.in
index 73e366f..35356a4 100644
--- a/include/module.modulemap.in
+++ b/include/module.modulemap.in
@@ -1031,6 +1031,7 @@
module size { private header "__ranges/size.h" }
module subrange { private header "__ranges/subrange.h" }
module take_view { private header "__ranges/take_view.h" }
+ module take_while_view { private header "__ranges/take_while_view.h" }
module transform_view {
private header "__ranges/transform_view.h"
export functional.__functional.bind_back
diff --git a/include/ranges b/include/ranges
index 0565b2f..9207298 100644
--- a/include/ranges
+++ b/include/ranges
@@ -198,6 +198,14 @@
template<class T>
inline constexpr bool enable_borrowed_range<take_view<T>> = enable_borrowed_range<T>;
+ // [range.take.while], take while view
+ template<view V, class Pred>
+ requires input_range<V> && is_object_v<Pred> &&
+ indirect_unary_predicate<const Pred, iterator_t<V>>
+ class take_while_view;
+
+ namespace views { inline constexpr unspecified take_while = unspecified; }
+
template<copy_constructible T>
requires is_object_v<T>
class single_view;
@@ -311,6 +319,7 @@
#include <__ranges/size.h>
#include <__ranges/subrange.h>
#include <__ranges/take_view.h>
+#include <__ranges/take_while_view.h>
#include <__ranges/transform_view.h>
#include <__ranges/view_interface.h>
#include <__ranges/views.h>