[libcxx-commits] [libcxx] [libc++][ranges] P1223R5: `find_last` (PR #99312)
Christopher Di Bella via libcxx-commits
libcxx-commits at lists.llvm.org
Wed Jul 17 10:40:36 PDT 2024
================
@@ -0,0 +1,294 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <algorithm>
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// ADDITIONAL_COMPILE_FLAGS(gcc-style-warnings): -Wno-sign-compare
+// MSVC warning C4242: 'argument': conversion from 'const _Ty' to 'ElementT', possible loss of data
+// MSVC warning C4244: 'argument': conversion from 'const _Ty' to 'ElementT', possible loss of data
+// ADDITIONAL_COMPILE_FLAGS(cl-style-warnings): /wd4242 /wd4244
+
+// template<forward_iterator I, sentinel_for<I> S, class T, class Proj = identity>
+// requires indirect_binary_predicate<ranges::equal_to, projected<I, Proj>, const T*>
+// constexpr subrange<I> ranges::find_last(I first, S last, const T& value, Proj proj = {});
+// template<forward_range R, class T, class Proj = identity>
+// requires indirect_binary_predicate<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*>
+// constexpr borrowed_subrange_t<R> ranges::find_last(R&& r, const T& value, Proj proj = {});
+
+#include <algorithm>
+#include <array>
+#include <cassert>
+#include <deque>
+#include <ranges>
+#include <vector>
+
+#include "almost_satisfies_types.h"
+#include "test_iterators.h"
+
+struct NotEqualityComparable {};
+
+template <class It, class Sent = It>
+concept HasFindLastIt = requires(It it, Sent sent) { std::ranges::find_last(it, sent, *it); };
+static_assert(HasFindLastIt<int*>);
+static_assert(HasFindLastIt<forward_iterator<int*>>);
+static_assert(!HasFindLastIt<cpp20_input_iterator<int*>>);
+static_assert(!HasFindLastIt<NotEqualityComparable*>);
+static_assert(!HasFindLastIt<ForwardIteratorNotDerivedFrom>);
+static_assert(!HasFindLastIt<ForwardIteratorNotIncrementable>);
+static_assert(!HasFindLastIt<forward_iterator<int*>, SentinelForNotSemiregular>);
+static_assert(!HasFindLastIt<forward_iterator<int*>, InputRangeNotSentinelEqualityComparableWith>);
+
+static_assert(!HasFindLastIt<int*, int>);
+static_assert(!HasFindLastIt<int, int*>);
+
+template <class Range, class ValT>
+concept HasFindLastR = requires(Range r) { std::ranges::find_last(r, ValT{}); };
+static_assert(HasFindLastR<std::array<int, 1>, int>);
+static_assert(!HasFindLastR<int, int>);
+static_assert(!HasFindLastR<std::array<NotEqualityComparable, 1>, NotEqualityComparable>);
+static_assert(!HasFindLastR<ForwardRangeNotDerivedFrom, int>);
+static_assert(!HasFindLastR<ForwardRangeNotIncrementable, int>);
+static_assert(!HasFindLastR<ForwardRangeNotSentinelSemiregular, int>);
+static_assert(!HasFindLastR<ForwardRangeNotSentinelEqualityComparableWith, int>);
+
+static std::vector<int> comparable_data;
+
+template <class It, class Sent = It>
+constexpr void test_iterators() {
+ using ValueT = std::iter_value_t<It>;
+ { // simple test
+ {
+ ValueT a[] = {1, 2, 3, 4};
+
+ std::same_as<std::ranges::subrange<It>> auto ret = std::ranges::find_last(It(a), Sent(It(a + 4)), 2);
+ assert(base(ret.begin()) == a + 1);
+ assert(*ret.begin() == 2);
+ }
+ {
+ ValueT a[] = {1, 2, 3, 4};
+ auto range = std::ranges::subrange(It(a), Sent(It(a + 4)));
+
+ std::same_as<std::ranges::subrange<It>> auto ret = std::ranges::find_last(range, 2);
+ assert(base(ret.begin()) == a + 1);
+ assert(*ret.begin() == 2);
+ }
+ }
+
+ { // check that an empty range works
+ {
+ std::array<ValueT, 0> a = {};
+
+ auto ret = std::ranges::find_last(It(a.data()), Sent(It(a.data())), 1).begin();
+ assert(base(ret) == a.data());
+ }
+ {
+ std::array<ValueT, 0> a = {};
+
+ auto range = std::ranges::subrange(It(a.data()), Sent(It(a.data())));
+ auto ret = std::ranges::find_last(range, 1).begin();
+ assert(base(ret) == a.data());
+ }
+ }
+
+ { // check that last is returned with no match
+ {
+ ValueT a[] = {1, 1, 1};
+
+ auto ret = std::ranges::find_last(a, a + 3, 0).begin();
+ assert(ret == a + 3);
+ }
+ {
+ ValueT a[] = {1, 1, 1};
+
+ auto ret = std::ranges::find_last(a, 0).begin();
+ assert(ret == a + 3);
+ }
+ }
+
+ if (!std::is_constant_evaluated())
+ comparable_data.clear();
+}
+
+template <class ElementT>
+class TriviallyComparable {
+ ElementT el_;
+
+public:
+ TEST_CONSTEXPR TriviallyComparable(ElementT el) : el_(el) {}
+ bool operator==(const TriviallyComparable&) const = default;
+};
+
+constexpr bool test() {
+ types::for_each(types::type_list<char, wchar_t, int, long, TriviallyComparable<char>, TriviallyComparable<wchar_t>>{},
+ []<class T> {
+ types::for_each(types::forward_iterator_list<T*>{}, []<class Iter> {
+ if constexpr (std::forward_iterator<Iter>)
+ test_iterators<Iter>();
+ test_iterators<Iter, sentinel_wrapper<Iter>>();
+ test_iterators<Iter, sized_sentinel<Iter>>();
+ });
+ });
+
+ {
+ std::vector<std::vector<int>> vec = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
+ auto view = vec | std::views::join;
+ assert(std::ranges::find_last(view.begin(), view.end(), 4).begin() == std::next(view.begin(), 3));
+ assert(std::ranges::find_last(view, 4).begin() == std::next(view.begin(), 3));
+ }
+
+ { // check that the last element is returned
+ {
+ struct S {
+ int comp;
+ int other;
+ };
+ S a[] = {{0, 0}, {0, 2}, {0, 1}};
+ auto ret = std::ranges::find_last(a, 0, &S::comp).begin();
+ assert(ret == a + 2);
+ assert(ret->comp == 0);
+ assert(ret->other == 1);
+ }
+ {
+ struct S {
+ int comp;
+ int other;
+ };
+ S a[] = {{0, 0}, {0, 2}, {0, 1}};
+ auto ret = std::ranges::find_last(a, a + 3, 0, &S::comp).begin();
+ assert(ret == a + 2);
+ assert(ret->comp == 0);
+ assert(ret->other == 1);
+ }
+ }
+
+ {
+ // check that an iterator is returned with a borrowing range
+ int a[] = {1, 2, 3, 4};
+ std::same_as<std::ranges::subrange<int*>> auto ret = std::ranges::find_last(std::views::all(a), 1);
+ assert(ret.begin() == a);
+ assert(*ret.begin() == 1);
+ }
+
+ {
+ // count invocations of the projection
+ {
+ int a[] = {1, 2, 3, 4};
+ int projection_count = 0;
+ auto ret = std::ranges::find_last(a, a + 4, 2, [&](int i) {
+ ++projection_count;
+ return i;
+ }).begin();
+ assert(ret == a + 1);
+ assert(*ret == 2);
+ assert(projection_count == 3);
+ }
+ {
+ int a[] = {1, 2, 3, 4};
+ int projection_count = 0;
+ auto ret = std::ranges::find_last(a, 2, [&](int i) {
+ ++projection_count;
+ return i;
+ }).begin();
+ assert(ret == a + 1);
+ assert(*ret == 2);
+ assert(projection_count == 3);
+ }
+ }
+
+ return true;
+}
+
+template <class IndexT>
+class Comparable {
+ IndexT index_;
+
+public:
+ Comparable(IndexT i)
+ : index_([&]() {
+ IndexT size = static_cast<IndexT>(comparable_data.size());
+ comparable_data.push_back(i);
+ return size;
+ }()) {}
+
+ bool operator==(const Comparable& other) const { return comparable_data[other.index_] == comparable_data[index_]; }
+
+ friend bool operator==(const Comparable& lhs, long long rhs) { return comparable_data[lhs.index_] == rhs; }
+};
+
+void test_deque() {
----------------
cjdb wrote:
Can we parameterise this and test all the sequence containers, please?
https://github.com/llvm/llvm-project/pull/99312
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