Fix take_while_view

lackhole · Jun 28, 2024 · 4cdb25e · 4cdb25e
1 parent 6aea1bb
commit 4cdb25e
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Showing 2 changed files with 61 additions and 3 deletions.
diff --git a/include/preview/__ranges/views/take_while_view.h b/include/preview/__ranges/views/take_while_view.h
@@ -35,7 +35,7 @@ namespace preview {
 namespace ranges {
 
 template<typename V, typename Pred>
-class take_while_view {
+class take_while_view : public view_interface<take_while_view<V, Pred>> {
  public:
   static_assert(ranges::view<V>::value, "Constraints not satisfied");
   static_assert(ranges::input_range<V>::value, "Constraints not satisfied");
@@ -81,6 +81,38 @@ class take_while_view {
       return !(x == y);
     }
 
+    template<bool OtherConst, std::enable_if_t<conjunction<
+        bool_constant<(Const != OtherConst)>,
+        sentinel_for<sentinel_t<Base>, iterator_t<maybe_const<OtherConst, V>>>
+    >::value, int> = 0>
+    friend constexpr bool operator==(const iterator_t<maybe_const<OtherConst, V>>& x, const sentinel& y) {
+      return x == y.end_ || !preview::invoke(*y.pred_, *x);
+    }
+
+    template<bool OtherConst, std::enable_if_t<conjunction<
+        bool_constant<(Const != OtherConst)>,
+        sentinel_for<sentinel_t<Base>, iterator_t<maybe_const<OtherConst, V>>>
+    >::value, int> = 0>
+    friend constexpr bool operator==(const sentinel& y, const iterator_t<maybe_const<OtherConst, V>>& x) {
+      return x == y;
+    }
+
+    template<bool OtherConst, std::enable_if_t<conjunction<
+        bool_constant<(Const != OtherConst)>,
+        sentinel_for<sentinel_t<Base>, iterator_t<maybe_const<OtherConst, V>>>
+    >::value, int> = 0>
+    friend constexpr bool operator!=(const iterator_t<maybe_const<OtherConst, V>>& x, const sentinel& y) {
+      return !(x == y);
+    }
+
+    template<bool OtherConst, std::enable_if_t<conjunction<
+        bool_constant<(Const != OtherConst)>,
+        sentinel_for<sentinel_t<Base>, iterator_t<maybe_const<OtherConst, V>>>
+    >::value, int> = 0>
+    friend constexpr bool operator!=(const sentinel& y, const iterator_t<maybe_const<OtherConst, V>>& x) {
+      return !(x == y);
+    }
+
    private:
     sentinel_t<Base> end_;
     const Pred* pred_;
@@ -125,15 +157,15 @@ class take_while_view {
       negation<simple_view<V>>
   >::value, int> = 0>
   PREVIEW_CONSTEXPR_AFTER_CXX17 auto end() {
-    return sentinel<false>{ranges::end(base_), pred_.operator->()};
+    return sentinel<false>{ranges::end(base_), std::addressof(*pred_)};
   }
 
   template<typename Dummy = void, std::enable_if_t<preview::conjunction<std::is_void<Dummy>,
       range<const V>,
       indirect_unary_predicate<const Pred, iterator_t<const V>>
   >::value, int> = 0>
   PREVIEW_CONSTEXPR_AFTER_CXX17 auto end() const {
-    return sentinel<true>{ranges::end(base_), pred_.operator->()};
+    return sentinel<true>{ranges::end(base_), std::addressof(*pred_)};
   }
 
  private:

diff --git a/test/ranges_views.cc b/test/ranges_views.cc
@@ -523,3 +523,29 @@ TEST(VERSIONED(RangesViews), take_view) {
 #endif
   EXPECT_EQ(out, "3.141592");
 }
+
+TEST(VERSIONED(RangesViews), take_while_view) {
+  using namespace std::literals;
+  using namespace preview::literals;
+
+  for (int year : views::iota(2020)
+      | views::take_while([](int y){ return y < 2026; })) { (void)year; }
+
+  auto r1 = views::iota(10) | views::take_while([](int x) { return true; });
+  auto r2 = views::iota(10, 20) | views::take_while([](int x) { return true; });
+
+  auto it1 = r1.end();
+  auto it2 = r2.end();
+
+  EXPECT_TRUE(ranges::equal(
+      views::iota(2020) | views::take_while([](int y){ return y < 2026; }),
+      {2020, 2021, 2022, 2023, 2024, 2025}
+  ));
+
+  const char note[]{"Today is yesterday's tomorrow!..."};
+  for (char x : ranges::take_while_view(note, [](char c){ return c != '.'; })) { (void)x; }
+  EXPECT_TRUE(ranges::equal(
+      ranges::take_while_view(note, [](char c){ return c != '.'; }),
+      "Today is yesterday's tomorrow!"_sv
+  ));
+}