bidirectional_iteratorに対応

acd1034 · Sep 18, 2022 · 29e9e75 · 29e9e75
1 parent 302027f
commit 29e9e75
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Showing 2 changed files with 31 additions and 1 deletion.
diff --git a/include/ns/enumerate_view.hpp b/include/ns/enumerate_view.hpp
@@ -44,8 +44,9 @@ namespace ns {
     using value_type = std::pair<std::size_t, std::ranges::range_value_t<View>>;
     // clang-format off
     using iterator_concept =
+      std::conditional_t<std::ranges::bidirectional_range<View>, std::bidirectional_iterator_tag,
       std::conditional_t<std::ranges::forward_range<View>,       std::forward_iterator_tag,
-      /* else */                                                 std::input_iterator_tag>;
+      /* else */                                                 std::input_iterator_tag>>;
     // clang-format on
 
     iterator() requires
@@ -79,6 +80,19 @@ namespace ns {
       return tmp;
     }
 
+    constexpr iterator&
+    operator--() requires std::ranges::bidirectional_range<View> {
+      --current_;
+      --count_;
+      return *this;
+    }
+    constexpr iterator
+    operator--(int) requires std::ranges::bidirectional_range<View> {
+      auto tmp = *this;
+      --*this;
+      return tmp;
+    }
+
     friend constexpr bool operator==(const iterator& x, const iterator& y) //
       requires std::equality_comparable<std::ranges::iterator_t<View>> {
       return x.current_ == y.current_;

diff --git a/tests/enumerate_view/enumerate_view.cpp b/tests/enumerate_view/enumerate_view.cpp
@@ -1,4 +1,5 @@
 #include <forward_list>
+#include <list>
 #include <catch2/catch_test_macros.hpp>
 #include <ns/enumerate_view.hpp>
 
@@ -85,4 +86,19 @@ TEST_CASE("enumerate_view", "[enumerate_view]") {
     CHECK(std::get<1>(*it++) == 'c');
     CHECK(it == std::ranges::end(ev));
   }
+  {
+    std::list<char> l{'a', 'b', 'c'};
+    ns::enumerate_view ev(l);
+    static_assert(std::ranges::bidirectional_range<decltype(ev)>);
+    static_assert(not std::ranges::random_access_range<decltype(ev)>);
+
+    std::bidirectional_iterator auto it = std::ranges::begin(ev);
+    CHECK(std::get<0>(*it) == 0);
+    CHECK(std::get<1>(*it++) == 'a');
+    CHECK(std::get<0>(*it) == 1);
+    CHECK(std::get<1>(*it++) == 'b');
+    CHECK(std::get<0>(*it) == 2);
+    CHECK(std::get<1>(*it++) == 'c');
+    CHECK(it == std::ranges::end(ev));
+  }
 }