sized_sentinel_for, sized_rangeに対応

acd1034 · Sep 18, 2022 · 12fc131 · 12fc131
1 parent bbdac64
commit 12fc131
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diff --git a/include/ns/enumerate_view.hpp b/include/ns/enumerate_view.hpp
@@ -25,6 +25,10 @@ namespace ns {
     constexpr iterator begin() { return {std::ranges::begin(base_), 0}; }
 
     constexpr auto end() { return sentinel(std::ranges::end(base_)); }
+
+    constexpr auto size() requires std::ranges::sized_range<View> {
+      return std::ranges::size(base_);
+    }
   };
 
   template <class Range>
@@ -179,5 +183,18 @@ namespace ns {
                         std::ranges::iterator_t<View>> {
       return x.base() == y.end_;
     }
+
+    friend constexpr std::ranges::range_difference_t<View> //
+    operator-(const iterator& x, const sentinel& y) requires
+      std::sized_sentinel_for<std::ranges::sentinel_t<View>,
+                              std::ranges::iterator_t<View>> {
+      return x.base() - y.end_;
+    }
+    friend constexpr std::ranges::range_difference_t<View>
+    operator-(const sentinel& x, const iterator& y) requires
+      std::sized_sentinel_for<std::ranges::sentinel_t<View>,
+                              std::ranges::iterator_t<View>> {
+      return x.end_ - y.base();
+    }
   };
 } // namespace ns
diff --git a/tests/enumerate_view/enumerate_view.cpp b/tests/enumerate_view/enumerate_view.cpp
@@ -116,4 +116,18 @@ TEST_CASE("enumerate_view", "[enumerate_view]") {
     CHECK(std::get<1>(*it++) == 'c');
     CHECK(it == std::ranges::end(ev));
   }
+  {
+    std::vector<char> v{'a', 'b', 'c'};
+    ns::enumerate_view ev(v);
+    std::random_access_iterator auto begin = std::ranges::begin(ev);
+    auto end = std::ranges::end(ev);
+    static_assert(std::sized_sentinel_for<decltype(end), decltype(begin)>);
+    CHECK(std::ranges::end(ev) - std::ranges::begin(ev) == 3);
+  }
+  {
+    std::vector<char> v{'a', 'b', 'c'};
+    ns::enumerate_view ev(v);
+    static_assert(std::ranges::sized_range<decltype(ev)>);
+    CHECK(std::ranges::size(ev) == 3);
+  }
 }