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huixie90 · Jun 9, 2023 · 82f202e · 82f202e
1 parent c7e8e23
commit 82f202e
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Showing 2 changed files with 45 additions and 15 deletions.
diff --git a/impl/concat/concat.hpp b/impl/concat/concat.hpp
@@ -85,8 +85,8 @@ concept concat_is_random_access = (all_random_access<Const, Views> && ...) &&
                                   (all_but_last<sized_range<__maybe_const<Const, Views>>...>);
 
 template <class R>
-concept constant_time_reversible = (bidirectional_range<R> && common_range<R>) ||
-                                   (sized_range<R> && random_access_range<R>);
+concept constant_time_reversible =
+    (bidirectional_range<R> && common_range<R>) || (sized_range<R> && random_access_range<R>);
 
 template <class... Rs>
 concept concat_bidirectional =
@@ -510,7 +510,15 @@ class concat_view : public view_interface<concat_view<Views...>> {
                 // distance(y, yend) + size(ranges_in_between)... + distance(xbegin, x)
                 const auto all_sizes = std::apply(
                     [&](const auto&... views) {
-                        return std::array{static_cast<difference_type>(ranges::size(views))...};
+                        const auto getSize = [](const auto& view) {
+                            if constexpr (ranges::sized_range<decay_t<decltype(view)>>) {
+                                return ranges::size(view);
+                            } else {
+                                return 0u; // only the last range can be non-sized, and its value is
+                                           // not used
+                            }
+                        };
+                        return std::array{static_cast<difference_type>(getSize(views))...};
                     },
                     x.get_parent_views());
                 auto in_between = std::accumulate(all_sizes.data() + iy + 1, all_sizes.data() + ix,
@@ -538,7 +546,8 @@ class concat_view : public view_interface<concat_view<Views...>> {
         }
 
         friend constexpr difference_type operator-(const iterator& it, default_sentinel_t)
-            requires xo::concat_is_random_access<Const, Views...>
+            requires(xo::concat_is_random_access<Const, Views...> &&
+                     sized_range<xo::back<__maybe_const<Const, Views>...>>)
         {
 
             const auto idx = it.it_.index();
@@ -558,7 +567,8 @@ class concat_view : public view_interface<concat_view<Views...>> {
         }
 
         friend constexpr difference_type operator-(default_sentinel_t, const iterator& it)
-            requires xo::concat_is_random_access<Const, Views...>
+            requires(xo::concat_is_random_access<Const, Views...> &&
+                     sized_range<xo::back<__maybe_const<Const, Views>...>>)
         {
             return -(it - default_sentinel);
         }

diff --git a/impl/concat/test/basics.cpp b/impl/concat/test/basics.cpp
@@ -14,9 +14,7 @@
 namespace {
 
 template <typename... R>
-concept concat_viewable = requires(R&&... r) {
-    std::ranges::views::concat((R &&) r...);
-};
+concept concat_viewable = requires(R&&... r) { std::ranges::views::concat((R&&)r...); };
 
 
 template <typename R>
@@ -163,14 +161,36 @@ TEST_POINT("end_last_range_non_common_but_random_sized") {
 
 TEST_POINT("end_last_range_non_common_but_random_and_not_sized") {
     std::vector<int> v1{1};
-    auto io = std::views::iota(0);
+    std::vector<int> v2{2, 3};
+    auto io = std::views::iota(4);
     static_assert(!std::ranges::sized_range<decltype(io)>);
-    std::ranges::concat_view cv1{v1, io};
-    std::ranges::concat_view cv2{io, v1};
+    std::ranges::concat_view cv1{v1, v2, io};
+    std::ranges::concat_view cv2{io, v1, v2};
     static_assert(std::ranges::random_access_range<decltype(cv1)>);
     static_assert(!std::ranges::random_access_range<decltype(cv2)>);
-    static_assert(std::ranges::sized_range<decltype(cv1)>);
+    static_assert(
+        !std::ranges::sized_range<decltype(cv1)>); // should not be sized! (fixed after constrained
+                                                   // the operator- (default_sentinel) properly)
     static_assert(!std::ranges::sized_range<decltype(cv2)>);
+
+    auto it1 = cv1.begin();
+    auto it2 = it1 + 1;
+    CHECK(*it2 == 2);
+
+    auto it3 = it1 + 5;
+    CHECK(*it3 == 6);
+
+    auto it4 = it3 - 1;
+    CHECK(*it4 == 5);
+
+    auto it5 = it3 - 3;
+    CHECK(*it5 == 3);
+
+    auto it6 = it3 - 5;
+    CHECK(*it6 == 1);
+
+    CHECK(it3 -it1 == 5);
+    CHECK(it3 -it2 == 4);
 }
 
 
@@ -336,13 +356,13 @@ TEST_POINT("bidirectional_noncommon_random_access_sized") {
 }
 
 
-struct NonCommonRandomSized : std::ranges::view_base{
+struct NonCommonRandomSized : std::ranges::view_base {
     const int* begin() const;
     std::nullptr_t end() const;
     std::size_t size() const;
 };
 
-TEST_POINT("random_but_not_bidi_impossible"){
+TEST_POINT("random_but_not_bidi_impossible") {
     using namespace std::ranges;
     static_assert(!common_range<NonCommonRandomSized>);
     static_assert(random_access_range<NonCommonRandomSized>);
@@ -729,7 +749,7 @@ TEST_POINT("cpp20 input range") {
 
 
 TEST_POINT("size") {
-    std::vector v1 = {1,2};
+    std::vector v1 = {1, 2};
     auto cv1 = std::ranges::concat_view(std::views::all(v1));
     CHECK(cv1.size() == 2);