From 2e4f38b176a0d314f603df506609287a8cd9a952 Mon Sep 17 00:00:00 2001
From: grcm10 <grcm10@outlook.com>
Date: Sun, 24 Mar 2024 09:56:29 +0900
Subject: [PATCH 1/3] Add empty to single_view

---
 stl/inc/ranges                                | 3 +++
 tests/std/tests/P0896R4_views_single/test.cpp | 7 +++++++
 2 files changed, 10 insertions(+)

diff --git a/stl/inc/ranges b/stl/inc/ranges
index 30d22d9c4f..0e10e1f96a 100644
--- a/stl/inc/ranges
+++ b/stl/inc/ranges
@@ -1042,6 +1042,9 @@ namespace ranges {
             return _STD addressof(*_Val);
         }
 
+        _NODISCARD static constexpr bool empty() noexcept {
+            return false;
+        }
     private:
         /* [[no_unique_address]] */ _Movable_box<_Ty> _Val{};
     };
diff --git a/tests/std/tests/P0896R4_views_single/test.cpp b/tests/std/tests/P0896R4_views_single/test.cpp
index 8671a90105..ccf315b8d2 100644
--- a/tests/std/tests/P0896R4_views_single/test.cpp
+++ b/tests/std/tests/P0896R4_views_single/test.cpp
@@ -52,6 +52,13 @@ constexpr bool test_one_type(T value, Args&&... args) {
     same_as<R> auto r0 = ranges::single_view{value};
     const R& cr0       = r0;
 
+    // validate member empty
+    static_assert(same_as<decltype(R::empty()), bool>);
+    static_assert(R::empty() == false);
+    static_assert(noexcept(R::empty()));
+    static_assert(noexcept(ranges::empty(r0)));
+    static_assert(noexcept(ranges::empty(cr0)));
+
     // validate member size
     static_assert(same_as<decltype(R::size()), size_t>);
     static_assert(R::size() == 1);

From 6373ccdc7d1876d9935acd8352124215b15671e5 Mon Sep 17 00:00:00 2001
From: grcm10 <grcm10@outlook.com>
Date: Sun, 24 Mar 2024 10:57:05 +0900
Subject: [PATCH 2/3] Fix the formatting error

---
 stl/inc/ranges | 1 +
 1 file changed, 1 insertion(+)

diff --git a/stl/inc/ranges b/stl/inc/ranges
index 0e10e1f96a..dcae94a040 100644
--- a/stl/inc/ranges
+++ b/stl/inc/ranges
@@ -1045,6 +1045,7 @@ namespace ranges {
         _NODISCARD static constexpr bool empty() noexcept {
             return false;
         }
+
     private:
         /* [[no_unique_address]] */ _Movable_box<_Ty> _Val{};
     };

From 93d7299fbcbe646e96f452cd601f7585708635a4 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@nuwen.net>
Date: Mon, 25 Mar 2024 14:40:29 -0700
Subject: [PATCH 3/3] Follow the Standard's declaration order.

---
 stl/inc/ranges | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/stl/inc/ranges b/stl/inc/ranges
index dcae94a040..d2949c677a 100644
--- a/stl/inc/ranges
+++ b/stl/inc/ranges
@@ -1031,6 +1031,10 @@ namespace ranges {
             return data() + 1;
         }
 
+        _NODISCARD static constexpr bool empty() noexcept {
+            return false;
+        }
+
         _NODISCARD static constexpr size_t size() noexcept {
             return 1;
         }
@@ -1042,10 +1046,6 @@ namespace ranges {
             return _STD addressof(*_Val);
         }
 
-        _NODISCARD static constexpr bool empty() noexcept {
-            return false;
-        }
-
     private:
         /* [[no_unique_address]] */ _Movable_box<_Ty> _Val{};
     };