From d48b6fcc2748e86e4dae842458869fed19d8347f Mon Sep 17 00:00:00 2001
From: Morwenn <morwenn29@hotmail.fr>
Date: Sun, 7 Jan 2024 21:20:31 +0100
Subject: [PATCH] constexpr drop_merge_adapter (#58)

---
 include/cpp-sort/adapters/drop_merge_adapter.h | 6 +++---
 include/cpp-sort/detail/drop_merge_sort.h      | 6 +++---
 tests/adapters/every_adapter_constexpr.cpp     | 5 +++--
 3 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/include/cpp-sort/adapters/drop_merge_adapter.h b/include/cpp-sort/adapters/drop_merge_adapter.h
index 4afd5639..2a66304c 100644
--- a/include/cpp-sort/adapters/drop_merge_adapter.h
+++ b/include/cpp-sort/adapters/drop_merge_adapter.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022 Morwenn
+ * Copyright (c) 2022-2024 Morwenn
  * SPDX-License-Identifier: MIT
  */
 #ifndef CPPSORT_ADAPTERS_DROP_MERGE_ADAPTER_H_
@@ -42,8 +42,8 @@ namespace cppsort
                 typename Projection = std::identity
             >
                 requires is_projection_iterator_v<Projection, Iterator, Compare>
-            auto operator()(Iterator first, Sentinel last,
-                            Compare compare={}, Projection projection={}) const
+            constexpr auto operator()(Iterator first, Sentinel last,
+                                      Compare compare={}, Projection projection={}) const
                 -> Iterator
             {
                 return drop_merge_sort(std::move(first), std::move(last),
diff --git a/include/cpp-sort/detail/drop_merge_sort.h b/include/cpp-sort/detail/drop_merge_sort.h
index 0d5d7f5a..36f07741 100644
--- a/include/cpp-sort/detail/drop_merge_sort.h
+++ b/include/cpp-sort/detail/drop_merge_sort.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2022 Morwenn
+ * Copyright (c) 2017-2024 Morwenn
  * SPDX-License-Identifier: MIT
  */
 
@@ -44,8 +44,8 @@ namespace cppsort::detail
         typename Projection,
         typename Sorter
     >
-    auto drop_merge_sort(BidirectionalIterator first, Sentinel last,
-                         Compare compare, Projection projection, Sorter&& sorter)
+    constexpr auto drop_merge_sort(BidirectionalIterator first, Sentinel last,
+                                   Compare compare, Projection projection, Sorter&& sorter)
         -> BidirectionalIterator
     {
         using difference_type = mstd::iter_difference_t<BidirectionalIterator>;
diff --git a/tests/adapters/every_adapter_constexpr.cpp b/tests/adapters/every_adapter_constexpr.cpp
index d7e733c5..1db69433 100644
--- a/tests/adapters/every_adapter_constexpr.cpp
+++ b/tests/adapters/every_adapter_constexpr.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022 Morwenn
+ * Copyright (c) 2022-2024 Morwenn
  * SPDX-License-Identifier: MIT
  */
 #include <cstddef>
@@ -28,7 +28,8 @@ namespace
 }
 
 TEMPLATE_TEST_CASE( "test most adapters in a constexpr context", "[adapters][constexpr]",
-                    cppsort::hybrid_adapter<cppsort::insertion_sorter> )
+                    cppsort::hybrid_adapter<cppsort::insertion_sorter>,
+                    cppsort::drop_merge_adapter<cppsort::insertion_sorter> )
 {
     constexpr bool is_sorted = test_constexpr_sorter<TestType>();
     STATIC_CHECK( is_sorted );