Sentinel support for timsort and timmerge

Author: Morwenn

README.md

@@ -30,11 +30,12 @@ The list of available signatures is as follows (in namespace `gfx`):
 
 template <
     std::random_access_iterator Iterator,
+    std::sentinel_for<Iterator> Sentinel,
     typename Compare = std::ranges::less,
     typename Projection = std::identity
 >
     requires std::sortable<Iterator, Compare, Projection>
-void timsort(Iterator first, Iterator last,
+void timsort(Iterator first, Sentinel last,
              Compare compare={}, Projection projection={});
 
 template <
@@ -49,11 +50,12 @@ void timsort(Range &range, Compare compare={}, Projection projection={});
 
 template <
     std::random_access_iterator Iterator,
+    std::sentinel_for<Iterator> Sentinel,
     typename Compare = std::ranges::less,
     typename Projection = std::identity
 >
     requires std::sortable<Iterator, Compare, Projection>
-void timmerge(Iterator first, Iterator middle, Iterator last,
+void timmerge(Iterator first, Iterator middle, Sentinel last,
               Compare compare={}, Projection projection={});
 
 template <

include/gfx/timsort.hpp

@@ -695,16 +695,18 @@ template <typename RandomAccessIterator, typename Compare, typename Projection>
  */
 template <
     std::random_access_iterator Iterator,
+    std::sentinel_for<Iterator> Sentinel,
     typename Compare = std::ranges::less,
     typename Projection = std::identity
 >
     requires std::sortable<Iterator, Compare, Projection>
-void timmerge(Iterator first, Iterator middle, Iterator last,
+void timmerge(Iterator first, Iterator middle, Sentinel last,
               Compare comp={}, Projection proj={}) {
+    auto last_it = std::ranges::next(first, last);
     GFX_TIMSORT_AUDIT(std::is_sorted(first, middle, comp, proj) && "Precondition");
-    GFX_TIMSORT_AUDIT(std::is_sorted(middle, last, comp, proj) && "Precondition");
-    detail::TimSort<Iterator, Compare, Projection>::merge(first, middle, last, comp, proj);
-    GFX_TIMSORT_AUDIT(std::is_sorted(first, last, comp, proj) && "Postcondition");
+    GFX_TIMSORT_AUDIT(std::is_sorted(middle, last_it, comp, proj) && "Precondition");
+    detail::TimSort<Iterator, Compare, Projection>::merge(first, middle, last_it, comp, proj);
+    GFX_TIMSORT_AUDIT(std::is_sorted(first, last_it, comp, proj) && "Postcondition");
 }
 
 /**
@@ -728,14 +730,16 @@ void timmerge(Range &&range, std::ranges::iterator_t<Range> middle,
  */
 template <
     std::random_access_iterator Iterator,
+    std::sentinel_for<Iterator> Sentinel,
     typename Compare = std::ranges::less,
     typename Projection = std::identity
 >
     requires std::sortable<Iterator, Compare, Projection>
-void timsort(Iterator first, Iterator last,
+void timsort(Iterator first, Sentinel last,
              Compare comp={}, Projection proj={}) {
-    detail::TimSort<Iterator, Compare, Projection>::sort(first, last, comp, proj);
-    GFX_TIMSORT_AUDIT(std::is_sorted(first, last, comp, proj) && "Postcondition");
+    auto last_it = std::ranges::next(first, last);
+    detail::TimSort<Iterator, Compare, Projection>::sort(first, last_it, comp, proj);
+    GFX_TIMSORT_AUDIT(std::is_sorted(first, last_it, comp, proj) && "Postcondition");
 }
 
 /**

tests/cxx_20_tests.cpp

@@ -3,6 +3,7 @@
  * SPDX-License-Identifier: MIT
  */
 #include <algorithm>
+#include <iterator>
 #include <numeric>
 #include <random>
 #include <span>
@@ -12,7 +13,7 @@
 #include "test_helpers.hpp"
 
 TEST_CASE( "support for temporary types" ) {
-    SECTION( "timsmerge over std::span" ) {
+    SECTION( "timmerge over std::span" ) {
         std::vector<int> vec(100);
         std::iota(vec.begin(), vec.end(), -25);
         test_helpers::shuffle(vec);
@@ -35,3 +36,31 @@ TEST_CASE( "support for temporary types" ) {
         CHECK(std::ranges::is_sorted(vec));
     }
 }
+
+TEST_CASE( "support for sentinels" )
+{
+    SECTION( "timmerge with sentinel" ) {
+        std::vector<int> vec(100);
+        std::iota(vec.begin(), vec.end(), -25);
+        test_helpers::shuffle(vec);
+
+        auto middle = vec.begin() + 38;
+        gfx::timsort(vec.begin(), middle);
+        gfx::timsort(middle, vec.end());
+
+        gfx::timmerge(std::counted_iterator(vec.begin(), 85),
+                      std::counted_iterator(middle, 85 - 38),
+                      std::default_sentinel);
+        CHECK(std::is_sorted(vec.begin(), vec.begin() + 85));
+    }
+
+    SECTION( "timsort with sentinel" ) {
+        std::vector<int> vec(100);
+        std::iota(vec.begin(), vec.end(), -25);
+        test_helpers::shuffle(vec);
+
+        gfx::timsort(std::counted_iterator(vec.begin(), 85),
+                     std::default_sentinel);
+        CHECK(std::is_sorted(vec.begin(), vec.begin() + 85));
+    }
+}