fix recursion depth: some algorithms

libs/algorithm/test/includes.cpp

@@ -91,6 +91,166 @@ namespace testspr {
 					);
 				TESTSPR_BOTH_ASSERT(!result);
 			}
+
+#if defined(__clang__)
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::includes(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr2)),
+					testspr::reduct_input(sprout::end(arr2))
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::includes(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr3)),
+					testspr::reduct_input(sprout::end(arr3))
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::includes(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::begin(arr1) + 5),
+					testspr::reduct_input(sprout::begin(arr2)),
+					testspr::reduct_input(sprout::end(arr2))
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::includes(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::begin(arr1) + 5),
+					testspr::reduct_input(sprout::begin(arr3)),
+					testspr::reduct_input(sprout::end(arr3))
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::includes(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr2)),
+					testspr::reduct_input(sprout::end(arr2)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::includes(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr3)),
+					testspr::reduct_input(sprout::end(arr3)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::includes(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::begin(arr1) + 5),
+					testspr::reduct_input(sprout::begin(arr2)),
+					testspr::reduct_input(sprout::end(arr2)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::includes(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::begin(arr1) + 5),
+					testspr::reduct_input(sprout::begin(arr3)),
+					testspr::reduct_input(sprout::end(arr3)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+#endif
+
+#if defined(__clang__)
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::includes(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::end(arr2))
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::includes(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr3)),
+					testspr::reduct_random_access(sprout::end(arr3))
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::includes(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::end(arr2))
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::includes(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::reduct_random_access(sprout::begin(arr3)),
+					testspr::reduct_random_access(sprout::end(arr3))
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::includes(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::end(arr2)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::includes(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr3)),
+					testspr::reduct_random_access(sprout::end(arr3)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::includes(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::end(arr2)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::includes(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::reduct_random_access(sprout::begin(arr3)),
+					testspr::reduct_random_access(sprout::end(arr3)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+#endif
 		}
 	}
 }	// namespace testspr

libs/algorithm/test/is_heap.cpp

@@ -73,6 +73,69 @@ namespace testspr {
 					);
 				TESTSPR_BOTH_ASSERT(result);
 			}
+
+#if defined(__clang__)
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::is_heap(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1))
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::is_heap(
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::end(arr2))
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::is_heap(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5)
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::is_heap(
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::begin(arr2) + 5)
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::is_heap(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::is_heap(
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::end(arr2)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::is_heap(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::is_heap(
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::begin(arr2) + 5),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+#endif
 		}
 	}
 }	// namespace testspr

libs/algorithm/test/is_heap_until.cpp

@@ -73,6 +73,69 @@ namespace testspr {
 					);
 				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr2) + 5);
 			}
+
+#if defined(__clang__)
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::is_heap_until(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1))
+					).base();
+				TESTSPR_BOTH_ASSERT(found == sprout::end(arr1));
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::is_heap_until(
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::end(arr2))
+					).base();
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 7);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::is_heap_until(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5)
+					).base();
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 5);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::is_heap_until(
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::begin(arr2) + 5)
+					).base();
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr2) + 5);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::is_heap_until(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::less<int>()
+					).base();
+				TESTSPR_BOTH_ASSERT(found == sprout::end(arr1));
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::is_heap_until(
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::end(arr2)),
+					testspr::less<int>()
+					).base();
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr2) + 7);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::is_heap_until(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::less<int>()
+					).base();
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 5);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::is_heap_until(
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::begin(arr2) + 5),
+					testspr::less<int>()
+					).base();
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr2) + 5);
+			}
+#endif
 		}
 	}
 }	// namespace testspr

libs/algorithm/test/lexicographical_compare.cpp

@@ -148,6 +148,278 @@ namespace testspr {
 					);
 				TESTSPR_BOTH_ASSERT(!result);
 			}
+
+#if defined(__clang__)
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr2)),
+					testspr::reduct_input(sprout::end(arr2))
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr3)),
+					testspr::reduct_input(sprout::end(arr3))
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr4)),
+					testspr::reduct_input(sprout::end(arr4))
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::begin(arr1) + 5),
+					testspr::reduct_input(sprout::begin(arr2)),
+					testspr::reduct_input(sprout::end(arr2))
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::begin(arr1) + 5),
+					testspr::reduct_input(sprout::begin(arr3)),
+					testspr::reduct_input(sprout::end(arr3))
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::begin(arr1) + 5),
+					testspr::reduct_input(sprout::begin(arr4)),
+					testspr::reduct_input(sprout::end(arr4))
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr2)),
+					testspr::reduct_input(sprout::begin(arr2) + 5)
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr2)),
+					testspr::reduct_input(sprout::end(arr2)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr3)),
+					testspr::reduct_input(sprout::end(arr3)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr4)),
+					testspr::reduct_input(sprout::end(arr4)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::begin(arr1) + 5),
+					testspr::reduct_input(sprout::begin(arr2)),
+					testspr::reduct_input(sprout::end(arr2)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::begin(arr1) + 5),
+					testspr::reduct_input(sprout::begin(arr3)),
+					testspr::reduct_input(sprout::end(arr3)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::begin(arr1) + 5),
+					testspr::reduct_input(sprout::begin(arr4)),
+					testspr::reduct_input(sprout::end(arr4)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr2)),
+					testspr::reduct_input(sprout::begin(arr2) + 5),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+#endif
+
+#if defined(__clang__)
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::end(arr2))
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr3)),
+					testspr::reduct_random_access(sprout::end(arr3))
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr4)),
+					testspr::reduct_random_access(sprout::end(arr4))
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::end(arr2))
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::reduct_random_access(sprout::begin(arr3)),
+					testspr::reduct_random_access(sprout::end(arr3))
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::reduct_random_access(sprout::begin(arr4)),
+					testspr::reduct_random_access(sprout::end(arr4))
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::begin(arr2) + 5)
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::end(arr2)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr3)),
+					testspr::reduct_random_access(sprout::end(arr3)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr4)),
+					testspr::reduct_random_access(sprout::end(arr4)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::end(arr2)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::reduct_random_access(sprout::begin(arr3)),
+					testspr::reduct_random_access(sprout::end(arr3)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::reduct_random_access(sprout::begin(arr4)),
+					testspr::reduct_random_access(sprout::end(arr4)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::begin(arr2) + 5),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+#endif
 		}
 	}
 }	// namespace testspr

libs/algorithm/test/max_element.cpp

@@ -42,6 +42,70 @@ namespace testspr {
 					);
 				TESTSPR_BOTH_ASSERT(result == sprout::begin(arr1) + 4);
 			}
+
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::max_element(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::end(arr1))
+					).base();
+				TESTSPR_BOTH_ASSERT(result == sprout::begin(arr1) + 8);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::max_element(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::begin(arr1) + 5)
+					).base();
+				TESTSPR_BOTH_ASSERT(result == sprout::begin(arr1) + 4);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::max_element(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::end(arr1)),
+					testspr::less<int>()
+					).base();
+				TESTSPR_BOTH_ASSERT(result == sprout::begin(arr1) + 8);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::max_element(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::begin(arr1) + 5),
+					testspr::less<int>()
+					).base();
+				TESTSPR_BOTH_ASSERT(result == sprout::begin(arr1) + 4);
+			}
+
+#if defined(__clang__)
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::max_element(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1))
+					).base();
+				TESTSPR_BOTH_ASSERT(result == sprout::begin(arr1) + 8);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::max_element(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5)
+					).base();
+				TESTSPR_BOTH_ASSERT(result == sprout::begin(arr1) + 4);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::max_element(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::less<int>()
+					).base();
+				TESTSPR_BOTH_ASSERT(result == sprout::begin(arr1) + 8);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::max_element(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::less<int>()
+					).base();
+				TESTSPR_BOTH_ASSERT(result == sprout::begin(arr1) + 4);
+			}
+#endif
 		}
 	}
 }	// namespace testspr

libs/algorithm/test/min_element.cpp

@@ -42,6 +42,70 @@ namespace testspr {
 					);
 				TESTSPR_BOTH_ASSERT(result == sprout::begin(arr1) + 3);
 			}
+
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::min_element(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::end(arr1))
+					).base();
+				TESTSPR_BOTH_ASSERT(result == sprout::begin(arr1) + 9);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::min_element(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::begin(arr1) + 5)
+					).base();
+				TESTSPR_BOTH_ASSERT(result == sprout::begin(arr1) + 3);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::min_element(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::end(arr1)),
+					testspr::less<int>()
+					).base();
+				TESTSPR_BOTH_ASSERT(result == sprout::begin(arr1) + 9);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::min_element(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::begin(arr1) + 5),
+					testspr::less<int>()
+					).base();
+				TESTSPR_BOTH_ASSERT(result == sprout::begin(arr1) + 3);
+			}
+
+#if defined(__clang__)
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::min_element(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1))
+					).base();
+				TESTSPR_BOTH_ASSERT(result == sprout::begin(arr1) + 9);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::min_element(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5)
+					).base();
+				TESTSPR_BOTH_ASSERT(result == sprout::begin(arr1) + 3);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::min_element(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::less<int>()
+					).base();
+				TESTSPR_BOTH_ASSERT(result == sprout::begin(arr1) + 9);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::min_element(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::less<int>()
+					).base();
+				TESTSPR_BOTH_ASSERT(result == sprout::begin(arr1) + 3);
+			}
+#endif
 		}
 	}
 }	// namespace testspr

libs/algorithm/test/minmax_element.cpp

@@ -46,6 +46,78 @@ namespace testspr {
 				TESTSPR_BOTH_ASSERT(result.first == sprout::begin(arr1) + 3);
 				TESTSPR_BOTH_ASSERT(result.second == sprout::begin(arr1) + 4);
 			}
+
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::minmax_element(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::end(arr1))
+					);
+				TESTSPR_BOTH_ASSERT(result.first.base() == sprout::begin(arr1) + 9);
+				TESTSPR_BOTH_ASSERT(result.second.base() == sprout::begin(arr1) + 8);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::minmax_element(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::begin(arr1) + 5)
+					);
+				TESTSPR_BOTH_ASSERT(result.first.base() == sprout::begin(arr1) + 3);
+				TESTSPR_BOTH_ASSERT(result.second.base() == sprout::begin(arr1) + 4);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::minmax_element(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::end(arr1)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result.first.base() == sprout::begin(arr1) + 9);
+				TESTSPR_BOTH_ASSERT(result.second.base() == sprout::begin(arr1) + 8);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::minmax_element(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::begin(arr1) + 5),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result.first.base() == sprout::begin(arr1) + 3);
+				TESTSPR_BOTH_ASSERT(result.second.base() == sprout::begin(arr1) + 4);
+			}
+
+#if defined(__clang__)
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::minmax_element(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1))
+					);
+				TESTSPR_BOTH_ASSERT(result.first.base() == sprout::begin(arr1) + 9);
+				TESTSPR_BOTH_ASSERT(result.second.base() == sprout::begin(arr1) + 8);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::minmax_element(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5)
+					);
+				TESTSPR_BOTH_ASSERT(result.first.base() == sprout::begin(arr1) + 3);
+				TESTSPR_BOTH_ASSERT(result.second.base() == sprout::begin(arr1) + 4);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::minmax_element(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result.first.base() == sprout::begin(arr1) + 9);
+				TESTSPR_BOTH_ASSERT(result.second.base() == sprout::begin(arr1) + 8);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::minmax_element(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result.first.base() == sprout::begin(arr1) + 3);
+				TESTSPR_BOTH_ASSERT(result.second.base() == sprout::begin(arr1) + 4);
+			}
+#endif
 		}
 	}
 }	// namespace testspr

libs/algorithm/test/non_modifying.cpp

@@ -45,6 +45,7 @@
 #include "./any_of_equal.cpp"
 #include "./none_of_equal.cpp"
 #include "./one_of_equal.cpp"
+#include "./tristate_lexicographical_compare.cpp"
 #include "./is_increasing.cpp"
 #include "./is_decreasing.cpp"
 #include "./is_strictly_increasing.cpp"
@@ -96,6 +97,7 @@ namespace testspr {
 		testspr::algorithm_any_of_equal_test();
 		testspr::algorithm_none_of_equal_test();
 		testspr::algorithm_one_of_equal_test();
+		testspr::algorithm_tristate_lexicographical_compare_test();
 		testspr::algorithm_is_increasing_test();
 		testspr::algorithm_is_decreasing_test();
 		testspr::algorithm_is_strictly_increasing_test();

libs/algorithm/test/tristate_lexicographical_compare.cpp

@@ -0,0 +1,432 @@
+#ifndef SPROUT_LIBS_ALGORITHM_TEST_TRISTATE_LEXICOGRAPHICAL_COMPARE_CPP
+#define SPROUT_LIBS_ALGORITHM_TEST_TRISTATE_LEXICOGRAPHICAL_COMPARE_CPP
+
+#include <sprout/algorithm/tristate_lexicographical_compare.hpp>
+#include <sprout/array.hpp>
+#include <sprout/container.hpp>
+#include <testspr/tools.hpp>
+
+namespace testspr {
+	static void algorithm_tristate_lexicographical_compare_test() {
+		using namespace sprout;
+		{
+			SPROUT_STATIC_CONSTEXPR auto arr1 = array<int, 10>{{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}};
+			SPROUT_STATIC_CONSTEXPR auto arr2 = array<int, 10>{{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}};
+			SPROUT_STATIC_CONSTEXPR auto arr3 = array<int, 10>{{1, 2, 3, 4, 5, 6, 7, 1, 2, 3}};
+			SPROUT_STATIC_CONSTEXPR auto arr4 = array<int, 10>{{1, 2, 3, 4, 5, 6, 7, 11, 12, 13}};
+
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					sprout::begin(arr2),
+					sprout::end(arr2)
+					);
+				TESTSPR_BOTH_ASSERT(result == 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					sprout::begin(arr3),
+					sprout::end(arr3)
+					);
+				TESTSPR_BOTH_ASSERT(result > 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					sprout::begin(arr4),
+					sprout::end(arr4)
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					sprout::begin(arr1),
+					sprout::begin(arr1) + 5,
+					sprout::begin(arr2),
+					sprout::end(arr2)
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					sprout::begin(arr1),
+					sprout::begin(arr1) + 5,
+					sprout::begin(arr3),
+					sprout::end(arr3)
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					sprout::begin(arr1),
+					sprout::begin(arr1) + 5,
+					sprout::begin(arr4),
+					sprout::end(arr4)
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					sprout::begin(arr2),
+					sprout::begin(arr2) + 5
+					);
+				TESTSPR_BOTH_ASSERT(result > 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					sprout::begin(arr2),
+					sprout::end(arr2),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result == 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					sprout::begin(arr3),
+					sprout::end(arr3),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result > 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					sprout::begin(arr4),
+					sprout::end(arr4),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					sprout::begin(arr1),
+					sprout::begin(arr1) + 5,
+					sprout::begin(arr2),
+					sprout::end(arr2),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					sprout::begin(arr1),
+					sprout::begin(arr1) + 5,
+					sprout::begin(arr3),
+					sprout::end(arr3),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					sprout::begin(arr1),
+					sprout::begin(arr1) + 5,
+					sprout::begin(arr4),
+					sprout::end(arr4),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					sprout::begin(arr2),
+					sprout::begin(arr2) + 5,
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result > 0);
+			}
+
+#if defined(__clang__)
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr2)),
+					testspr::reduct_input(sprout::end(arr2))
+					);
+				TESTSPR_BOTH_ASSERT(result == 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr3)),
+					testspr::reduct_input(sprout::end(arr3))
+					);
+				TESTSPR_BOTH_ASSERT(result > 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr4)),
+					testspr::reduct_input(sprout::end(arr4))
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::begin(arr1) + 5),
+					testspr::reduct_input(sprout::begin(arr2)),
+					testspr::reduct_input(sprout::end(arr2))
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::begin(arr1) + 5),
+					testspr::reduct_input(sprout::begin(arr3)),
+					testspr::reduct_input(sprout::end(arr3))
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::begin(arr1) + 5),
+					testspr::reduct_input(sprout::begin(arr4)),
+					testspr::reduct_input(sprout::end(arr4))
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr2)),
+					testspr::reduct_input(sprout::begin(arr2) + 5)
+					);
+				TESTSPR_BOTH_ASSERT(result > 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr2)),
+					testspr::reduct_input(sprout::end(arr2)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result == 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr3)),
+					testspr::reduct_input(sprout::end(arr3)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result > 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr4)),
+					testspr::reduct_input(sprout::end(arr4)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::begin(arr1) + 5),
+					testspr::reduct_input(sprout::begin(arr2)),
+					testspr::reduct_input(sprout::end(arr2)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::begin(arr1) + 5),
+					testspr::reduct_input(sprout::begin(arr3)),
+					testspr::reduct_input(sprout::end(arr3)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::begin(arr1) + 5),
+					testspr::reduct_input(sprout::begin(arr4)),
+					testspr::reduct_input(sprout::end(arr4)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_input(sprout::begin(arr1)),
+					testspr::reduct_input(sprout::end(arr1)),
+					testspr::reduct_input(sprout::begin(arr2)),
+					testspr::reduct_input(sprout::begin(arr2) + 5),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result > 0);
+			}
+#endif
+
+#if defined(__clang__)
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::end(arr2))
+					);
+				TESTSPR_BOTH_ASSERT(result == 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr3)),
+					testspr::reduct_random_access(sprout::end(arr3))
+					);
+				TESTSPR_BOTH_ASSERT(result > 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr4)),
+					testspr::reduct_random_access(sprout::end(arr4))
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::end(arr2))
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::reduct_random_access(sprout::begin(arr3)),
+					testspr::reduct_random_access(sprout::end(arr3))
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::reduct_random_access(sprout::begin(arr4)),
+					testspr::reduct_random_access(sprout::end(arr4))
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::begin(arr2) + 5)
+					);
+				TESTSPR_BOTH_ASSERT(result > 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::end(arr2)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result == 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr3)),
+					testspr::reduct_random_access(sprout::end(arr3)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result > 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr4)),
+					testspr::reduct_random_access(sprout::end(arr4)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::end(arr2)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::reduct_random_access(sprout::begin(arr3)),
+					testspr::reduct_random_access(sprout::end(arr3)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					testspr::reduct_random_access(sprout::begin(arr4)),
+					testspr::reduct_random_access(sprout::end(arr4)),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result < 0);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::tristate_lexicographical_compare(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr2)),
+					testspr::reduct_random_access(sprout::begin(arr2) + 5),
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(result > 0);
+			}
+#endif
+		}
+	}
+}	// namespace testspr
+
+#ifndef TESTSPR_CPP_INCLUDE
+#	define TESTSPR_TEST_FUNCTION testspr::algorithm_tristate_lexicographical_compare_test
+#	include <testspr/include_main.hpp>
+#endif
+
+#endif	// #ifndef SPROUT_LIBS_ALGORITHM_TEST_TRISTATE_LEXICOGRAPHICAL_COMPARE_CPP

sprout/algorithm/includes.hpp

@@ -2,16 +2,19 @@
 #define SPROUT_ALGORITHM_INCLUDES_HPP
 
 #include <iterator>
+#include <type_traits>
 #include <sprout/config.hpp>
 #include <sprout/iterator/operation.hpp>
+#include <sprout/iterator/type_traits/is_iterator.hpp>
 #include <sprout/functional/less.hpp>
+#include <sprout/utility/pair.hpp>
 
 namespace sprout {
 	namespace detail {
-		template<typename RandomAccessIterator1, typename RandomAccessIterator2, typename Compare>
+		template<typename RandomAccessIterator1, typename InputIterator2, typename Compare>
-		inline SPROUT_CONSTEXPR RandomAccessIterator2
+		inline SPROUT_CONSTEXPR InputIterator2
 		includes_impl_ra(
-			RandomAccessIterator1 first1, RandomAccessIterator1 last1, RandomAccessIterator2 first2, RandomAccessIterator2 last2, Compare comp,
+			RandomAccessIterator1 first1, RandomAccessIterator1 last1, InputIterator2 first2, InputIterator2 last2, Compare comp,
 			typename std::iterator_traits<RandomAccessIterator1>::difference_type pivot
 			)
 		{
@@ -30,10 +33,13 @@ namespace sprout {
 					)
 				;
 		}
-		template<typename RandomAccessIterator1, typename RandomAccessIterator2, typename Compare>
+		template<typename RandomAccessIterator1, typename InputIterator2, typename Compare>
-		inline SPROUT_CONSTEXPR bool
+		inline SPROUT_CONSTEXPR typename std::enable_if<
+			sprout::is_constant_distance_iterator<RandomAccessIterator1>::value,
+			bool
+		>::type
 		includes(
-			RandomAccessIterator1 first1, RandomAccessIterator1 last1, RandomAccessIterator2 first2, RandomAccessIterator2 last2, Compare comp,
+			RandomAccessIterator1 first1, RandomAccessIterator1 last1, InputIterator2 first2, InputIterator2 last2, Compare comp,
 			std::random_access_iterator_tag*
 			)
 		{
@@ -46,33 +52,67 @@ namespace sprout {
 				;
 		}
 
-		// Copyright (C) 2011 RiSK (sscrisk)
 		template<typename InputIterator1, typename InputIterator2, typename Compare>
-		inline SPROUT_CONSTEXPR bool
+		inline SPROUT_CONSTEXPR sprout::pair<InputIterator1, InputIterator2>
-		includes_impl(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, Compare comp) {
+		includes_impl_1(
-			return first2 == last2 ? true
+			sprout::pair<InputIterator1, InputIterator2> const& current,
-				: first1 == last1 ? false
+			InputIterator1 last1, InputIterator2 last2, Compare comp,
-				: !comp(*first1, *first2) && !comp(*first2, *first1)
+			typename std::iterator_traits<InputIterator1>::difference_type n
-					? sprout::detail::includes_impl(sprout::next(first1), last1, sprout::next(first2), last2)
+			)
-				: sprout::detail::includes_impl(sprout::next(first1), last1, first2, last2)
+		{
+			typedef sprout::pair<InputIterator1, InputIterator2> type;
+			return current.second == last2 || current.first == last1 ? current
+				: n == 1 ? !comp(*current.first, *current.second) && !comp(*current.second, *current.first)
+					? type(sprout::next(current.first), sprout::next(current.second))
+					: type(sprout::next(current.first), current.second)
+				: sprout::detail::includes_impl_1(
+					sprout::detail::includes_impl_1(
+						current,
+						last1, last2, comp, n / 2
+						),
+					last1, last2, comp, n - n / 2
+					)
+				;
+		}
+		template<typename InputIterator1, typename InputIterator2, typename Compare>
+		inline SPROUT_CONSTEXPR sprout::pair<InputIterator1, InputIterator2>
+		includes_impl(
+			sprout::pair<InputIterator1, InputIterator2> const& current,
+			InputIterator1 last1, InputIterator2 last2, Compare comp,
+			typename std::iterator_traits<InputIterator1>::difference_type n
+			)
+		{
+			typedef sprout::pair<InputIterator1, InputIterator2> type;
+			return current.second == last2 || current.first == last1 ? current
+				: sprout::detail::includes_impl(
+					sprout::detail::includes_impl_1(
+						current,
+						last1, last2, comp, n
+						),
+					last1, last2, comp, n * 2
+					)
 				;
 		}
 		template<typename InputIterator1, typename InputIterator2, typename Compare>
 		inline SPROUT_CONSTEXPR bool
 		includes(
-			InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, Compare comp,
+			InputIterator1 first1, InputIterator1 last1,
+			InputIterator2 first2, InputIterator2 last2,
+			Compare comp,
 			void*
 			)
 		{
-			return sprout::detail::includes_impl(first1, last1, first2, comp);
+			typedef sprout::pair<InputIterator1, InputIterator2> type;
+			return first2 == last2 ? true
+				: sprout::detail::includes_impl(type(first1, first2), last1, last2, comp, 1).second == last2
+				;
 		}
 	}	// namespace detail
 
 	// 25.4.5.1 includes
 	//
 	//	recursion depth:
-	//		[first, last) is RandomAccessIterator -> O(log N)
+	//		O(log(N1+N2))
-	//		otherwise -> O(N)
 	//
 	template<typename InputIterator1, typename InputIterator2, typename Compare>
 	inline SPROUT_CONSTEXPR bool

sprout/algorithm/lexicographical_compare.hpp

@@ -1,8 +1,11 @@
 #ifndef SPROUT_ALGORITHM_LEXICOGRAPHICAL_COMPARE_HPP
 #define SPROUT_ALGORITHM_LEXICOGRAPHICAL_COMPARE_HPP
 
+#include <iterator>
+#include <type_traits>
 #include <sprout/config.hpp>
 #include <sprout/iterator/operation.hpp>
+#include <sprout/iterator/type_traits/is_iterator.hpp>
 #include <sprout/iterator/type_traits/common.hpp>
 #include <sprout/utility/pair.hpp>
 #include <sprout/algorithm/min.hpp>
@@ -12,7 +15,7 @@ namespace sprout {
 	namespace detail {
 		template<typename RandomAccessIterator1, typename RandomAccessIterator2, typename Compare>
 		inline SPROUT_CONSTEXPR bool
-		lexicographical_compare_impl_ra_2(
+		lexicographical_compare_impl_check(
 			RandomAccessIterator1 last1, RandomAccessIterator2 last2, Compare comp,
 			sprout::pair<RandomAccessIterator1, RandomAccessIterator2> const& found
 			)
@@ -21,6 +24,7 @@ namespace sprout {
 				: found.first == last1 || comp(*found.first, *found.second)
 				;
 		}
+
 		template<typename RandomAccessIterator1, typename RandomAccessIterator2, typename Compare>
 		inline SPROUT_CONSTEXPR sprout::pair<RandomAccessIterator1, RandomAccessIterator2>
 		lexicographical_compare_impl_ra_1(
@@ -50,7 +54,7 @@ namespace sprout {
 			)
 		{
 			typedef sprout::pair<RandomAccessIterator1, RandomAccessIterator2> found_type;
-			return sprout::detail::lexicographical_compare_impl_ra_2(
+			return sprout::detail::lexicographical_compare_impl_check(
 				last1, last2, comp,
 				sprout::detail::lexicographical_compare_impl_ra_1(
 					first1, sprout::next(first1, size), first2, sprout::next(first2, size), comp,
@@ -59,7 +63,10 @@ namespace sprout {
 				);
 		}
 		template<typename RandomAccessIterator1, typename RandomAccessIterator2, typename Compare>
-		inline SPROUT_CONSTEXPR bool
+		inline SPROUT_CONSTEXPR typename std::enable_if<
+			sprout::is_constant_distance_iterator<RandomAccessIterator1>::value,
+			bool
+		>::type
 		lexicographical_compare(
 			RandomAccessIterator1 first1, RandomAccessIterator1 last1, RandomAccessIterator2 first2, RandomAccessIterator2 last2, Compare comp,
 			std::random_access_iterator_tag*
@@ -74,14 +81,45 @@ namespace sprout {
 				;
 		}
 
-		// Copyright (C) 2011 RiSK (sscrisk)
 		template<typename InputIterator1, typename InputIterator2, typename Compare>
-		inline SPROUT_CONSTEXPR bool
+		inline SPROUT_CONSTEXPR sprout::pair<InputIterator1, InputIterator2>
-		lexicographical_compare_impl(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, InputIterator2 last2, Compare comp) {
+		lexicographical_compare_impl_1(
-			return first2 == last2 ? false
+			sprout::pair<InputIterator1, InputIterator2> current,
-				: first1 == last1 || comp(*first1, *first2) ? true
+			InputIterator1 last1, InputIterator2 last2, Compare comp,
-				: comp(*first2, *first1) ? false
+			typename std::iterator_traits<InputIterator1>::difference_type n
-				: sprout::detail::lexicographical_compare_impl(sprout::next(first1), last1, sprout::next(first2), last2, comp)
+			)
+		{
+			typedef sprout::pair<InputIterator1, InputIterator2> type;
+			return current.second == last2 || current.first == last1 ? current
+				: n == 1 ? comp(*current.first, *current.second) ? type(last1, current.second)
+					: comp(*current.second, *current.first) ? type(current.first, last2)
+					: type(sprout::next(current.first), sprout::next(current.second))
+				: sprout::detail::lexicographical_compare_impl_1(
+					sprout::detail::lexicographical_compare_impl_1(
+						current,
+						last1, last2, comp, n / 2
+						),
+					last1, last2, comp, n - n / 2
+					)
+				;
+		}
+		template<typename InputIterator1, typename InputIterator2, typename Compare>
+		inline SPROUT_CONSTEXPR sprout::pair<InputIterator1, InputIterator2>
+		lexicographical_compare_impl(
+			sprout::pair<InputIterator1, InputIterator2> current,
+			InputIterator1 last1, InputIterator2 last2, Compare comp,
+			typename std::iterator_traits<InputIterator1>::difference_type n
+			)
+		{
+			typedef sprout::pair<InputIterator1, InputIterator2> type;
+			return current.second == last2 || current.first == last1 ? current
+				: sprout::detail::lexicographical_compare_impl(
+					sprout::detail::lexicographical_compare_impl_1(
+						current,
+						last1, last2, comp, n
+						),
+					last1, last2, comp, n * 2
+					)
 				;
 		}
 		template<typename InputIterator1, typename InputIterator2, typename Compare>
@@ -91,15 +129,18 @@ namespace sprout {
 			void*
 			)
 		{
-			return sprout::detail::lexicographical_compare_impl(first1, last1, first2, last2, comp);
+			typedef sprout::pair<InputIterator1, InputIterator2> type;
+			return sprout::detail::lexicographical_compare_impl_check(
+				last1, last2, comp,
+				sprout::detail::lexicographical_compare_impl(type(first1, first2), last1, last2, comp, 1)
+				);
 		}
 	}	// namespace detail
 
 	// 25.4.8 Lexicographical comparison
 	//
 	//	recursion depth:
-	//		[first1, last1), [first2, last2) are RandomAccessIterator -> O(log N)
+	//		O(log(N1+N2))
-	//		otherwise -> O(N)
 	//
 	template<typename InputIterator1, typename InputIterator2, typename Compare>
 	inline SPROUT_CONSTEXPR bool

sprout/algorithm/max_element.hpp

@@ -2,8 +2,11 @@
 #define SPROUT_ALGORITHM_MAX_ELEMENT_HPP
 
 #include <iterator>
+#include <type_traits>
 #include <sprout/config.hpp>
 #include <sprout/iterator/operation.hpp>
+#include <sprout/iterator/type_traits/is_iterator.hpp>
+#include <sprout/utility/pair.hpp>
 #include HDR_FUNCTIONAL_SSCRISK_CEL_OR_SPROUT
 
 namespace sprout {
@@ -36,7 +39,10 @@ namespace sprout {
 				;
 		}
 		template<typename RandomAccessIterator, typename Compare>
-		inline SPROUT_CONSTEXPR RandomAccessIterator
+		inline SPROUT_CONSTEXPR typename std::enable_if<
+			sprout::is_constant_distance_iterator<RandomAccessIterator>::value,
+			RandomAccessIterator
+		>::type
 		max_element(
 			RandomAccessIterator first, RandomAccessIterator last, Compare comp,
 			std::random_access_iterator_tag*
@@ -50,16 +56,41 @@ namespace sprout {
 				;
 		}
 
-		// Copyright (C) 2011 RiSK (sscrisk)
 		template<typename ForwardIterator, typename Compare>
-		inline SPROUT_CONSTEXPR ForwardIterator
+		inline SPROUT_CONSTEXPR sprout::pair<ForwardIterator, ForwardIterator>
-		max_element_impl(
+		max_element_impl_1(
-			ForwardIterator first, ForwardIterator last, Compare comp,
+			sprout::pair<ForwardIterator, ForwardIterator> const& current,
-			ForwardIterator found
+			ForwardIterator last, Compare comp, typename std::iterator_traits<ForwardIterator>::difference_type n
 			)
 		{
-			return first == last ? found
+			typedef sprout::pair<ForwardIterator, ForwardIterator> type;
-				: sprout::detail::max_element_impl(sprout::next(first), last, comp, sprout::detail::iter_max(found, first, comp))
+			return current.first == last ? current
+				: n == 1 ? type(sprout::next(current.first), sprout::detail::iter_max(current.second, current.first, comp))
+				: sprout::detail::max_element_impl_1(
+					sprout::detail::max_element_impl_1(
+						current,
+						last, comp, n / 2
+						),
+					last, comp, n - n / 2
+					)
+				;
+		}
+		template<typename ForwardIterator, typename Compare>
+		inline SPROUT_CONSTEXPR sprout::pair<ForwardIterator, ForwardIterator>
+		max_element_impl(
+			sprout::pair<ForwardIterator, ForwardIterator> const& current,
+			ForwardIterator last, Compare comp, typename std::iterator_traits<ForwardIterator>::difference_type n
+			)
+		{
+			typedef sprout::pair<ForwardIterator, ForwardIterator> type;
+			return current.first == last ? current
+				: sprout::detail::max_element_impl(
+					sprout::detail::max_element_impl_1(
+						current,
+						last, comp, n
+						),
+					last, comp, n * 2
+					)
 				;
 		}
 		template<typename ForwardIterator, typename Compare>
@@ -69,8 +100,9 @@ namespace sprout {
 			void*
 			)
 		{
+			typedef sprout::pair<ForwardIterator, ForwardIterator> type;
 			return first == last ? last
-				: sprout::detail::max_element_impl(sprout::next(first), last, comp, first)
+				: sprout::detail::max_element_impl(type(sprout::next(first), first), last, comp, 1).second
 				;
 		}
 	}	// namespace detail
@@ -78,8 +110,7 @@ namespace sprout {
 	// 25.4.7 Minimum and maximum
 	//
 	//	recursion depth:
-	//		[first, last) is RandomAccessIterator -> O(log N)
+	//		O(log N)
-	//		otherwise -> O(N)
 	//
 	template<typename ForwardIterator, typename Compare>
 	inline SPROUT_CONSTEXPR ForwardIterator

sprout/algorithm/min_element.hpp

@@ -2,15 +2,18 @@
 #define SPROUT_ALGORITHM_MIN_ELEMENT_HPP
 
 #include <iterator>
+#include <type_traits>
 #include <sprout/config.hpp>
 #include <sprout/iterator/operation.hpp>
+#include <sprout/iterator/type_traits/is_iterator.hpp>
+#include <sprout/utility/pair.hpp>
 #include HDR_FUNCTIONAL_SSCRISK_CEL_OR_SPROUT
 
 namespace sprout {
 	namespace detail {
-		template<typename InputIterator, typename Compare>
+		template<typename ForwardIterator, typename Compare>
-		inline SPROUT_CONSTEXPR InputIterator
+		inline SPROUT_CONSTEXPR ForwardIterator
-		iter_min(InputIterator a, InputIterator b, Compare comp) {
+		iter_min(ForwardIterator a, ForwardIterator b, Compare comp) {
 			return comp(*b, *a) ? b : a;
 		}
 
@@ -36,7 +39,10 @@ namespace sprout {
 				;
 		}
 		template<typename RandomAccessIterator, typename Compare>
-		inline SPROUT_CONSTEXPR RandomAccessIterator
+		inline SPROUT_CONSTEXPR typename std::enable_if<
+			sprout::is_constant_distance_iterator<RandomAccessIterator>::value,
+			RandomAccessIterator
+		>::type
 		min_element(
 			RandomAccessIterator first, RandomAccessIterator last, Compare comp,
 			std::random_access_iterator_tag*
@@ -50,16 +56,41 @@ namespace sprout {
 				;
 		}
 
-		// Copyright (C) 2011 RiSK (sscrisk)
 		template<typename ForwardIterator, typename Compare>
-		inline SPROUT_CONSTEXPR ForwardIterator
+		inline SPROUT_CONSTEXPR sprout::pair<ForwardIterator, ForwardIterator>
-		min_element_impl(
+		min_element_impl_1(
-			ForwardIterator first, ForwardIterator last, Compare comp,
+			sprout::pair<ForwardIterator, ForwardIterator> const& current,
-			ForwardIterator found
+			ForwardIterator last, Compare comp, typename std::iterator_traits<ForwardIterator>::difference_type n
 			)
 		{
-			return first == last ? found
+			typedef sprout::pair<ForwardIterator, ForwardIterator> type;
-				: sprout::detail::min_element_impl(sprout::next(first), last, comp, sprout::detail::iter_min(found, first, comp))
+			return current.first == last ? current
+				: n == 1 ? type(sprout::next(current.first), sprout::detail::iter_min(current.second, current.first, comp))
+				: sprout::detail::min_element_impl_1(
+					sprout::detail::min_element_impl_1(
+						current,
+						last, comp, n / 2
+						),
+					last, comp, n - n / 2
+					)
+				;
+		}
+		template<typename ForwardIterator, typename Compare>
+		inline SPROUT_CONSTEXPR sprout::pair<ForwardIterator, ForwardIterator>
+		min_element_impl(
+			sprout::pair<ForwardIterator, ForwardIterator> const& current,
+			ForwardIterator last, Compare comp, typename std::iterator_traits<ForwardIterator>::difference_type n
+			)
+		{
+			typedef sprout::pair<ForwardIterator, ForwardIterator> type;
+			return current.first == last ? current
+				: sprout::detail::min_element_impl(
+					sprout::detail::min_element_impl_1(
+						current,
+						last, comp, n
+						),
+					last, comp, n * 2
+					)
 				;
 		}
 		template<typename ForwardIterator, typename Compare>
@@ -69,8 +100,9 @@ namespace sprout {
 			void*
 			)
 		{
+			typedef sprout::pair<ForwardIterator, ForwardIterator> type;
 			return first == last ? last
-				: sprout::detail::min_element_impl(sprout::next(first), last, comp, first)
+				: sprout::detail::min_element_impl(type(sprout::next(first), first), last, comp, 1).second
 				;
 		}
 	}	// namespace detail
@@ -78,8 +110,7 @@ namespace sprout {
 	// 25.4.7 Minimum and maximum
 	//
 	//	recursion depth:
-	//		[first, last) is RandomAccessIterator -> O(log N)
+	//		O(log N)
-	//		otherwise -> O(N)
 	//
 	template<typename ForwardIterator, typename Compare>
 	inline SPROUT_CONSTEXPR ForwardIterator

sprout/algorithm/minmax_element.hpp

@@ -2,8 +2,10 @@
 #define SPROUT_ALGORITHM_MINMAX_ELEMENT_HPP
 
 #include <iterator>
+#include <type_traits>
 #include <sprout/config.hpp>
 #include <sprout/iterator/operation.hpp>
+#include <sprout/iterator/type_traits/is_iterator.hpp>
 #include <sprout/utility/pair.hpp>
 #include HDR_FUNCTIONAL_SSCRISK_CEL_OR_SPROUT
 
@@ -11,12 +13,20 @@ namespace sprout {
 	namespace detail {
 		template<typename InputIteratorPair, typename Compare>
 		inline SPROUT_CONSTEXPR InputIteratorPair
-		iter_minmax(InputIteratorPair a, InputIteratorPair b, Compare comp) {
+		iter_minmax_pair(InputIteratorPair const& a, InputIteratorPair const& b, Compare comp) {
 			return InputIteratorPair(
 				comp(*sprout::first(b), *sprout::first(a)) ? sprout::first(b) : sprout::first(a),
 				comp(*sprout::second(a), *sprout::second(b)) ? sprout::second(b) : sprout::second(a)
 				);
 		}
+		template<typename InputIteratorPair, typename InputIterator, typename Compare>
+		inline SPROUT_CONSTEXPR InputIteratorPair
+		iter_minmax(InputIteratorPair const& a, InputIterator b, Compare comp) {
+			return InputIteratorPair(
+				comp(*b, *sprout::first(a)) ? b : sprout::first(a),
+				comp(*sprout::second(a), *b) ? b : sprout::second(a)
+				);
+		}
 
 		template<typename RandomAccessIterator, typename Compare>
 		inline SPROUT_CONSTEXPR sprout::pair<RandomAccessIterator, RandomAccessIterator>
@@ -26,7 +36,7 @@ namespace sprout {
 			)
 		{
 			return pivot == 0 ? sprout::pair<RandomAccessIterator, RandomAccessIterator>(first, first)
-				: sprout::detail::iter_minmax(
+				: sprout::detail::iter_minmax_pair(
 					sprout::detail::minmax_element_impl_ra(
 						first, sprout::next(first, pivot), comp,
 						pivot / 2
@@ -40,7 +50,10 @@ namespace sprout {
 				;
 		}
 		template<typename RandomAccessIterator, typename Compare>
-		inline SPROUT_CONSTEXPR sprout::pair<RandomAccessIterator, RandomAccessIterator>
+		inline SPROUT_CONSTEXPR typename std::enable_if<
+			sprout::is_constant_distance_iterator<RandomAccessIterator>::value,
+			sprout::pair<RandomAccessIterator, RandomAccessIterator>
+		>::type
 		minmax_element(
 			RandomAccessIterator first, RandomAccessIterator last, Compare comp,
 			std::random_access_iterator_tag*
@@ -54,17 +67,41 @@ namespace sprout {
 				;
 		}
 
-		// Copyright (C) 2011 RiSK (sscrisk)
 		template<typename ForwardIterator, typename Compare>
-		inline SPROUT_CONSTEXPR sprout::pair<ForwardIterator, ForwardIterator>
+		inline SPROUT_CONSTEXPR sprout::pair<ForwardIterator, sprout::pair<ForwardIterator, ForwardIterator> >
-		minmax_element_impl(
+		minmax_element_impl_1(
-			ForwardIterator first, ForwardIterator last, Compare comp,
+			sprout::pair<ForwardIterator, sprout::pair<ForwardIterator, ForwardIterator> > const& current,
-			ForwardIterator min, ForwardIterator max
+			ForwardIterator last, Compare comp, typename std::iterator_traits<ForwardIterator>::difference_type n
 			)
 		{
-			return first == last ? sprout::pair<ForwardIterator, ForwardIterator>(min, max)
+			typedef sprout::pair<ForwardIterator, sprout::pair<ForwardIterator, ForwardIterator> > type;
-				: comp(*first, *min) ? sprout::detail::minmax_element_impl(sprout::next(first), last, comp, first, max)
+			return current.first == last ? current
-				: sprout::detail::minmax_element_impl(sprout::next(first), last, comp, min, comp(*first, *max) ? max : first)
+				: n == 1 ? type(sprout::next(current.first), sprout::detail::iter_minmax(current.second, current.first, comp))
+				: sprout::detail::minmax_element_impl_1(
+					sprout::detail::minmax_element_impl_1(
+						current,
+						last, comp, n / 2
+						),
+					last, comp, n - n / 2
+					)
+				;
+		}
+		template<typename ForwardIterator, typename Compare>
+		inline SPROUT_CONSTEXPR sprout::pair<ForwardIterator, sprout::pair<ForwardIterator, ForwardIterator> >
+		minmax_element_impl(
+			sprout::pair<ForwardIterator, sprout::pair<ForwardIterator, ForwardIterator> > const& current,
+			ForwardIterator last, Compare comp, typename std::iterator_traits<ForwardIterator>::difference_type n
+			)
+		{
+			typedef sprout::pair<ForwardIterator, sprout::pair<ForwardIterator, ForwardIterator> > type;
+			return current.first == last ? current
+				: sprout::detail::minmax_element_impl(
+					sprout::detail::minmax_element_impl_1(
+						current,
+						last, comp, n
+						),
+					last, comp, n * 2
+					)
 				;
 		}
 		template<typename ForwardIterator, typename Compare>
@@ -74,8 +111,9 @@ namespace sprout {
 			void*
 			)
 		{
-			return first == last ? sprout::pair<ForwardIterator, ForwardIterator>(last, last)
+			typedef sprout::pair<ForwardIterator, sprout::pair<ForwardIterator, ForwardIterator> > type;
-				: sprout::detail::minmax_element_impl(sprout::next(first), last, comp, first, first)
+			return first == last ? sprout::pair<ForwardIterator, ForwardIterator>(first, first)
+				: sprout::detail::minmax_element_impl(type(sprout::next(first), sprout::pair<ForwardIterator, ForwardIterator>(first, first)), last, comp, 1).second
 				;
 		}
 	}	// namespace detail
@@ -83,8 +121,7 @@ namespace sprout {
 	// 25.4.7 Minimum and maximum
 	//
 	//	recursion depth:
-	//		[first, last) is RandomAccessIterator -> O(log N)
+	//		O(log N)
-	//		otherwise -> O(N)
 	//
 	template<typename ForwardIterator, typename Compare>
 	inline SPROUT_CONSTEXPR sprout::pair<ForwardIterator, ForwardIterator>