diff --git a/libs/algorithm/test/binary_search.cpp b/libs/algorithm/test/binary_search.cpp
index 5a7176c9..c7ec0b1e 100644
--- a/libs/algorithm/test/binary_search.cpp
+++ b/libs/algorithm/test/binary_search.cpp
@@ -29,6 +29,46 @@ namespace testspr {
 					);
 				TESTSPR_BOTH_ASSERT(!result);
 			}
+
+#if defined(__clang__)
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::binary_search(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::end(arr1)),
+					7
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::binary_search(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::begin(arr1) + 5),
+					7,
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+#endif
+
+#if defined(__clang__)
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::binary_search(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					7
+					);
+				TESTSPR_BOTH_ASSERT(result);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto result = sprout::binary_search(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					7,
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(!result);
+			}
+#endif
 		}
 	}
 }	// namespace testspr
diff --git a/libs/algorithm/test/equal_range.cpp b/libs/algorithm/test/equal_range.cpp
index 2b659b07..5c413ade 100644
--- a/libs/algorithm/test/equal_range.cpp
+++ b/libs/algorithm/test/equal_range.cpp
@@ -4,6 +4,7 @@
 #include <sprout/algorithm/equal_range.hpp>
 #include <sprout/array.hpp>
 #include <sprout/container.hpp>
+#include <sprout/iterator.hpp>
 #include <testspr/tools.hpp>
 
 namespace testspr {
@@ -20,7 +21,7 @@ namespace testspr {
 					);
 				TESTSPR_BOTH_ASSERT(found.first == sprout::begin(arr1) + 6);
 				TESTSPR_BOTH_ASSERT(found.second == sprout::begin(arr1) + 9);
-				TESTSPR_BOTH_ASSERT(found.second - found.first == 3);
+				TESTSPR_BOTH_ASSERT(sprout::distance(found.first, found.second) == 3);
 			}
 			{
 				SPROUT_STATIC_CONSTEXPR auto found = sprout::equal_range(
@@ -31,8 +32,54 @@ namespace testspr {
 					);
 				TESTSPR_BOTH_ASSERT(found.first == sprout::begin(arr1) + 5);
 				TESTSPR_BOTH_ASSERT(found.second == sprout::begin(arr1) + 5);
-				TESTSPR_BOTH_ASSERT(found.second - found.first == 0);
+				TESTSPR_BOTH_ASSERT(sprout::distance(found.first, found.second) == 0);
 			}
+
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::equal_range(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::end(arr1)),
+					7
+					);
+				TESTSPR_BOTH_ASSERT(found.first.base() == sprout::begin(arr1) + 6);
+				TESTSPR_BOTH_ASSERT(found.second.base() == sprout::begin(arr1) + 9);
+				TESTSPR_BOTH_ASSERT(sprout::distance(found.first.base(), found.second.base()) == 3);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::equal_range(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::begin(arr1) + 5),
+					7,
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(found.first.base() == sprout::begin(arr1) + 5);
+				TESTSPR_BOTH_ASSERT(found.second.base() == sprout::begin(arr1) + 5);
+				TESTSPR_BOTH_ASSERT(sprout::distance(found.first.base(), found.second.base()) == 0);
+			}
+
+#if defined(__clang__)
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::equal_range(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					7
+					);
+				TESTSPR_BOTH_ASSERT(found.first.base() == sprout::begin(arr1) + 6);
+				TESTSPR_BOTH_ASSERT(found.second.base() == sprout::begin(arr1) + 9);
+				TESTSPR_BOTH_ASSERT(sprout::distance(found.first.base(), found.second.base()) == 3);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::equal_range(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					7,
+					testspr::less<int>()
+					);
+				TESTSPR_BOTH_ASSERT(found.first.base() == sprout::begin(arr1) + 5);
+				TESTSPR_BOTH_ASSERT(found.second.base() == sprout::begin(arr1) + 5);
+				TESTSPR_BOTH_ASSERT(sprout::distance(found.first.base(), found.second.base()) == 0);
+			}
+#endif
 		}
 	}
 }	// namespace testspr
diff --git a/libs/algorithm/test/lower_bound.cpp b/libs/algorithm/test/lower_bound.cpp
index 5442d142..7130d33c 100644
--- a/libs/algorithm/test/lower_bound.cpp
+++ b/libs/algorithm/test/lower_bound.cpp
@@ -29,6 +29,44 @@ namespace testspr {
 					);
 				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 5);
 			}
+
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::lower_bound(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::end(arr1)),
+					7
+					).base();
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 6);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::lower_bound(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::begin(arr1) + 5),
+					7,
+					testspr::less<int>()
+					).base();
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 5);
+			}
+
+#if defined(__clang__)
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::lower_bound(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					7
+					).base();
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 6);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::lower_bound(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					7,
+					testspr::less<int>()
+					).base();
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 5);
+			}
+#endif
 		}
 	}
 }	// namespace testspr
diff --git a/libs/algorithm/test/upper_bound.cpp b/libs/algorithm/test/upper_bound.cpp
index 8f846bd3..fab9dd17 100644
--- a/libs/algorithm/test/upper_bound.cpp
+++ b/libs/algorithm/test/upper_bound.cpp
@@ -29,6 +29,44 @@ namespace testspr {
 					);
 				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 5);
 			}
+
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::upper_bound(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::end(arr1)),
+					7
+					).base();
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 9);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::upper_bound(
+					testspr::reduct_forward(sprout::begin(arr1)),
+					testspr::reduct_forward(sprout::begin(arr1) + 5),
+					7,
+					testspr::less<int>()
+					).base();
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 5);
+			}
+
+#if defined(__clang__)
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::upper_bound(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::end(arr1)),
+					7
+					).base();
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 9);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::upper_bound(
+					testspr::reduct_random_access(sprout::begin(arr1)),
+					testspr::reduct_random_access(sprout::begin(arr1) + 5),
+					7,
+					testspr::less<int>()
+					).base();
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 5);
+			}
+#endif
 		}
 	}
 }	// namespace testspr
diff --git a/sprout/algorithm/binary_search.hpp b/sprout/algorithm/binary_search.hpp
index 45f1add6..39ef394e 100644
--- a/sprout/algorithm/binary_search.hpp
+++ b/sprout/algorithm/binary_search.hpp
@@ -1,6 +1,7 @@
 #ifndef SPROUT_ALGORITHM_BINARY_SEARCH_HPP
 #define SPROUT_ALGORITHM_BINARY_SEARCH_HPP
 
+#include <iterator>
 #include <sprout/config.hpp>
 #include <sprout/algorithm/lower_bound.hpp>
 #include HDR_FUNCTIONAL_SSCRISK_CEL_OR_SPROUT
@@ -17,8 +18,7 @@ namespace sprout {
 	// 25.4.3.4 binary_search
 	//
 	//	recursion depth:
-	//		[first, last) is RandomAccessIterator -> O(log N)
-	//		otherwise -> O(N)
+	//		O(log N)
 	//
 	template<typename ForwardIterator, typename T, typename Compare>
 	inline SPROUT_CONSTEXPR bool
diff --git a/sprout/algorithm/equal_range.hpp b/sprout/algorithm/equal_range.hpp
index bd79726d..0705b554 100644
--- a/sprout/algorithm/equal_range.hpp
+++ b/sprout/algorithm/equal_range.hpp
@@ -1,6 +1,7 @@
 #ifndef SPROUT_ALGORITHM_EQUAL_RANGE_HPP
 #define SPROUT_ALGORITHM_EQUAL_RANGE_HPP
 
+#include <iterator>
 #include <sprout/config.hpp>
 #include <sprout/algorithm/lower_bound.hpp>
 #include <sprout/algorithm/upper_bound.hpp>
@@ -13,13 +14,15 @@ namespace sprout {
 	// 25.4.3.3 equal_range
 	//
 	//	recursion depth:
-	//		[first, last) is RandomAccessIterator -> O(log N)
-	//		otherwise -> O(N)
+	//		O(log N)
 	//
 	template<typename ForwardIterator, typename T, typename Compare>
-	inline SPROUT_CONSTEXPR pair<ForwardIterator, ForwardIterator>
+	inline SPROUT_CONSTEXPR sprout::pair<ForwardIterator, ForwardIterator>
 	equal_range(ForwardIterator first, ForwardIterator last, T const& value, Compare comp) {
-		return {sprout::lower_bound(first, last, value, comp), sprout::upper_bound(first, last, value, comp)};
+		return sprout::pair<ForwardIterator, ForwardIterator>{
+			sprout::lower_bound(first, last, value, comp),
+			sprout::upper_bound(first, last, value, comp)
+			};
 	}
 
 	template<typename ForwardIterator, typename T>
diff --git a/sprout/algorithm/lower_bound.hpp b/sprout/algorithm/lower_bound.hpp
index 06e50661..974bca39 100644
--- a/sprout/algorithm/lower_bound.hpp
+++ b/sprout/algorithm/lower_bound.hpp
@@ -12,8 +12,7 @@ namespace sprout {
 	// 25.4.3.1 lower_bound
 	//
 	//	recursion depth:
-	//		[first, last) is RandomAccessIterator -> O(log N)
-	//		otherwise -> O(N)
+	//		O(log N)
 	//
 	template<typename ForwardIterator, typename T, typename Compare>
 	inline SPROUT_CONSTEXPR ForwardIterator
diff --git a/sprout/algorithm/upper_bound.hpp b/sprout/algorithm/upper_bound.hpp
index e1331629..051f4708 100644
--- a/sprout/algorithm/upper_bound.hpp
+++ b/sprout/algorithm/upper_bound.hpp
@@ -12,8 +12,7 @@ namespace sprout {
 	// 25.4.3.2 upper_bound
 	//
 	//	recursion depth:
-	//		[first, last) is RandomAccessIterator -> O(log N)
-	//		otherwise -> O(N)
+	//		O(log N)
 	//
 	template<typename ForwardIterator, typename T, typename Compare>
 	inline SPROUT_CONSTEXPR ForwardIterator