diff --git a/sprout/algorithm/equal_range.hpp b/sprout/algorithm/equal_range.hpp
index fc891363..590c9a7d 100644
--- a/sprout/algorithm/equal_range.hpp
+++ b/sprout/algorithm/equal_range.hpp
@@ -13,10 +13,30 @@
 #include <sprout/config.hpp>
 #include <sprout/algorithm/lower_bound.hpp>
 #include <sprout/algorithm/upper_bound.hpp>
+#include <sprout/iterator/operation.hpp>
 #include <sprout/utility/pair/pair.hpp>
-#include HDR_FUNCTIONAL_SSCRISK_CEL_OR_SPROUT
 
 namespace sprout {
+	namespace detail {
+		template<typename ForwardIterator, typename T, typename Compare>
+		inline SPROUT_CONSTEXPR sprout::pair<ForwardIterator, ForwardIterator>
+		equal_range(
+			ForwardIterator first, typename std::iterator_traits<ForwardIterator>::difference_type len,
+			T const& value, Compare comp
+			)
+		{
+			return len == 0 ? sprout::pair<ForwardIterator, ForwardIterator>(first, first)
+				: comp(*sprout::next(first, len / 2), value)
+					? sprout::detail::equal_range(sprout::next(first, len / 2 + 1), len - (len / 2 + 1), value, comp)
+				: comp(value, *sprout::next(first, len / 2))
+					? sprout::detail::equal_range(first, len / 2, value, comp)
+				: sprout::pair<ForwardIterator, ForwardIterator>(
+					sprout::detail::lower_bound(first, len / 2, value, comp),
+					sprout::detail::upper_bound(sprout::next(first, len / 2 + 1), len - (len / 2 + 1), value, comp)
+					)
+				;
+		}
+	}	// namespace detail
 
 	// 25.4.3.3 equal_range
 	//
@@ -26,19 +46,13 @@ namespace sprout {
 	template<typename ForwardIterator, typename T, typename Compare>
 	inline SPROUT_CONSTEXPR sprout::pair<ForwardIterator, ForwardIterator>
 	equal_range(ForwardIterator first, ForwardIterator last, T const& value, Compare comp) {
-		return sprout::pair<ForwardIterator, ForwardIterator>(
-			sprout::lower_bound(first, last, value, comp),
-			sprout::upper_bound(first, last, value, comp)
-			);
+		return sprout::detail::equal_range(first, sprout::distance(first, last), value, comp);
 	}
 
 	template<typename ForwardIterator, typename T>
 	inline SPROUT_CONSTEXPR sprout::pair<ForwardIterator, ForwardIterator>
 	equal_range(ForwardIterator first, ForwardIterator last, T const& value) {
-		return sprout::equal_range(
-			first, last, value,
-			NS_SSCRISK_CEL_OR_SPROUT::less<typename std::iterator_traits<ForwardIterator>::value_type>()
-			);
+		return sprout::equal_range(first, last, value, sprout::less<>());
 	}
 }	// namespace sprout
 
diff --git a/sprout/algorithm/lower_bound.hpp b/sprout/algorithm/lower_bound.hpp
index eff2721e..ed15284e 100644
--- a/sprout/algorithm/lower_bound.hpp
+++ b/sprout/algorithm/lower_bound.hpp
@@ -9,10 +9,10 @@
 #ifndef SPROUT_ALGORITHM_LOWER_BOUND_HPP
 #define SPROUT_ALGORITHM_LOWER_BOUND_HPP
 
-#include <iterator>
 #include <sprout/config.hpp>
-#include <sprout/iterator/operation.hpp>
+#include <sprout/iterator/distance.hpp>
 #include <sprout/functional/less.hpp>
+#include <sprout/detail/algorithm/lower_bound.hpp>
 
 namespace sprout {
 
@@ -24,12 +24,7 @@ namespace sprout {
 	template<typename ForwardIterator, typename T, typename Compare>
 	inline SPROUT_CONSTEXPR ForwardIterator
 	lower_bound(ForwardIterator first, ForwardIterator last, T const& value, Compare comp) {
-		return first == last ? last
-			: sprout::next(first) == last ? comp(*first, value) ? last : first
-			: comp(*sprout::next(first, sprout::distance(first, last) / 2), value)
-				? sprout::lower_bound(sprout::next(first, sprout::distance(first, last) / 2 + 1), last, value, comp)
-			: sprout::lower_bound(first, sprout::next(first, sprout::distance(first, last) / 2), value, comp)
-			;
+		return sprout::detail::lower_bound(first, sprout::distance(first, last), value, comp);
 	}
 
 	template<typename ForwardIterator, typename T>
diff --git a/sprout/algorithm/upper_bound.hpp b/sprout/algorithm/upper_bound.hpp
index 56532f7c..9e96f589 100644
--- a/sprout/algorithm/upper_bound.hpp
+++ b/sprout/algorithm/upper_bound.hpp
@@ -9,10 +9,10 @@
 #ifndef SPROUT_ALGORITHM_UPPER_BOUND_HPP
 #define SPROUT_ALGORITHM_UPPER_BOUND_HPP
 
-#include <iterator>
 #include <sprout/config.hpp>
-#include <sprout/iterator/operation.hpp>
+#include <sprout/iterator/distance.hpp>
 #include <sprout/functional/less.hpp>
+#include <sprout/detail/algorithm/upper_bound.hpp>
 
 namespace sprout {
 
@@ -24,12 +24,7 @@ namespace sprout {
 	template<typename ForwardIterator, typename T, typename Compare>
 	inline SPROUT_CONSTEXPR ForwardIterator
 	upper_bound(ForwardIterator first, ForwardIterator last, T const& value, Compare comp) {
-		return first == last ? last
-			: sprout::next(first) == last ? !comp(value, *first) ? last : first
-			: !comp(value, *sprout::next(first, sprout::distance(first, last) / 2))
-				? sprout::upper_bound(sprout::next(first, sprout::distance(first, last) / 2 + 1), last, value, comp)
-			: sprout::upper_bound(first, sprout::next(first, sprout::distance(first, last) / 2), value, comp)
-			;
+		return sprout::detail::upper_bound(first, sprout::distance(first, last), value, comp);
 	}
 
 	template<typename ForwardIterator, typename T>
diff --git a/sprout/detail/algorithm/lower_bound.hpp b/sprout/detail/algorithm/lower_bound.hpp
new file mode 100644
index 00000000..2f43c7be
--- /dev/null
+++ b/sprout/detail/algorithm/lower_bound.hpp
@@ -0,0 +1,34 @@
+/*=============================================================================
+  Copyright (c) 2011-2013 Bolero MURAKAMI
+  Copyright (C) 2011 RiSK (sscrisk)
+  https://github.com/bolero-MURAKAMI/Sprout
+
+  Distributed under the Boost Software License, Version 1.0. (See accompanying
+  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+=============================================================================*/
+#ifndef SPROUT_DETAIL_ALGORITHM_LOWER_BOUND_HPP
+#define SPROUT_DETAIL_ALGORITHM_LOWER_BOUND_HPP
+
+#include <iterator>
+#include <sprout/config.hpp>
+#include <sprout/iterator/next.hpp>
+
+namespace sprout {
+	namespace detail {
+		template<typename ForwardIterator, typename T, typename Compare>
+		inline SPROUT_CONSTEXPR ForwardIterator
+		lower_bound(
+			ForwardIterator first, typename std::iterator_traits<ForwardIterator>::difference_type len,
+			T const& value, Compare comp
+			)
+		{
+			return len == 0 ? first
+				: comp(*sprout::next(first, len / 2), value)
+					? sprout::detail::lower_bound(sprout::next(first, len / 2 + 1), len - (len / 2 + 1), value, comp)
+				: sprout::detail::lower_bound(first, len / 2, value, comp)
+				;
+		}
+	}	// namespace detail
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_DETAIL_ALGORITHM_LOWER_BOUND_HPP
diff --git a/sprout/detail/algorithm/upper_bound.hpp b/sprout/detail/algorithm/upper_bound.hpp
new file mode 100644
index 00000000..7b688cbd
--- /dev/null
+++ b/sprout/detail/algorithm/upper_bound.hpp
@@ -0,0 +1,34 @@
+/*=============================================================================
+  Copyright (c) 2011-2013 Bolero MURAKAMI
+  Copyright (C) 2011 RiSK (sscrisk)
+  https://github.com/bolero-MURAKAMI/Sprout
+
+  Distributed under the Boost Software License, Version 1.0. (See accompanying
+  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+=============================================================================*/
+#ifndef SPROUT_DETAIL_ALGORITHM_UPPER_BOUND_HPP
+#define SPROUT_DETAIL_ALGORITHM_UPPER_BOUND_HPP
+
+#include <iterator>
+#include <sprout/config.hpp>
+#include <sprout/iterator/next.hpp>
+
+namespace sprout {
+	namespace detail {
+		template<typename ForwardIterator, typename T, typename Compare>
+		inline SPROUT_CONSTEXPR ForwardIterator
+		upper_bound(
+			ForwardIterator first, typename std::iterator_traits<ForwardIterator>::difference_type len,
+			T const& value, Compare comp
+			)
+		{
+			return len == 0 ? first
+				: comp(value, *sprout::next(first, len / 2))
+					? sprout::detail::upper_bound(first, len / 2, value, comp)
+				: sprout::detail::upper_bound(sprout::next(first, len / 2 + 1), len - (len / 2 + 1), value, comp)
+				;
+		}
+	}	// namespace detail
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_DETAIL_ALGORITHM_UPPER_BOUND_HPP