diff --git a/libs/algorithm/test/non_modifying.cpp b/libs/algorithm/test/non_modifying.cpp
index 51435d14..1799a515 100644
--- a/libs/algorithm/test/non_modifying.cpp
+++ b/libs/algorithm/test/non_modifying.cpp
@@ -21,6 +21,7 @@
 #include "./mismatch.cpp"
 #include "./equal.cpp"
 #include "./is_permutation.cpp"
+#include "./search.cpp"
 
 #ifdef TESTSPR_CPP_INCLUDE_DISABLE_SPROUT_LIBS_ALGORITHM_TEST_NON_MODIFYIING_CPP
 #	undef TESTSPR_CPP_INCLUDE
@@ -43,6 +44,7 @@ namespace testspr {
 		testspr::algorithm_mismatch_test();
 		testspr::algorithm_equal_test();
 		testspr::algorithm_is_permutation_test();
+		testspr::algorithm_search_test();
 	}
 }	// namespace testspr
 
diff --git a/libs/algorithm/test/search.cpp b/libs/algorithm/test/search.cpp
new file mode 100644
index 00000000..d4b4a865
--- /dev/null
+++ b/libs/algorithm/test/search.cpp
@@ -0,0 +1,103 @@
+#ifndef SPROUT_LIBS_ALGORITHM_TEST_SEARCH_CPP
+#define SPROUT_LIBS_ALGORITHM_TEST_SEARCH_CPP
+
+#include <sprout/algorithm/search.hpp>
+#include <sprout/array.hpp>
+#include <sprout/container.hpp>
+#include <testspr/tools.hpp>
+
+namespace testspr {
+	static void algorithm_search_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, 3>{{4, 5, 6}};
+			SPROUT_STATIC_CONSTEXPR auto arr3 = array<int, 3>{{6, 5, 4}};
+
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::search(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					sprout::begin(arr2),
+					sprout::end(arr2)
+					);
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 3);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::search(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					sprout::begin(arr3),
+					sprout::end(arr3)
+					);
+				TESTSPR_BOTH_ASSERT(found == sprout::end(arr1));
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::search(
+					sprout::begin(arr1),
+					sprout::begin(arr1) + 5,
+					sprout::begin(arr2),
+					sprout::end(arr2)
+					);
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 5);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::search(
+					sprout::begin(arr1),
+					sprout::begin(arr1) + 5,
+					sprout::begin(arr3),
+					sprout::end(arr3)
+					);
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 5);
+			}
+
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::search(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					sprout::begin(arr2),
+					sprout::end(arr2),
+					testspr::equal_to<int>()
+					);
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 3);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::search(
+					sprout::begin(arr1),
+					sprout::end(arr1),
+					sprout::begin(arr3),
+					sprout::end(arr3),
+					testspr::equal_to<int>()
+					);
+				TESTSPR_BOTH_ASSERT(found == sprout::end(arr1));
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::search(
+					sprout::begin(arr1),
+					sprout::begin(arr1) + 5,
+					sprout::begin(arr2),
+					sprout::end(arr2),
+					testspr::equal_to<int>()
+					);
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 5);
+			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto found = sprout::search(
+					sprout::begin(arr1),
+					sprout::begin(arr1) + 5,
+					sprout::begin(arr3),
+					sprout::end(arr3),
+					testspr::equal_to<int>()
+					);
+				TESTSPR_BOTH_ASSERT(found == sprout::begin(arr1) + 5);
+			}
+		}
+	}
+}	// namespace testspr
+
+#ifndef TESTSPR_CPP_INCLUDE
+#	define TESTSPR_TEST_FUNCTION testspr::algorithm_search_test
+#	include <testspr/include_main.hpp>
+#endif
+
+#endif	// #ifndef SPROUT_LIBS_ALGORITHM_TEST_SEARCH_CPP
diff --git a/sprout/algorithm/search.hpp b/sprout/algorithm/search.hpp
index 38061b82..8b19a2ed 100644
--- a/sprout/algorithm/search.hpp
+++ b/sprout/algorithm/search.hpp
@@ -3,28 +3,91 @@
 
 #include <sprout/config.hpp>
 #include <sprout/iterator/operation.hpp>
+#include <sprout/functional/equal_to.hpp>
+#include <sprout/detail/algorithm/search_one.hpp>
 #include HDR_ITERATOR_SSCRISK_CEL_OR_SPROUT
 
 namespace sprout {
-	// Copyright (C) 2011 RiSK (sscrisk)
+	namespace detail {
+		template<typename RandomAccessIterator1, typename ForwardIterator2, typename BinaryPredicate>
+		inline SPROUT_CONSTEXPR RandomAccessIterator1
+		search_impl_ra(
+			RandomAccessIterator1 first1, RandomAccessIterator1 last1,
+			ForwardIterator2 first2, ForwardIterator2 last2,
+			BinaryPredicate pred,
+			typename std::iterator_traits<RandomAccessIterator1>::difference_type pivot, RandomAccessIterator1 last1_, RandomAccessIterator1 searched
+			)
+		{
+			return searched < first1 || searched == last1_ ? searched
+				: pivot == 0 ? sprout::detail::search_one(first1, last1_, first2, last2, pred)
+				: sprout::detail::search_impl_ra(
+					sprout::next(first1, pivot), last1, first2, last2, pred,
+					(NS_SSCRISK_CEL_OR_SPROUT::distance(first1, last1) - pivot) / 2, last1_,
+					sprout::detail::search_impl_ra(
+						first1, sprout::next(first1, pivot), first2, last2, pred,
+						pivot / 2, last1_,
+						first1
+						)
+					)
+				;
+		}
+		template<typename RandomAccessIterator1, typename ForwardIterator2, typename BinaryPredicate>
+		inline SPROUT_CONSTEXPR RandomAccessIterator1
+		search(
+			RandomAccessIterator1 first1, RandomAccessIterator1 last1,
+			ForwardIterator2 first2, ForwardIterator2 last2,
+			BinaryPredicate pred,
+			std::random_access_iterator_tag*
+			)
+		{
+			return first1 == last1 ? last1
+				: sprout::detail::search_impl_ra(
+					first1, last1, first2, last2, pred,
+					NS_SSCRISK_CEL_OR_SPROUT::distance(first1, last1) / 2, last1, first1
+					)
+				;
+		}
+
+		template<typename ForwardIterator1, typename ForwardIterator2, typename BinaryPredicate>
+		inline SPROUT_CONSTEXPR ForwardIterator1
+		search_impl(
+			ForwardIterator1 first1, ForwardIterator1 last1,
+			ForwardIterator2 first2, ForwardIterator2 last2,
+			BinaryPredicate pred,
+			ForwardIterator1 searched
+			)
+		{
+			return searched == first1 || searched == last1 ? searched
+				: sprout::detail::search_impl(
+					sprout::next(first1), last1, first2, last2, pred,
+					sprout::detail::search_one(sprout::next(first1), last1, first2, last2, pred)
+					)
+				;
+		}
+		template<typename ForwardIterator1, typename ForwardIterator2, typename BinaryPredicate>
+		inline SPROUT_CONSTEXPR ForwardIterator1
+		search(
+			ForwardIterator1 first1, ForwardIterator1 last1,
+			ForwardIterator2 first2, ForwardIterator2 last2,
+			BinaryPredicate pred,
+			void*
+			)
+		{
+			return sprout::detail::search_impl(
+				first1, last1, first2, last2, pred,
+				sprout::detail::search_one(first1, last1, first2, last2, pred)
+				);
+		}
+	}	//namespace detail
 
 	// 25.2.13 Search
-	template<typename ForwardIterator1, typename ForwardIterator2>
-	inline SPROUT_CONSTEXPR ForwardIterator1
-	search(
-		ForwardIterator1 first1, ForwardIterator1 last1,
-		ForwardIterator2 first2, ForwardIterator2 last2
-		)
-	{
-		return first1 == last1 || first2 == last2 ? first1
-			: NS_SSCRISK_CEL_OR_SPROUT::distance(first1, last1) < NS_SSCRISK_CEL_OR_SPROUT::distance(first2, last2) ? last1
-			: *first1 == *first2
-				&& sprout::search(sprout::next(first1), last1, sprout::next(first2), last2) == sprout::next(first1)
-				? first1
-			: sprout::search(sprout::next(first1), last1, first2, last2)
-			;
-	}
-
+	//
+	//	recursion depth:
+	//		[first1, last1) is RandomAccessIterator -> O(log N1)
+	//		otherwise -> O(N1)
+	//		[first2, last2) is RandomAccessIterator -> O(log N2)
+	//		otherwise -> O(N2)
+	//
 	template<typename ForwardIterator1, typename ForwardIterator2, typename BinaryPredicate>
 	inline SPROUT_CONSTEXPR ForwardIterator1
 	search(
@@ -33,13 +96,18 @@ namespace sprout {
 		BinaryPredicate pred
 		)
 	{
-		return first1 == last1 || first2 == last2 ? first1
-			: NS_SSCRISK_CEL_OR_SPROUT::distance(first1, last1) < NS_SSCRISK_CEL_OR_SPROUT::distance(first2, last2) ? last1
-			: *first1 == *first2
-				&& sprout::search(sprout::next(first1), last1, sprout::next(first2), last2, pred) == sprout::next(first1)
-				? first1
-			: sprout::search(sprout::next(first1), last1, first2, last2, pred)
-			;
+		typedef typename std::iterator_traits<ForwardIterator1>::iterator_category* category;
+		return sprout::detail::search(first1, last1, first2, last2, pred, category());
+	}
+
+	template<typename ForwardIterator1, typename ForwardIterator2>
+	inline SPROUT_CONSTEXPR ForwardIterator1
+	search(
+		ForwardIterator1 first1, ForwardIterator1 last1,
+		ForwardIterator2 first2, ForwardIterator2 last2
+		)
+	{
+		return sprout::search(first1, last1, first2, last2, sprout::equal_to<>());
 	}
 }	// namespace sprout
 
diff --git a/sprout/detail/algorithm/search_one.hpp b/sprout/detail/algorithm/search_one.hpp
new file mode 100644
index 00000000..02a869f0
--- /dev/null
+++ b/sprout/detail/algorithm/search_one.hpp
@@ -0,0 +1,83 @@
+#ifndef SPROUT_DETAIL_ALGORITHM_SEARCH_ONE_HPP
+#define SPROUT_DETAIL_ALGORITHM_SEARCH_ONE_HPP
+
+#include <iterator>
+#include <sprout/config.hpp>
+#include <sprout/iterator/operation.hpp>
+#include <sprout/functional/equal_to.hpp>
+#include <sprout/algorithm/mismatch.hpp>
+#include HDR_ITERATOR_SSCRISK_CEL_OR_SPROUT
+
+namespace sprout {
+	namespace detail {
+		template<typename RandomAccessIterator1, typename RandomAccessIterator2, typename BinaryPredicate>
+		inline SPROUT_CONSTEXPR RandomAccessIterator1
+		search_one_impl_ra(
+			RandomAccessIterator1 first1, RandomAccessIterator1 last1, RandomAccessIterator2 first2, RandomAccessIterator2 last2, BinaryPredicate pred
+			)
+		{
+			return sprout::detail::mismatch_impl_ra(
+					first1, last1, first2, pred,
+					NS_SSCRISK_CEL_OR_SPROUT::distance(first1, last1) / 2, first1
+					)
+					== last1
+				? first1
+				: last1
+				;
+		}
+		template<typename RandomAccessIterator1, typename RandomAccessIterator2, typename BinaryPredicate>
+		inline SPROUT_CONSTEXPR RandomAccessIterator1
+		search_one(
+			RandomAccessIterator1 first1, RandomAccessIterator1 last1, RandomAccessIterator2 first2, RandomAccessIterator2 last2, BinaryPredicate pred,
+			std::random_access_iterator_tag*
+			)
+		{
+			return NS_SSCRISK_CEL_OR_SPROUT::distance(first1, last1) < NS_SSCRISK_CEL_OR_SPROUT::distance(first2, last2) ? last1
+				: first1 == last1 ? first1
+				: sprout::detail::search_one_impl_ra(
+					first1, sprout::next(first1, NS_SSCRISK_CEL_OR_SPROUT::distance(first2, last2)), first2, last2, pred
+					)
+				;
+		}
+
+		template<typename ForwardIterator1, typename ForwardIterator2, typename BinaryPredicate>
+		inline SPROUT_CONSTEXPR ForwardIterator1
+		search_one_impl(
+			ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred,
+			ForwardIterator1 first1_
+			)
+		{
+			return first2 == last2 ? first1_
+				: first1 == last1 ? last1
+				: !pred(*first1, *first2) ? first1
+				: sprout::detail::search_one_impl(sprout::next(first1), last1, sprout::next(first2), last2, pred, first1_)
+				;
+		}
+		template<typename ForwardIterator1, typename ForwardIterator2, typename BinaryPredicate>
+		inline SPROUT_CONSTEXPR ForwardIterator1
+		search_one(
+			ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred,
+			void*
+			)
+		{
+			return sprout::detail::search_one_impl(first1, last1, first2, last2, pred, first1);
+		}
+
+		//
+		// search_one
+		//
+		template<typename ForwardIterator1, typename ForwardIterator2, typename BinaryPredicate>
+		inline SPROUT_CONSTEXPR ForwardIterator1
+		search_one(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2, BinaryPredicate pred) {
+			typedef typename sprout::common_iterator_category<ForwardIterator1, ForwardIterator2>::type* category;
+			return sprout::detail::search_one(first1, last1, first2, last2, pred, category());
+		}
+		template<typename ForwardIterator1, typename ForwardIterator2>
+		inline SPROUT_CONSTEXPR ForwardIterator1
+		search_one(ForwardIterator1 first1, ForwardIterator1 last1, ForwardIterator2 first2, ForwardIterator2 last2) {
+			return sprout::detail::search_one(first1, last1, first2, last2, sprout::equal_to<>());
+		}
+	}	//namespace detail
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_DETAIL_ALGORITHM_SEARCH_ONE_HPP
diff --git a/sprout/functional/ref.hpp b/sprout/functional/ref.hpp
index 19103589..e5646e73 100644
--- a/sprout/functional/ref.hpp
+++ b/sprout/functional/ref.hpp
@@ -8,6 +8,7 @@
 #include <sprout/type_traits/inherit_if_xxx.hpp>
 #include <sprout/functional/base.hpp>
 #include <sprout/functional/type_traits/weak_result_type.hpp>
+#include <sprout/functional/type_traits/has_type.hpp>
 
 namespace sprout {
 	// 20.8.3 reference_wrapper