diff --git a/sprout/algorithm/fixed/copy.hpp b/sprout/algorithm/fixed/copy.hpp
index d524b16a..198ad235 100644
--- a/sprout/algorithm/fixed/copy.hpp
+++ b/sprout/algorithm/fixed/copy.hpp
@@ -2,6 +2,8 @@
 #define SPROUT_ALGORITHM_FIXED_COPY_HPP
 
 #include <cstddef>
+#include <iterator>
+#include <type_traits>
 #include <sprout/config.hpp>
 #include <sprout/index_tuple.hpp>
 #include <sprout/fixed_container/traits.hpp>
@@ -13,10 +15,10 @@
 namespace sprout {
 	namespace fixed {
 		namespace detail {
-			template<typename Iterator, typename Result, std::ptrdiff_t... Indexes>
-			SPROUT_CONSTEXPR inline typename sprout::fixed::result_of::algorithm<Result>::type copy_impl(
-				Iterator first,
-				Iterator last,
+			template<typename RandomAccessIterator, typename Result, std::ptrdiff_t... Indexes>
+			SPROUT_CONSTEXPR inline typename sprout::fixed::result_of::algorithm<Result>::type copy_impl_ra(
+				RandomAccessIterator first,
+				RandomAccessIterator last,
 				Result const& result,
 				sprout::index_tuple<Indexes...>,
 				typename sprout::fixed_container_traits<Result>::difference_type offset,
@@ -33,25 +35,148 @@ namespace sprout {
 						)...
 					);
 			}
+			template<typename RandomAccessIterator, typename Result>
+			SPROUT_CONSTEXPR inline typename sprout::fixed::result_of::algorithm<Result>::type copy(
+				RandomAccessIterator first,
+				RandomAccessIterator last,
+				Result const& result,
+				std::random_access_iterator_tag*
+				)
+			{
+				return sprout::fixed::detail::copy_impl_ra(
+					first,
+					last,
+					result,
+					typename sprout::index_range<0, sprout::fixed_container_traits<Result>::fixed_size>::type(),
+					sprout::fixed_begin_offset(result),
+					sprout::size(result),
+					NS_SSCRISK_CEL_OR_SPROUT_DETAIL::distance(first, last)
+					);
+			}
+			template<typename Result, typename... Args>
+			SPROUT_CONSTEXPR inline typename std::enable_if<
+				sprout::fixed_container_traits<Result>::fixed_size == sizeof...(Args),
+				typename sprout::fixed::result_of::algorithm<Result>::type
+			>::type copy_impl_3(
+				Result const& result,
+				Args const&... args
+				)
+			{
+				return sprout::remake_clone<Result, Result>(result, sprout::size(result), args...);
+			}
+			template<typename Result, typename... Args>
+			SPROUT_CONSTEXPR inline typename std::enable_if<
+				sprout::fixed_container_traits<Result>::fixed_size != sizeof...(Args),
+				typename sprout::fixed::result_of::algorithm<Result>::type
+			>::type copy_impl_3(
+				Result const& result,
+				Args const&... args
+				)
+			{
+				return copy_impl_3(result, args..., *sprout::next(sprout::fixed_begin(result), sizeof...(Args)));
+			}
+			template<typename InputIterator, typename Result, typename... Args>
+			SPROUT_CONSTEXPR inline typename std::enable_if<
+				sprout::fixed_container_traits<Result>::fixed_size == sizeof...(Args),
+				typename sprout::fixed::result_of::algorithm<Result>::type
+			>::type copy_impl_2(
+				InputIterator first,
+				InputIterator last,
+				Result const& result,
+				typename sprout::fixed_container_traits<Result>::difference_type offset,
+				Args const&... args
+				)
+			{
+				return sprout::remake_clone<Result, Result>(result, sprout::size(result), args...);
+			}
+			template<typename InputIterator, typename Result, typename... Args>
+			SPROUT_CONSTEXPR inline typename std::enable_if<
+				sprout::fixed_container_traits<Result>::fixed_size != sizeof...(Args),
+				typename sprout::fixed::result_of::algorithm<Result>::type
+			>::type copy_impl_2(
+				InputIterator first,
+				InputIterator last,
+				Result const& result,
+				typename sprout::fixed_container_traits<Result>::difference_type offset,
+				Args const&... args
+				)
+			{
+				return first != last && sizeof...(Args) < static_cast<std::size_t>(offset)
+					? copy_impl_2(sprout::next(first), last, result, offset, args..., *first)
+					: copy_impl_3(result, args...)
+					;
+			}
+			template<typename InputIterator, typename Result, typename... Args>
+			SPROUT_CONSTEXPR inline typename std::enable_if<
+				sprout::fixed_container_traits<Result>::fixed_size == sizeof...(Args),
+				typename sprout::fixed::result_of::algorithm<Result>::type
+			>::type copy_impl_1(
+				InputIterator first,
+				InputIterator last,
+				Result const& result,
+				typename sprout::fixed_container_traits<Result>::difference_type offset,
+				Args const&... args
+				)
+			{
+				return sprout::remake_clone<Result, Result>(result, sprout::size(result), args...);
+			}
+			template<typename InputIterator, typename Result, typename... Args>
+			SPROUT_CONSTEXPR inline typename std::enable_if<
+				sprout::fixed_container_traits<Result>::fixed_size != sizeof...(Args),
+				typename sprout::fixed::result_of::algorithm<Result>::type
+			>::type copy_impl_1(
+				InputIterator first,
+				InputIterator last,
+				Result const& result,
+				typename sprout::fixed_container_traits<Result>::difference_type offset,
+				Args const&... args
+				)
+			{
+				return sizeof...(Args) < static_cast<std::size_t>(offset)
+					? copy_impl_1(first, last, result, offset, args..., *sprout::next(sprout::fixed_begin(result), sizeof...(Args)))
+					: copy_impl_2(first, last, result, offset + sprout::size(result), args...)
+					;
+			}
+			template<typename InputIterator, typename Result>
+			SPROUT_CONSTEXPR inline typename sprout::fixed::result_of::algorithm<Result>::type copy_impl(
+				InputIterator first,
+				InputIterator last,
+				Result const& result
+				)
+			{
+				return copy_impl_1(first, last, result, sprout::fixed_begin_offset(result));
+			}
+			template<typename InputIterator, typename Result>
+			SPROUT_CONSTEXPR inline typename sprout::fixed::result_of::algorithm<Result>::type copy(
+				InputIterator first,
+				InputIterator last,
+				Result const& result,
+				void*
+				)
+			{
+				return sprout::fixed::detail::copy_impl(
+					first,
+					last,
+					result
+					);
+			}
 		}	// namespace detail
 		//
 		// copy
 		//
-		template<typename Iterator, typename Result>
+		template<typename InputIterator, typename Result>
 		SPROUT_CONSTEXPR inline typename sprout::fixed::result_of::algorithm<Result>::type copy(
-			Iterator first,
-			Iterator last,
+			InputIterator first,
+			InputIterator last,
 			Result const& result
 			)
 		{
-			return sprout::fixed::detail::copy_impl(
+			typedef typename std::iterator_traits<InputIterator>::iterator_category* category;
+			return sprout::fixed::detail::copy(
 				first,
 				last,
 				result,
-				typename sprout::index_range<0, sprout::fixed_container_traits<Result>::fixed_size>::type(),
-				sprout::fixed_begin_offset(result),
-				sprout::size(result),
-				NS_SSCRISK_CEL_OR_SPROUT_DETAIL::distance(first, last)
+				category()
 				);
 		}
 	}	// namespace fixed
diff --git a/sprout/algorithm/fixed/copy_if.hpp b/sprout/algorithm/fixed/copy_if.hpp
index e8c44bb3..13d9e2d7 100644
--- a/sprout/algorithm/fixed/copy_if.hpp
+++ b/sprout/algorithm/fixed/copy_if.hpp
@@ -5,7 +5,7 @@
 #include <sprout/config.hpp>
 #include <sprout/fixed_container/traits.hpp>
 #include <sprout/fixed_container/functions.hpp>
-#include <sprout/iterator/operation.hpp>
+#include <sprout/iterator/operation.hpp>
 #include <sprout/algorithm/fixed/result_of.hpp>
 
 namespace sprout {
@@ -33,13 +33,13 @@ namespace sprout {
 			{
 				return copy_if_impl_3(result, args..., *sprout::next(sprout::fixed_begin(result), sizeof...(Args)));
 			}
-			template<typename Iterator, typename Result, typename Predicate, typename... Args>
+			template<typename InputIterator, typename Result, typename Predicate, typename... Args>
 			SPROUT_CONSTEXPR inline typename std::enable_if<
 				sprout::fixed_container_traits<Result>::fixed_size == sizeof...(Args),
 				typename sprout::fixed::result_of::algorithm<Result>::type
 			>::type copy_if_impl_2(
-				Iterator first,
-				Iterator last,
+				InputIterator first,
+				InputIterator last,
 				Result const& result,
 				Predicate pred,
 				typename sprout::fixed_container_traits<Result>::difference_type offset,
@@ -48,33 +48,33 @@ namespace sprout {
 			{
 				return sprout::remake_clone<Result, Result>(result, sprout::size(result), args...);
 			}
-			template<typename Iterator, typename Result, typename Predicate, typename... Args>
+			template<typename InputIterator, typename Result, typename Predicate, typename... Args>
 			SPROUT_CONSTEXPR inline typename std::enable_if<
 				sprout::fixed_container_traits<Result>::fixed_size != sizeof...(Args),
 				typename sprout::fixed::result_of::algorithm<Result>::type
 			>::type copy_if_impl_2(
-				Iterator first,
-				Iterator last,
+				InputIterator first,
+				InputIterator last,
 				Result const& result,
 				Predicate pred,
 				typename sprout::fixed_container_traits<Result>::difference_type offset,
 				Args const&... args
 				)
 			{
-				return first != last && sizeof...(Args) < offset
+				return first != last && sizeof...(Args) < static_cast<std::size_t>(offset)
 					? pred(*first)
 						? copy_if_impl_2(sprout::next(first), last, result, pred, offset, args..., *first)
 						: copy_if_impl_2(sprout::next(first), last, result, pred, offset, args...)
 					: copy_if_impl_3(result, args...)
 					;
 			}
-			template<typename Iterator, typename Result, typename Predicate, typename... Args>
+			template<typename InputIterator, typename Result, typename Predicate, typename... Args>
 			SPROUT_CONSTEXPR inline typename std::enable_if<
 				sprout::fixed_container_traits<Result>::fixed_size == sizeof...(Args),
 				typename sprout::fixed::result_of::algorithm<Result>::type
 			>::type copy_if_impl_1(
-				Iterator first,
-				Iterator last,
+				InputIterator first,
+				InputIterator last,
 				Result const& result,
 				Predicate pred,
 				typename sprout::fixed_container_traits<Result>::difference_type offset,
@@ -83,28 +83,28 @@ namespace sprout {
 			{
 				return sprout::remake_clone<Result, Result>(result, sprout::size(result), args...);
 			}
-			template<typename Iterator, typename Result, typename Predicate, typename... Args>
+			template<typename InputIterator, typename Result, typename Predicate, typename... Args>
 			SPROUT_CONSTEXPR inline typename std::enable_if<
 				sprout::fixed_container_traits<Result>::fixed_size != sizeof...(Args),
 				typename sprout::fixed::result_of::algorithm<Result>::type
 			>::type copy_if_impl_1(
-				Iterator first,
-				Iterator last,
+				InputIterator first,
+				InputIterator last,
 				Result const& result,
 				Predicate pred,
 				typename sprout::fixed_container_traits<Result>::difference_type offset,
 				Args const&... args
 				)
 			{
-				return sizeof...(Args) < offset
+				return sizeof...(Args) < static_cast<std::size_t>(offset)
 					? copy_if_impl_1(first, last, result, pred, offset, args..., *sprout::next(sprout::fixed_begin(result), sizeof...(Args)))
 					: copy_if_impl_2(first, last, result, pred, offset + sprout::size(result), args...)
 					;
 			}
-			template<typename Iterator, typename Result, typename Predicate>
+			template<typename InputIterator, typename Result, typename Predicate>
 			SPROUT_CONSTEXPR inline typename sprout::fixed::result_of::algorithm<Result>::type copy_if_impl(
-				Iterator first,
-				Iterator last,
+				InputIterator first,
+				InputIterator last,
 				Result const& result,
 				Predicate pred
 				)
@@ -115,10 +115,10 @@ namespace sprout {
 		//
 		// copy_if
 		//
-		template<typename Iterator, typename Result, typename Predicate>
+		template<typename InputIterator, typename Result, typename Predicate>
 		SPROUT_CONSTEXPR inline typename sprout::fixed::result_of::algorithm<Result>::type copy_if(
-			Iterator first,
-			Iterator last,
+			InputIterator first,
+			InputIterator last,
 			Result const& result,
 			Predicate pred
 			)
diff --git a/sprout/algorithm/fixed/copy_n.hpp b/sprout/algorithm/fixed/copy_n.hpp
index d554faf8..88f26f96 100644
--- a/sprout/algorithm/fixed/copy_n.hpp
+++ b/sprout/algorithm/fixed/copy_n.hpp
@@ -20,14 +20,10 @@ namespace sprout {
 			Result const& result
 			)
 		{
-			return sprout::fixed::detail::copy_impl(
+			return sprout::fixed::copy(
 				first,
 				sprout::next(first, n),
-				result,
-				typename sprout::index_range<0, sprout::fixed_container_traits<Result>::fixed_size>::type(),
-				sprout::fixed_begin_offset(result),
-				sprout::size(result),
-				n
+				result
 				);
 		}
 	}	// namespace fixed
diff --git a/sprout/iterator/next.hpp b/sprout/iterator/next.hpp
index 13324e2e..54843544 100644
--- a/sprout/iterator/next.hpp
+++ b/sprout/iterator/next.hpp
@@ -20,12 +20,13 @@ namespace sprout {
 			return sprout::forward<Iterator>(it) + 1;
 		}
 		template<typename Iterator>
-		Iterator next_impl(
+		SPROUT_CONSTEXPR typename std::decay<Iterator>::type next_impl(
 			Iterator&& it,
 			void*
 			)
 		{
-			return std::next(sprout::forward<Iterator>(it));
+			using std::next;
+			return next(sprout::forward<Iterator>(it));
 		}
 
 		template<typename Iterator>
@@ -41,13 +42,14 @@ namespace sprout {
 			return sprout::forward<Iterator>(it) + n;
 		}
 		template<typename Iterator>
-		Iterator next_impl(
+		SPROUT_CONSTEXPR typename std::decay<Iterator>::type next_impl(
 			Iterator it,
 			typename std::iterator_traits<typename std::decay<Iterator>::type>::difference_type n,
 			void*
 			)
 		{
-			return std::next(sprout::forward<Iterator>(it), n);
+			using std::next;
+			return next(sprout::forward<Iterator>(it), n);
 		}
 	}	// namespace detail
 	//
diff --git a/sprout/random/random_iterator.hpp b/sprout/random/random_iterator.hpp
index 0969dfe9..4ac68dea 100644
--- a/sprout/random/random_iterator.hpp
+++ b/sprout/random/random_iterator.hpp
@@ -306,18 +306,18 @@ namespace sprout {
 		{
 			return sprout::random::random_iterator<Engine>();
 		}
-	}	// namespace random
 
-	//
-	// next
-	//
-	template<typename Engine, typename Distribution>
-	SPROUT_CONSTEXPR sprout::random::random_iterator<Engine, Distribution> next(
-		sprout::random::random_iterator<Engine, Distribution> const& it
-		)
-	{
-		return it();
-	}
+		//
+		// next
+		//
+		template<typename Engine, typename Distribution>
+		SPROUT_CONSTEXPR sprout::random::random_iterator<Engine, Distribution> next(
+			sprout::random::random_iterator<Engine, Distribution> const& it
+			)
+		{
+			return it();
+		}
+	}	// namespace random
 
 	using sprout::random::random_iterator;
 }	// namespace sprout
diff --git a/sprout/random/random_result.hpp b/sprout/random/random_result.hpp
index 6e70298b..c24dda70 100644
--- a/sprout/random/random_result.hpp
+++ b/sprout/random/random_result.hpp
@@ -23,7 +23,7 @@ namespace sprout {
 			typename std::enable_if<!std::is_same<Distribution, void>::value>::type
 		>
 			: public std::iterator<
-				std::forward_iterator_tag,
+				std::input_iterator_tag,
 				typename Distribution::result_type,
 				std::ptrdiff_t,
 				typename Distribution::result_type const*,
@@ -36,7 +36,7 @@ namespace sprout {
 			typedef typename distribution_type::result_type result_type;
 		private:
 			typedef std::iterator<
-				std::forward_iterator_tag,
+				std::input_iterator_tag,
 				result_type,
 				std::ptrdiff_t,
 				result_type const*,
@@ -137,7 +137,7 @@ namespace sprout {
 			typename std::enable_if<std::is_same<Distribution, void>::value>::type
 		>
 			: public std::iterator<
-				std::forward_iterator_tag,
+				std::input_iterator_tag,
 				typename Engine::result_type,
 				std::ptrdiff_t,
 				typename Engine::result_type const*,
@@ -149,7 +149,7 @@ namespace sprout {
 			typedef typename engine_type::result_type result_type;
 		private:
 			typedef std::iterator<
-				std::forward_iterator_tag,
+				std::input_iterator_tag,
 				result_type,
 				std::ptrdiff_t,
 				result_type const*,