diff --git a/sprout/algorithm/string/join.hpp b/sprout/algorithm/string/join.hpp
index ceba474f..b51bb47b 100644
--- a/sprout/algorithm/string/join.hpp
+++ b/sprout/algorithm/string/join.hpp
@@ -7,7 +7,7 @@
 #include <sprout/container/functions.hpp>
 #include <sprout/index_tuple.hpp>
 #include <sprout/pit.hpp>
-#include <sprout/iterator/traits.hpp>
+#include <sprout/iterator/type_traits/is_iterator.hpp>
 #include <sprout/type_traits/enabler_if.hpp>
 #include <sprout/range/adaptor/size_enumed.hpp>
 #include <sprout/range/algorithm/lower_bound.hpp>
diff --git a/sprout/iterator.hpp b/sprout/iterator.hpp
index b01316d3..47dd921f 100644
--- a/sprout/iterator.hpp
+++ b/sprout/iterator.hpp
@@ -2,7 +2,7 @@
 #define SPROUT_ITERATOR_HPP
 
 #include <sprout/config.hpp>
-#include <sprout/iterator/traits.hpp>
+#include <sprout/iterator/type_traits.hpp>
 #include <sprout/iterator/operation.hpp>
 #include <sprout/iterator/predefined.hpp>
 
diff --git a/sprout/iterator/adaptor.hpp b/sprout/iterator/adaptor.hpp
index 3b2d6b70..2a91aa8a 100644
--- a/sprout/iterator/adaptor.hpp
+++ b/sprout/iterator/adaptor.hpp
@@ -7,6 +7,7 @@
 #include <sprout/iterator/filter_iterator.hpp>
 #include <sprout/iterator/indexed_iterator.hpp>
 #include <sprout/iterator/valued_iterator.hpp>
+#include <sprout/iterator/joint_iterator.hpp>
 #include <sprout/iterator/size_enum_iterator.hpp>
 #include <sprout/iterator/bytes_iterator.hpp>
 
diff --git a/sprout/iterator/joint_iterator.hpp b/sprout/iterator/joint_iterator.hpp
new file mode 100644
index 00000000..802a5bd3
--- /dev/null
+++ b/sprout/iterator/joint_iterator.hpp
@@ -0,0 +1,364 @@
+#ifndef SPROUT_ITERATOR_JOINT_ITERATOR_HPP
+#define SPROUT_ITERATOR_JOINT_ITERATOR_HPP
+
+#include <iterator>
+#include <utility>
+#include <type_traits>
+#include <sprout/config.hpp>
+#include <sprout/iterator/next.hpp>
+#include <sprout/iterator/prev.hpp>
+#include <sprout/iterator/distance.hpp>
+#include <sprout/iterator/type_traits/common.hpp>
+#include <sprout/utility/swap.hpp>
+#include HDR_ITERATOR_SSCRISK_CEL_OR_SPROUT
+
+namespace sprout {
+	//
+	// joint_iterator
+	//
+	template<typename LIterator, typename RIterator>
+	class joint_iterator
+		: public std::iterator<
+			typename sprout::common_iterator_category<LIterator, RIterator>::type,
+			typename sprout::common_iterator_value_type<LIterator, RIterator>::type,
+			typename sprout::common_iterator_difference_type<LIterator, RIterator>::type,
+			typename sprout::common_iterator_pointer<LIterator, RIterator>::type,
+			typename sprout::common_iterator_reference<LIterator, RIterator>::type
+		>
+	{
+	public:
+		typedef LIterator iterator_type;
+		typedef RIterator iterator2_type;
+		typedef typename sprout::common_iterator_category<LIterator, RIterator>::type iterator_category;
+		typedef typename sprout::common_iterator_value_type<LIterator, RIterator>::type value_type;
+		typedef typename sprout::common_iterator_difference_type<LIterator, RIterator>::type difference_type;
+		typedef typename sprout::common_iterator_pointer<LIterator, RIterator>::type pointer;
+		typedef typename sprout::common_iterator_reference<LIterator, RIterator>::type reference;
+	protected:
+		iterator_type current1;
+		iterator_type last1;
+		iterator2_type first2;
+		iterator2_type current2;
+	private:
+		SPROUT_CONSTEXPR joint_iterator advance_impl_posite(difference_type n, difference_type d) const {
+			return n > d ? joint_iterator(last1, last1, first2, sprout::next(current2, n - d))
+				: joint_iterator(sprout::next(current1, n), last1, first2, current2)
+				;
+		}
+		SPROUT_CONSTEXPR joint_iterator advance_impl_negate(difference_type n, difference_type d) const {
+			return !(n > d) ? joint_iterator(sprout::next(current1, n - d), last1, first2, first2)
+				: joint_iterator(current1, last1, first2, sprout::next(current2, n))
+				;
+		}
+		SPROUT_CONSTEXPR joint_iterator advance_impl(difference_type n) const {
+			return n >= 0
+				? is_in_left()
+					? advance_impl_posite(n, NS_SSCRISK_CEL_OR_SPROUT::distance(current1, last1))
+					: joint_iterator(current1, last1, first2, sprout::next(current2, n))
+				: first2 == current2
+					? joint_iterator(sprout::next(current1, n), last1, first2, current2)
+					: advance_impl_negate(n, -NS_SSCRISK_CEL_OR_SPROUT::distance(first2, current2))
+				;
+		}
+	public:
+		joint_iterator() = default;
+		joint_iterator(joint_iterator const&) = default;
+		SPROUT_CONSTEXPR joint_iterator(iterator_type it1, iterator_type last1, iterator2_type first2, iterator2_type it2)
+			: current1(it1)
+			, last1(last1)
+			, first2(first2)
+			, current2(it2)
+		{}
+		template<typename U, typename V>
+		SPROUT_CONSTEXPR joint_iterator(joint_iterator<U, V> const& it)
+			: current1(it.base())
+			, last1(it.left_end())
+			, first2(it.right_begin())
+			, current2(it.base2())
+		{}
+		template<typename U, typename V>
+		joint_iterator& operator=(joint_iterator<U, V> const& it) {
+			joint_iterator temp(it);
+			temp.swap(*this);
+			return *this;
+		}
+		SPROUT_CONSTEXPR iterator_type base() const {
+			return current1;
+		}
+		SPROUT_CONSTEXPR iterator_type left_end() const {
+			return last1;
+		}
+		SPROUT_CONSTEXPR iterator2_type right_begin() const {
+			return first2;
+		}
+		SPROUT_CONSTEXPR iterator2_type base2() const {
+			return current2;
+		}
+		SPROUT_CONSTEXPR bool is_in_left() const {
+			return current1 != last1;
+		}
+		SPROUT_CONSTEXPR reference operator*() const {
+			return is_in_left() ? *current1 : *current2;
+		}
+		SPROUT_CONSTEXPR pointer operator->() const {
+			return &*(*this);
+		}
+		joint_iterator& operator++() {
+			if (is_in_left()) {
+				++current1;
+			} else {
+				++current2;
+			}
+			return *this;
+		}
+		joint_iterator operator++(int) {
+			joint_iterator result(*this);
+			if (is_in_left()) {
+				++current1;
+			} else {
+				++current2;
+			}
+			return result;
+		}
+		joint_iterator& operator--() {
+			if (first2 == current2) {
+				--current1;
+			} else {
+				--current2;
+			}
+			return *this;
+		}
+		joint_iterator operator--(int) {
+			joint_iterator temp(*this);
+			if (first2 == current2) {
+				--current1;
+			} else {
+				--current2;
+			}
+			return temp;
+		}
+		SPROUT_CONSTEXPR joint_iterator operator+(difference_type n) const {
+			return advance_impl(n);
+		}
+		SPROUT_CONSTEXPR joint_iterator operator-(difference_type n) const {
+			return advance_impl(-n);
+		}
+		joint_iterator& operator+=(difference_type n) {
+			joint_iterator temp(*this + n);
+			temp.swap(*this);
+			return *this;
+		}
+		joint_iterator& operator-=(difference_type n) {
+			joint_iterator temp(*this - n);
+			temp.swap(*this);
+			return *this;
+		}
+		SPROUT_CONSTEXPR reference operator[](difference_type n) const {
+			return *(*this + n);
+		}
+		SPROUT_CONSTEXPR joint_iterator next() const {
+			return is_in_left() ? joint_iterator(sprout::next(current1), last1, first2, current2)
+				: joint_iterator(current1, last1, first2, sprout::next(current2))
+				;
+		}
+		SPROUT_CONSTEXPR joint_iterator prev() const {
+			return first2 == current2 ? joint_iterator(sprout::prev(current1), last1, first2, current2)
+				: joint_iterator(current1, last1, first2, sprout::prev(current2))
+				;
+		}
+		void swap(joint_iterator& other)
+		SPROUT_NOEXCEPT_EXPR(
+			SPROUT_NOEXCEPT_EXPR(sprout::swap(current1, other.current1))
+			&& SPROUT_NOEXCEPT_EXPR(sprout::swap(last1, other.last1))
+			&& SPROUT_NOEXCEPT_EXPR(sprout::swap(first2, other.first2))
+			&& SPROUT_NOEXCEPT_EXPR(sprout::swap(current2, other.current2))
+			)
+		{
+			sprout::swap(current1, other.current1);
+			sprout::swap(last1, other.last1);
+			sprout::swap(first2, other.first2);
+			sprout::swap(current2, other.current2);
+		}
+	};
+
+	template<
+		typename LIterator1, typename RIterator1,
+		typename LIterator2, typename RIterator2
+	>
+	inline SPROUT_CONSTEXPR bool operator==(
+		sprout::joint_iterator<LIterator1, RIterator1> const& lhs,
+		sprout::joint_iterator<LIterator2, RIterator2> const& rhs
+		)
+	{
+		return lhs.base() == rhs.base() && lhs.base2() == rhs.base2();
+	}
+	template<
+		typename LIterator1, typename RIterator1,
+		typename LIterator2, typename RIterator2
+	>
+	inline SPROUT_CONSTEXPR bool operator!=(
+		sprout::joint_iterator<LIterator1, RIterator1> const& lhs,
+		sprout::joint_iterator<LIterator2, RIterator2> const& rhs
+		)
+	{
+		return !(lhs == rhs);
+	}
+	template<
+		typename LIterator1, typename RIterator1,
+		typename LIterator2, typename RIterator2
+	>
+	inline SPROUT_CONSTEXPR bool operator<(
+		sprout::joint_iterator<LIterator1, RIterator1> const& lhs,
+		sprout::joint_iterator<LIterator2, RIterator2> const& rhs
+		)
+	{
+		return lhs.is_in_left() && rhs.is_in_left() ? lhs.base() < rhs.base()
+			: !lhs.is_in_left() && !rhs.is_in_left() ? lhs.base2() < rhs.base2()
+			: lhs.is_in_left()
+			;
+	}
+	template<
+		typename LIterator1, typename RIterator1,
+		typename LIterator2, typename RIterator2
+	>
+	inline SPROUT_CONSTEXPR bool operator>(
+		sprout::joint_iterator<LIterator1, RIterator1> const& lhs,
+		sprout::joint_iterator<LIterator2, RIterator2> const& rhs
+		)
+	{
+		return rhs < lhs;
+	}
+	template<
+		typename LIterator1, typename RIterator1,
+		typename LIterator2, typename RIterator2
+	>
+	inline SPROUT_CONSTEXPR bool operator<=(
+		sprout::joint_iterator<LIterator1, RIterator1> const& lhs,
+		sprout::joint_iterator<LIterator2, RIterator2> const& rhs
+		)
+	{
+		return !(rhs < lhs);
+	}
+	template<
+		typename LIterator1, typename RIterator1,
+		typename LIterator2, typename RIterator2
+	>
+	inline SPROUT_CONSTEXPR bool operator>=(
+		sprout::joint_iterator<LIterator1, RIterator1> const& lhs,
+		sprout::joint_iterator<LIterator2, RIterator2> const& rhs
+		)
+	{
+		return !(lhs < rhs);
+	}
+	template<
+		typename LIterator1, typename RIterator1,
+		typename LIterator2, typename RIterator2
+	>
+	inline SPROUT_CONSTEXPR typename std::common_type<
+		typename sprout::joint_iterator<LIterator1, RIterator1>::difference_type,
+		typename sprout::joint_iterator<LIterator2, RIterator2>::difference_type
+	>::type
+	operator-(
+		sprout::joint_iterator<LIterator1, RIterator1> const& lhs,
+		sprout::joint_iterator<LIterator2, RIterator2> const& rhs
+		)
+	{
+		return lhs.is_in_left() && rhs.is_in_left() ? rhs.base() - lhs.base()
+			: !lhs.is_in_left() && !rhs.is_in_left() ? rhs.base2() - lhs.base2()
+			: lhs.is_in_left() ? (lhs.left_end() - lhs.base()) + (rhs.base2() - rhs.right_begin())
+			: (lhs.base2() - lhs.right_begin()) + (rhs.left_end() - rhs.base())
+			;
+	}
+	template<typename LIterator, typename RIterator>
+	inline SPROUT_CONSTEXPR sprout::joint_iterator<LIterator, RIterator> operator+(
+		typename sprout::joint_iterator<LIterator, RIterator>::difference_type n,
+		sprout::joint_iterator<LIterator, RIterator> const& it
+		)
+	{
+		return it + n;
+	}
+
+	//
+	// make_joint_iterator
+	//
+	template<typename LIterator, typename RIterator>
+	inline SPROUT_CONSTEXPR sprout::joint_iterator<LIterator, RIterator>
+	make_joint_iterator(LIterator it1, LIterator last1, RIterator first2, RIterator it2) {
+		return sprout::joint_iterator<LIterator, RIterator>(it1, last1, first2, it2);
+	}
+	template<typename LIterator, typename RIterator>
+	inline SPROUT_CONSTEXPR sprout::joint_iterator<LIterator, RIterator>
+	make_joint_iterator(LIterator it1, LIterator last1, RIterator first2) {
+		return sprout::joint_iterator<LIterator, RIterator>(it1, last1, first2, first2);
+	}
+	template<typename LIterator, typename RIterator>
+	inline SPROUT_CONSTEXPR sprout::joint_iterator<LIterator, RIterator>
+	make_joint_iterator(LIterator last1, RIterator first2, RIterator it2) {
+		return sprout::joint_iterator<LIterator, RIterator>(last1, last1, first2, it2);
+	}
+
+	//
+	// swap
+	//
+	template<typename LIterator, typename RIterator>
+	inline void
+	swap(
+		sprout::joint_iterator<LIterator, RIterator>& lhs,
+		sprout::joint_iterator<LIterator, RIterator>& rhs
+		)
+	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
+	{
+		lhs.swap(rhs);
+	}
+
+	//
+	// iterator_distance
+	//
+	template<typename LIterator, typename RIterator>
+	inline SPROUT_CONSTEXPR typename std::iterator_traits<sprout::joint_iterator<LIterator, RIterator> >::difference_type
+	iterator_distance(
+		sprout::joint_iterator<LIterator, RIterator> first,
+		sprout::joint_iterator<LIterator, RIterator> last
+		)
+	{
+		return last - first;
+	}
+
+	//
+	// iterator_next
+	//
+	template<typename LIterator, typename RIterator>
+	inline SPROUT_CONSTEXPR sprout::joint_iterator<LIterator, RIterator>
+	iterator_next(sprout::joint_iterator<LIterator, RIterator> const& it) {
+		return it.next();
+	}
+	template<typename LIterator, typename RIterator>
+	inline SPROUT_CONSTEXPR sprout::joint_iterator<LIterator, RIterator>
+	iterator_next(
+		sprout::joint_iterator<LIterator, RIterator> const& it,
+		typename sprout::joint_iterator<LIterator, RIterator>::difference_type n
+		)
+	{
+		return it + n;
+	}
+
+	//
+	// iterator_prev
+	//
+	template<typename LIterator, typename RIterator>
+	inline SPROUT_CONSTEXPR sprout::joint_iterator<LIterator, RIterator>
+	iterator_prev(sprout::joint_iterator<LIterator, RIterator> const& it) {
+		return it.prev();
+	}
+	template<typename LIterator, typename RIterator>
+	inline SPROUT_CONSTEXPR sprout::joint_iterator<LIterator, RIterator>
+	iterator_prev(
+		sprout::joint_iterator<LIterator, RIterator> const& it,
+		typename sprout::joint_iterator<LIterator, RIterator>::difference_type n
+		)
+	{
+		return it - n;
+	}
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_ITERATOR_JOINT_ITERATOR_HPP
diff --git a/sprout/iterator/traits.hpp b/sprout/iterator/traits.hpp
index 1707214b..ce473c08 100644
--- a/sprout/iterator/traits.hpp
+++ b/sprout/iterator/traits.hpp
@@ -153,6 +153,96 @@ namespace sprout {
 			typename sprout::min_iterator_category<Tail...>::type
 		>
 	{};
+
+	//
+	// common_iterator_category
+	//
+	template<typename... Iterators>
+	struct common_iterator_category
+		: public sprout::min_iterator_category<
+			typename std::iterator_traits<Iterators>::iterator_category...
+		>
+	{};
+
+	namespace detail {
+		template<typename... Types>
+		struct common_iterator_reference_impl;
+		template<typename T>
+		struct common_iterator_reference_impl<T> {
+		public:
+			typedef T type;
+		};
+		template<typename T, typename U>
+		struct common_iterator_reference_impl<T, U>
+			: public std::conditional<
+				std::is_reference<T>::value && std::is_reference<U>::value,
+				typename std::conditional<
+					std::is_convertible<T, U>::value
+						&& (std::is_same<typename std::decay<T>::type, typename std::decay<U>::type>::value
+							|| std::is_base_of<typename std::decay<U>::type, typename std::decay<T>::type>::value
+							)
+						,
+					U,
+					typename std::conditional<
+						std::is_convertible<U, T>::value
+							&& (std::is_same<typename std::decay<U>::type, typename std::decay<T>::type>::value
+								|| std::is_base_of<typename std::decay<T>::type, typename std::decay<U>::type>::value
+								)
+							,
+						T,
+						typename std::common_type<typename std::decay<T>::type, typename std::decay<U>::type>::type
+					>::type
+				>::type,
+				typename std::common_type<typename std::decay<T>::type, typename std::decay<U>::type>::type
+			>
+		{};
+		template<typename T, typename U, typename... Tail>
+		struct common_iterator_reference_impl<T, U, Tail...>
+			: public sprout::detail::common_iterator_reference_impl<
+				typename sprout::detail::common_iterator_reference_impl<T, U>::type,
+				Tail...
+			>
+		{};
+	}	// namespace detail
+	//
+	// common_iterator_reference
+	//
+	template<typename... Iterators>
+	struct common_iterator_reference
+		: public sprout::detail::common_iterator_reference_impl<
+			typename std::iterator_traits<Iterators>::reference...
+		>
+	{};
+
+	//
+	// common_iterator_value_type
+	//
+	template<typename... Iterators>
+	struct common_iterator_value_type
+		: public std::decay<
+			typename sprout::common_iterator_reference<Iterators...>::type
+		>
+	{};
+
+	//
+	// common_iterator_pointer
+	//
+	template<typename... Iterators>
+	struct common_iterator_pointer
+		: public std::add_pointer<
+			typename std::remove_reference<typename sprout::common_iterator_reference<Iterators...>::type>::type
+		>
+	{};
+
+	//
+	// common_iterator_difference_type
+	//
+	template<typename... Iterators>
+	struct common_iterator_difference_type
+		: public std::common_type<
+			typename std::iterator_traits<Iterators>::difference_type...
+		>
+	{};
 }	// namespace sprout
 
 #endif	// #ifndef SPROUT_ITERATOR_TRAITS_HPP
diff --git a/sprout/iterator/transform_iterator.hpp b/sprout/iterator/transform_iterator.hpp
index f03abb45..b67d7a5b 100644
--- a/sprout/iterator/transform_iterator.hpp
+++ b/sprout/iterator/transform_iterator.hpp
@@ -8,7 +8,7 @@
 #include <sprout/iterator/next.hpp>
 #include <sprout/iterator/prev.hpp>
 #include <sprout/iterator/distance.hpp>
-#include <sprout/iterator/traits.hpp>
+#include <sprout/iterator/type_traits/common.hpp>
 #include <sprout/utility/swap.hpp>
 
 namespace sprout {
@@ -18,10 +18,7 @@ namespace sprout {
 	template<typename BinaryFunction, typename LIterator, typename RIterator = void>
 	class transform_iterator
 		: public std::iterator<
-			typename sprout::min_iterator_category<
-				typename std::iterator_traits<LIterator>::iterator_category,
-				typename std::iterator_traits<RIterator>::iterator_category
-			>::type,
+			typename sprout::common_iterator_category<LIterator, RIterator>::type,
 			typename std::remove_reference<
 				typename std::result_of<
 					BinaryFunction (
@@ -51,10 +48,7 @@ namespace sprout {
 		typedef BinaryFunction functor_type;
 		typedef LIterator iterator_type;
 		typedef RIterator iterator2_type;
-		typedef typename sprout::min_iterator_category<
-			typename std::iterator_traits<LIterator>::iterator_category,
-			typename std::iterator_traits<RIterator>::iterator_category
-		>::type iterator_category;
+		typedef typename sprout::common_iterator_category<LIterator, RIterator>::type iterator_category;
 		typedef typename std::result_of<
 			BinaryFunction (
 				typename std::iterator_traits<LIterator>::reference,
diff --git a/sprout/iterator/type_traits.hpp b/sprout/iterator/type_traits.hpp
new file mode 100644
index 00000000..6e63ae1a
--- /dev/null
+++ b/sprout/iterator/type_traits.hpp
@@ -0,0 +1,8 @@
+#ifndef SPROUT_ITERATOR_TYPE_TRAITS_HPP
+#define SPROUT_ITERATOR_TYPE_TRAITS_HPP
+
+#include <sprout/config.hpp>
+#include <sprout/iterator/type_traits/is_iterator.hpp>
+#include <sprout/iterator/type_traits/common.hpp>
+
+#endif	// #ifndef SPROUT_ITERATOR_TYPE_TRAITS_HPP
diff --git a/sprout/iterator/type_traits/common.hpp b/sprout/iterator/type_traits/common.hpp
new file mode 100644
index 00000000..177f51d6
--- /dev/null
+++ b/sprout/iterator/type_traits/common.hpp
@@ -0,0 +1,164 @@
+#ifndef SPROUT_ITERATOR_TYPE_TRAITS_COMMON_HPP
+#define SPROUT_ITERATOR_TYPE_TRAITS_COMMON_HPP
+
+#include <iterator>
+#include <type_traits>
+#include <sprout/config.hpp>
+#include <sprout/iterator/type_traits/is_iterator.hpp>
+
+namespace sprout {
+	namespace detail {
+		template<typename Category, bool IsRandomAccess, bool IsBidirectional, bool IsForward, bool IsSinglePassOrIncrementable>
+		struct iterator_category_hierarchy_impl;
+		template<typename Category, bool IsBidirectional, bool IsForward, bool IsSinglePassOrIncrementable>
+		struct iterator_category_hierarchy_impl<Category, true, IsBidirectional, IsForward, IsSinglePassOrIncrementable>
+			: public std::integral_constant<int, 4>
+		{};
+		template<typename Category, bool IsForward, bool IsSinglePassOrIncrementable>
+		struct iterator_category_hierarchy_impl<Category, false, true, IsForward, IsSinglePassOrIncrementable>
+			: public std::integral_constant<int, 3>
+		{};
+		template<typename Category, bool IsSinglePassOrIncrementable>
+		struct iterator_category_hierarchy_impl<Category, false, false, true, IsSinglePassOrIncrementable>
+			: public std::integral_constant<int, 2>
+		{};
+		template<typename Category>
+		struct iterator_category_hierarchy_impl<Category, false, false, false, true>
+			: public std::integral_constant<int, 1>
+		{};
+
+		template<typename Category>
+		struct iterator_category_hierarchy
+			: public sprout::detail::iterator_category_hierarchy_impl<
+				Category,
+				sprout::is_random_access_iterator_category<Category>::value,
+				sprout::is_bidirectional_iterator_category<Category>::value,
+				sprout::is_forward_iterator_category<Category>::value,
+				sprout::is_input_iterator_category<Category>::value || sprout::is_output_iterator_category<Category>::value
+			>
+		{};
+
+		template<typename Category1, typename Category2>
+		struct iterator_category_less
+			: public std::integral_constant<
+				bool,
+				(sprout::detail::iterator_category_hierarchy<Category1>::value < sprout::detail::iterator_category_hierarchy<Category2>::value)
+			>
+		{};
+	}	// namespace detail
+	//
+	// min_iterator_category
+	//
+	template<typename Head, typename... Tail>
+	struct min_iterator_category;
+	template<typename Category>
+	struct min_iterator_category<Category>
+		: public std::common_type<Category>
+	{};
+	template<typename Category1, typename Category2>
+	struct min_iterator_category<Category1, Category2>
+		: public std::conditional<
+			sprout::detail::iterator_category_less<Category1, Category2>::value,
+			Category1, Category2
+		>
+	{};
+	template<typename Head, typename... Tail>
+	struct min_iterator_category
+		: public sprout::min_iterator_category<
+			Head,
+			typename sprout::min_iterator_category<Tail...>::type
+		>
+	{};
+
+	//
+	// common_iterator_category
+	//
+	template<typename... Iterators>
+	struct common_iterator_category
+		: public sprout::min_iterator_category<
+			typename std::iterator_traits<Iterators>::iterator_category...
+		>
+	{};
+
+	namespace detail {
+		template<typename... Types>
+		struct common_iterator_reference_impl;
+		template<typename T>
+		struct common_iterator_reference_impl<T> {
+		public:
+			typedef T type;
+		};
+		template<typename T, typename U>
+		struct common_iterator_reference_impl<T, U>
+			: public std::conditional<
+				std::is_reference<T>::value && std::is_reference<U>::value,
+				typename std::conditional<
+					std::is_convertible<T, U>::value
+						&& (std::is_same<typename std::decay<T>::type, typename std::decay<U>::type>::value
+							|| std::is_base_of<typename std::decay<U>::type, typename std::decay<T>::type>::value
+							)
+						,
+					U,
+					typename std::conditional<
+						std::is_convertible<U, T>::value
+							&& (std::is_same<typename std::decay<U>::type, typename std::decay<T>::type>::value
+								|| std::is_base_of<typename std::decay<T>::type, typename std::decay<U>::type>::value
+								)
+							,
+						T,
+						typename std::common_type<typename std::decay<T>::type, typename std::decay<U>::type>::type
+					>::type
+				>::type,
+				typename std::common_type<typename std::decay<T>::type, typename std::decay<U>::type>::type
+			>
+		{};
+		template<typename T, typename U, typename... Tail>
+		struct common_iterator_reference_impl<T, U, Tail...>
+			: public sprout::detail::common_iterator_reference_impl<
+				typename sprout::detail::common_iterator_reference_impl<T, U>::type,
+				Tail...
+			>
+		{};
+	}	// namespace detail
+	//
+	// common_iterator_reference
+	//
+	template<typename... Iterators>
+	struct common_iterator_reference
+		: public sprout::detail::common_iterator_reference_impl<
+			typename std::iterator_traits<Iterators>::reference...
+		>
+	{};
+
+	//
+	// common_iterator_value_type
+	//
+	template<typename... Iterators>
+	struct common_iterator_value_type
+		: public std::decay<
+			typename sprout::common_iterator_reference<Iterators...>::type
+		>
+	{};
+
+	//
+	// common_iterator_pointer
+	//
+	template<typename... Iterators>
+	struct common_iterator_pointer
+		: public std::add_pointer<
+			typename std::remove_reference<typename sprout::common_iterator_reference<Iterators...>::type>::type
+		>
+	{};
+
+	//
+	// common_iterator_difference_type
+	//
+	template<typename... Iterators>
+	struct common_iterator_difference_type
+		: public std::common_type<
+			typename std::iterator_traits<Iterators>::difference_type...
+		>
+	{};
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_ITERATOR_TYPE_TRAITS_COMMON_HPP
diff --git a/sprout/iterator/type_traits/is_iterator.hpp b/sprout/iterator/type_traits/is_iterator.hpp
new file mode 100644
index 00000000..e12498d1
--- /dev/null
+++ b/sprout/iterator/type_traits/is_iterator.hpp
@@ -0,0 +1,97 @@
+#ifndef SPROUT_ITERATOR_TYPE_TRAITS_IS_ITERATOR_HPP
+#define SPROUT_ITERATOR_TYPE_TRAITS_IS_ITERATOR_HPP
+
+#include <iterator>
+#include <type_traits>
+#include <sprout/config.hpp>
+#include <sprout/type_traits/has_xxx.hpp>
+
+namespace sprout {
+	namespace detail {
+		//
+		// has_iterator_category
+		//
+		SPROUT_HAS_XXX_TYPE_DEF_LAZY(iterator_category);
+	}	// namespace detail
+	//
+	// is_iterator
+	//
+	template<typename Iterator>
+	struct is_iterator
+		: public sprout::detail::has_iterator_category<std::iterator_traits<Iterator> >
+	{};
+
+	//
+	// is_input_iterator_category
+	//
+	template<typename Category>
+	struct is_input_iterator_category
+		: public std::is_convertible<Category, std::input_iterator_tag>
+	{};
+	//
+	// is_output_iterator_category
+	//
+	template<typename Category>
+	struct is_output_iterator_category
+		: public std::is_convertible<Category, std::output_iterator_tag>
+	{};
+	//
+	// is_forward_iterator_category
+	//
+	template<typename Category>
+	struct is_forward_iterator_category
+		: public std::is_convertible<Category, std::forward_iterator_tag>
+	{};
+	//
+	// is_bidirectional_iterator_category
+	//
+	template<typename Category>
+	struct is_bidirectional_iterator_category
+		: public std::is_convertible<Category, std::bidirectional_iterator_tag>
+	{};
+	//
+	// is_random_access_iterator_category
+	//
+	template<typename Category>
+	struct is_random_access_iterator_category
+		: public std::is_convertible<Category, std::random_access_iterator_tag>
+	{};
+
+	//
+	// is_input_iterator
+	//
+	template<typename Iterator>
+	struct is_input_iterator
+		: public sprout::is_input_iterator_category<typename std::iterator_traits<Iterator>::iterator_category>
+	{};
+	//
+	// is_output_iterator
+	//
+	template<typename Iterator>
+	struct is_output_iterator
+		: public sprout::is_output_iterator_category<typename std::iterator_traits<Iterator>::iterator_category>
+	{};
+	//
+	// is_forward_iterator
+	//
+	template<typename Iterator>
+	struct is_forward_iterator
+		: public sprout::is_forward_iterator_category<typename std::iterator_traits<Iterator>::iterator_category>
+	{};
+	//
+	// is_bidirectional_iterator
+	//
+	template<typename Iterator>
+	struct is_bidirectional_iterator
+		: public sprout::is_bidirectional_iterator_category<typename std::iterator_traits<Iterator>::iterator_category>
+	{};
+	//
+	// is_random_access_iterator
+	//
+	template<typename Iterator>
+	struct is_random_access_iterator
+		: public sprout::is_random_access_iterator_category<typename std::iterator_traits<Iterator>::iterator_category>
+	{};
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_ITERATOR_TYPE_TRAITS_IS_ITERATOR_HPP
diff --git a/sprout/random.hpp b/sprout/random.hpp
index cda73e2d..b7cf38b7 100644
--- a/sprout/random.hpp
+++ b/sprout/random.hpp
@@ -2,23 +2,8 @@
 #define SPROUT_RANDOM_HPP
 
 #include <sprout/config.hpp>
-#include <sprout/random/linear_congruential.hpp>
-#include <sprout/random/inversive_congruential.hpp>
-#include <sprout/random/mersenne_twister.hpp>
-#include <sprout/random/linear_feedback_shift.hpp>
-#include <sprout/random/shuffle_order.hpp>
-#include <sprout/random/additive_combine.hpp>
-#include <sprout/random/xor_combine.hpp>
-#include <sprout/random/taus88.hpp>
-#include <sprout/random/default_random_engine.hpp>
-#include <sprout/random/uniform_smallint.hpp>
-#include <sprout/random/uniform_int_distribution.hpp>
-#include <sprout/random/uniform_01.hpp>
-#include <sprout/random/uniform_real_distribution.hpp>
-#include <sprout/random/bernoulli_distribution.hpp>
-#include <sprout/random/binomial_distribution.hpp>
-#include <sprout/random/geometric_distribution.hpp>
-#include <sprout/random/normal_distribution.hpp>
+#include <sprout/random/engine.hpp>
+#include <sprout/random/distribution.hpp>
 #include <sprout/random/variate_generator.hpp>
 #include <sprout/random/random_result.hpp>
 #include <sprout/random/iterator.hpp>
diff --git a/sprout/random/distribution.hpp b/sprout/random/distribution.hpp
new file mode 100644
index 00000000..89f6d922
--- /dev/null
+++ b/sprout/random/distribution.hpp
@@ -0,0 +1,14 @@
+#ifndef SPROUT_RANDOM_DISTRIBUTION_HPP
+#define SPROUT_RANDOM_DISTRIBUTION_HPP
+
+#include <sprout/config.hpp>
+#include <sprout/random/uniform_smallint.hpp>
+#include <sprout/random/uniform_int_distribution.hpp>
+#include <sprout/random/uniform_01.hpp>
+#include <sprout/random/uniform_real_distribution.hpp>
+#include <sprout/random/bernoulli_distribution.hpp>
+#include <sprout/random/binomial_distribution.hpp>
+#include <sprout/random/geometric_distribution.hpp>
+#include <sprout/random/normal_distribution.hpp>
+
+#endif // #ifndef SPROUT_RANDOM_DISTRIBUTION_HPP
diff --git a/sprout/random/engine.hpp b/sprout/random/engine.hpp
new file mode 100644
index 00000000..8918defa
--- /dev/null
+++ b/sprout/random/engine.hpp
@@ -0,0 +1,15 @@
+#ifndef SPROUT_RANDOM_ENGINE_HPP
+#define SPROUT_RANDOM_ENGINE_HPP
+
+#include <sprout/config.hpp>
+#include <sprout/random/linear_congruential.hpp>
+#include <sprout/random/inversive_congruential.hpp>
+#include <sprout/random/mersenne_twister.hpp>
+#include <sprout/random/linear_feedback_shift.hpp>
+#include <sprout/random/shuffle_order.hpp>
+#include <sprout/random/additive_combine.hpp>
+#include <sprout/random/xor_combine.hpp>
+#include <sprout/random/taus88.hpp>
+#include <sprout/random/default_random_engine.hpp>
+
+#endif // #ifndef SPROUT_RANDOM_ENGINE_HPP
diff --git a/sprout/range/adaptor.hpp b/sprout/range/adaptor.hpp
index 38da08e1..6e275f30 100644
--- a/sprout/range/adaptor.hpp
+++ b/sprout/range/adaptor.hpp
@@ -12,6 +12,7 @@
 #include <sprout/range/adaptor/outdirected.hpp>
 #include <sprout/range/adaptor/indexed.hpp>
 #include <sprout/range/adaptor/valued.hpp>
+#include <sprout/range/adaptor/jointed.hpp>
 #include <sprout/range/adaptor/deep_copied.hpp>
 #include <sprout/range/adaptor/sized.hpp>
 #include <sprout/range/adaptor/size_enumed.hpp>
diff --git a/sprout/range/adaptor/jointed.hpp b/sprout/range/adaptor/jointed.hpp
new file mode 100644
index 00000000..fe55435e
--- /dev/null
+++ b/sprout/range/adaptor/jointed.hpp
@@ -0,0 +1,146 @@
+#ifndef SPROUT_RANGE_ADAPTOR_JOINTED_HPP
+#define SPROUT_RANGE_ADAPTOR_JOINTED_HPP
+
+#include <type_traits>
+#include <sprout/config.hpp>
+#include <sprout/pit.hpp>
+#include <sprout/container/traits.hpp>
+#include <sprout/container/functions.hpp>
+#include <sprout/iterator/joint_iterator.hpp>
+#include <sprout/range/range_container.hpp>
+#include <sprout/range/algorithm/copy.hpp>
+#include <sprout/type_traits/lvalue_reference.hpp>
+#include <sprout/utility/forward.hpp>
+#include <sprout/utility/lvalue_forward.hpp>
+#include <sprout/utility/value_holder.hpp>
+
+namespace sprout {
+	namespace adaptors {
+		//
+		// jointed_range
+		//
+		template<typename LRange, typename RRange>
+		class jointed_range
+			: public sprout::range::range_container<
+				sprout::joint_iterator<
+					typename sprout::container_traits<LRange>::iterator,
+					typename sprout::container_traits<RRange>::iterator
+				>
+			>
+			, public sprout::detail::container_nosy_static_size<LRange>
+			, public sprout::detail::container_nosy_fixed_size<LRange>
+		{
+		public:
+			typedef LRange range_type;
+			typedef RRange range2_type;
+			typedef sprout::range::range_container<
+				sprout::joint_iterator<
+					typename sprout::container_traits<LRange>::iterator,
+					typename sprout::container_traits<RRange>::iterator
+				>
+			> base_type;
+			typedef typename base_type::iterator iterator;
+		public:
+			jointed_range() = default;
+			jointed_range(jointed_range const&) = default;
+			SPROUT_CONSTEXPR jointed_range(range_type& range1, range2_type& range2)
+				: base_type(
+					iterator(sprout::begin(range1), sprout::end(range1), sprout::begin(range2), sprout::begin(range2)),
+					iterator(sprout::end(range1), sprout::end(range1), sprout::begin(range2), sprout::end(range2))
+					)
+			{}
+		};
+
+		//
+		// joint_holder
+		//
+		template<typename RRange>
+		class joint_holder {
+		public:
+			typedef RRange range2_type;
+		private:
+			sprout::value_holder<range2_type&> range_;
+		public:
+			joint_holder() = default;
+			joint_holder(joint_holder const&) = default;
+			explicit SPROUT_CONSTEXPR joint_holder(range2_type& range)
+				: range_(range)
+			{}
+			SPROUT_CONSTEXPR range2_type& range() const {
+				return range_;
+			}
+		};
+
+		//
+		// jointed_forwarder
+		//
+		class jointed_forwarder {
+		public:
+			template<typename RRange>
+			SPROUT_CONSTEXPR sprout::adaptors::joint_holder<
+				typename std::remove_reference<typename sprout::lvalue_reference<RRange>::type>::type
+			>
+			operator()(RRange&& range) {
+				return sprout::adaptors::joint_holder<
+					typename std::remove_reference<typename sprout::lvalue_reference<RRange>::type>::type
+				>(
+					sprout::lvalue_forward<RRange>(range)
+					);
+			}
+		};
+
+		//
+		// jointed
+		//
+		namespace {
+			SPROUT_STATIC_CONSTEXPR sprout::adaptors::jointed_forwarder jointed{};
+		}	// anonymous-namespace
+
+		//
+		// operator|
+		//
+		template<typename LRange, typename RRange>
+		inline SPROUT_CONSTEXPR sprout::adaptors::jointed_range<
+			typename std::remove_reference<typename sprout::lvalue_reference<LRange>::type>::type,
+			RRange
+		>
+		operator|(LRange&& lhs, sprout::adaptors::joint_holder<RRange> const& rhs) {
+			return sprout::adaptors::jointed_range<
+				typename std::remove_reference<typename sprout::lvalue_reference<LRange>::type>::type,
+				RRange
+			>(
+				sprout::lvalue_forward<LRange>(lhs),
+				rhs.range()
+				);
+		}
+	}	// namespace adaptors
+
+	//
+	// container_construct_traits
+	//
+	template<typename LRange, typename RRange>
+	struct container_construct_traits<sprout::adaptors::jointed_range<LRange, RRange> > {
+	public:
+		typedef typename sprout::container_construct_traits<LRange>::copied_type copied_type;
+	public:
+		template<typename Cont>
+		static SPROUT_CONSTEXPR copied_type deep_copy(Cont&& cont) {
+			return sprout::range::fixed::copy(sprout::forward<Cont>(cont), sprout::pit<copied_type>());
+		}
+		template<typename... Args>
+		static SPROUT_CONSTEXPR copied_type make(Args&&... args) {
+			return sprout::make<copied_type>(sprout::forward<Args>(args)...);
+		}
+		template<typename Cont, typename... Args>
+		static SPROUT_CONSTEXPR copied_type remake(
+			Cont&& cont,
+			typename sprout::container_traits<sprout::adaptors::jointed_range<LRange, RRange> >::difference_type size,
+			Args&&... args
+			)
+		{
+			return sprout::remake<copied_type>(sprout::forward<Cont>(cont), size, sprout::forward<Args>(args)...);
+		}
+	};
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_RANGE_ADAPTOR_JOINTED_HPP