diff --git a/sprout/complex.hpp b/sprout/complex.hpp
index 9b8bd196..d4d45138 100644
--- a/sprout/complex.hpp
+++ b/sprout/complex.hpp
@@ -2,6 +2,8 @@
 #define SPROUT_COMPLEX_HPP
 
 #include <cmath>
+#include <iosfwd>
+#include <ios>
 #include <sprout/config.hpp>
 #include <sprout/math/constants.hpp>
 
diff --git a/sprout/detail/param_at.hpp b/sprout/detail/param_at.hpp
index 27b33bc1..65933db2 100644
--- a/sprout/detail/param_at.hpp
+++ b/sprout/detail/param_at.hpp
@@ -31,6 +31,33 @@ namespace sprout {
 		{
 			return n == 0 ? v : sprout::detail::param_at<R>(n - 1, values...);
 		}
+
+		template<typename R, typename T, typename... Values>
+		inline SPROUT_CONSTEXPR typename std::enable_if<
+			sizeof...(Values) == 0,
+			R
+		>::type param_seq_at(
+			std::size_t n,
+			std::size_t m,
+			T const& v,
+			Values const&... values
+			)
+		{
+			return v[m];
+		}
+		template<typename R, typename T, typename... Values>
+		inline SPROUT_CONSTEXPR typename std::enable_if<
+			sizeof...(Values) != 0,
+			R
+		>::type param_seq_at(
+			std::size_t n,
+			std::size_t m,
+			T const& v,
+			Values const&... values
+			)
+		{
+			return n == 0 ? v[m] : sprout::detail::param_seq_at<R>(n - 1, m, values...);
+		}
 	}	// namespace detail
 }	// namespace sprout
 
diff --git a/sprout/io.hpp b/sprout/io.hpp
new file mode 100644
index 00000000..abbb439c
--- /dev/null
+++ b/sprout/io.hpp
@@ -0,0 +1,766 @@
+#ifndef SPROUT_IO_HPP
+#define SPROUT_IO_HPP
+
+#include <cstddef>
+#include <iosfwd>
+#include <utility>
+#include <type_traits>
+#include <sprout/config.hpp>
+#include <sprout/index_tuple.hpp>
+#include <sprout/array.hpp>
+#include <sprout/string.hpp>
+#include <sprout/pit.hpp>
+#include <sprout/utility/value_holder.hpp>
+#include <sprout/utility/enabler_if.hpp>
+#include <sprout/range/algorithm/lower_bound.hpp>
+#include <sprout/range/numeric/partial_sum.hpp>
+#include <sprout/weed/traits/type/is_char_type.hpp>
+#include <sprout/detail/param_at.hpp>
+#include HDR_ALGORITHM_SSCRISK_CEL_OR_SPROUT
+
+namespace sprout {
+	namespace io {
+		namespace flags {
+			//
+			// fmtflags
+			//
+			enum fmtflags { 
+				boolalpha = 1L << 0,
+				showbase = 1L << 1,
+				showpoint = 1L << 2,
+				showpos = 1L << 3,
+				uppercase = 1L << 4,
+				skipws = 1L << 5,
+				right = 1L << 6,
+				left = 1L << 7,
+				internal = 1L << 8,
+				dec = 1L << 9,
+				hex = 1L << 10,
+				oct = 1L << 11,
+				fixed = 1L << 12,
+				scientific = 1L << 13,
+				adjustfield = right | left | internal,
+				basefield = dec | hex | oct,
+				floatfield = fixed | scientific,
+				booleanfield = boolalpha | showbase | showpoint | showpos | uppercase | skipws,
+				default_flags = right | dec | fixed,
+				precision_ = 1L << 14,
+				width_ = 1L << 15,
+				fill_ = 1L << 16,
+				modified_shift_ = 17,
+			};
+			//
+			// boolean_flag
+			//
+			template<sprout::io::flags::fmtflags Flag>
+			struct boolean_flag
+				: public std::integral_constant<sprout::io::flags::fmtflags, Flag>
+			{
+			private:
+				bool flag_;
+			public:
+				boolean_flag() = default;
+				boolean_flag(boolean_flag const&) = default;
+				SPROUT_CONSTEXPR boolean_flag(bool flag)
+					: flag_(flag)
+				{}
+				SPROUT_CONSTEXPR boolean_flag operator()(bool flag) const {
+					return boolean_flag(flag);
+				}
+				SPROUT_CONSTEXPR operator bool() const {
+					return flag_;
+				}
+				SPROUT_CONSTEXPR bool operator!() const {
+					return !flag_;
+				}
+			};
+			//
+			// field_flag
+			//
+			template<sprout::io::flags::fmtflags Flag, sprout::io::flags::fmtflags Mask>
+			struct field_flag
+				: public std::integral_constant<sprout::io::flags::fmtflags, Flag>
+			{
+			public:
+				SPROUT_STATIC_CONSTEXPR sprout::io::flags::fmtflags mask = Mask;
+			public:
+				field_flag() = default;
+				field_flag(field_flag const&) = default;
+			};
+			template<sprout::io::flags::fmtflags Flag, sprout::io::flags::fmtflags Mask>
+			SPROUT_CONSTEXPR sprout::io::flags::fmtflags sprout::io::flags::field_flag<Flag, Mask>::mask;
+
+			//
+			// precision_t
+			//
+			struct precision_t {
+			public:
+				typedef std::streamsize type;
+			public:
+				type value;
+			public:
+				SPROUT_CONSTEXPR precision_t(type value)
+					: value(value)
+				{}
+				SPROUT_CONSTEXPR operator type() const {
+					return value;
+				}
+			};
+
+			//
+			// width_t
+			//
+			struct width_t {
+			public:
+				typedef std::streamsize type;
+			public:
+				type value;
+			public:
+				SPROUT_CONSTEXPR width_t(type value)
+					: value(value)
+				{}
+				SPROUT_CONSTEXPR operator type() const {
+					return value;
+				}
+			};
+
+			//
+			// fill_t
+			//
+			struct fill_t {
+			public:
+				typedef char type;
+			public:
+				type value;
+			public:
+				SPROUT_CONSTEXPR fill_t(type value)
+					: value(value)
+				{}
+				SPROUT_CONSTEXPR operator type() const {
+					return value;
+				}
+			};
+		}	// namespace flags
+
+		SPROUT_STATIC_CONSTEXPR sprout::io::flags::boolean_flag<sprout::io::flags::boolalpha> boolalpha = true;
+		SPROUT_STATIC_CONSTEXPR sprout::io::flags::boolean_flag<sprout::io::flags::showbase> showbase = true;
+		SPROUT_STATIC_CONSTEXPR sprout::io::flags::boolean_flag<sprout::io::flags::showpoint> showpoint = true;
+		SPROUT_STATIC_CONSTEXPR sprout::io::flags::boolean_flag<sprout::io::flags::showpos> showpos = true;
+		SPROUT_STATIC_CONSTEXPR sprout::io::flags::boolean_flag<sprout::io::flags::uppercase> uppercase = true;
+		SPROUT_STATIC_CONSTEXPR sprout::io::flags::boolean_flag<sprout::io::flags::skipws> skipws = true;
+		SPROUT_STATIC_CONSTEXPR sprout::io::flags::field_flag<sprout::io::flags::right, sprout::io::flags::adjustfield> right{};
+		SPROUT_STATIC_CONSTEXPR sprout::io::flags::field_flag<sprout::io::flags::left, sprout::io::flags::adjustfield> left{};
+		SPROUT_STATIC_CONSTEXPR sprout::io::flags::field_flag<sprout::io::flags::internal, sprout::io::flags::adjustfield> internal{};
+		SPROUT_STATIC_CONSTEXPR sprout::io::flags::field_flag<sprout::io::flags::dec, sprout::io::flags::basefield> dec{};
+		SPROUT_STATIC_CONSTEXPR sprout::io::flags::field_flag<sprout::io::flags::hex, sprout::io::flags::basefield> hex{};
+		SPROUT_STATIC_CONSTEXPR sprout::io::flags::field_flag<sprout::io::flags::oct, sprout::io::flags::basefield> oct{};
+		SPROUT_STATIC_CONSTEXPR sprout::io::flags::field_flag<sprout::io::flags::fixed, sprout::io::flags::floatfield> fixed{};
+		SPROUT_STATIC_CONSTEXPR sprout::io::flags::field_flag<sprout::io::flags::scientific, sprout::io::flags::floatfield> scientific{};
+
+		//
+		// precision
+		// width
+		// fill
+		//
+		inline SPROUT_CONSTEXPR sprout::io::flags::precision_t
+		precision(sprout::io::flags::precision_t::type value) {
+			return sprout::io::flags::precision_t(value);
+		}
+		inline SPROUT_CONSTEXPR sprout::io::flags::width_t
+		width(sprout::io::flags::width_t::type value) {
+			return sprout::io::flags::width_t(value);
+		}
+		inline SPROUT_CONSTEXPR sprout::io::flags::fill_t
+		fill(sprout::io::flags::fill_t::type value) {
+			return sprout::io::flags::fill_t(value);
+		}
+
+		//
+		// format_settings
+		//
+		class format_settings {
+		private:
+			sprout::io::flags::fmtflags flags_;
+			sprout::io::flags::precision_t precision_;
+			sprout::io::flags::width_t width_;
+			sprout::io::flags::fill_t fill_;
+		private:
+			SPROUT_CONSTEXPR format_settings(format_settings const& other, sprout::io::flags::fmtflags flags)
+				: flags_(flags)
+				, precision_(other.precision_)
+				, width_(other.width_)
+				, fill_(other.fill_)
+			{}
+			SPROUT_CONSTEXPR format_settings(format_settings const& other, sprout::io::flags::precision_t precision)
+				: flags_(static_cast<sprout::io::flags::fmtflags>(other.flags_ | sprout::io::flags::precision_))
+				, precision_(precision)
+				, width_(other.width_)
+				, fill_(other.fill_)
+			{}
+			SPROUT_CONSTEXPR format_settings(format_settings const& other, sprout::io::flags::width_t width)
+				: flags_(static_cast<sprout::io::flags::fmtflags>(other.flags_ | sprout::io::flags::width_))
+				, precision_(other.precision_)
+				, width_(width)
+				, fill_(other.fill_)
+			{}
+			SPROUT_CONSTEXPR format_settings(format_settings const& other, sprout::io::flags::fill_t fill)
+				: flags_(static_cast<sprout::io::flags::fmtflags>(other.flags_ | sprout::io::flags::fill_))
+				, precision_(other.precision_)
+				, width_(other.width_)
+				, fill_(fill)
+			{}
+			SPROUT_CONSTEXPR format_settings(
+				sprout::io::flags::fmtflags flags,
+				sprout::io::flags::precision_t precision,
+				sprout::io::flags::width_t width,
+				sprout::io::flags::fill_t fill
+				)
+				: flags_(flags)
+				, precision_(precision)
+				, width_(width)
+				, fill_(fill)
+			{}
+		public:
+			SPROUT_CONSTEXPR format_settings()
+				: flags_(sprout::io::flags::default_flags)
+				, precision_(6)
+				, width_(0)
+				, fill_(' ')
+			{}
+			format_settings(format_settings const&) = default;
+			explicit SPROUT_CONSTEXPR format_settings(sprout::io::flags::fmtflags flags)
+				: flags_(flags)
+				, precision_(6)
+				, width_(0)
+				, fill_(' ')
+			{}
+			explicit SPROUT_CONSTEXPR format_settings(sprout::io::flags::precision_t precision)
+				: flags_(sprout::io::flags::default_flags)
+				, precision_(precision)
+				, width_(0)
+				, fill_(' ')
+			{}
+			explicit SPROUT_CONSTEXPR format_settings(sprout::io::flags::width_t width)
+				: flags_(sprout::io::flags::default_flags)
+				, precision_(6)
+				, width_(width)
+				, fill_(' ')
+			{}
+			explicit SPROUT_CONSTEXPR format_settings(sprout::io::flags::fill_t fill)
+				: flags_(sprout::io::flags::default_flags)
+				, precision_(6)
+				, width_(0)
+				, fill_(fill)
+			{}
+			SPROUT_CONSTEXPR sprout::io::flags::fmtflags flags() const {
+				return flags_;
+			}
+			template<sprout::io::flags::fmtflags Flag>
+			SPROUT_CONSTEXPR format_settings flags(sprout::io::flags::boolean_flag<Flag> flag) const {
+				return format_settings(
+					*this,
+					static_cast<sprout::io::flags::fmtflags>(
+						(flag ? flags_ | Flag : flags_ & ~Flag) | (Flag << sprout::io::flags::modified_shift_)
+						)
+					);
+			}
+			template<sprout::io::flags::fmtflags Flag, sprout::io::flags::fmtflags Mask>
+			SPROUT_CONSTEXPR format_settings flags(sprout::io::flags::field_flag<Flag, Mask> flag) const {
+				return format_settings(
+					*this,
+					static_cast<sprout::io::flags::fmtflags>(
+						(flags_ & ~Mask) | (Flag & Mask) | (Mask << sprout::io::flags::modified_shift_)
+						)
+					);
+			}
+			SPROUT_CONSTEXPR sprout::io::flags::precision_t::type precision() const {
+				return precision_;
+			}
+			SPROUT_CONSTEXPR format_settings precision(sprout::io::flags::precision_t precision) const {
+				return format_settings(*this, precision);
+			}
+			SPROUT_CONSTEXPR sprout::io::flags::width_t::type width() const {
+				return width_;
+			}
+			SPROUT_CONSTEXPR format_settings width(sprout::io::flags::width_t width) const {
+				return format_settings(*this, width);
+			}
+			SPROUT_CONSTEXPR sprout::io::flags::fill_t::type fill() const {
+				return fill_;
+			}
+			SPROUT_CONSTEXPR format_settings fill(sprout::io::flags::fill_t fill) const {
+				return format_settings(*this, fill);
+			}
+			SPROUT_CONSTEXPR format_settings combine(format_settings const& base) const {
+				return format_settings(
+					static_cast<sprout::io::flags::fmtflags>(
+						(base.flags_ & ~(flags_ >> sprout::io::flags::modified_shift_)) | flags_
+						),
+					flags_ & sprout::io::flags::precision_ ? precision_ : base.precision_,
+					flags_ & sprout::io::flags::width_ ? width_ : base.width_,
+					flags_ & sprout::io::flags::fill_ ? fill_ : base.fill_
+					);
+			}
+		};
+
+		//
+		// format_holder
+		//
+		template<typename T>
+		class format_holder {
+		private:
+			sprout::value_holder<T const&> holder_;
+			sprout::io::format_settings settings_;
+		public:
+			format_holder() = default;
+			format_holder(format_holder const&) = default;
+			explicit SPROUT_CONSTEXPR format_holder(T const& value)
+				: holder_(value)
+				, settings_()
+			{}
+			SPROUT_CONSTEXPR format_holder(
+				T const& value,
+				sprout::io::format_settings const& settings
+				)
+				: holder_(value)
+				, settings_(settings)
+			{}
+			SPROUT_CONSTEXPR format_holder(
+				format_holder const& holder,
+				sprout::io::format_settings const& settings
+				)
+				: holder_(holder)
+				, settings_(settings)
+			{}
+			SPROUT_CONSTEXPR T const& value() const {
+				return holder_;
+			}
+			SPROUT_CONSTEXPR sprout::io::format_settings const& settings() const {
+				return settings_;
+			}
+			SPROUT_CONSTEXPR format_holder settings(sprout::io::format_settings const& settings) const {
+				return format_holder(holder_, settings);
+			}
+		};
+
+		namespace flags {
+			template<typename T, sprout::io::flags::fmtflags Flag>
+			inline SPROUT_CONSTEXPR sprout::io::format_holder<T>
+			operator|(T const& value, sprout::io::flags::boolean_flag<Flag> flag) {
+				return sprout::io::format_holder<T>(value, sprout::io::format_settings().flags(flag));
+			}
+			template<typename T, sprout::io::flags::fmtflags Flag, sprout::io::flags::fmtflags Mask>
+			inline SPROUT_CONSTEXPR sprout::io::format_holder<T>
+			operator|(T const& value, sprout::io::flags::field_flag<Flag, Mask> flag) {
+				return sprout::io::format_holder<T>(value, sprout::io::format_settings().flags(flag));
+			}
+			template<typename T>
+			inline SPROUT_CONSTEXPR sprout::io::format_holder<T>
+			operator|(T const& value, sprout::io::flags::precision_t precision) {
+				return sprout::io::format_holder<T>(value, sprout::io::format_settings(precision));
+			}
+			template<typename T>
+			inline SPROUT_CONSTEXPR sprout::io::format_holder<T>
+			operator|(T const& value, sprout::io::flags::width_t width) {
+				return sprout::io::format_holder<T>(value, sprout::io::format_settings(width));
+			}
+			template<typename T>
+			inline SPROUT_CONSTEXPR sprout::io::format_holder<T>
+			operator|(T const& value, sprout::io::flags::fill_t fill) {
+				return sprout::io::format_holder<T>(value, sprout::io::format_settings(fill));
+			}
+
+			template<typename T, sprout::io::flags::fmtflags Flag>
+			inline SPROUT_CONSTEXPR sprout::io::format_holder<T>
+			operator|(sprout::io::format_holder<T> const& holder, sprout::io::flags::boolean_flag<Flag> flag) {
+				return holder.settings(holder.settings().flags(flag));
+			}
+			template<typename T, sprout::io::flags::fmtflags Flag, sprout::io::flags::fmtflags Mask>
+			inline SPROUT_CONSTEXPR sprout::io::format_holder<T>
+			operator|(sprout::io::format_holder<T> const& holder, sprout::io::flags::field_flag<Flag, Mask> flag) {
+				return holder.settings(holder.settings().flags(flag));
+			}
+			template<typename T>
+			inline SPROUT_CONSTEXPR sprout::io::format_holder<T>
+			operator|(sprout::io::format_holder<T> const& holder, sprout::io::flags::precision_t precision) {
+				return holder.settings(holder.settings().precision(precision));
+			}
+			template<typename T>
+			inline SPROUT_CONSTEXPR sprout::io::format_holder<T>
+			operator|(sprout::io::format_holder<T> const& holder, sprout::io::flags::width_t width) {
+				return holder.settings(holder.settings().width(width));
+			}
+			template<typename T>
+			inline SPROUT_CONSTEXPR sprout::io::format_holder<T>
+			operator|(sprout::io::format_holder<T> const& holder, sprout::io::flags::fill_t fill) {
+				return holder.settings(holder.settings().fill(fill));
+			}
+		}	// namespace flags
+
+		//
+		// nil_expression
+		//
+		class nil_expression {};
+
+		//
+		// root_expression
+		//
+		class root_expression {
+		private:
+			sprout::io::format_settings settings_;
+		public:
+			SPROUT_CONSTEXPR root_expression()
+				: settings_()
+			{}
+			root_expression(root_expression const&) = default;
+			explicit SPROUT_CONSTEXPR root_expression(sprout::io::format_settings const& settings)
+				: settings_(settings)
+			{}
+			SPROUT_CONSTEXPR sprout::io::format_settings const& settings() const {
+				return settings_;
+			}
+		};
+
+		//
+		// leaf_expression
+		//
+		template<typename T>
+		class leaf_expression {
+		private:
+			sprout::value_holder<T const&> value_;
+		public:
+			SPROUT_CONSTEXPR leaf_expression()
+				: value_()
+			{}
+			leaf_expression(leaf_expression const&) = default;
+			explicit SPROUT_CONSTEXPR leaf_expression(T const& value)
+				: value_(value)
+			{}
+			SPROUT_CONSTEXPR T const& value() const {
+				return value_;
+			}
+		};
+
+		//
+		// format_expression
+		//
+		template<typename Left, typename Right>
+		class format_expression {
+		private:
+			typedef typename std::conditional<
+				std::is_same<Left, sprout::io::root_expression>::value,
+				Left,
+				Left const&
+			>::type left_held_type;
+			typedef typename std::conditional<
+				std::is_same<Right, sprout::io::nil_expression>::value,
+				Right,
+				Right const&
+			>::type right_held_type;
+		private:
+			sprout::value_holder<left_held_type> left_;
+			sprout::value_holder<right_held_type> right_;
+		public:
+			SPROUT_CONSTEXPR format_expression()
+				: left_()
+				, right_()
+			{}
+			format_expression(format_expression const&) = default;
+			explicit SPROUT_CONSTEXPR format_expression(Left const& left)
+				: left_(left)
+			{}
+			explicit SPROUT_CONSTEXPR format_expression(sprout::value_holder<left_held_type> left)
+				: left_(left)
+			{}
+			SPROUT_CONSTEXPR format_expression(
+				Left const& left,
+				Right const& right
+				)
+				: left_(left)
+				, right_(right)
+			{}
+			SPROUT_CONSTEXPR format_expression(
+				sprout::value_holder<left_held_type> left,
+				sprout::value_holder<right_held_type> right
+				)
+				: left_(left)
+				, right_(right)
+			{}
+			SPROUT_CONSTEXPR Left const& left() const {
+				return left_;
+			}
+			SPROUT_CONSTEXPR Right const& right() const {
+				return right_;
+			}
+			SPROUT_CONSTEXPR sprout::io::format_settings const& settings() const {
+				return left().settings();
+			}
+		};
+
+		//
+		//  root_t
+		//
+		typedef sprout::io::format_expression<
+			sprout::io::root_expression,
+			sprout::io::nil_expression
+		> root_t;
+
+		//
+		// root
+		//
+		SPROUT_STATIC_CONSTEXPR sprout::io::root_t root{};
+
+		template<typename Left, typename Right, typename T>
+		inline SPROUT_CONSTEXPR auto
+		operator<<(sprout::io::format_expression<Left, Right> const& lhs, sprout::io::format_holder<T> const& rhs)
+			-> sprout::io::format_expression<
+				sprout::io::format_expression<Left, Right>,
+				decltype(std::declval<sprout::io::root_t>() << rhs.value())
+			>
+		{
+			typedef decltype(sprout::io::root << rhs.value()) type;
+			return sprout::io::format_expression<sprout::io::format_expression<Left, Right>, type>(
+				lhs,
+				sprout::io::root_t(sprout::io::root_expression(rhs.settings().combine(lhs.settings()))) << rhs.value()
+				);
+		}
+		template<typename Left, typename Right, typename T>
+		inline SPROUT_CONSTEXPR sprout::io::format_expression<
+			sprout::io::format_expression<Left, Right>,
+			sprout::io::leaf_expression<T>
+		>
+		operator<<(sprout::io::format_expression<Left, Right> const& lhs, T const& rhs) {
+			return sprout::io::format_expression<
+				sprout::io::format_expression<Left, Right>,
+				sprout::io::leaf_expression<T>
+			>(lhs, sprout::io::leaf_expression<T>(rhs));
+		}
+
+		//
+		// leaf_count
+		//
+		namespace detail {
+			template<typename Expression>
+			struct leaf_count;
+			template<>
+			struct leaf_count<sprout::io::root_t>
+				: public std::integral_constant<std::size_t, 0>
+			{};
+			template<typename T>
+			struct leaf_count<sprout::io::leaf_expression<T> >
+				: public std::integral_constant<std::size_t, 1>
+			{};
+			template<typename Left, typename Right>
+			struct leaf_count<sprout::io::format_expression<Left, Right> >
+				: public std::integral_constant<
+					std::size_t,
+					sprout::io::detail::leaf_count<Left>::value + sprout::io::detail::leaf_count<Right>::value
+				>
+			{};
+		}	// namespace detail
+		template<typename Expression>
+		struct leaf_count
+			: public sprout::io::detail::leaf_count<Expression>
+		{};
+		template<typename Expression>
+		struct leaf_count<Expression const>
+			: public sprout::io::leaf_count<Expression>
+		{};
+		template<typename Expression>
+		struct leaf_count<Expression const volatile>
+			: public sprout::io::leaf_count<Expression>
+		{};
+
+		//
+		// leaf_at
+		//
+		namespace detail {
+			template<std::size_t I, typename Expression>
+			struct leaf_at;
+			template<std::size_t I, typename T>
+			struct leaf_at<I, sprout::io::leaf_expression<T> > {
+			public:
+				typedef T type;
+			};
+			template<std::size_t I, typename Left, typename Right>
+			struct leaf_at<I, sprout::io::format_expression<Left, Right> >
+				: public std::conditional<
+					I < sprout::io::leaf_count<Left>::value,
+					sprout::io::detail::leaf_at<I, Left>,
+					sprout::io::detail::leaf_at<I - sprout::io::leaf_count<Left>::value, Right>
+				>::type
+			{};
+		}	// namespace detail
+		template<std::size_t I, typename Expression>
+		struct leaf_at
+			: public sprout::io::detail::leaf_at<I, Expression>
+		{};
+		template<std::size_t I, typename Expression>
+		struct leaf_at<I, Expression const>
+			: public sprout::io::leaf_at<I, Expression>
+		{};
+		template<std::size_t I, typename Expression>
+		struct leaf_at<I, Expression const volatile>
+			: public sprout::io::leaf_at<I, Expression>
+		{};
+
+		//
+		// get_leaf
+		//
+		namespace detail {
+			template<
+				std::size_t I, typename Left, typename Right,
+				typename sprout::enabler_if<(I >= sprout::io::leaf_count<Left>::value)>::type = sprout::enabler
+			>
+			inline SPROUT_CONSTEXPR sprout::io::format_holder<
+				typename sprout::io::leaf_at<I, sprout::io::format_expression<Left, Right> >::type
+			>
+			get_leaf(sprout::io::format_expression<Left, Right> const& expr);
+
+			template<
+				std::size_t I, typename Left, typename T,
+				typename sprout::enabler_if<(I == sprout::io::leaf_count<Left>::value)>::type = sprout::enabler
+			>
+			inline SPROUT_CONSTEXPR sprout::io::format_holder<
+				typename sprout::io::leaf_at<I, sprout::io::format_expression<Left, sprout::io::leaf_expression<T> > >::type
+			>
+			get_leaf(sprout::io::format_expression<Left, sprout::io::leaf_expression<T> > const& expr) {
+				return sprout::io::format_holder<
+					typename sprout::io::leaf_at<I, sprout::io::format_expression<Left, sprout::io::leaf_expression<T> > >::type
+				>(expr.right().value(), expr.settings());
+			}
+
+			template<
+				std::size_t I, typename Left, typename Right,
+				typename sprout::enabler_if<(I < sprout::io::leaf_count<Left>::value)>::type = sprout::enabler
+			>
+			inline SPROUT_CONSTEXPR sprout::io::format_holder<
+				typename sprout::io::leaf_at<I, sprout::io::format_expression<Left, Right> >::type
+			>
+			get_leaf(sprout::io::format_expression<Left, Right> const& expr) {
+				return sprout::io::detail::get_leaf<I>(expr.left());
+			}
+			template<
+				std::size_t I, typename Left, typename Right,
+				typename sprout::enabler_if<(I >= sprout::io::leaf_count<Left>::value)>::type = sprout::enabler
+			>
+			inline SPROUT_CONSTEXPR sprout::io::format_holder<
+				typename sprout::io::leaf_at<I, sprout::io::format_expression<Left, Right> >::type
+			>
+			get_leaf(sprout::io::format_expression<Left, Right> const& expr) {
+				return sprout::io::detail::get_leaf<I - sprout::io::leaf_count<Left>::value>(expr.right());
+			}
+		}	// namespace detail
+		template<std::size_t I, typename Expression>
+		inline SPROUT_CONSTEXPR sprout::io::format_holder<typename sprout::io::leaf_at<I, Expression>::type>
+		get_leaf(Expression const& expr) {
+			return sprout::io::detail::get_leaf<I>(expr);
+		}
+
+		//
+		// eval
+		//
+		template<
+			typename Elem, std::size_t N, typename T,
+			typename sprout::enabler_if<std::is_integral<T>::value>::type = sprout::enabler
+		>
+		inline SPROUT_CONSTEXPR auto
+		eval(sprout::io::format_holder<T> const& holder)
+			-> decltype(sprout::int_to_string<Elem>(holder.value()))
+		{
+			return sprout::int_to_string<Elem>(holder.value());
+		}
+		template<
+			typename Elem, std::size_t N, typename T,
+			typename sprout::enabler_if<std::is_floating_point<T>::value>::type = sprout::enabler
+		>
+		inline SPROUT_CONSTEXPR auto
+		eval(sprout::io::format_holder<T> const& holder)
+			-> decltype(sprout::float_to_string<Elem>(holder.value()))
+		{
+			return sprout::float_to_string<Elem>(holder.value());
+		}
+		template<
+			typename Elem, std::size_t N, typename T,
+			typename sprout::enabler_if<sprout::weed::traits::is_char_type<T>::value>::type = sprout::enabler
+		>
+		inline SPROUT_CONSTEXPR auto
+		eval(sprout::io::format_holder<T> const& holder)
+			-> decltype(sprout::basic_string<Elem, 1>{{static_cast<Elem>(holder.value())}, 1})
+		{
+			return sprout::basic_string<Elem, 1>{{static_cast<Elem>(holder.value())}, 1};
+		}
+		template<
+			typename Elem, std::size_t N, typename T,
+			typename sprout::enabler_if<std::is_array<T>::value>::type = sprout::enabler
+		>
+		inline SPROUT_CONSTEXPR auto
+		eval(sprout::io::format_holder<T> const& holder)
+			-> decltype(sprout::to_string(holder.value()))
+		{
+			return sprout::to_string(holder.value());
+		}
+
+		//
+		// output
+		//
+		namespace detail {
+			template<typename Elem, typename Iterator, std::size_t K, typename... Args>
+			inline SPROUT_CONSTEXPR Elem
+			get_param(Iterator found, sprout::array<std::size_t, K> const& sizes, std::size_t idx, Args const&... args) {
+				return found == sizes.end() ? static_cast<Elem>('\0')
+					: sprout::detail::param_seq_at<Elem>(
+						found - sizes.begin(),
+						idx - (found != sizes.begin() ? found[-1] : 0),
+						args...
+						)
+					;
+			}
+
+			template<typename Elem, std::size_t N, sprout::index_t... Indexes, std::size_t K, typename... Args>
+			inline SPROUT_CONSTEXPR sprout::basic_string<Elem, N>
+			output_impl_1(sprout::index_tuple<Indexes...>, sprout::array<std::size_t, K> const& sizes, Args const&... args) {
+				return sprout::basic_string<Elem, N>{
+					{
+						sprout::io::detail::get_param<Elem>(
+							sprout::range::lower_bound(sizes, static_cast<std::size_t>(Indexes + 1)),
+							sizes,
+							Indexes,
+							args...
+							)...
+						},
+					NS_SSCRISK_CEL_OR_SPROUT::min(sizes.back(), N)
+					};
+			}
+			template<typename Elem, std::size_t N, typename... Args>
+			inline SPROUT_CONSTEXPR sprout::basic_string<Elem, N>
+			output_impl(Args const&... args) {
+				return sprout::io::detail::output_impl_1<Elem, N>(
+					sprout::index_range<0, N>::make(),
+					sprout::range::partial_sum(
+						sprout::array<std::size_t, sizeof...(Args)>{{args.size()...}},
+						sprout::pit<sprout::array<std::size_t, sizeof...(Args)> >()
+						),
+					args...
+					);
+			}
+			template<typename Elem, std::size_t N, typename Expression, sprout::index_t... Indexes>
+			inline SPROUT_CONSTEXPR sprout::basic_string<Elem, N>
+			output(Expression const& expr, sprout::index_tuple<Indexes...>) {
+				return sprout::io::detail::output_impl<Elem, N>(
+					sprout::io::eval<Elem, N>(sprout::io::get_leaf<Indexes>(expr))...
+					);
+			}
+		}	// namespace detail
+		template<std::size_t N, typename Elem = char, typename Expression>
+		inline SPROUT_CONSTEXPR sprout::basic_string<Elem, N>
+		output(Expression const& expr) {
+			return sprout::io::detail::output<Elem, N>(
+				expr,
+				sprout::index_range<0, sprout::io::leaf_count<Expression>::value>::make()
+				);
+		}
+	}	// namespace io
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_IO_HPP
diff --git a/sprout/numeric/fixed/partial_sum.hpp b/sprout/numeric/fixed/partial_sum.hpp
index d9c222b6..b7b1d435 100644
--- a/sprout/numeric/fixed/partial_sum.hpp
+++ b/sprout/numeric/fixed/partial_sum.hpp
@@ -7,6 +7,7 @@
 #include <sprout/container/functions.hpp>
 #include <sprout/iterator/operation.hpp>
 #include <sprout/algorithm/fixed/result_of.hpp>
+#include <sprout/detail/container_complate.hpp>
 
 namespace sprout {
 	namespace fixed {
@@ -24,7 +25,7 @@ namespace sprout {
 				Args const&... args
 				)
 			{
-				return sprout::remake<Result>(result, sprout::size(result), args...);
+				return sprout::remake<Result>(result, sprout::size(result), args..., value);
 			}
 			template<typename InputIterator, typename Result, typename... Args>
 			inline SPROUT_CONSTEXPR typename std::enable_if<
@@ -61,7 +62,7 @@ namespace sprout {
 			inline SPROUT_CONSTEXPR typename std::enable_if<
 				sprout::container_traits<Result>::static_size != 0,
 				typename sprout::fixed::result_of::algorithm<Result>::type
-			>::type partial_sum_impl_1(
+			>::type partial_sum_impl(
 				InputIterator first,
 				InputIterator last,
 				Result const& result,
@@ -102,7 +103,7 @@ namespace sprout {
 				Args const&... args
 				)
 			{
-				return sprout::remake<Result>(result, sprout::size(result), args...);
+				return sprout::remake<Result>(result, sprout::size(result), args..., value);
 			}
 			template<typename InputIterator, typename Result, typename BinaryOperation, typename... Args>
 			inline SPROUT_CONSTEXPR typename std::enable_if<
@@ -141,7 +142,7 @@ namespace sprout {
 			inline SPROUT_CONSTEXPR typename std::enable_if<
 				sprout::container_traits<Result>::static_size != 0,
 				typename sprout::fixed::result_of::algorithm<Result>::type
-			>::type partial_sum_impl_1(
+			>::type partial_sum_impl(
 				InputIterator first,
 				InputIterator last,
 				Result const& result,
diff --git a/sprout/range/range_container.hpp b/sprout/range/range_container.hpp
index 85ef0155..9b3fcb09 100644
--- a/sprout/range/range_container.hpp
+++ b/sprout/range/range_container.hpp
@@ -118,6 +118,18 @@ namespace sprout {
 		struct is_range_container<sprout::range::range_container<Iterator> >
 			: public std::true_type
 		{};
+
+		//
+		// make_range_container
+		//
+		template<typename Range>
+		inline SPROUT_CONSTEXPR sprout::range::range_container<typename sprout::range::lvalue_iterator<Range>::type>
+		make_range_container(Range&& range) {
+			return sprout::range::range_container<typename sprout::range::lvalue_iterator<Range>::type>(
+				sprout::begin(sprout::forward<Range>(range)),
+				sprout::end(sprout::forward<Range>(range))
+				);
+		}
 	}	// namespace range
 
 	//
diff --git a/sprout/range/range_return.hpp b/sprout/range/range_return.hpp
index b680be59..77fdf524 100644
--- a/sprout/range/range_return.hpp
+++ b/sprout/range/range_return.hpp
@@ -31,7 +31,7 @@ namespace sprout {
 			typedef typename sprout::range::lvalue_iterator<Range>::type type;
 		public:
 			static SPROUT_CONSTEXPR type pack(
-				typename sprout::container_traits<Range>::iterator found,
+				typename sprout::range::lvalue_iterator<Range>::type found,
 				Range&& range
 				)
 			{
@@ -44,7 +44,7 @@ namespace sprout {
 			typedef typename sprout::range::lvalue_range<Range>::type type;
 		public:
 			static SPROUT_CONSTEXPR type pack(
-				typename sprout::container_traits<Range>::iterator found,
+				typename sprout::range::lvalue_iterator<Range>::type found,
 				Range&& range
 				)
 			{
@@ -57,7 +57,7 @@ namespace sprout {
 			typedef typename sprout::range::lvalue_range<Range>::type type;
 		public:
 			static SPROUT_CONSTEXPR type pack(
-				typename sprout::container_traits<Range>::iterator found,
+				typename sprout::range::lvalue_iterator<Range>::type found,
 				Range&& range
 				)
 			{