From 5cb070b3b373565cf60ad4c0336c91b6613fd2e4 Mon Sep 17 00:00:00 2001
From: bolero-MURAKAMI <bolero.murakami@gmail.com>
Date: Wed, 24 Oct 2012 20:52:09 +0900
Subject: [PATCH] add variant/io

---
 sprout/utility.hpp                           |   2 -
 sprout/utility/compare_pointees.hpp          |  96 +++++++-
 sprout/utility/operation.hpp                 |   1 +
 sprout/utility/operation_ext.hpp             |   1 +
 sprout/utility/rel_ops.hpp                   |  15 +-
 sprout/utility/value_holder.hpp              | 233 +------------------
 sprout/utility/value_holder/get.hpp          |  47 ++++
 sprout/utility/value_holder/value_holder.hpp | 211 +++++++++++++++++
 sprout/variant.hpp                           |   1 +
 sprout/variant/io.hpp                        |  40 ++++
 10 files changed, 403 insertions(+), 244 deletions(-)
 create mode 100644 sprout/utility/value_holder/get.hpp
 create mode 100644 sprout/utility/value_holder/value_holder.hpp
 create mode 100644 sprout/variant/io.hpp

diff --git a/sprout/utility.hpp b/sprout/utility.hpp
index 56e6feda..f9f4beae 100644
--- a/sprout/utility.hpp
+++ b/sprout/utility.hpp
@@ -3,10 +3,8 @@
 
 #include <sprout/config.hpp>
 #include <sprout/utility/pair.hpp>
-#include <sprout/utility/rel_ops.hpp>
 #include <sprout/utility/operation.hpp>
 #include <sprout/utility/operation_ext.hpp>
-#include <sprout/utility/compare_pointees.hpp>
 #include <sprout/utility/noncopyable.hpp>
 #include <sprout/utility/enabler_if.hpp>
 #include <sprout/utility/pack.hpp>
diff --git a/sprout/utility/compare_pointees.hpp b/sprout/utility/compare_pointees.hpp
index 6c88783e..33ae7a1c 100644
--- a/sprout/utility/compare_pointees.hpp
+++ b/sprout/utility/compare_pointees.hpp
@@ -8,44 +8,124 @@ namespace sprout {
 	//
 	// equal_pointees
 	//
-	template<class OptionalPointee>
+	template<typename OptionalPointee>
 	inline SPROUT_CONSTEXPR bool
 	equal_pointees(OptionalPointee const& lhs, OptionalPointee const& rhs) {
 		return (!lhs) != (!rhs) ? false : (!lhs ? true : (*lhs) == (*rhs));
 	}
 	//
+	// not_equal_pointees
+	//
+	template<typename OptionalPointee>
+	inline SPROUT_CONSTEXPR bool
+	not_equal_pointees(OptionalPointee const& lhs, OptionalPointee const& rhs) {
+		return !sprout::equal_pointees(lhs, rhs);
+	}
+	//
 	// less_pointees
 	//
-	template<class OptionalPointee>
+	template<typename OptionalPointee>
 	inline SPROUT_CONSTEXPR bool
 	less_pointees(OptionalPointee const& lhs, OptionalPointee const& rhs) {
 		return !rhs ? false : (!lhs ? true : (*lhs) < (*rhs));
 	}
+	//
+	// greater_pointees
+	//
+	template<typename OptionalPointee>
+	inline SPROUT_CONSTEXPR bool
+	greater_pointees(OptionalPointee const& lhs, OptionalPointee const& rhs) {
+		return sprout::less_pointees(rhs, lhs);
+	}
+	//
+	// less_equal_pointees
+	//
+	template<typename OptionalPointee>
+	inline SPROUT_CONSTEXPR bool
+	less_equal_pointees(OptionalPointee const& lhs, OptionalPointee const& rhs) {
+		return !sprout::less_pointees(rhs, lhs);
+	}
+	//
+	// greater_equal_pointees
+	//
+	template<typename OptionalPointee>
+	inline SPROUT_CONSTEXPR bool
+	greater_equal_pointees(OptionalPointee const& lhs, OptionalPointee const& rhs) {
+		return !sprout::less_pointees(lhs, rhs);
+	}
 
 	//
 	// equal_pointees_t
 	//
-	template<class OptionalPointee>
+	template<typename OptionalPointee>
 	struct equal_pointees_t
 		: public sprout::binary_function<OptionalPointee, OptionalPointee, bool>
 	{
 		SPROUT_CONSTEXPR bool
 		operator()(OptionalPointee const& lhs, OptionalPointee const& rhs) const {
-			return sprout::equal_pointees(lhs, rhs) ;
+			return sprout::equal_pointees(lhs, rhs);
 		}
-	} ;
+	};
+	//
+	// not_equal_pointees_t
+	//
+	template<typename OptionalPointee>
+	struct not_equal_pointees_t
+		: public sprout::binary_function<OptionalPointee, OptionalPointee, bool>
+	{
+		SPROUT_CONSTEXPR bool
+		operator()(OptionalPointee const& lhs, OptionalPointee const& rhs) const {
+			return sprout::not_equal_pointees(lhs, rhs);
+		}
+	};
 	//
 	// less_pointees_t
 	//
-	template<class OptionalPointee>
+	template<typename OptionalPointee>
 	struct less_pointees_t
 		: public sprout::binary_function<OptionalPointee, OptionalPointee, bool>
 	{
 		SPROUT_CONSTEXPR bool
 		operator()(OptionalPointee const& lhs, OptionalPointee const& rhs) const {
-			return sprout::less_pointees(lhs, rhs) ;
+			return sprout::less_pointees(lhs, rhs);
 		}
-	} ;
+	};
+	//
+	// greater_pointees_t
+	//
+	template<typename OptionalPointee>
+	struct greater_pointees_t
+		: public sprout::binary_function<OptionalPointee, OptionalPointee, bool>
+	{
+		SPROUT_CONSTEXPR bool
+		operator()(OptionalPointee const& lhs, OptionalPointee const& rhs) const {
+			return sprout::greater_pointees(lhs, rhs);
+		}
+	};
+	//
+	// less_equal_pointees_t
+	//
+	template<typename OptionalPointee>
+	struct less_equal_pointees_t
+		: public sprout::binary_function<OptionalPointee, OptionalPointee, bool>
+	{
+		SPROUT_CONSTEXPR bool
+		operator()(OptionalPointee const& lhs, OptionalPointee const& rhs) const {
+			return sprout::less_equal_pointees(lhs, rhs);
+		}
+	};
+	//
+	// greater_equal_pointees_t
+	//
+	template<typename OptionalPointee>
+	struct greater_equal_pointees_t
+		: public sprout::binary_function<OptionalPointee, OptionalPointee, bool>
+	{
+		SPROUT_CONSTEXPR bool
+		operator()(OptionalPointee const& lhs, OptionalPointee const& rhs) const {
+			return sprout::greater_equal_pointees(lhs, rhs);
+		}
+	};
 }	// namespace sprout
 
 #endif // #ifndef SPROUT_UTILITY_COMPARE_POINTEES_HPP
diff --git a/sprout/utility/operation.hpp b/sprout/utility/operation.hpp
index 5c2dd996..11f00bd0 100644
--- a/sprout/utility/operation.hpp
+++ b/sprout/utility/operation.hpp
@@ -2,6 +2,7 @@
 #define SPROUT_UTILITY_OPERATION_HPP
 
 #include <sprout/config.hpp>
+#include <sprout/utility/rel_ops.hpp>
 #include <sprout/utility/forward.hpp>
 #include <sprout/utility/move.hpp>
 #include <sprout/utility/swap.hpp>
diff --git a/sprout/utility/operation_ext.hpp b/sprout/utility/operation_ext.hpp
index 924d4edf..a79ca805 100644
--- a/sprout/utility/operation_ext.hpp
+++ b/sprout/utility/operation_ext.hpp
@@ -2,6 +2,7 @@
 #define SPROUT_UTILITY_OPERATION_EXT_HPP
 
 #include <sprout/config.hpp>
+#include <sprout/utility/compare_pointees.hpp>
 #include <sprout/utility/as_lvalue.hpp>
 #include <sprout/utility/as_const.hpp>
 #include <sprout/utility/lvalue_forward.hpp>
diff --git a/sprout/utility/rel_ops.hpp b/sprout/utility/rel_ops.hpp
index a74456b8..74fff4f8 100644
--- a/sprout/utility/rel_ops.hpp
+++ b/sprout/utility/rel_ops.hpp
@@ -5,24 +5,33 @@
 
 namespace sprout {
 	namespace rel_ops {
+		//
+		// operator!=
+		//
 		template <typename T>
 		inline SPROUT_CONSTEXPR bool
 		operator!=(T const& x, T const& y) {
 			return !(x == y);
 		}
-
+		//
+		// operator>
+		//
 		template <typename T>
 		inline SPROUT_CONSTEXPR bool
 		operator>(T const& x, T const& y) {
 			return y < x;
 		}
-
+		//
+		// operator<=
+		//
 		template <typename T>
 		inline SPROUT_CONSTEXPR bool
 		operator<=(T const& x, T const& y) {
 			return !(y < x);
 		}
-
+		//
+		// operator>=
+		//
 		template <typename T>
 		inline SPROUT_CONSTEXPR bool
 		operator>=(T const& x, T const& y) {
diff --git a/sprout/utility/value_holder.hpp b/sprout/utility/value_holder.hpp
index 822df021..9105852b 100644
--- a/sprout/utility/value_holder.hpp
+++ b/sprout/utility/value_holder.hpp
@@ -2,236 +2,7 @@
 #define SPROUT_UTILITY_VALUE_HOLDER_HPP
 
 #include <sprout/config.hpp>
-#include <sprout/utility/swap.hpp>
-
-namespace sprout {
-	namespace detail {
-		template<typename T>
-		struct holder_helper {
-		public:
-			typedef T value_type;
-			typedef T& reference;
-			typedef T const& const_reference;
-			typedef T const& mutable_or_const_reference;
-			typedef T* pointer;
-			typedef T const* const_pointer;
-			typedef T const* mutable_or_const_pointer;
-			typedef T const& param_type;
-			typedef T holder_type;
-		public:
-			static SPROUT_CONSTEXPR holder_type const& hold(param_type p) {
-				return p;
-			}
-			static SPROUT_CONSTEXPR reference ref(holder_type& r) {
-				return r;
-			}
-			static SPROUT_CONSTEXPR const_reference ref(holder_type const& r) {
-				return r;
-			}
-			static SPROUT_CONSTEXPR pointer ptr(holder_type& r) {
-				return &r;
-			}
-			static SPROUT_CONSTEXPR const_pointer ptr(holder_type const& r) {
-				return &r;
-			}
-		};
-		template<typename T>
-		struct holder_helper<T const> {
-		public:
-			typedef T value_type;
-			typedef T const& reference;
-			typedef T const& const_reference;
-			typedef T const& mutable_or_const_reference;
-			typedef T const* pointer;
-			typedef T const* const_pointer;
-			typedef T const* mutable_or_const_pointer;
-			typedef T const& param_type;
-			typedef T holder_type;
-		public:
-			static SPROUT_CONSTEXPR holder_type const& hold(param_type p) {
-				return &p;
-			}
-			static SPROUT_CONSTEXPR reference ref(holder_type& r) {
-				return *r;
-			}
-			static SPROUT_CONSTEXPR const_reference ref(holder_type const& r) {
-				return *r;
-			}
-			static SPROUT_CONSTEXPR pointer ptr(holder_type& r) {
-				return &r;
-			}
-			static SPROUT_CONSTEXPR const_pointer ptr(holder_type const& r) {
-				return &r;
-			}
-		};
-		template<typename T>
-		struct holder_helper<T&> {
-		public:
-			typedef T value_type;
-			typedef T& reference;
-			typedef T const& const_reference;
-			typedef T& mutable_or_const_reference;
-			typedef T* pointer;
-			typedef T const* const_pointer;
-			typedef T* mutable_or_const_pointer;
-			typedef T& param_type;
-			typedef T* holder_type;
-		public:
-			static SPROUT_CONSTEXPR holder_type hold(param_type p) {
-				return &p;
-			}
-			static SPROUT_CONSTEXPR reference ref(holder_type r) {
-				return *r;
-			}
-			static SPROUT_CONSTEXPR pointer ptr(holder_type r) {
-				return r;
-			}
-		};
-		template<typename T>
-		struct holder_helper<T const&> {
-		public:
-			typedef T value_type;
-			typedef T const& reference;
-			typedef T const& const_reference;
-			typedef T const& mutable_or_const_reference;
-			typedef T const* pointer;
-			typedef T const* const_pointer;
-			typedef T const* mutable_or_const_pointer;
-			typedef T const& param_type;
-			typedef T const* holder_type;
-		public:
-			static SPROUT_CONSTEXPR holder_type hold(param_type p) {
-				return &p;
-			}
-			static SPROUT_CONSTEXPR reference ref(holder_type r) {
-				return *r;
-			}
-			static SPROUT_CONSTEXPR pointer ptr(holder_type r) {
-				return r;
-			}
-		};
-	}	// namespace detail
-	//
-	// value_holder
-	//
-	template<typename T>
-	class value_holder {
-	public:
-		typedef T type;
-	private:
-		typedef sprout::detail::holder_helper<type> helper_type;
-		typedef typename helper_type::holder_type holder_type;
-	public:
-		typedef typename helper_type::value_type value_type;
-		typedef typename helper_type::reference reference;
-		typedef typename helper_type::const_reference const_reference;
-		typedef typename helper_type::mutable_or_const_reference mutable_or_const_reference;
-		typedef typename helper_type::pointer pointer;
-		typedef typename helper_type::const_pointer const_pointer;
-		typedef typename helper_type::mutable_or_const_pointer mutable_or_const_pointer;
-		typedef typename helper_type::param_type param_type;
-		typedef reference reference_type;
-		typedef mutable_or_const_reference reference_const_type;
-		typedef pointer pointer_type;
-		typedef mutable_or_const_pointer pointer_const_type;
-		typedef param_type argument_type;
-	private:
-		holder_type holder_;
-	public:
-		value_holder() = default;
-		value_holder(value_holder const&) = default;
-		explicit SPROUT_CONSTEXPR value_holder(param_type p)
-			: holder_(helper_type::hold(p))
-		{}
-
-		void swap(value_holder& other)
-		SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(sprout::swap(holder_, other.holder_)))
-		{
-			sprout::swap(holder_, other.holder_);
-		}
-
-		operator reference() {
-			return helper_type::ref(holder_);
-		}
-		SPROUT_CONSTEXPR operator mutable_or_const_reference() const {
-			return helper_type::ref(holder_);
-		}
-		pointer operator->() {
-			return helper_type::ptr(holder_);
-		}
-		SPROUT_CONSTEXPR mutable_or_const_pointer operator->() const {
-			return helper_type::ptr(holder_);
-		}
-
-		reference get() {
-			return helper_type::ref(holder_);
-		}
-		SPROUT_CONSTEXPR mutable_or_const_reference get() const {
-			return helper_type::ref(holder_);
-		}
-
-		pointer get_pointer() {
-			return helper_type::ptr(holder_);
-		}
-		SPROUT_CONSTEXPR mutable_or_const_pointer get_pointer() const {
-			return helper_type::ptr(holder_);
-		}
-		pointer get_ptr() {
-			return get_pointer();
-		}
-		SPROUT_CONSTEXPR mutable_or_const_pointer get_ptr() const {
-			return get_pointer();
-		}
-	};
-
-	//
-	// swap
-	//
-	template<typename T>
-	inline void
-	swap(sprout::value_holder<T>& lhs, sprout::value_holder<T>& rhs)
-	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
-	{
-		lhs.swap(rhs);
-	}
-
-	//
-	// get
-	//
-	template<typename T>
-	inline SPROUT_CONSTEXPR typename sprout::value_holder<T>::reference_const_type
-	get(sprout::value_holder<T> const& x) {
-		return x.get();
-	}
-	template<typename T>
-	inline typename sprout::value_holder<T>::reference_type
-	get(sprout::value_holder<T>& x) {
-		return x.get();
-	}
-	template<typename T>
-	inline SPROUT_CONSTEXPR typename sprout::value_holder<T>::pointer_const_type
-	get(sprout::value_holder<T> const* x) {
-		return x->get_pointer();
-	}
-	template<typename T>
-	inline typename sprout::value_holder<T>::pointer_type
-	get(sprout::value_holder<T>* x) {
-		return x->get_pointer();
-	}
-
-	//
-	// get_pointer
-	//
-	template<typename T>
-	inline SPROUT_CONSTEXPR typename sprout::value_holder<T>::pointer_const_type
-	get_pointer(sprout::value_holder<T> const& x) {
-		return x.get_pointer();
-	}
-	template<typename T>
-	inline typename sprout::value_holder<T>::pointer_type
-	get_pointer(sprout::value_holder<T>& x) {
-		return x.get_pointer();
-	}
-}	// namespace sprout
+#include <sprout/utility/value_holder/value_holder.hpp>
+#include <sprout/utility/value_holder/get.hpp>
 
 #endif // #ifndef SPROUT_UTILITY_VALUE_HOLDER_HPP
diff --git a/sprout/utility/value_holder/get.hpp b/sprout/utility/value_holder/get.hpp
new file mode 100644
index 00000000..1b70b481
--- /dev/null
+++ b/sprout/utility/value_holder/get.hpp
@@ -0,0 +1,47 @@
+#ifndef SPROUT_UTILITY_VALUE_HOLDER_GET_HPP
+#define SPROUT_UTILITY_VALUE_HOLDER_GET_HPP
+
+#include <sprout/config.hpp>
+#include <sprout/utility/value_holder/value_holder.hpp>
+
+namespace sprout {
+	//
+	// get
+	//
+	template<typename T>
+	inline SPROUT_CONSTEXPR typename sprout::value_holder<T>::reference_const_type
+	get(sprout::value_holder<T> const& x) {
+		return x.get();
+	}
+	template<typename T>
+	inline typename sprout::value_holder<T>::reference_type
+	get(sprout::value_holder<T>& x) {
+		return x.get();
+	}
+	template<typename T>
+	inline SPROUT_CONSTEXPR typename sprout::value_holder<T>::pointer_const_type
+	get(sprout::value_holder<T> const* x) {
+		return x->get_pointer();
+	}
+	template<typename T>
+	inline typename sprout::value_holder<T>::pointer_type
+	get(sprout::value_holder<T>* x) {
+		return x->get_pointer();
+	}
+
+	//
+	// get_pointer
+	//
+	template<typename T>
+	inline SPROUT_CONSTEXPR typename sprout::value_holder<T>::pointer_const_type
+	get_pointer(sprout::value_holder<T> const& x) {
+		return x.get_pointer();
+	}
+	template<typename T>
+	inline typename sprout::value_holder<T>::pointer_type
+	get_pointer(sprout::value_holder<T>& x) {
+		return x.get_pointer();
+	}
+}	// namespace sprout
+
+#endif // #ifndef SPROUT_UTILITY_VALUE_HOLDER_GET_HPP
diff --git a/sprout/utility/value_holder/value_holder.hpp b/sprout/utility/value_holder/value_holder.hpp
new file mode 100644
index 00000000..d9b9cdd0
--- /dev/null
+++ b/sprout/utility/value_holder/value_holder.hpp
@@ -0,0 +1,211 @@
+#ifndef SPROUT_UTILITY_VALUE_HOLDER_VALUE_HOLDER_HPP
+#define SPROUT_UTILITY_VALUE_HOLDER_VALUE_HOLDER_HPP
+
+#include <sprout/config.hpp>
+#include <sprout/utility/swap.hpp>
+
+namespace sprout {
+	namespace detail {
+		template<typename T>
+		struct holder_helper {
+		public:
+			typedef T value_type;
+			typedef T& reference;
+			typedef T const& const_reference;
+			typedef T const& mutable_or_const_reference;
+			typedef T* pointer;
+			typedef T const* const_pointer;
+			typedef T const* mutable_or_const_pointer;
+			typedef T const& param_type;
+			typedef T holder_type;
+		public:
+			static SPROUT_CONSTEXPR holder_type const& hold(param_type p) {
+				return p;
+			}
+			static SPROUT_CONSTEXPR reference ref(holder_type& r) {
+				return r;
+			}
+			static SPROUT_CONSTEXPR const_reference ref(holder_type const& r) {
+				return r;
+			}
+			static SPROUT_CONSTEXPR pointer ptr(holder_type& r) {
+				return &r;
+			}
+			static SPROUT_CONSTEXPR const_pointer ptr(holder_type const& r) {
+				return &r;
+			}
+		};
+		template<typename T>
+		struct holder_helper<T const> {
+		public:
+			typedef T value_type;
+			typedef T const& reference;
+			typedef T const& const_reference;
+			typedef T const& mutable_or_const_reference;
+			typedef T const* pointer;
+			typedef T const* const_pointer;
+			typedef T const* mutable_or_const_pointer;
+			typedef T const& param_type;
+			typedef T holder_type;
+		public:
+			static SPROUT_CONSTEXPR holder_type const& hold(param_type p) {
+				return &p;
+			}
+			static SPROUT_CONSTEXPR reference ref(holder_type& r) {
+				return *r;
+			}
+			static SPROUT_CONSTEXPR const_reference ref(holder_type const& r) {
+				return *r;
+			}
+			static SPROUT_CONSTEXPR pointer ptr(holder_type& r) {
+				return &r;
+			}
+			static SPROUT_CONSTEXPR const_pointer ptr(holder_type const& r) {
+				return &r;
+			}
+		};
+		template<typename T>
+		struct holder_helper<T&> {
+		public:
+			typedef T value_type;
+			typedef T& reference;
+			typedef T const& const_reference;
+			typedef T& mutable_or_const_reference;
+			typedef T* pointer;
+			typedef T const* const_pointer;
+			typedef T* mutable_or_const_pointer;
+			typedef T& param_type;
+			typedef T* holder_type;
+		public:
+			static SPROUT_CONSTEXPR holder_type hold(param_type p) {
+				return &p;
+			}
+			static SPROUT_CONSTEXPR reference ref(holder_type r) {
+				return *r;
+			}
+			static SPROUT_CONSTEXPR pointer ptr(holder_type r) {
+				return r;
+			}
+		};
+		template<typename T>
+		struct holder_helper<T const&> {
+		public:
+			typedef T value_type;
+			typedef T const& reference;
+			typedef T const& const_reference;
+			typedef T const& mutable_or_const_reference;
+			typedef T const* pointer;
+			typedef T const* const_pointer;
+			typedef T const* mutable_or_const_pointer;
+			typedef T const& param_type;
+			typedef T const* holder_type;
+		public:
+			static SPROUT_CONSTEXPR holder_type hold(param_type p) {
+				return &p;
+			}
+			static SPROUT_CONSTEXPR reference ref(holder_type r) {
+				return *r;
+			}
+			static SPROUT_CONSTEXPR pointer ptr(holder_type r) {
+				return r;
+			}
+		};
+	}	// namespace detail
+	//
+	// value_holder
+	//
+	template<typename T>
+	class value_holder {
+	public:
+		typedef T type;
+	private:
+		typedef sprout::detail::holder_helper<type> helper_type;
+		typedef typename helper_type::holder_type holder_type;
+	public:
+		typedef typename helper_type::value_type value_type;
+		typedef typename helper_type::reference reference;
+		typedef typename helper_type::const_reference const_reference;
+		typedef typename helper_type::mutable_or_const_reference mutable_or_const_reference;
+		typedef typename helper_type::pointer pointer;
+		typedef typename helper_type::const_pointer const_pointer;
+		typedef typename helper_type::mutable_or_const_pointer mutable_or_const_pointer;
+		typedef typename helper_type::param_type param_type;
+		typedef reference reference_type;
+		typedef mutable_or_const_reference reference_const_type;
+		typedef pointer pointer_type;
+		typedef mutable_or_const_pointer pointer_const_type;
+		typedef param_type argument_type;
+	private:
+		holder_type holder_;
+	public:
+		value_holder() = default;
+		value_holder(value_holder const&) = default;
+		explicit SPROUT_CONSTEXPR value_holder(param_type p)
+			: holder_(helper_type::hold(p))
+		{}
+
+		value_holder& operator=(value_holder const&) = default;
+		value_holder& operator=(param_type p) {
+			value_holder temp(p);
+			temp.swap(p);
+			return *this;
+		}
+
+		void swap(value_holder& other)
+		SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(sprout::swap(holder_, other.holder_)))
+		{
+			sprout::swap(holder_, other.holder_);
+		}
+
+		operator reference() {
+			return helper_type::ref(holder_);
+		}
+		SPROUT_CONSTEXPR operator mutable_or_const_reference() const {
+			return helper_type::ref(holder_);
+		}
+		reference operator*() {
+			return helper_type::ref(holder_);
+		}
+		SPROUT_CONSTEXPR mutable_or_const_reference operator*() const {
+			return helper_type::ref(holder_);
+		}
+		reference get() {
+			return helper_type::ref(holder_);
+		}
+		SPROUT_CONSTEXPR mutable_or_const_reference get() const {
+			return helper_type::ref(holder_);
+		}
+
+		pointer operator->() {
+			return helper_type::ptr(holder_);
+		}
+		SPROUT_CONSTEXPR mutable_or_const_pointer operator->() const {
+			return helper_type::ptr(holder_);
+		}
+		pointer get_pointer() {
+			return helper_type::ptr(holder_);
+		}
+		SPROUT_CONSTEXPR mutable_or_const_pointer get_pointer() const {
+			return helper_type::ptr(holder_);
+		}
+		pointer get_ptr() {
+			return get_pointer();
+		}
+		SPROUT_CONSTEXPR mutable_or_const_pointer get_ptr() const {
+			return get_pointer();
+		}
+	};
+
+	//
+	// swap
+	//
+	template<typename T>
+	inline void
+	swap(sprout::value_holder<T>& lhs, sprout::value_holder<T>& rhs)
+	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
+	{
+		lhs.swap(rhs);
+	}
+}	// namespace sprout
+
+#endif // #ifndef SPROUT_UTILITY_VALUE_HOLDER_VALUE_HOLDER_HPP
diff --git a/sprout/variant.hpp b/sprout/variant.hpp
index 1640face..d95fb9b7 100644
--- a/sprout/variant.hpp
+++ b/sprout/variant.hpp
@@ -3,6 +3,7 @@
 
 #include <sprout/config.hpp>
 #include <sprout/variant/variant.hpp>
+#include <sprout/variant/io.hpp>
 #include <sprout/variant/tuple.hpp>
 #include <sprout/variant/get.hpp>
 #include <sprout/variant/static_visitor.hpp>
diff --git a/sprout/variant/io.hpp b/sprout/variant/io.hpp
new file mode 100644
index 00000000..76c3f10c
--- /dev/null
+++ b/sprout/variant/io.hpp
@@ -0,0 +1,40 @@
+#ifndef SPROUT_VARIANT_IO_HPP
+#define SPROUT_VARIANT_IO_HPP
+
+#include <sprout/config.hpp>
+#include <sprout/variant/variant.hpp>
+#include <sprout/variant/static_visitor.hpp>
+
+namespace sprout {
+	namespace detail {
+		template<typename OStream>
+		class variant_output_visitor
+			: public sprout::static_visitor<>
+		{
+		public:
+			typedef OStream ostream_type;
+		private:
+			ostream_type& out_;
+		public:
+			explicit variant_output_visitor(ostream_type& out)
+				: out_(out)
+			{}
+			template<typename T>
+			void operator()(T const& operand) const {
+				out_ << operand;
+			}
+		};
+	}	// namespace detail
+	//
+	// operator<<
+	//
+	template<typename Elem, typename Traits, typename... Types>
+	inline std::basic_ostream<Elem, Traits>&
+	operator<<(std::basic_ostream<Elem, Traits>& lhs, sprout::variant<Types...> const& rhs) {
+	    sprout::detail::variant_output_visitor<std::basic_ostream<Elem, Traits> > visitor(lhs);
+		rhs.apply_visitor(visitor);
+	    return lhs;
+	}
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_VARIANT_IO_HPP