From 8103682fdbb9aa830509e71676e9762eccc3e463 Mon Sep 17 00:00:00 2001
From: bolero-MURAKAMI <bolero.murakami@gmail.com>
Date: Sat, 12 Nov 2011 20:24:42 +0900
Subject: [PATCH] =?UTF-8?q?sprout/variant/apply=5Fvisitor.hpp=20=E8=BF=BD?=
 =?UTF-8?q?=E5=8A=A0?=
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---
 sprout/tuple/tuple.hpp            |  4 ++--
 sprout/variant.hpp                |  2 ++
 sprout/variant/apply_visitor.hpp  | 18 ++++++++++++++++++
 sprout/variant/static_visitor.hpp | 14 ++++++++++++++
 sprout/variant/variant.hpp        | 30 +++++++++++++++++++++++++++++-
 5 files changed, 65 insertions(+), 3 deletions(-)
 create mode 100644 sprout/variant/apply_visitor.hpp
 create mode 100644 sprout/variant/static_visitor.hpp

diff --git a/sprout/tuple/tuple.hpp b/sprout/tuple/tuple.hpp
index 1661c759..aa5c1242 100644
--- a/sprout/tuple/tuple.hpp
+++ b/sprout/tuple/tuple.hpp
@@ -61,7 +61,7 @@ namespace sprout {
 			};
 
 			template<std::size_t Index, typename... Types>
-			class tuple_impl; 
+			class tuple_impl;
 			template<std::size_t Index>
 			class tuple_impl<Index> {
 			public:
@@ -200,7 +200,7 @@ namespace sprout {
 		//
 		// tuple
 		//
-		template<typename... Types> 
+		template<typename... Types>
 		class tuple
 			: public sprout::tuples::detail::tuple_impl<0, Types...>
 		{
diff --git a/sprout/variant.hpp b/sprout/variant.hpp
index c9c77ab2..754eccf5 100644
--- a/sprout/variant.hpp
+++ b/sprout/variant.hpp
@@ -4,5 +4,7 @@
 #include <sprout/config.hpp>
 #include <sprout/variant/variant.hpp>
 #include <sprout/variant/get.hpp>
+#include <sprout/variant/static_visitor.hpp>
+#include <sprout/variant/apply_visitor.hpp>
 
 #endif	// #ifndef SPROUT_VARIANT_HPP
diff --git a/sprout/variant/apply_visitor.hpp b/sprout/variant/apply_visitor.hpp
new file mode 100644
index 00000000..05e84b32
--- /dev/null
+++ b/sprout/variant/apply_visitor.hpp
@@ -0,0 +1,18 @@
+#ifndef SPROUT_VARIANT_APPLY_VISITOR_HPP
+#define SPROUT_VARIANT_APPLY_VISITOR_HPP
+
+#include <sprout/config.hpp>
+#include <sprout/utility/forward.hpp>
+
+namespace sprout {
+	template<typename Visitor, typename Visitable>
+	SPROUT_CONSTEXPR inline typename Visitor::result_type apply_visitor(
+		Visitor&& visitor,
+		Visitable&& visitable
+		)
+	{
+		return sprout::forward<Visitable>(visitable).apply_visitor(sprout::forward<Visitor>(visitor));
+	}
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_VARIANT_APPLY_VISITOR_HPP
diff --git a/sprout/variant/static_visitor.hpp b/sprout/variant/static_visitor.hpp
new file mode 100644
index 00000000..265c13cf
--- /dev/null
+++ b/sprout/variant/static_visitor.hpp
@@ -0,0 +1,14 @@
+#ifndef SPROUT_VARIANT_STATIC_VISITOR_HPP
+#define SPROUT_VARIANT_STATIC_VISITOR_HPP
+
+#include <sprout/config.hpp>
+
+namespace sprout {
+	template<typename R = void>
+	class static_visitor {
+	public:
+		typedef R result_type;
+	};
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_VARIANT_STATIC_VISITOR_HPP
diff --git a/sprout/variant/variant.hpp b/sprout/variant/variant.hpp
index 3439b47c..c4272b3c 100644
--- a/sprout/variant/variant.hpp
+++ b/sprout/variant/variant.hpp
@@ -114,6 +114,23 @@ namespace sprout {
 				: output<I + 1>(os, t, which)
 				;
 		}
+		template<int I, typename Tuple, typename Visitor>
+		static SPROUT_CONSTEXPR typename std::enable_if<
+			I == sizeof...(Types),
+			typename Visitor::result_type
+		>::type visit(Tuple&& t, Visitor&& v, int which) {
+			return typename Visitor::result_type();
+		}
+		template<int I, typename Tuple, typename Visitor>
+		static SPROUT_CONSTEXPR typename std::enable_if<
+			I != sizeof...(Types),
+			typename Visitor::result_type
+		>::type visit(Tuple&& t, Visitor&& v, int which) {
+			return I == which
+				? sprout::forward<Visitor>(v)(sprout::tuples::get<I>(sprout::forward<Tuple>(t)))
+				: visit<I + 1>(sprout::forward<Tuple>(t), sprout::forward<Visitor>(v), which)
+				;
+		}
 	private:
 		using impl_type::tuple_;
 		using impl_type::which_;
@@ -149,7 +166,7 @@ namespace sprout {
 			return which_;
 		}
 		SPROUT_CONSTEXPR bool empty() const {
-			return sizeof...(Types) == 0;
+			return false;
 		}
 		// relational
 		friend SPROUT_CONSTEXPR bool operator==(variant const& lhs, variant const& rhs) {
@@ -177,6 +194,7 @@ namespace sprout {
 		friend std::basic_ostream<Elem, Traits>& operator<<(std::basic_ostream<Elem, Traits>& lhs, variant const& rhs) {
 			return output<0>(lhs, rhs.tuple_, rhs.which_);
 		}
+		// get support
 		template<typename U>
 		SPROUT_CONSTEXPR typename std::enable_if<
 			sprout::types::find_index<tuple_type, U>::value != sizeof...(Types),
@@ -197,6 +215,15 @@ namespace sprout {
 				: (throw std::domain_error("variant<>: bad get"), sprout::tuples::get<sprout::types::find_index<tuple_type, U>::value>(tuple_))
 				;
 		}
+		// visitation support
+		template<typename Visitor>
+		SPROUT_CONSTEXPR typename Visitor::result_type apply_visitor(Visitor&& visitor) const {
+			return visit(tuple_, sprout::forward<Visitor>(visitor), which_);
+		}
+		template<typename Visitor>
+		typename Visitor::result_type apply_visitor(Visitor&& visitor) {
+			return visit(tuple_, sprout::forward<Visitor>(visitor), which_);
+		}
 	};
 
 	//
@@ -217,6 +244,7 @@ namespace std {
 	// tuple_size
 	//
 	template<typename... Types>
+
 	struct tuple_size<sprout::variant<Types...> >
 		: public std::tuple_size<typename sprout::variant<Types...>::tuple_tyep>
 	{};