diff --git a/sprout/weed/context/parse_context/operator/address_of.hpp b/sprout/weed/context/parse_context/operator/address_of.hpp
index 5a021fb3..b5f916d5 100644
--- a/sprout/weed/context/parse_context/operator/address_of.hpp
+++ b/sprout/weed/context/parse_context/operator/address_of.hpp
@@ -4,6 +4,7 @@
 #include <type_traits>
 #include <sprout/config.hpp>
 #include <sprout/tuple/tuple.hpp>
+#include <sprout/weed/unused.hpp>
 #include <sprout/weed/eval_result.hpp>
 #include <sprout/weed/expr/tag.hpp>
 #include <sprout/weed/expr/eval.hpp>
@@ -30,7 +31,7 @@ namespace sprout {
 		private:
 			typedef sprout::weed::parse_context<Iterator> context_type;
 		public:
-			typedef typename sprout::weed::traits::attribute_of<Expr, Iterator, context_type>::type attribute_type;
+			typedef sprout::weed::unused attribute_type;
 			typedef sprout::weed::eval_result<context_type, Iterator, attribute_type> result_type;
 		public:
 			SPROUT_CONSTEXPR result_type operator()(
diff --git a/sprout/weed/context/parse_context/operator/bitwise_or.hpp b/sprout/weed/context/parse_context/operator/bitwise_or.hpp
index 3928cab1..79513e39 100644
--- a/sprout/weed/context/parse_context/operator/bitwise_or.hpp
+++ b/sprout/weed/context/parse_context/operator/bitwise_or.hpp
@@ -7,6 +7,7 @@
 #include <sprout/weed/eval_result.hpp>
 #include <sprout/weed/expr/tag.hpp>
 #include <sprout/weed/expr/eval.hpp>
+#include <sprout/weed/attr_cnv/result_of/bitwise_or.hpp>
 #include <sprout/weed/attr_cnv/bitwise_or.hpp>
 #include <sprout/weed/traits/expr/tag_of.hpp>
 #include <sprout/weed/traits/parser/attribute_of.hpp>
@@ -35,7 +36,10 @@ namespace sprout {
 			typedef typename sprout::weed::traits::attribute_of<expr1_type, Iterator, context_type>::type attr1_type;
 			typedef typename sprout::weed::traits::attribute_of<expr2_type, Iterator, context_type>::type attr2_type;
 		public:
-			typedef typename sprout::weed::traits::attribute_of<Expr, Iterator, context_type>::type attribute_type;
+			typedef typename sprout::weed::attr_cnv::result_of::bitwise_or<
+				typename sprout::weed::traits::attribute_of<expr1_type, Iterator, context_type>::type,
+				typename sprout::weed::traits::attribute_of<expr2_type, Iterator, context_type>::type
+			>::type attribute_type;
 			typedef sprout::weed::eval_result<context_type, Iterator, attribute_type> result_type;
 		private:
 			template<typename Result2>
diff --git a/sprout/weed/context/parse_context/operator/dereference.hpp b/sprout/weed/context/parse_context/operator/dereference.hpp
index 0d874951..f7623763 100644
--- a/sprout/weed/context/parse_context/operator/dereference.hpp
+++ b/sprout/weed/context/parse_context/operator/dereference.hpp
@@ -8,6 +8,7 @@
 #include <sprout/weed/limited.hpp>
 #include <sprout/weed/expr/tag.hpp>
 #include <sprout/weed/expr/eval.hpp>
+#include <sprout/weed/attr_cnv/result_of/times.hpp>
 #include <sprout/weed/attr_cnv/times.hpp>
 #include <sprout/weed/traits/expr/tag_of.hpp>
 #include <sprout/weed/traits/parser/attribute_of.hpp>
@@ -36,7 +37,10 @@ namespace sprout {
 			typedef typename sprout::weed::traits::limit_of<expr_type, Iterator, context_type>::type limit;
 			typedef typename sprout::weed::traits::attribute_of<expr_type, Iterator, context_type>::type attr_type;
 		public:
-			typedef typename sprout::weed::traits::attribute_of<Expr, Iterator, context_type>::type attribute_type;
+			typedef typename sprout::weed::attr_cnv::result_of::times<
+				limit::value,
+				typename sprout::weed::traits::attribute_of<expr_type, Iterator, context_type>::type
+			>::type attribute_type;
 			typedef sprout::weed::eval_result<context_type, Iterator, attribute_type> result_type;
 		private:
 			template<typename Result, typename Head, typename... Attrs>
diff --git a/sprout/weed/context/parse_context/operator/logical_not.hpp b/sprout/weed/context/parse_context/operator/logical_not.hpp
index 644a2cea..abd2a14c 100644
--- a/sprout/weed/context/parse_context/operator/logical_not.hpp
+++ b/sprout/weed/context/parse_context/operator/logical_not.hpp
@@ -4,6 +4,7 @@
 #include <type_traits>
 #include <sprout/config.hpp>
 #include <sprout/tuple/tuple.hpp>
+#include <sprout/weed/unused.hpp>
 #include <sprout/weed/eval_result.hpp>
 #include <sprout/weed/expr/tag.hpp>
 #include <sprout/weed/expr/eval.hpp>
@@ -30,7 +31,7 @@ namespace sprout {
 		private:
 			typedef sprout::weed::parse_context<Iterator> context_type;
 		public:
-			typedef typename sprout::weed::traits::attribute_of<Expr, Iterator, context_type>::type attribute_type;
+			typedef sprout::weed::unused attribute_type;
 			typedef sprout::weed::eval_result<context_type, Iterator, attribute_type> result_type;
 		public:
 			SPROUT_CONSTEXPR result_type operator()(
diff --git a/sprout/weed/context/parse_context/operator/minus.hpp b/sprout/weed/context/parse_context/operator/minus.hpp
index 3a4a32d8..a095b124 100644
--- a/sprout/weed/context/parse_context/operator/minus.hpp
+++ b/sprout/weed/context/parse_context/operator/minus.hpp
@@ -29,8 +29,10 @@ namespace sprout {
 		> {
 		private:
 			typedef sprout::weed::parse_context<Iterator> context_type;
+			typedef typename sprout::tuples::tuple_element<0, typename Expr::args_type>::type expr1_type;
+			typedef typename sprout::tuples::tuple_element<1, typename Expr::args_type>::type expr2_type;
 		public:
-			typedef typename sprout::weed::traits::attribute_of<Expr, Iterator, context_type>::type attribute_type;
+			typedef typename sprout::weed::traits::attribute_of<expr1_type, Iterator, context_type>::type attribute_type;
 			typedef sprout::weed::eval_result<context_type, Iterator, attribute_type> result_type;
 		private:
 			template<typename Result1>
diff --git a/sprout/weed/context/parse_context/operator/modulus.hpp b/sprout/weed/context/parse_context/operator/modulus.hpp
index 228cf242..4b728ec1 100644
--- a/sprout/weed/context/parse_context/operator/modulus.hpp
+++ b/sprout/weed/context/parse_context/operator/modulus.hpp
@@ -8,6 +8,7 @@
 #include <sprout/weed/limited.hpp>
 #include <sprout/weed/expr/tag.hpp>
 #include <sprout/weed/expr/eval.hpp>
+#include <sprout/weed/attr_cnv/result_of/modulus.hpp>
 #include <sprout/weed/attr_cnv/modulus.hpp>
 #include <sprout/weed/traits/expr/tag_of.hpp>
 #include <sprout/weed/traits/parser/attribute_of.hpp>
@@ -37,7 +38,10 @@ namespace sprout {
 			typedef typename sprout::weed::traits::limit_of<expr1_type, Iterator, context_type>::type limit;
 			typedef typename sprout::weed::traits::attribute_of<expr1_type, Iterator, context_type>::type attr_type;
 		public:
-			typedef typename sprout::weed::traits::attribute_of<Expr, Iterator, context_type>::type attribute_type;
+			typedef typename sprout::weed::attr_cnv::result_of::modulus<
+				limit::value,
+				typename sprout::weed::traits::attribute_of<expr1_type, Iterator, context_type>::type
+			>::type attribute_type;
 			typedef sprout::weed::eval_result<context_type, Iterator, attribute_type> result_type;
 		private:
 			template<typename Result, typename... Attrs>
diff --git a/sprout/weed/context/parse_context/operator/negate.hpp b/sprout/weed/context/parse_context/operator/negate.hpp
index d74606f9..0da860d7 100644
--- a/sprout/weed/context/parse_context/operator/negate.hpp
+++ b/sprout/weed/context/parse_context/operator/negate.hpp
@@ -7,6 +7,7 @@
 #include <sprout/weed/eval_result.hpp>
 #include <sprout/weed/expr/tag.hpp>
 #include <sprout/weed/expr/eval.hpp>
+#include <sprout/weed/attr_cnv/result_of/negate.hpp>
 #include <sprout/weed/attr_cnv/negate.hpp>
 #include <sprout/weed/traits/expr/tag_of.hpp>
 #include <sprout/weed/traits/parser/attribute_of.hpp>
@@ -30,8 +31,11 @@ namespace sprout {
 		> {
 		private:
 			typedef sprout::weed::parse_context<Iterator> context_type;
+			typedef typename sprout::tuples::tuple_element<0, typename Expr::args_type>::type expr_type;
 		public:
-			typedef typename sprout::weed::traits::attribute_of<Expr, Iterator, context_type>::type attribute_type;
+			typedef typename sprout::weed::attr_cnv::result_of::negate<
+				typename sprout::weed::traits::attribute_of<expr_type, Iterator, context_type>::type
+			>::type attribute_type;
 			typedef sprout::weed::eval_result<context_type, Iterator, attribute_type> result_type;
 		private:
 			template<typename Result>
diff --git a/sprout/weed/context/parse_context/operator/shift_left.hpp b/sprout/weed/context/parse_context/operator/shift_left.hpp
index a6ba5875..d3054cac 100644
--- a/sprout/weed/context/parse_context/operator/shift_left.hpp
+++ b/sprout/weed/context/parse_context/operator/shift_left.hpp
@@ -7,6 +7,7 @@
 #include <sprout/weed/eval_result.hpp>
 #include <sprout/weed/expr/tag.hpp>
 #include <sprout/weed/expr/eval.hpp>
+#include <sprout/weed/attr_cnv/result_of/shift_left.hpp>
 #include <sprout/weed/attr_cnv/shift_left.hpp>
 #include <sprout/weed/traits/expr/tag_of.hpp>
 #include <sprout/weed/traits/parser/attribute_of.hpp>
@@ -30,8 +31,13 @@ namespace sprout {
 		> {
 		private:
 			typedef sprout::weed::parse_context<Iterator> context_type;
+			typedef typename sprout::tuples::tuple_element<0, typename Expr::args_type>::type expr1_type;
+			typedef typename sprout::tuples::tuple_element<1, typename Expr::args_type>::type expr2_type;
 		public:
-			typedef typename sprout::weed::traits::attribute_of<Expr, Iterator, context_type>::type attribute_type;
+			typedef typename sprout::weed::attr_cnv::result_of::shift_left<
+				typename sprout::weed::traits::attribute_of<expr1_type, Iterator, context_type>::type,
+				typename sprout::weed::traits::attribute_of<expr2_type, Iterator, context_type>::type
+			>::type attribute_type;
 			typedef sprout::weed::eval_result<context_type, Iterator, attribute_type> result_type;
 		private:
 			template<typename Attr1, typename Result2>
diff --git a/sprout/weed/context/parse_context/operator/unary_plus.hpp b/sprout/weed/context/parse_context/operator/unary_plus.hpp
index 272ca7f3..ffc9bd71 100644
--- a/sprout/weed/context/parse_context/operator/unary_plus.hpp
+++ b/sprout/weed/context/parse_context/operator/unary_plus.hpp
@@ -8,6 +8,7 @@
 #include <sprout/weed/limited.hpp>
 #include <sprout/weed/expr/tag.hpp>
 #include <sprout/weed/expr/eval.hpp>
+#include <sprout/weed/attr_cnv/result_of/times.hpp>
 #include <sprout/weed/attr_cnv/times.hpp>
 #include <sprout/weed/traits/expr/tag_of.hpp>
 #include <sprout/weed/traits/parser/attribute_of.hpp>
@@ -36,7 +37,10 @@ namespace sprout {
 			typedef typename sprout::weed::traits::limit_of<expr_type, Iterator, context_type>::type limit;
 			typedef typename sprout::weed::traits::attribute_of<expr_type, Iterator, context_type>::type attr_type;
 		public:
-			typedef typename sprout::weed::traits::attribute_of<Expr, Iterator, context_type>::type attribute_type;
+			typedef typename sprout::weed::attr_cnv::result_of::times<
+				limit::value,
+				typename sprout::weed::traits::attribute_of<expr_type, Iterator, context_type>::type
+			>::type attribute_type;
 			typedef sprout::weed::eval_result<context_type, Iterator, attribute_type> result_type;
 		private:
 			template<typename Result, typename Head, typename... Attrs>
diff --git a/sprout/weed/context/parse_context/terminal/char_type.hpp b/sprout/weed/context/parse_context/terminal/char_type.hpp
index 4e1340a6..a7643a8e 100644
--- a/sprout/weed/context/parse_context/terminal/char_type.hpp
+++ b/sprout/weed/context/parse_context/terminal/char_type.hpp
@@ -35,7 +35,7 @@ namespace sprout {
 		private:
 			typedef sprout::weed::parse_context<Iterator> context_type;
 		public:
-			typedef typename sprout::weed::traits::attribute_of<Expr, Iterator, context_type>::type attribute_type;
+			typedef sprout::weed::unused attribute_type;
 			typedef sprout::weed::eval_result<context_type, Iterator, attribute_type> result_type;
 		public:
 			SPROUT_CONSTEXPR result_type operator()(
diff --git a/sprout/weed/context/parse_context/terminal/parser.hpp b/sprout/weed/context/parse_context/terminal/parser.hpp
index 2b8a24c8..e1afc741 100644
--- a/sprout/weed/context/parse_context/terminal/parser.hpp
+++ b/sprout/weed/context/parse_context/terminal/parser.hpp
@@ -38,7 +38,11 @@ namespace sprout {
 			typedef sprout::weed::parse_context<Iterator> context_type;
 			typedef typename sprout::tuples::tuple_element<0, typename Expr::args_type>::type parser_type;
 		public:
-			typedef typename sprout::weed::traits::attribute_of<Expr, Iterator, context_type>::type attribute_type;
+			typedef typename sprout::weed::traits::attribute_of<
+				parser_type,
+				Iterator,
+				context_type
+			>::type attribute_type;
 			typedef sprout::weed::eval_result<context_type, Iterator, attribute_type> result_type;
 		private:
 			template<typename Result>
diff --git a/sprout/weed/context/parse_context/terminal/string.hpp b/sprout/weed/context/parse_context/terminal/string.hpp
index eed0f2e2..6ab54a4d 100644
--- a/sprout/weed/context/parse_context/terminal/string.hpp
+++ b/sprout/weed/context/parse_context/terminal/string.hpp
@@ -39,7 +39,7 @@ namespace sprout {
 		private:
 			typedef sprout::weed::parse_context<Iterator> context_type;
 		public:
-			typedef typename sprout::weed::traits::attribute_of<Expr, Iterator, context_type>::type attribute_type;
+			typedef sprout::weed::unused attribute_type;
 			typedef sprout::weed::eval_result<context_type, Iterator, attribute_type> result_type;
 		private:
 			template<typename Arg>
diff --git a/sprout/weed/traits/parser/attribute_of.hpp b/sprout/weed/traits/parser/attribute_of.hpp
index 52e4a85c..f6b22caa 100644
--- a/sprout/weed/traits/parser/attribute_of.hpp
+++ b/sprout/weed/traits/parser/attribute_of.hpp
@@ -10,12 +10,8 @@
 #include <sprout/weed/traits/type/is_c_str.hpp>
 #include <sprout/weed/traits/type/is_string.hpp>
 #include <sprout/weed/traits/expr/is_expr.hpp>
+#include <sprout/weed/traits/expr/terminal_of.hpp>
 #include <sprout/weed/traits/parser/is_parser.hpp>
-#include <sprout/weed/traits/parser/limit_of.hpp>
-#include <sprout/weed/attr_cnv/result_of/times.hpp>
-#include <sprout/weed/attr_cnv/result_of/shift_left.hpp>
-#include <sprout/weed/attr_cnv/result_of/modulus.hpp>
-#include <sprout/weed/attr_cnv/result_of/bitwise_or.hpp>
 
 namespace sprout {
 	namespace weed {
@@ -46,6 +42,18 @@ namespace sprout {
 				typedef typename T::template attribute<Context, Iterator>::type type;
 			};
 			template<typename T, typename Iterator, typename Context>
+			struct attribute_of<
+				T,
+				Iterator,
+				Context,
+				typename std::enable_if<
+					sprout::weed::traits::is_expr<T>::value
+				>::type
+			> {
+			public:
+				typedef typename Context::template eval<T>::attribute_type type;
+			};
+			template<typename T, typename Iterator, typename Context>
 			struct attribute_of<
 				T,
 				Iterator,
@@ -55,68 +63,11 @@ namespace sprout {
 					|| sprout::weed::traits::is_c_str<T>::value
 					|| sprout::weed::traits::is_string<T>::value
 				>::type
-			> {
-			public:
-				typedef sprout::weed::unused type;
-			};
-			template<typename Arg, typename Iterator, typename Context>
-			struct attribute_of<sprout::weed::expr<sprout::weed::tag::terminal, Arg>, Iterator, Context>
-				: public sprout::weed::traits::attribute_of<Arg, Iterator, Context>
-			{};
-			template<typename Arg, typename Iterator, typename Context>
-			struct attribute_of<sprout::weed::expr<sprout::weed::tag::unary_plus, Arg>, Iterator, Context>
-				: public sprout::weed::attr_cnv::result_of::times<
-					sprout::weed::traits::limit_of<Arg, Iterator, Context>::value,
-					typename sprout::weed::traits::attribute_of<Arg, Iterator, Context>::type
-				>
-			{};
-			template<typename Arg, typename Iterator, typename Context>
-			struct attribute_of<sprout::weed::expr<sprout::weed::tag::negate, Arg>, Iterator, Context>
-				: public sprout::weed::attr_cnv::result_of::negate<
-					typename sprout::weed::traits::attribute_of<Arg, Iterator, Context>::type
-				>
-			{};
-			template<typename Arg, typename Iterator, typename Context>
-			struct attribute_of<sprout::weed::expr<sprout::weed::tag::dereference, Arg>, Iterator, Context>
-				: public sprout::weed::attr_cnv::result_of::times<
-					sprout::weed::traits::limit_of<Arg, Iterator, Context>::value,
-					typename sprout::weed::traits::attribute_of<Arg, Iterator, Context>::type
-				>
-			{};
-			template<typename Arg, typename Iterator, typename Context>
-			struct attribute_of<sprout::weed::expr<sprout::weed::tag::address_of, Arg>, Iterator, Context> {
-			public:
-				typedef sprout::weed::unused type;
-			};
-			template<typename Arg, typename Iterator, typename Context>
-			struct attribute_of<sprout::weed::expr<sprout::weed::tag::logical_not, Arg>, Iterator, Context> {
-			public:
-				typedef sprout::weed::unused type;
-			};
-			template<typename Arg1, typename Arg2, typename Iterator, typename Context>
-			struct attribute_of<sprout::weed::expr<sprout::weed::tag::shift_left, Arg1, Arg2>, Iterator, Context>
-				: public sprout::weed::attr_cnv::result_of::shift_left<
-					typename sprout::weed::traits::attribute_of<Arg1, Iterator, Context>::type,
-					typename sprout::weed::traits::attribute_of<Arg2, Iterator, Context>::type
-				>
-			{};
-			template<typename Arg1, typename Arg2, typename Iterator, typename Context>
-			struct attribute_of<sprout::weed::expr<sprout::weed::tag::modulus, Arg1, Arg2>, Iterator, Context>
-				: public sprout::weed::attr_cnv::result_of::modulus<
-					sprout::weed::traits::limit_of<Arg1, Iterator, Context>::value,
-					typename sprout::weed::traits::attribute_of<Arg1, Iterator, Context>::type
-				>
-			{};
-			template<typename Arg1, typename Arg2, typename Iterator, typename Context>
-			struct attribute_of<sprout::weed::expr<sprout::weed::tag::minus, Arg1, Arg2>, Iterator, Context> {
-			public:
-				typedef typename sprout::weed::traits::attribute_of<Arg1, Iterator, Context>::type type;
-			};
-			template<typename Arg1, typename Arg2, typename Iterator, typename Context>
-			struct attribute_of<sprout::weed::expr<sprout::weed::tag::bitwise_or, Arg1, Arg2>, Iterator, Context>
-				: public sprout::weed::attr_cnv::result_of::bitwise_or<
-					typename sprout::weed::traits::attribute_of<Arg1, Iterator, Context>::type,
-					typename sprout::weed::traits::attribute_of<Arg2, Iterator, Context>::type
+			>
+				: public sprout::weed::traits::attribute_of<
+					typename sprout::weed::traits::terminal_of<T>::type,
+					Iterator,
+					Context
 				>
 			{};
 		}	// namespace traits