diff --git a/libs/tuple/test/tuple.cpp b/libs/tuple/test/tuple.cpp
index 82c414b2..b67aca1f 100644
--- a/libs/tuple/test/tuple.cpp
+++ b/libs/tuple/test/tuple.cpp
@@ -34,6 +34,12 @@ namespace testspr {
 				TESTSPR_BOTH_ASSERT(sprout::tuples::get<0>(tup3) == 1);
 				TESTSPR_BOTH_ASSERT(sprout::tuples::get<1>(tup3) == 1.0);
 			}
+			{
+				SPROUT_STATIC_CONSTEXPR auto tup3 = sprout::tuples::tuple<int, double>(sprout::tuples::tuple<long, float>(1l, 1.0f));
+				TESTSPR_BOTH_ASSERT(sprout::tuples::get<0>(tup3) == 1);
+				TESTSPR_BOTH_ASSERT(sprout::tuples::get<1>(tup3) == 1.0);
+			}
+
 			{
 				SPROUT_STATIC_CONSTEXPR auto tup3 = sprout::tuples::tuple<int, double>(sprout::tuples::flexibly_construct, 1l);
 				TESTSPR_BOTH_ASSERT(sprout::tuples::get<0>(tup3) == 1);
@@ -50,11 +56,6 @@ namespace testspr {
 				TESTSPR_BOTH_ASSERT(sprout::tuples::get<1>(tup3) == 1.0);
 			}
 
-			{
-				SPROUT_STATIC_CONSTEXPR auto tup3 = sprout::tuples::tuple<int, double>(sprout::tuples::tuple<long, float>(1l, 1.0f));
-				TESTSPR_BOTH_ASSERT(sprout::tuples::get<0>(tup3) == 1);
-				TESTSPR_BOTH_ASSERT(sprout::tuples::get<1>(tup3) == 1.0);
-			}
 			{
 				SPROUT_STATIC_CONSTEXPR auto tup3 = sprout::tuples::tuple<int, double>(sprout::tuples::flexibly_construct, sprout::tuples::tuple<long>(1l));
 				TESTSPR_BOTH_ASSERT(sprout::tuples::get<0>(tup3) == 1);
@@ -78,24 +79,12 @@ namespace testspr {
 				TESTSPR_ASSERT(sprout::tuples::get<0>(tup3) == 1);
 				TESTSPR_ASSERT(sprout::tuples::get<1>(tup3) == 1.0);
 			}
-			{
-				auto tup3 = tup2;
-				tup3 = sprout::tuples::tuple<long>(1l);
-				TESTSPR_ASSERT(sprout::tuples::get<0>(tup3) == 1);
-				TESTSPR_ASSERT(sprout::tuples::get<1>(tup3) == 0.0);
-			}
 			{
 				auto tup3 = tup2;
 				tup3 = sprout::tuples::tuple<long, float>(1l, 1.0f);
 				TESTSPR_ASSERT(sprout::tuples::get<0>(tup3) == 1);
 				TESTSPR_ASSERT(sprout::tuples::get<1>(tup3) == 1.0);
 			}
-			{
-				auto tup3 = tup2;
-				tup3 = sprout::tuples::tuple<long, float, char>(1l, 1.0f, '-');
-				TESTSPR_ASSERT(sprout::tuples::get<0>(tup3) == 1);
-				TESTSPR_ASSERT(sprout::tuples::get<1>(tup3) == 1.0);
-			}
 
 			// swap
 			{
diff --git a/sprout/tuple/tuple/tuple.hpp b/sprout/tuple/tuple/tuple.hpp
index bafddac3..15e7841d 100644
--- a/sprout/tuple/tuple/tuple.hpp
+++ b/sprout/tuple/tuple/tuple.hpp
@@ -69,32 +69,47 @@ namespace sprout {
 			typename
 		>
 		inline SPROUT_CONSTEXPR sprout::tuples::tuple<Types...>::tuple(sprout::pair<UTypes...>&& t)
-			: impl_type(sprout::move(t.first), sprout::move(t.second))
+			: impl_type(sprout::forward<typename sprout::pair<UTypes...>::first_type>(t.first), sprout::forward<typename sprout::pair<UTypes...>::second_type>(t.second))
 		{}
 		template<typename... Types>
-		template<typename... UTypes>
+		template<
+			typename... UTypes,
+			typename
+		>
 		inline SPROUT_CONSTEXPR sprout::tuples::tuple<Types...>::tuple(sprout::tuples::flexibly_construct_t, UTypes&&... elements)
 			: impl_type(sprout::forward<UTypes>(elements)...)
 		{}
 		template<typename... Types>
-		template<typename... UTypes>
+		template<
+			typename... UTypes,
+			typename
+		>
 		inline SPROUT_CONSTEXPR sprout::tuples::tuple<Types...>::tuple(sprout::tuples::flexibly_construct_t, sprout::tuples::tuple<UTypes...> const& t)
 			: impl_type(static_cast<sprout::tuples::detail::tuple_impl<0, UTypes...> const&>(t))
 		{}
 		template<typename... Types>
-		template<typename... UTypes>
+		template<
+			typename... UTypes,
+			typename
+		>
 		inline SPROUT_CONSTEXPR sprout::tuples::tuple<Types...>::tuple(sprout::tuples::flexibly_construct_t, sprout::tuples::tuple<UTypes...>&& t)
 			: impl_type(static_cast<sprout::tuples::detail::tuple_impl<0, UTypes...>&&>(t))
 		{}
 		template<typename... Types>
-		template<typename... UTypes>
+		template<
+			typename... UTypes,
+			typename
+		>
 		inline SPROUT_CONSTEXPR sprout::tuples::tuple<Types...>::tuple(sprout::tuples::flexibly_construct_t, sprout::pair<UTypes...> const& t)
 			: impl_type(t.first, t.second)
 		{}
 		template<typename... Types>
-		template<typename... UTypes>
+		template<
+			typename... UTypes,
+			typename
+		>
 		inline SPROUT_CONSTEXPR sprout::tuples::tuple<Types...>::tuple(sprout::tuples::flexibly_construct_t, sprout::pair<UTypes...>&& t)
-			: impl_type(sprout::move(t.first), sprout::move(t.second))
+			: impl_type(sprout::forward<typename sprout::pair<UTypes...>::first_type>(t.first), sprout::forward<typename sprout::pair<UTypes...>::second_type>(t.second))
 		{}
 		// tuple assignment
 		template<typename... Types>
@@ -110,13 +125,19 @@ namespace sprout {
 			return *this;
 		}
 		template<typename... Types>
-		template<typename... UTypes>
+		template<
+			typename... UTypes,
+			typename
+		>
 		sprout::tuples::tuple<Types...>& sprout::tuples::tuple<Types...>::operator=(sprout::tuples::tuple<UTypes...> const& rhs) {
 			static_cast<impl_type&>(*this) = rhs;
 			return *this;
 		}
 		template<typename... Types>
-		template<typename... UTypes>
+		template<
+			typename... UTypes,
+			typename
+		>
 		sprout::tuples::tuple<Types...>& sprout::tuples::tuple<Types...>::operator=(sprout::tuples::tuple<UTypes...>&& rhs) {
 			static_cast<impl_type&>(*this) = sprout::move(rhs);
 			return *this;
diff --git a/sprout/tuple/tuple/tuple_decl.hpp b/sprout/tuple/tuple/tuple_decl.hpp
index 150aadba..8ef46639 100644
--- a/sprout/tuple/tuple/tuple_decl.hpp
+++ b/sprout/tuple/tuple/tuple_decl.hpp
@@ -6,9 +6,11 @@
 #include <type_traits>
 #include <tuple>
 #include <sprout/config.hpp>
+#include <sprout/index_tuple.hpp>
 #include <sprout/utility/forward.hpp>
 #include <sprout/utility/move.hpp>
 #include <sprout/utility/swap.hpp>
+#include <sprout/utility/pack.hpp>
 #include <sprout/utility/pair/pair_fwd.hpp>
 #include <sprout/type_traits/is_convert_constructible.hpp>
 #include <sprout/tpp/algorithm/all_of.hpp>
@@ -241,12 +243,39 @@ namespace sprout {
 		{
 		private:
 			typedef sprout::tuples::detail::tuple_impl<0, Types...> impl_type;
+		private:
+			template<typename TndexTuple, typename... Utypes>
+			struct is_flexibly_constructible_impl;
+			template<sprout::index_t... Indexes, typename... Utypes>
+			struct is_flexibly_constructible_impl<sprout::index_tuple<Indexes...>, Utypes...>
+				: public sprout::tpp::all_of<
+					sprout::is_convert_constructible<
+						typename sprout::tppack_at<Indexes, Types...>::type,
+						typename sprout::tppack_at<Indexes, Utypes...>::type
+					>...
+				>
+			{};
 		public:
 			struct has_nothrow_swap
 				: public sprout::tpp::all_of_c<
 					SPROUT_NOEXCEPT_EXPR_OR_DEFAULT(sprout::swap(std::declval<Types&>(), std::declval<Types&>()), false)...
 				>
 			{};
+			template<typename... UTypes>
+			struct is_flexibly_constructible
+				: public is_flexibly_constructible_impl<
+					typename sprout::index_range<0, (sizeof...(UTypes) < sizeof...(Types) ? sizeof...(UTypes) : sizeof...(Types))>::type,
+					UTypes...
+				>
+			{};
+			template<typename... UTypes>
+			struct is_rvref_flexibly_constructible
+				: public is_flexibly_constructible<UTypes&&...>
+			{};
+			template<typename... UTypes>
+			struct is_clvref_flexibly_constructible
+				: public is_flexibly_constructible<UTypes const&...>
+			{};
 		public:
 			// tuple construction
 			SPROUT_CONSTEXPR tuple();
@@ -288,23 +317,58 @@ namespace sprout {
 				>::type
 			>
 			SPROUT_CONSTEXPR tuple(sprout::pair<UTypes...>&& t);
-			template<typename... UTypes>
+			template<
+				typename... UTypes,
+				typename = typename std::enable_if<
+					is_rvref_flexibly_constructible<UTypes...>::value
+				>::type
+			>
 			explicit SPROUT_CONSTEXPR tuple(sprout::tuples::flexibly_construct_t, UTypes&&... elements);
-			template<typename... UTypes>
+			template<
+				typename... UTypes,
+				typename = typename std::enable_if<
+					is_clvref_flexibly_constructible<UTypes...>::value
+				>::type
+			>
 			SPROUT_CONSTEXPR tuple(sprout::tuples::flexibly_construct_t, sprout::tuples::tuple<UTypes...> const& t);
-			template<typename... UTypes>
+			template<
+				typename... UTypes,
+				typename = typename std::enable_if<
+					is_rvref_flexibly_constructible<UTypes...>::value
+				>::type
+			>
 			SPROUT_CONSTEXPR tuple(sprout::tuples::flexibly_construct_t, sprout::tuples::tuple<UTypes...>&& t);
-			template<typename... UTypes>
+			template<
+				typename... UTypes,
+				typename = typename std::enable_if<
+					is_clvref_flexibly_constructible<UTypes...>::value
+				>::type
+			>
 			SPROUT_CONSTEXPR tuple(sprout::tuples::flexibly_construct_t, sprout::pair<UTypes...> const& t);
-			template<typename... UTypes>
+			template<
+				typename... UTypes,
+				typename = typename std::enable_if<
+					is_rvref_flexibly_constructible<UTypes...>::value
+				>::type
+			>
 			SPROUT_CONSTEXPR tuple(sprout::tuples::flexibly_construct_t, sprout::pair<UTypes...>&& t);
 			// tuple assignment
 			tuple& operator=(tuple const& rhs);
 			tuple& operator=(tuple&& rhs)
 			SPROUT_NOEXCEPT_EXPR(sprout::tpp::all_of<std::is_nothrow_move_assignable<Types>...>::value);
-			template<typename... UTypes>
+			template<
+				typename... UTypes,
+				typename = typename std::enable_if<
+					sizeof...(Types) == sizeof...(UTypes) && sprout::tpp::all_of<std::is_assignable<Types&, UTypes const&>...>::value
+				>::type
+			>
 			tuple& operator=(sprout::tuples::tuple<UTypes...> const& rhs);
-			template<typename... UTypes>
+			template<
+				typename... UTypes,
+				typename = typename std::enable_if<
+					sizeof...(Types) == sizeof...(UTypes) && sprout::tpp::all_of<std::is_assignable<Types&, UTypes&&>...>::value
+				>::type
+			>
 			tuple& operator=(sprout::tuples::tuple<UTypes...>&& rhs);
 			// tuple swap
 			void swap(tuple& other)