diff --git a/libs/array/test/array.cpp b/libs/array/test/array.cpp
index afb17483..0d14b7e0 100644
--- a/libs/array/test/array.cpp
+++ b/libs/array/test/array.cpp
@@ -90,17 +90,19 @@ namespace testspr {
 			}
 
 			// assign
+			TESTSPR_BOTH_ASSERT(testspr::equal(arr1.assign(-1), array<int, 10>{{-1, -1, -1, -1, -1, -1, -1, -1, -1, -1}}));
 			{
 				auto arr = arr1;
 				arr.assign(-1);
-				TESTSPR_ASSERT(arr[0] == -1);
+				TESTSPR_ASSERT(testspr::equal(arr, array<int, 10>{{-1, -1, -1, -1, -1, -1, -1, -1, -1, -1}}));
 			}
 
 			// fill
+			TESTSPR_BOTH_ASSERT(testspr::equal(arr1.fill(-1), array<int, 10>{{-1, -1, -1, -1, -1, -1, -1, -1, -1, -1}}));
 			{
 				auto arr = arr1;
 				arr.fill(-1);
-				TESTSPR_ASSERT(arr[0] == -1);
+				TESTSPR_ASSERT(testspr::equal(arr, array<int, 10>{{-1, -1, -1, -1, -1, -1, -1, -1, -1, -1}}));
 			}
 
 			// swap
diff --git a/sprout/array/array.hpp b/sprout/array/array.hpp
index bdb13afe..9aeb73ff 100644
--- a/sprout/array/array.hpp
+++ b/sprout/array/array.hpp
@@ -17,6 +17,19 @@
 #endif
 
 namespace sprout {
+	namespace detail {
+		template<sprout::index_t Index, typename T>
+		inline SPROUT_CONSTEXPR T const&
+		array_dummy_get(T const& value) {
+			return value;
+		}
+		template<typename Array, typename T, sprout::index_t... Indexes>
+		inline SPROUT_CONSTEXPR Array
+		array_fill_impl(T const& value, sprout::index_tuple<Indexes...>) {
+			return Array{{array_dummy_get<Indexes>(value)...}};
+		}
+	}	// namespace detail
+
 	//
 	// array
 	//
@@ -47,6 +60,9 @@ namespace sprout {
 		void fill(const_reference value) {
 			std::fill_n(begin(), size(), value);
 		}
+		SPROUT_CONSTEXPR array fill(const_reference value) const {
+			return sprout::detail::array_fill_impl<array>(value, sprout::index_n<0, N>::make());
+		}
 		void swap(array<T, N>& other) SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(std::swap(std::declval<T&>(), std::declval<T&>()))) {
 			std::swap_ranges(other.begin(), other.end(), begin());
 		}
@@ -176,6 +192,9 @@ namespace sprout {
 		void assign(const_reference value) {
 			fill(value);
 		}
+		SPROUT_CONSTEXPR array assign(const_reference value) const {
+			return fill(value);
+		}
 		void rangecheck(size_type i) const {
 			if (i >= size()) {
 				throw std::out_of_range("array<>: index out of range");
@@ -189,17 +208,16 @@ namespace sprout {
 	// swap
 	//
 	template<typename T, std::size_t N>
-	inline void swap(sprout::array<T, N>& lhs, sprout::array<T, N>& rhs) SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs))) {
+	inline void swap(sprout::array<T, N>& lhs, sprout::array<T, N>& rhs)
+		SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
+	{
 		lhs.swap(rhs);
 	}
 
 	namespace detail {
 		template<typename T, std::size_t N, sprout::index_t... Indexes>
-		inline SPROUT_CONSTEXPR sprout::array<T, N> to_array_impl(
-			T const (& arr)[N],
-			sprout::index_tuple<Indexes...>
-			)
-		{
+		inline SPROUT_CONSTEXPR sprout::array<T, N>
+		to_array_impl(T const (& arr)[N], sprout::index_tuple<Indexes...>) {
 			return sprout::array<T, N>{{arr[Indexes]...}};
 		}
 	}	// namespace detail
@@ -207,7 +225,8 @@ namespace sprout {
 	// to_array
 	//
 	template<typename T, std::size_t N>
-	inline SPROUT_CONSTEXPR sprout::array<T, N> to_array(T const (& arr)[N]) {
+	inline SPROUT_CONSTEXPR sprout::array<T, N>
+	to_array(T const (& arr)[N]) {
 		return sprout::detail::to_array_impl(arr, sprout::index_range<0, N>::make());
 	}
 }	// namespace sprout
diff --git a/sprout/array/hash.hpp b/sprout/array/hash.hpp
index c81f620c..0abd56f9 100644
--- a/sprout/array/hash.hpp
+++ b/sprout/array/hash.hpp
@@ -8,7 +8,8 @@
 
 namespace sprout {
 	template<typename T, std::size_t N>
-	inline SPROUT_CONSTEXPR std::size_t hash_value(sprout::array<T, N> const& v) {
+	inline SPROUT_CONSTEXPR std::size_t
+	hash_value(sprout::array<T, N> const& v) {
 		return sprout::hash_range(v.begin(), v.end());
 	}
 }	// namespace sprout
diff --git a/sprout/array/make_array.hpp b/sprout/array/make_array.hpp
index c990b4f3..46b6c128 100644
--- a/sprout/array/make_array.hpp
+++ b/sprout/array/make_array.hpp
@@ -13,7 +13,8 @@ namespace sprout {
 	// make_array
 	//
 	template<typename T, typename... Types>
-	inline SPROUT_CONSTEXPR sprout::array<T, sizeof...(Types)> make_array(Types&&... args) {
+	inline SPROUT_CONSTEXPR sprout::array<T, sizeof...(Types)>
+	make_array(Types&&... args) {
 		return sprout::array<T, sizeof...(Types)>{{sprout::forward<Types>(args)...}};
 	}
 
@@ -24,11 +25,13 @@ namespace sprout {
 	inline SPROUT_CONSTEXPR sprout::array<
 		typename std::decay<typename std::common_type<typename std::decay<Types>::type...>::type>::type,
 		sizeof...(Types)
-	> make_common_array(Types&&... args) {
-		return sprout::array<
+	>
+	make_common_array(Types&&... args) {
+		typedef sprout::array<
 			typename std::decay<typename std::common_type<typename std::decay<Types>::type...>::type>::type,
 			sizeof...(Types)
-		>{{sprout::forward<Types>(args)...}};
+		> type;
+		return type{{sprout::forward<Types>(args)...}};
 	}
 }	// namespace sprout
 
diff --git a/sprout/array/tuple.hpp b/sprout/array/tuple.hpp
index 0feaaed0..96405cdb 100644
--- a/sprout/array/tuple.hpp
+++ b/sprout/array/tuple.hpp
@@ -4,11 +4,12 @@
 #include <cstddef>
 #include <tuple>
 #include <type_traits>
+#include <sprout/config.hpp>
 #include <sprout/array/array.hpp>
 #include <sprout/utility/move.hpp>
 #include <sprout/tuple/tuple/get.hpp>
 
-namespace sprout {
+namespace sprout_adl {
 	//
 	// tuple_get
 	//
@@ -29,7 +30,7 @@ namespace sprout {
 	tuple_get(sprout::array<T, N>&& t) SPROUT_NOEXCEPT {
 		return sprout::move(sprout::tuples::get<I>(t));
 	}
-}	// namespace sprout
+}	// namespace sprout_adl
 
 namespace std {
 	//
diff --git a/sprout/type_traits/has_xxx.hpp b/sprout/type_traits/has_xxx.hpp
index bcfabc63..7df75581 100644
--- a/sprout/type_traits/has_xxx.hpp
+++ b/sprout/type_traits/has_xxx.hpp
@@ -7,6 +7,7 @@
 
 //
 // SPROUT_HAS_XXX_TYPE_DEF
+// SPROUT_HAS_XXX_TYPE_DEF_LAZY
 //
 #define SPROUT_HAS_XXX_TYPE_DEF(NAME, TYPE) \
 	template<typename T, typename = typename T::TYPE> \
@@ -17,15 +18,12 @@
 	struct NAME \
 		: decltype(SPROUT_PP_CAT(SPROUT_PP_CAT(sprout_has_xxx_impl_check_type_, TYPE), __LINE__)<T>(0)) \
 	{}
-
-//
-// SPROUT_HAS_XXX_TYPE_DEF_LAZY
-//
 #define SPROUT_HAS_XXX_TYPE_DEF_LAZY(TYPE) \
 	SPROUT_HAS_XXX_TYPE_DEF(SPROUT_PP_CAT(has_, TYPE), TYPE)
 
 //
 // SPROUT_HAS_XXX_VALUE_DEF
+// SPROUT_HAS_XXX_VALUE_DEF_LAZY
 //
 #define SPROUT_HAS_XXX_VALUE_DEF(NAME, VALUE) \
 	template<typename T, decltype(&T::VALUE) = &T::VALUE> \
@@ -36,10 +34,6 @@
 	struct NAME \
 		: decltype(SPROUT_PP_CAT(SPROUT_PP_CAT(sprout_has_xxx_impl_check_value_, VALUE), __LINE__)<T>(0)) \
 	{}
-
-//
-// SPROUT_HAS_XXX_VALUE_DEF_LAZY
-//
 #define SPROUT_HAS_XXX_VALUE_DEF_LAZY(VALUE) \
 	SPROUT_HAS_XXX_VALUE_DEF(SPROUT_PP_CAT(has_, VALUE), VALUE)
 
diff --git a/sprout/variant.hpp b/sprout/variant.hpp
index 754eccf5..1640face 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/tuple.hpp>
 #include <sprout/variant/get.hpp>
 #include <sprout/variant/static_visitor.hpp>
 #include <sprout/variant/apply_visitor.hpp>
diff --git a/sprout/variant/get.hpp b/sprout/variant/get.hpp
index 88216f10..0731da4d 100644
--- a/sprout/variant/get.hpp
+++ b/sprout/variant/get.hpp
@@ -11,35 +11,15 @@ namespace sprout {
 	// get
 	//
 	template<typename U, typename... Types>
-	inline SPROUT_CONSTEXPR U const& get(sprout::variant<Types...> const& operand) {
+	inline SPROUT_CONSTEXPR U const&
+	get(sprout::variant<Types...> const& operand) {
 		return operand.template get<U>();
 	}
 	template<typename U, typename... Types>
-	inline SPROUT_CONSTEXPR U& get(sprout::variant<Types...>& operand) {
+	inline SPROUT_CONSTEXPR U&
+	get(sprout::variant<Types...>& operand) {
 		return operand.template get<U>();
 	}
 }	// namespace sprout
 
-namespace sprout_adl {
-	//
-	// tuple_get
-	//
-	template<std::size_t I, typename... Types>
-	inline SPROUT_CONSTEXPR typename sprout::tuples::tuple_element<
-		I,
-		sprout::variant<Types...>
-	>::type const&
-	tuple_get(sprout::variant<Types...> const& operand) {
-		return operand.template get_at<I>();
-	}
-	template<std::size_t I, typename... Types>
-	inline SPROUT_CONSTEXPR typename sprout::tuples::tuple_element<
-		I,
-		sprout::variant<Types...>
-	>::type&
-	tuple_get(sprout::variant<Types...>& operand) {
-		return operand.template get_at<I>();
-	}
-}	// namespace sprout_adl
-
 #endif	// #ifndef SPROUT_VARIANT_GET_HPP
diff --git a/sprout/variant/tuple.hpp b/sprout/variant/tuple.hpp
new file mode 100644
index 00000000..f0abe6b7
--- /dev/null
+++ b/sprout/variant/tuple.hpp
@@ -0,0 +1,59 @@
+#ifndef SPROUT_VARIANT_TUPLE_HPP
+#define SPROUT_VARIANT_TUPLE_HPP
+
+#include <cstddef>
+#include <tuple>
+#include <sprout/config.hpp>
+#include <sprout/variant/variant.hpp>
+#include <sprout/utility/move.hpp>
+#include <sprout/tuple/tuple/get.hpp>
+
+namespace sprout_adl {
+	//
+	// tuple_get
+	//
+	template<std::size_t I, typename... Types>
+	inline SPROUT_CONSTEXPR typename sprout::tuples::tuple_element<
+		I,
+		sprout::variant<Types...>
+	>::type const&
+	tuple_get(sprout::variant<Types...> const& t) {
+		return t.template get_at<I>();
+	}
+	template<std::size_t I, typename... Types>
+	inline SPROUT_CONSTEXPR typename sprout::tuples::tuple_element<
+		I,
+		sprout::variant<Types...>
+	>::type&
+	tuple_get(sprout::variant<Types...>& t) {
+		return t.template get_at<I>();
+	}
+	template<std::size_t I, typename... Types>
+	inline SPROUT_CONSTEXPR typename sprout::tuples::tuple_element<
+		I,
+		sprout::variant<Types...>
+	>::type&&
+	tuple_get(sprout::variant<Types...>&& t) {
+		return sprout::move(sprout::tuples::get<I>(t));
+	}
+}	// namespace sprout_adl
+
+namespace std {
+	//
+	// tuple_size
+	//
+	template<typename... Types>
+	struct tuple_size<sprout::variant<Types...> >
+		: public std::tuple_size<typename sprout::variant<Types...>::tuple_type>
+	{};
+
+	//
+	// tuple_element
+	//
+	template<std::size_t I, typename... Types>
+	struct tuple_element<I, sprout::variant<Types...> >
+		: public std::tuple_element<I, typename sprout::variant<Types...>::tuple_type>
+	{};
+}	// namespace std
+
+#endif	// #ifndef SPROUT_VARIANT_TUPLE_HPP
diff --git a/sprout/variant/variant.hpp b/sprout/variant/variant.hpp
index ea335353..3155883c 100644
--- a/sprout/variant/variant.hpp
+++ b/sprout/variant/variant.hpp
@@ -252,31 +252,11 @@ namespace sprout {
 	// swap
 	//
 	template<typename... Types>
-	inline void swap(
-		sprout::variant<Types...>& lhs,
-		sprout::variant<Types...>& rhs
-		) SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
+	inline void swap(sprout::variant<Types...>& lhs, sprout::variant<Types...>& rhs)
+		SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
 		lhs.swap(rhs);
 	}
 }	// namespace sprout
 
-namespace std {
-	//
-	// tuple_size
-	//
-	template<typename... Types>
-	struct tuple_size<sprout::variant<Types...> >
-		: public std::tuple_size<typename sprout::variant<Types...>::tuple_type>
-	{};
-
-	//
-	// tuple_element
-	//
-	template<std::size_t I, typename... Types>
-	struct tuple_element<I, sprout::variant<Types...> >
-		: public std::tuple_element<I, typename sprout::variant<Types...>::tuple_type>
-	{};
-}	// namespace std
-
 #endif	// #ifndef SPROUT_VARIANT_VARIANT_HPP