diff --git a/sprout/iterator/adjacent_filter_iterator.hpp b/sprout/iterator/adjacent_filter_iterator.hpp
index 419c3cad..6d405d28 100644
--- a/sprout/iterator/adjacent_filter_iterator.hpp
+++ b/sprout/iterator/adjacent_filter_iterator.hpp
@@ -68,7 +68,9 @@ namespace sprout {
 			, pred(pred)
 		{}
 	public:
-		adjacent_filter_iterator() = default;
+		SPROUT_CONSTEXPR adjacent_filter_iterator()
+			: current(), last(), pred()
+		{}
 		adjacent_filter_iterator(adjacent_filter_iterator const&) = default;
 		SPROUT_CONSTEXPR adjacent_filter_iterator(Predicate pred, iterator_type it, iterator_type last = iterator_type())
 			: current(find_next(it, last, pred))
@@ -82,7 +84,7 @@ namespace sprout {
 			, pred(it.pred)
 		{}
 		template<typename U>
-		adjacent_filter_iterator& operator=(adjacent_filter_iterator<Predicate, U> const& it) {
+		SPROUT_CXX14_CONSTEXPR adjacent_filter_iterator& operator=(adjacent_filter_iterator<Predicate, U> const& it) {
 			adjacent_filter_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -103,14 +105,14 @@ namespace sprout {
 			return &*current;
 		}
 
-		adjacent_filter_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR adjacent_filter_iterator& operator++() {
 			satisfy_predicate();
 			if (current != last) {
 				++current;
 			}
 			return *this;
 		}
-		adjacent_filter_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR adjacent_filter_iterator operator++(int) {
 			adjacent_filter_iterator result(*this);
 			satisfy_predicate();
 			if (current != last) {
@@ -121,7 +123,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR adjacent_filter_iterator next() const {
 			return adjacent_filter_iterator(pred, checked_next(find_next(current, last, pred), last), last, private_construct_t());
 		}
-		void swap(adjacent_filter_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(adjacent_filter_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(sprout::swap(current, other.current))
 			&& SPROUT_NOEXCEPT_EXPR(sprout::swap(last, other.last))
@@ -164,7 +166,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename Predicate, typename Iterator>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::adjacent_filter_iterator<Predicate, Iterator>& lhs, sprout::adjacent_filter_iterator<Predicate, Iterator>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
diff --git a/sprout/iterator/alternate_iterator.hpp b/sprout/iterator/alternate_iterator.hpp
index e0f42cce..3dc43a9b 100644
--- a/sprout/iterator/alternate_iterator.hpp
+++ b/sprout/iterator/alternate_iterator.hpp
@@ -56,7 +56,7 @@ namespace sprout {
 			: current1(it1), current2(it2), in_left(in_left)
 		{}
 	public:
-		alternate_iterator()
+		SPROUT_CONSTEXPR alternate_iterator()
 			: current1(), current2(), in_left(true)
 		{}
 		alternate_iterator(alternate_iterator const&) = default;
@@ -68,7 +68,7 @@ namespace sprout {
 			: current1(it.base()), current2(it.base2()), in_left(it.is_in_left())
 		{}
 		template<typename U, typename V>
-		alternate_iterator& operator=(alternate_iterator<U, V> const& it) {
+		SPROUT_CXX14_CONSTEXPR alternate_iterator& operator=(alternate_iterator<U, V> const& it) {
 			alternate_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -88,7 +88,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &*(*this);
 		}
-		alternate_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR alternate_iterator& operator++() {
 			if (is_in_left()) {
 				in_left = false;
 			} else {
@@ -98,7 +98,7 @@ namespace sprout {
 			}
 			return *this;
 		}
-		alternate_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR alternate_iterator operator++(int) {
 			alternate_iterator result(*this);
 			if (is_in_left()) {
 				in_left = false;
@@ -109,7 +109,7 @@ namespace sprout {
 			}
 			return result;
 		}
-		alternate_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR alternate_iterator& operator--() {
 			if (is_in_left()) {
 				in_left = false;
 				--current1;
@@ -119,7 +119,7 @@ namespace sprout {
 			}
 			return *this;
 		}
-		alternate_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR alternate_iterator operator--(int) {
 			alternate_iterator temp(*this);
 			if (is_in_left()) {
 				in_left = false;
@@ -136,12 +136,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR alternate_iterator operator-(difference_type n) const {
 			return advance_impl(-n);
 		}
-		alternate_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR alternate_iterator& operator+=(difference_type n) {
 			alternate_iterator temp(*this + n);
 			temp.swap(*this);
 			return *this;
 		}
-		alternate_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR alternate_iterator& operator-=(difference_type n) {
 			alternate_iterator temp(*this - n);
 			temp.swap(*this);
 			return *this;
@@ -159,7 +159,7 @@ namespace sprout {
 				: alternate_iterator(current1, current2, true)
 				;
 		}
-		void swap(alternate_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(alternate_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(sprout::swap(current1, other.current1))
 			&& SPROUT_NOEXCEPT_EXPR(sprout::swap(current2, other.current2))
@@ -275,7 +275,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename LIterator, typename RIterator>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(
 		sprout::alternate_iterator<LIterator, RIterator>& lhs,
 		sprout::alternate_iterator<LIterator, RIterator>& rhs
diff --git a/sprout/iterator/back_insert_iterator.hpp b/sprout/iterator/back_insert_iterator.hpp
index f2988003..38bb4bf5 100644
--- a/sprout/iterator/back_insert_iterator.hpp
+++ b/sprout/iterator/back_insert_iterator.hpp
@@ -50,33 +50,30 @@ namespace sprout {
 	protected:
 		using base_type::container;
 	public:
-		SPROUT_CONSTEXPR back_insert_iterator() = default;
+		back_insert_iterator() = default;
 		explicit SPROUT_CONSTEXPR back_insert_iterator(param_type x)
 			: base_type(x)
 		{}
 		SPROUT_CONSTEXPR back_insert_iterator(back_insert_iterator const&) = default;
-		back_insert_iterator& operator=(typename container_type::value_type const& value) {
+		SPROUT_CXX14_CONSTEXPR back_insert_iterator& operator=(typename container_type::value_type const& value) {
 			container->push_back(value);
 			return *this;
 		}
-		back_insert_iterator& operator=(typename container_type::value_type&& value) {
+		SPROUT_CXX14_CONSTEXPR back_insert_iterator& operator=(typename container_type::value_type&& value) {
 			container->push_back(sprout::move(value));
 			return *this;
 		}
-		SPROUT_CONSTEXPR back_insert_iterator const& operator*() const {
+		SPROUT_CXX14_CONSTEXPR back_insert_iterator& operator*() {
 			return *this;
 		}
-		back_insert_iterator& operator*() {
+		SPROUT_CXX14_CONSTEXPR back_insert_iterator& operator++() {
 			return *this;
 		}
-		back_insert_iterator& operator++() {
-			return *this;
-		}
-		back_insert_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR back_insert_iterator operator++(int) {
 			return *this;
 		}
 
-		void swap(back_insert_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(back_insert_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(base_type::swap(other)))
 		{
 			base_type::swap(other);
@@ -87,7 +84,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename Container>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::back_insert_iterator<Container>& lhs, sprout::back_insert_iterator<Container>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
diff --git a/sprout/iterator/bytes_iterator.hpp b/sprout/iterator/bytes_iterator.hpp
index d920948f..078ff470 100644
--- a/sprout/iterator/bytes_iterator.hpp
+++ b/sprout/iterator/bytes_iterator.hpp
@@ -60,8 +60,7 @@ namespace sprout {
 		difference_type i_;
 	private:
 		SPROUT_CONSTEXPR bytes_iterator(iterator_type it, difference_type i)
-			: it_(it)
-			, i_(i)
+			: it_(it) , i_(i)
 		{}
 		SPROUT_CONSTEXPR bytes_iterator(iterator_type it, difference_type i, next_tag)
 			: it_(i / traits_type::size() == 0 ? it : sprout::next(it))
@@ -101,7 +100,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR bytes_iterator prev() const {
 			return bytes_iterator(it_, i_ - 1, prev_tag());
 		}
-		void swap(bytes_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(bytes_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(sprout::swap(it_, other.it_)))
 		{
 			sprout::swap(it_, other.it_);
@@ -110,22 +109,22 @@ namespace sprout {
 		SPROUT_CONSTEXPR reference operator*() const {
 			return traits_type::get_byte(*it_, i_);
 		}
-		bytes_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR bytes_iterator& operator++() {
 			bytes_iterator temp(next());
 			temp.swap(*this);
 			return *this;
 		}
-		bytes_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR bytes_iterator operator++(int) {
 			bytes_iterator result(*this);
 			++*this;
 			return result;
 		}
-		bytes_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR bytes_iterator& operator--() {
 			bytes_iterator temp(prev());
 			temp.swap(*this);
 			return *this;
 		}
-		bytes_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR bytes_iterator operator--(int) {
 			bytes_iterator result(*this);
 			--*this;
 			return result;
@@ -136,12 +135,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR bytes_iterator operator-(difference_type n) const {
 			return bytes_iterator(it_, i_ - n, ra_tag());
 		}
-		bytes_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR bytes_iterator& operator+=(difference_type n) {
 			bytes_iterator temp(it_, i_ + n, ra_tag());
 			temp.swap(*this);
 			return *this;
 		}
-		bytes_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR bytes_iterator& operator-=(difference_type n) {
 			bytes_iterator temp(it_, i_ - n, ra_tag());
 			temp.swap(*this);
 			return *this;
@@ -196,7 +195,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename Iterator, typename Traits>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::bytes_iterator<Iterator, Traits>& lhs, sprout::bytes_iterator<Iterator, Traits>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
diff --git a/sprout/iterator/dft_iterator.hpp b/sprout/iterator/dft_iterator.hpp
index df6cb1a8..8d0b788d 100644
--- a/sprout/iterator/dft_iterator.hpp
+++ b/sprout/iterator/dft_iterator.hpp
@@ -74,7 +74,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR dft_iterator prev() const {
 			return dft_iterator(first_, last_, index_, index_ - 1, size_);
 		}
-		void swap(dft_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(dft_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(sprout::swap(first_, other.first_)) && SPROUT_NOEXCEPT_EXPR(sprout::swap(last_, other.last_)))
 		{
 			sprout::swap(first_, other.first_);
@@ -85,22 +85,22 @@ namespace sprout {
 		SPROUT_CONSTEXPR reference operator*() const {
 			return sprout::detail::dft_element_impl(first_, last_, index_, size_);
 		}
-		dft_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR dft_iterator& operator++() {
 			dft_iterator temp(next());
 			temp.swap(*this);
 			return *this;
 		}
-		dft_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR dft_iterator operator++(int) {
 			dft_iterator result(*this);
 			++*this;
 			return result;
 		}
-		dft_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR dft_iterator& operator--() {
 			dft_iterator temp(prev());
 			temp.swap(*this);
 			return *this;
 		}
-		dft_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR dft_iterator operator--(int) {
 			dft_iterator result(*this);
 			--*this;
 			return result;
@@ -111,12 +111,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR dft_iterator operator-(difference_type n) const {
 			return dft_iterator(first_, last_, index_, index_ - n, size_);
 		}
-		dft_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR dft_iterator& operator+=(difference_type n) {
 			dft_iterator temp(first_, last_, index_, index_ + n, size_);
 			temp.swap(*this);
 			return *this;
 		}
-		dft_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR dft_iterator& operator-=(difference_type n) {
 			dft_iterator temp(first_, last_, index_, index_ - n, size_);
 			temp.swap(*this);
 			return *this;
@@ -180,7 +180,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename Iterator>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::dft_iterator<Iterator>& lhs, sprout::dft_iterator<Iterator>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
diff --git a/sprout/iterator/filter_iterator.hpp b/sprout/iterator/filter_iterator.hpp
index 048bd41b..7d8dafe5 100644
--- a/sprout/iterator/filter_iterator.hpp
+++ b/sprout/iterator/filter_iterator.hpp
@@ -60,10 +60,10 @@ namespace sprout {
 		iterator_type last;
 		Predicate pred;
 	private:
-		void satisfy_predicate() {
+		SPROUT_CXX14_CONSTEXPR void satisfy_predicate() {
 			current = sprout::find_if(current, last, pred);
 		}
-		void satisfy_predicate_backward() {
+		SPROUT_CXX14_CONSTEXPR void satisfy_predicate_backward() {
 			while (!pred(*current)) {
 				--current;
 			}
@@ -74,7 +74,9 @@ namespace sprout {
 			, pred(pred)
 		{}
 	public:
-		filter_iterator() = default;
+		SPROUT_CONSTEXPR filter_iterator()
+			: current(), last(), pred()
+		{}
 		filter_iterator(filter_iterator const&) = default;
 		SPROUT_CONSTEXPR filter_iterator(Predicate pred, iterator_type it, iterator_type last = iterator_type())
 			: current(find_next(it, last, pred))
@@ -88,7 +90,7 @@ namespace sprout {
 			, pred(it.pred)
 		{}
 		template<typename U>
-		filter_iterator& operator=(filter_iterator<Predicate, U> const& it) {
+		SPROUT_CXX14_CONSTEXPR filter_iterator& operator=(filter_iterator<Predicate, U> const& it) {
 			filter_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -109,23 +111,23 @@ namespace sprout {
 			return &*current;
 		}
 
-		filter_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR filter_iterator& operator++() {
 			++current;
 			satisfy_predicate();
 			return *this;
 		}
-		filter_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR filter_iterator operator++(int) {
 			filter_iterator result(*this);
 			++current;
 			satisfy_predicate();
 			return result;
 		}
-		filter_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR filter_iterator& operator--() {
 			--current;
 			satisfy_predicate_backward();
 			return *this;
 		}
-		filter_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR filter_iterator operator--(int) {
 			filter_iterator temp(*this);
 			--current;
 			satisfy_predicate_backward();
@@ -137,7 +139,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR filter_iterator prev() const {
 			return filter_iterator(pred, find_prev(sprout::prev(current), pred), last, private_construct_t());
 		}
-		void swap(filter_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(filter_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(sprout::swap(current, other.current))
 			&& SPROUT_NOEXCEPT_EXPR(sprout::swap(last, other.last))
@@ -180,7 +182,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename Predicate, typename Iterator>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::filter_iterator<Predicate, Iterator>& lhs, sprout::filter_iterator<Predicate, Iterator>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
diff --git a/sprout/iterator/front_insert_iterator.hpp b/sprout/iterator/front_insert_iterator.hpp
index 503ade6c..7253796d 100644
--- a/sprout/iterator/front_insert_iterator.hpp
+++ b/sprout/iterator/front_insert_iterator.hpp
@@ -50,29 +50,26 @@ namespace sprout {
 	protected:
 		using base_type::container;
 	public:
-		SPROUT_CONSTEXPR front_insert_iterator() = default;
+		front_insert_iterator() = default;
 		explicit SPROUT_CONSTEXPR front_insert_iterator(param_type x)
 			: base_type(x)
 		{}
 		SPROUT_CONSTEXPR front_insert_iterator(front_insert_iterator const&) = default;
-		front_insert_iterator& operator=(typename container_type::value_type const& value) {
+		SPROUT_CXX14_CONSTEXPR front_insert_iterator& operator=(typename container_type::value_type const& value) {
 			container->push_front(value);
 			return *this;
 		}
-		front_insert_iterator& operator=(typename container_type::value_type&& value) {
+		SPROUT_CXX14_CONSTEXPR front_insert_iterator& operator=(typename container_type::value_type&& value) {
 			container->push_front(sprout::move(value));
 			return *this;
 		}
-		SPROUT_CONSTEXPR front_insert_iterator const& operator*() const {
+		SPROUT_CXX14_CONSTEXPR front_insert_iterator& operator*() {
 			return *this;
 		}
-		front_insert_iterator& operator*() {
+		SPROUT_CXX14_CONSTEXPR front_insert_iterator& operator++() {
 			return *this;
 		}
-		front_insert_iterator& operator++() {
-			return *this;
-		}
-		front_insert_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR front_insert_iterator operator++(int) {
 			return *this;
 		}
 
@@ -87,7 +84,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename Container>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::front_insert_iterator<Container>& lhs, sprout::front_insert_iterator<Container>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
diff --git a/sprout/iterator/idft_iterator.hpp b/sprout/iterator/idft_iterator.hpp
index 1d987f76..4778c374 100644
--- a/sprout/iterator/idft_iterator.hpp
+++ b/sprout/iterator/idft_iterator.hpp
@@ -74,7 +74,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR idft_iterator prev() const {
 			return idft_iterator(first_, last_, index_, index_ - 1, size_);
 		}
-		void swap(idft_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(idft_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(sprout::swap(first_, other.first_)) && SPROUT_NOEXCEPT_EXPR(sprout::swap(last_, other.last_)))
 		{
 			sprout::swap(first_, other.first_);
@@ -85,22 +85,22 @@ namespace sprout {
 		SPROUT_CONSTEXPR reference operator*() const {
 			return sprout::detail::idft_element_impl(first_, last_, index_, size_);
 		}
-		idft_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR idft_iterator& operator++() {
 			idft_iterator temp(next());
 			temp.swap(*this);
 			return *this;
 		}
-		idft_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR idft_iterator operator++(int) {
 			idft_iterator result(*this);
 			++*this;
 			return result;
 		}
-		idft_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR idft_iterator& operator--() {
 			idft_iterator temp(prev());
 			temp.swap(*this);
 			return *this;
 		}
-		idft_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR idft_iterator operator--(int) {
 			idft_iterator result(*this);
 			--*this;
 			return result;
@@ -111,12 +111,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR idft_iterator operator-(difference_type n) const {
 			return idft_iterator(first_, last_, index_, index_ - n, size_);
 		}
-		idft_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR idft_iterator& operator+=(difference_type n) {
 			idft_iterator temp(first_, last_, index_, index_ + n, size_);
 			temp.swap(*this);
 			return *this;
 		}
-		idft_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR idft_iterator& operator-=(difference_type n) {
 			idft_iterator temp(first_, last_, index_, index_ - n, size_);
 			temp.swap(*this);
 			return *this;
@@ -180,7 +180,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename Iterator>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::idft_iterator<Iterator>& lhs, sprout::idft_iterator<Iterator>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
diff --git a/sprout/iterator/indexed_iterator.hpp b/sprout/iterator/indexed_iterator.hpp
index 02e8febd..e8872400 100644
--- a/sprout/iterator/indexed_iterator.hpp
+++ b/sprout/iterator/indexed_iterator.hpp
@@ -42,7 +42,9 @@ namespace sprout {
 		iterator_type current;
 		index_type idx;
 	public:
-		indexed_iterator() = default;
+		SPROUT_CONSTEXPR indexed_iterator()
+			: current(), idx()
+		{}
 		SPROUT_CONSTEXPR indexed_iterator(indexed_iterator const& other)
 			: current(other.current)
 			, idx(other.idx)
@@ -57,7 +59,7 @@ namespace sprout {
 			, idx(it.index())
 		{}
 		template<typename U>
-		indexed_iterator& operator=(indexed_iterator<U> const& it) {
+		SPROUT_CXX14_CONSTEXPR indexed_iterator& operator=(indexed_iterator<U> const& it) {
 			indexed_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -74,23 +76,23 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &*current;
 		}
-		indexed_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR indexed_iterator& operator++() {
 			++current;
 			++idx;
 			return *this;
 		}
-		indexed_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR indexed_iterator operator++(int) {
 			indexed_iterator result(*this);
 			++current;
 			++idx;
 			return result;
 		}
-		indexed_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR indexed_iterator& operator--() {
 			--current;
 			--idx;
 			return *this;
 		}
-		indexed_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR indexed_iterator operator--(int) {
 			indexed_iterator temp(*this);
 			--current;
 			--idx;
@@ -102,12 +104,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR indexed_iterator operator-(difference_type n) const {
 			return indexed_iterator(current - n, idx - n);
 		}
-		indexed_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR indexed_iterator& operator+=(difference_type n) {
 			indexed_iterator temp(current + n, idx + n);
 			temp.swap(*this);
 			return *this;
 		}
-		indexed_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR indexed_iterator& operator-=(difference_type n) {
 			indexed_iterator temp(current - n, idx - n);
 			temp.swap(*this);
 			return *this;
@@ -121,7 +123,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR indexed_iterator prev() const {
 			return indexed_iterator(sprout::prev(current), idx - 1);
 		}
-		void swap(indexed_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(indexed_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(swap(current, other.current))
 			&& SPROUT_NOEXCEPT_EXPR(swap(idx, other.idx))
@@ -190,7 +192,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename Iterator>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::indexed_iterator<Iterator>& lhs, sprout::indexed_iterator<Iterator>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
diff --git a/sprout/iterator/insert_iterator.hpp b/sprout/iterator/insert_iterator.hpp
index 81a90070..585ea1aa 100644
--- a/sprout/iterator/insert_iterator.hpp
+++ b/sprout/iterator/insert_iterator.hpp
@@ -52,7 +52,9 @@ namespace sprout {
 		using base_type::container;
 		iterator iter;
 	public:
-		SPROUT_CONSTEXPR insert_iterator() = default;
+		SPROUT_CONSTEXPR insert_iterator()
+			: base_type(), iter()
+		{}
 		SPROUT_CONSTEXPR insert_iterator(param_type x, iterator pos)
 			: base_type(x), iter(pos)
 		{}
@@ -60,28 +62,25 @@ namespace sprout {
 		SPROUT_CONSTEXPR iterator position() const {
 			return iter;
 		}
-		insert_iterator& operator=(typename container_type::value_type const& value) {
+		SPROUT_CXX14_CONSTEXPR insert_iterator& operator=(typename container_type::value_type const& value) {
 			container->insert(iter, value);
 			return *this;
 		}
-		insert_iterator& operator=(typename container_type::value_type&& value) {
+		SPROUT_CXX14_CONSTEXPR insert_iterator& operator=(typename container_type::value_type&& value) {
 			container->insert(iter, sprout::move(value));
 			return *this;
 		}
-		SPROUT_CONSTEXPR insert_iterator const& operator*() const {
+		SPROUT_CXX14_CONSTEXPR insert_iterator& operator*() {
 			return *this;
 		}
-		insert_iterator& operator*() {
+		SPROUT_CXX14_CONSTEXPR insert_iterator& operator++() {
 			return *this;
 		}
-		insert_iterator& operator++() {
-			return *this;
-		}
-		insert_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR insert_iterator operator++(int) {
 			return *this;
 		}
 
-		void swap(insert_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(insert_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(base_type::swap(other))
 			&& SPROUT_NOEXCEPT_EXPR(sprout::swap(other.iter, iter))
@@ -96,7 +95,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename Container>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::insert_iterator<Container>& lhs, sprout::insert_iterator<Container>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
diff --git a/sprout/iterator/insert_range_iterator.hpp b/sprout/iterator/insert_range_iterator.hpp
index cd2bccf3..b9a2c74c 100644
--- a/sprout/iterator/insert_range_iterator.hpp
+++ b/sprout/iterator/insert_range_iterator.hpp
@@ -70,7 +70,9 @@ namespace sprout {
 				;
 		}
 	public:
-		insert_range_iterator() = default;
+		SPROUT_CONSTEXPR insert_range_iterator()
+			: current1(), pos1(), current2(), first2(), last2()
+		{}
 		insert_range_iterator(insert_range_iterator const&) = default;
 		SPROUT_CONSTEXPR insert_range_iterator(iterator_type it1, iterator_type pos1, iterator2_type it2, iterator2_type first2, iterator2_type last2)
 			: current1(it1), pos1(pos1)
@@ -82,7 +84,7 @@ namespace sprout {
 			, current2(it.base2()), first2(it.first()), last2(it.last())
 		{}
 		template<typename U, typename V>
-		insert_range_iterator& operator=(insert_range_iterator<U, V> const& it) {
+		SPROUT_CXX14_CONSTEXPR insert_range_iterator& operator=(insert_range_iterator<U, V> const& it) {
 			insert_range_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -111,7 +113,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &*(*this);
 		}
-		insert_range_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR insert_range_iterator& operator++() {
 			if (is_in_base()) {
 				++current1;
 			} else {
@@ -119,7 +121,7 @@ namespace sprout {
 			}
 			return *this;
 		}
-		insert_range_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR insert_range_iterator operator++(int) {
 			insert_range_iterator result(*this);
 			if (is_in_base()) {
 				++current1;
@@ -128,7 +130,7 @@ namespace sprout {
 			}
 			return result;
 		}
-		insert_range_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR insert_range_iterator& operator--() {
 			if (current1 != pos1 || current2 == first2) {
 				--current1;
 			} else {
@@ -136,7 +138,7 @@ namespace sprout {
 			}
 			return *this;
 		}
-		insert_range_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR insert_range_iterator operator--(int) {
 			insert_range_iterator temp(*this);
 			if (current1 != pos1 || current2 == first2) {
 				--current1;
@@ -151,12 +153,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR insert_range_iterator operator-(difference_type n) const {
 			return advance_impl(-n);
 		}
-		insert_range_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR insert_range_iterator& operator+=(difference_type n) {
 			insert_range_iterator temp(*this + n);
 			temp.swap(*this);
 			return *this;
 		}
-		insert_range_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR insert_range_iterator& operator-=(difference_type n) {
 			insert_range_iterator temp(*this - n);
 			temp.swap(*this);
 			return *this;
@@ -174,7 +176,7 @@ namespace sprout {
 				: insert_range_iterator(current1, pos1, sprout::prev(current2), first2, last2)
 				;
 		}
-		void swap(insert_range_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(insert_range_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(sprout::swap(current1, other.current1))
 			&& SPROUT_NOEXCEPT_EXPR(sprout::swap(pos1, other.pos1))
@@ -297,7 +299,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename DstIterator, typename SrcIterator>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(
 		sprout::insert_range_iterator<DstIterator, SrcIterator>& lhs,
 		sprout::insert_range_iterator<DstIterator, SrcIterator>& rhs
diff --git a/sprout/iterator/joint_iterator.hpp b/sprout/iterator/joint_iterator.hpp
index 014ec980..f89406d0 100644
--- a/sprout/iterator/joint_iterator.hpp
+++ b/sprout/iterator/joint_iterator.hpp
@@ -69,13 +69,13 @@ namespace sprout {
 				;
 		}
 	public:
-		joint_iterator() = default;
+		SPROUT_CONSTEXPR joint_iterator()
+			: current1(), last1(), first2(), current2()
+		{}
 		joint_iterator(joint_iterator const&) = default;
 		SPROUT_CONSTEXPR joint_iterator(iterator_type it1, iterator_type last1, iterator2_type first2, iterator2_type it2)
-			: current1(it1)
-			, last1(last1)
-			, first2(first2)
-			, current2(it2)
+			: current1(it1) , last1(last1)
+			, first2(first2) , current2(it2)
 		{}
 		template<typename U, typename V>
 		SPROUT_CONSTEXPR joint_iterator(joint_iterator<U, V> const& it)
@@ -85,7 +85,7 @@ namespace sprout {
 			, current2(it.base2())
 		{}
 		template<typename U, typename V>
-		joint_iterator& operator=(joint_iterator<U, V> const& it) {
+		SPROUT_CXX14_CONSTEXPR joint_iterator& operator=(joint_iterator<U, V> const& it) {
 			joint_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -111,7 +111,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &*(*this);
 		}
-		joint_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR joint_iterator& operator++() {
 			if (is_in_left()) {
 				++current1;
 			} else {
@@ -119,7 +119,7 @@ namespace sprout {
 			}
 			return *this;
 		}
-		joint_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR joint_iterator operator++(int) {
 			joint_iterator result(*this);
 			if (is_in_left()) {
 				++current1;
@@ -128,7 +128,7 @@ namespace sprout {
 			}
 			return result;
 		}
-		joint_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR joint_iterator& operator--() {
 			if (first2 == current2) {
 				--current1;
 			} else {
@@ -136,7 +136,7 @@ namespace sprout {
 			}
 			return *this;
 		}
-		joint_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR joint_iterator operator--(int) {
 			joint_iterator temp(*this);
 			if (first2 == current2) {
 				--current1;
@@ -151,12 +151,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR joint_iterator operator-(difference_type n) const {
 			return advance_impl(-n);
 		}
-		joint_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR joint_iterator& operator+=(difference_type n) {
 			joint_iterator temp(*this + n);
 			temp.swap(*this);
 			return *this;
 		}
-		joint_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR joint_iterator& operator-=(difference_type n) {
 			joint_iterator temp(*this - n);
 			temp.swap(*this);
 			return *this;
@@ -174,7 +174,7 @@ namespace sprout {
 				: joint_iterator(current1, last1, first2, sprout::prev(current2))
 				;
 		}
-		void swap(joint_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(joint_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(sprout::swap(current1, other.current1))
 			&& SPROUT_NOEXCEPT_EXPR(sprout::swap(last1, other.last1))
@@ -309,7 +309,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename LIterator, typename RIterator>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(
 		sprout::joint_iterator<LIterator, RIterator>& lhs,
 		sprout::joint_iterator<LIterator, RIterator>& rhs
diff --git a/sprout/iterator/merge_iterator.hpp b/sprout/iterator/merge_iterator.hpp
index d4ad833d..ec8e531a 100644
--- a/sprout/iterator/merge_iterator.hpp
+++ b/sprout/iterator/merge_iterator.hpp
@@ -68,7 +68,7 @@ namespace sprout {
 		Compare comp;
 		bool in_left;
 	public:
-		merge_iterator()
+		SPROUT_CONSTEXPR merge_iterator()
 			: current1(), lst1(), current2(), lst2(), comp(), in_left(true)
 		{}
 		merge_iterator(merge_iterator const&) = default;
@@ -90,7 +90,7 @@ namespace sprout {
 			, in_left(it.is_in_left())
 		{}
 		template<typename U, typename V, typename W>
-		merge_iterator& operator=(merge_iterator<U, V, W> const& it) {
+		SPROUT_CXX14_CONSTEXPR merge_iterator& operator=(merge_iterator<U, V, W> const& it) {
 			merge_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -119,7 +119,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &*(*this);
 		}
-		merge_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR merge_iterator& operator++() {
 			if (current1 != lst1) {
 				if (current2 != lst2) {
 					if (comp(*current2, *current1)) {
@@ -136,7 +136,7 @@ namespace sprout {
 			in_left = check_in_left(current1, lst1, current2, lst2, comp);
 			return *this;
 		}
-		merge_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR merge_iterator operator++(int) {
 			merge_iterator result(*this);
 			if (current1 != lst1) {
 				if (current2 != lst2) {
@@ -166,7 +166,7 @@ namespace sprout {
 				: *this
 				;
 		}
-		void swap(merge_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(merge_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(sprout::swap(current1, other.current1))
 			&& SPROUT_NOEXCEPT_EXPR(sprout::swap(lst1, other.lst1))
@@ -226,7 +226,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename LIterator, typename RIterator, typename Compare>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(
 		sprout::merge_iterator<LIterator, RIterator, Compare>& lhs,
 		sprout::merge_iterator<LIterator, RIterator, Compare>& rhs
diff --git a/sprout/iterator/next_iterator.hpp b/sprout/iterator/next_iterator.hpp
index 50780829..9357a460 100644
--- a/sprout/iterator/next_iterator.hpp
+++ b/sprout/iterator/next_iterator.hpp
@@ -43,7 +43,9 @@ namespace sprout {
 	protected:
 		iterator_type current;
 	public:
-		next_iterator() = default;
+		SPROUT_CONSTEXPR next_iterator()
+			: holder_(), current()
+		{}
 		SPROUT_CONSTEXPR next_iterator(next_iterator const& other)
 			: holder_(other.holder_), current(other.current)
 		{}
@@ -55,7 +57,7 @@ namespace sprout {
 			: holder_(*it), current(it.base())
 		{}
 		template<typename U>
-		next_iterator& operator=(next_iterator<U> const& it) {
+		SPROUT_CXX14_CONSTEXPR next_iterator& operator=(next_iterator<U> const& it) {
 			next_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -69,12 +71,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &*(*this);
 		}
-		next_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR next_iterator& operator++() {
 			holder_ = holder_type(*current);
 			++current;
 			return *this;
 		}
-		next_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR next_iterator operator++(int) {
 			next_iterator result(*this);
 			holder_ = holder_type(*current);
 			++current;
@@ -83,7 +85,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR next_iterator next() const {
 			return next_iterator(current);
 		}
-		void swap(next_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(next_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(swap(holder_, other.holder_)) && SPROUT_NOEXCEPT_EXPR(swap(current, other.current))
 			)
@@ -117,7 +119,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename Iterator>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::next_iterator<Iterator>& lhs, sprout::next_iterator<Iterator>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
diff --git a/sprout/iterator/remake_iterator.hpp b/sprout/iterator/remake_iterator.hpp
index 20c7ac77..000e69ff 100644
--- a/sprout/iterator/remake_iterator.hpp
+++ b/sprout/iterator/remake_iterator.hpp
@@ -75,7 +75,11 @@ namespace sprout {
 		difference_type begin_off;
 		difference_type end_off;
 	public:
-		remake_iterator() = default;
+		SPROUT_CONSTEXPR remake_iterator()
+			: current(), current2()
+			, fst(), lst()
+			, begin_off(), end_off()
+		{}
 		SPROUT_CONSTEXPR remake_iterator(remake_iterator const& other)
 			: current(other.current), current2(other.current2)
 			, fst(other.fst), lst(other.lst)
@@ -93,7 +97,7 @@ namespace sprout {
 			, begin_off(it.begin_offset()), end_off(it.end_offset())
 		{}
 		template<typename U, typename V>
-		remake_iterator& operator=(remake_iterator<U, V> const& it) {
+		SPROUT_CXX14_CONSTEXPR remake_iterator& operator=(remake_iterator<U, V> const& it) {
 			remake_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -125,7 +129,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &*(*this);
 		}
-		remake_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR remake_iterator& operator++() {
 			++current;
 			if (is_in_copying()) {
 				++current2;
@@ -134,7 +138,7 @@ namespace sprout {
 			--end_off;
 			return *this;
 		}
-		remake_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR remake_iterator operator++(int) {
 			remake_iterator result(*this);
 			++current;
 			if (is_in_copying()) {
@@ -144,7 +148,7 @@ namespace sprout {
 			--end_off;
 			return result;
 		}
-		remake_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR remake_iterator& operator--() {
 			--current;
 			if (begin_off < 0 && end_off >= 0) {
 				--current2;
@@ -153,7 +157,7 @@ namespace sprout {
 			++end_off;
 			return *this;
 		}
-		remake_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR remake_iterator operator--(int) {
 			remake_iterator temp(*this);
 			--current;
 			if (begin_off < 0 && end_off >= 0) {
@@ -169,12 +173,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR remake_iterator operator-(difference_type n) const {
 			return advance_impl(-n);
 		}
-		remake_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR remake_iterator& operator+=(difference_type n) {
 			remake_iterator temp(*this + n);
 			temp.swap(*this);
 			return *this;
 		}
-		remake_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR remake_iterator& operator-=(difference_type n) {
 			remake_iterator temp(*this - n);
 			temp.swap(*this);
 			return *this;
@@ -196,7 +200,7 @@ namespace sprout {
 				begin_off + 1, end_off + 1
 				);
 		}
-		void swap(remake_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(remake_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(swap(current, other.current))
 			&& SPROUT_NOEXCEPT_EXPR(swap(current2, other.current2))
@@ -321,7 +325,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename DstIterator, typename SrcIterator>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::remake_iterator<DstIterator, SrcIterator>& lhs, sprout::remake_iterator<DstIterator, SrcIterator>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
diff --git a/sprout/iterator/reverse_iterator.hpp b/sprout/iterator/reverse_iterator.hpp
index 4e110d56..25444737 100644
--- a/sprout/iterator/reverse_iterator.hpp
+++ b/sprout/iterator/reverse_iterator.hpp
@@ -52,7 +52,7 @@ namespace sprout {
 			: current(it.base())
 		{}
 		template<typename U>
-		reverse_iterator& operator=(reverse_iterator<U> const& it) {
+		SPROUT_CXX14_CONSTEXPR reverse_iterator& operator=(reverse_iterator<U> const& it) {
 			reverse_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -66,20 +66,20 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &*(*this);
 		}
-		reverse_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR reverse_iterator& operator++() {
 			--current;
 			return *this;
 		}
-		reverse_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR reverse_iterator operator++(int) {
 			reverse_iterator result(*this);
 			--current;
 			return result;
 		}
-		reverse_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR reverse_iterator& operator--() {
 			++current;
 			return *this;
 		}
-		reverse_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR reverse_iterator operator--(int) {
 			reverse_iterator temp(*this);
 			++current;
 			return temp;
@@ -90,12 +90,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR reverse_iterator operator-(difference_type n) const {
 			return reverse_iterator(current + n);
 		}
-		reverse_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR reverse_iterator& operator+=(difference_type n) {
 			reverse_iterator temp(current - n);
 			temp.swap(*this);
 			return *this;
 		}
-		reverse_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR reverse_iterator& operator-=(difference_type n) {
 			reverse_iterator temp(current + n);
 			temp.swap(*this);
 			return *this;
@@ -109,7 +109,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR reverse_iterator prev() const {
 			return reverse_iterator(sprout::next(current));
 		}
-		void swap(reverse_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(reverse_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(swap(current, other.current))
 			)
@@ -176,7 +176,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename Iterator>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::reverse_iterator<Iterator>& lhs, sprout::reverse_iterator<Iterator>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
diff --git a/sprout/iterator/sawtooth_iterator.hpp b/sprout/iterator/sawtooth_iterator.hpp
index ad4bc972..39e7bdbd 100644
--- a/sprout/iterator/sawtooth_iterator.hpp
+++ b/sprout/iterator/sawtooth_iterator.hpp
@@ -78,7 +78,7 @@ namespace sprout {
 			, phase_(it.phase_)
 		{}
 		template<typename U>
-		sawtooth_iterator& operator=(sawtooth_iterator<U> const& it) {
+		SPROUT_CXX14_CONSTEXPR sawtooth_iterator& operator=(sawtooth_iterator<U> const& it) {
 			sawtooth_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -103,20 +103,20 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &operator*()();
 		}
-		sawtooth_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR sawtooth_iterator& operator++() {
 			++index_;
 			return *this;
 		}
-		sawtooth_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR sawtooth_iterator operator++(int) {
 			sawtooth_iterator result(*this);
 			++index_;
 			return result;
 		}
-		sawtooth_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR sawtooth_iterator& operator--() {
 			--index_;
 			return *this;
 		}
-		sawtooth_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR sawtooth_iterator operator--(int) {
 			sawtooth_iterator temp(*this);
 			--index_;
 			return temp;
@@ -127,12 +127,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR sawtooth_iterator operator-(difference_type n) const {
 			return sawtooth_iterator(*this, index_ - n);
 		}
-		sawtooth_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR sawtooth_iterator& operator+=(difference_type n) {
 			sawtooth_iterator temp(*this, index_ + n);
 			temp.swap(*this);
 			return *this;
 		}
-		sawtooth_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR sawtooth_iterator& operator-=(difference_type n) {
 			sawtooth_iterator temp(*this, index_ - n);
 			temp.swap(*this);
 			return *this;
@@ -148,7 +148,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR sawtooth_iterator prev() const {
 			return sawtooth_iterator(*this, index_ - 1);
 		}
-		void swap(sawtooth_iterator& other) SPROUT_NOEXCEPT {
+		SPROUT_CXX14_CONSTEXPR void swap(sawtooth_iterator& other) SPROUT_NOEXCEPT {
 			sprout::swap(index_, other.index_);
 			sprout::swap(frequency_, other.frequency_);
 			sprout::swap(amplitude_, other.amplitude_);
@@ -201,7 +201,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename Value>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::sawtooth_iterator<Value>& lhs, sprout::sawtooth_iterator<Value>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
diff --git a/sprout/iterator/set_difference_iterator.hpp b/sprout/iterator/set_difference_iterator.hpp
index 98400ad7..8657d869 100644
--- a/sprout/iterator/set_difference_iterator.hpp
+++ b/sprout/iterator/set_difference_iterator.hpp
@@ -86,7 +86,7 @@ namespace sprout {
 			, comp(it.compare())
 		{}
 		template<typename U, typename V, typename W>
-		set_difference_iterator& operator=(set_difference_iterator<U, V, W> const& it) {
+		SPROUT_CXX14_CONSTEXPR set_difference_iterator& operator=(set_difference_iterator<U, V, W> const& it) {
 			set_difference_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -115,11 +115,11 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &*(*this);
 		}
-		set_difference_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR set_difference_iterator& operator++() {
 			current = sprout::next_difference(current.first, lst1, current.second, lst2, comp);
 			return *this;
 		}
-		set_difference_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR set_difference_iterator operator++(int) {
 			set_difference_iterator result(*this);
 			current = sprout::next_difference(current.first, lst1, current.second, lst2, comp);
 			return result;
@@ -130,7 +130,7 @@ namespace sprout {
 				sprout::next_difference(current.first, lst1, current.second, lst2, comp)
 				);
 		}
-		void swap(set_difference_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(set_difference_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(sprout::swap(current, other.current))
 			&& SPROUT_NOEXCEPT_EXPR(sprout::swap(lst1, other.lst1))
@@ -186,7 +186,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename LIterator, typename RIterator, typename Compare>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(
 		sprout::set_difference_iterator<LIterator, RIterator, Compare>& lhs,
 		sprout::set_difference_iterator<LIterator, RIterator, Compare>& rhs
diff --git a/sprout/iterator/set_intersection_iterator.hpp b/sprout/iterator/set_intersection_iterator.hpp
index c5e50930..34132c93 100644
--- a/sprout/iterator/set_intersection_iterator.hpp
+++ b/sprout/iterator/set_intersection_iterator.hpp
@@ -86,7 +86,7 @@ namespace sprout {
 			, comp(it.compare())
 		{}
 		template<typename U, typename V, typename W>
-		set_intersection_iterator& operator=(set_intersection_iterator<U, V, W> const& it) {
+		SPROUT_CXX14_CONSTEXPR set_intersection_iterator& operator=(set_intersection_iterator<U, V, W> const& it) {
 			set_intersection_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -115,11 +115,11 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &*(*this);
 		}
-		set_intersection_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR set_intersection_iterator& operator++() {
 			current = sprout::next_intersection(current.first, lst1, current.second, lst2, comp);
 			return *this;
 		}
-		set_intersection_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR set_intersection_iterator operator++(int) {
 			set_intersection_iterator result(*this);
 			current = sprout::next_intersection(current.first, lst1, current.second, lst2, comp);
 			return result;
@@ -130,7 +130,7 @@ namespace sprout {
 				sprout::next_intersection(current.first, lst1, current.second, lst2, comp)
 				);
 		}
-		void swap(set_intersection_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(set_intersection_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(sprout::swap(current, other.current))
 			&& SPROUT_NOEXCEPT_EXPR(sprout::swap(lst1, other.lst1))
@@ -186,7 +186,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename LIterator, typename RIterator, typename Compare>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(
 		sprout::set_intersection_iterator<LIterator, RIterator, Compare>& lhs,
 		sprout::set_intersection_iterator<LIterator, RIterator, Compare>& rhs
diff --git a/sprout/iterator/set_symmetric_difference_iterator.hpp b/sprout/iterator/set_symmetric_difference_iterator.hpp
index 49bf251c..ff9948b1 100644
--- a/sprout/iterator/set_symmetric_difference_iterator.hpp
+++ b/sprout/iterator/set_symmetric_difference_iterator.hpp
@@ -151,7 +151,7 @@ namespace sprout {
 			: impl_type(pair_type(it.base(), it.base2()), it.last1(), it.last2(), it.compare(), it.is_in_left())
 		{}
 		template<typename U, typename V, typename W>
-		set_symmetric_difference_iterator& operator=(set_symmetric_difference_iterator<U, V, W> const& it) {
+		SPROUT_CXX14_CONSTEXPR set_symmetric_difference_iterator& operator=(set_symmetric_difference_iterator<U, V, W> const& it) {
 			set_symmetric_difference_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -180,12 +180,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &*(*this);
 		}
-		set_symmetric_difference_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR set_symmetric_difference_iterator& operator++() {
 			current = sprout::next_symmetric_difference(current.first, lst1, current.second, lst2, comp);
 			in_left = check_in_left(current.first, lst1, current.second, lst2, comp);
 			return *this;
 		}
-		set_symmetric_difference_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR set_symmetric_difference_iterator operator++(int) {
 			set_symmetric_difference_iterator result(*this);
 			current = sprout::next_symmetric_difference(current.first, lst1, current.second, lst2, comp);
 			in_left = check_in_left(current.first, lst1, current.second, lst2, comp);
@@ -197,7 +197,7 @@ namespace sprout {
 				sprout::next_symmetric_difference(current.first, lst1, current.second, lst2, comp)
 				);
 		}
-		void swap(set_symmetric_difference_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(set_symmetric_difference_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(sprout::swap(current, other.current))
 			&& SPROUT_NOEXCEPT_EXPR(sprout::swap(lst1, other.lst1))
@@ -254,7 +254,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename LIterator, typename RIterator, typename Compare>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(
 		sprout::set_symmetric_difference_iterator<LIterator, RIterator, Compare>& lhs,
 		sprout::set_symmetric_difference_iterator<LIterator, RIterator, Compare>& rhs
diff --git a/sprout/iterator/set_union_iterator.hpp b/sprout/iterator/set_union_iterator.hpp
index ff91a33e..de79865b 100644
--- a/sprout/iterator/set_union_iterator.hpp
+++ b/sprout/iterator/set_union_iterator.hpp
@@ -101,7 +101,7 @@ namespace sprout {
 			, in_left(it.is_in_left())
 		{}
 		template<typename U, typename V, typename W>
-		set_union_iterator& operator=(set_union_iterator<U, V, W> const& it) {
+		SPROUT_CXX14_CONSTEXPR set_union_iterator& operator=(set_union_iterator<U, V, W> const& it) {
 			set_union_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -130,12 +130,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &*(*this);
 		}
-		set_union_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR set_union_iterator& operator++() {
 			current = sprout::next_union(current.first, lst1, current.second, lst2, comp);
 			in_left = check_in_left(current.first, lst1, current.second, lst2, comp);
 			return *this;
 		}
-		set_union_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR set_union_iterator operator++(int) {
 			set_union_iterator result(*this);
 			current = sprout::next_union(current.first, lst1, current.second, lst2, comp);
 			in_left = check_in_left(current.first, lst1, current.second, lst2, comp);
@@ -147,7 +147,7 @@ namespace sprout {
 				sprout::next_union(current.first, lst1, current.second, lst2, comp)
 				);
 		}
-		void swap(set_union_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(set_union_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(sprout::swap(current, other.current))
 			&& SPROUT_NOEXCEPT_EXPR(sprout::swap(lst1, other.lst1))
@@ -204,7 +204,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename LIterator, typename RIterator, typename Compare>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(
 		sprout::set_union_iterator<LIterator, RIterator, Compare>& lhs,
 		sprout::set_union_iterator<LIterator, RIterator, Compare>& rhs
diff --git a/sprout/iterator/sinusoid_iterator.hpp b/sprout/iterator/sinusoid_iterator.hpp
index 0e3207d0..2fb61193 100644
--- a/sprout/iterator/sinusoid_iterator.hpp
+++ b/sprout/iterator/sinusoid_iterator.hpp
@@ -84,7 +84,7 @@ namespace sprout {
 			, d_(it.d_)
 		{}
 		template<typename U>
-		sinusoid_iterator& operator=(sinusoid_iterator<U> const& it) {
+		SPROUT_CXX14_CONSTEXPR sinusoid_iterator& operator=(sinusoid_iterator<U> const& it) {
 			sinusoid_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -110,20 +110,20 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &operator*()();
 		}
-		sinusoid_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR sinusoid_iterator& operator++() {
 			++index_;
 			return *this;
 		}
-		sinusoid_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR sinusoid_iterator operator++(int) {
 			sinusoid_iterator result(*this);
 			++index_;
 			return result;
 		}
-		sinusoid_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR sinusoid_iterator& operator--() {
 			--index_;
 			return *this;
 		}
-		sinusoid_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR sinusoid_iterator operator--(int) {
 			sinusoid_iterator temp(*this);
 			--index_;
 			return temp;
@@ -134,12 +134,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR sinusoid_iterator operator-(difference_type n) const {
 			return sinusoid_iterator(*this, index_ - n);
 		}
-		sinusoid_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR sinusoid_iterator& operator+=(difference_type n) {
 			sinusoid_iterator temp(*this, index_ + n);
 			temp.swap(*this);
 			return *this;
 		}
-		sinusoid_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR sinusoid_iterator& operator-=(difference_type n) {
 			sinusoid_iterator temp(*this, index_ - n);
 			temp.swap(*this);
 			return *this;
@@ -156,7 +156,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR sinusoid_iterator prev() const {
 			return sinusoid_iterator(*this, index_ - 1);
 		}
-		void swap(sinusoid_iterator& other) SPROUT_NOEXCEPT {
+		SPROUT_CXX14_CONSTEXPR void swap(sinusoid_iterator& other) SPROUT_NOEXCEPT {
 			sprout::swap(index_, other.index_);
 			sprout::swap(frequency_, other.frequency_);
 			sprout::swap(amplitude_, other.amplitude_);
@@ -210,7 +210,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename Value>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::sinusoid_iterator<Value>& lhs, sprout::sinusoid_iterator<Value>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
diff --git a/sprout/iterator/size_enum_iterator.hpp b/sprout/iterator/size_enum_iterator.hpp
index 7b4b3d46..6f172e55 100644
--- a/sprout/iterator/size_enum_iterator.hpp
+++ b/sprout/iterator/size_enum_iterator.hpp
@@ -50,7 +50,9 @@ namespace sprout {
 	protected:
 		iterator_type current;
 	public:
-		size_enum_iterator() = default;
+		SPROUT_CONSTEXPR size_enum_iterator()
+			: current()
+		{}
 		size_enum_iterator(size_enum_iterator const&) = default;
 		explicit SPROUT_CONSTEXPR size_enum_iterator(iterator_type it)
 			: current(it)
@@ -60,7 +62,7 @@ namespace sprout {
 			: current(it.current)
 		{}
 		template<typename U>
-		size_enum_iterator& operator=(size_enum_iterator<U> const& it) {
+		SPROUT_CXX14_CONSTEXPR size_enum_iterator& operator=(size_enum_iterator<U> const& it) {
 			size_enum_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -77,20 +79,20 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &sprout::size(*current);
 		}
-		size_enum_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR size_enum_iterator& operator++() {
 			++current;
 			return *this;
 		}
-		size_enum_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR size_enum_iterator operator++(int) {
 			size_enum_iterator result(*this);
 			++current;
 			return result;
 		}
-		size_enum_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR size_enum_iterator& operator--() {
 			--current;
 			return *this;
 		}
-		size_enum_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR size_enum_iterator operator--(int) {
 			size_enum_iterator temp(*this);
 			--current;
 			return temp;
@@ -101,12 +103,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR size_enum_iterator operator-(difference_type n) const {
 			return size_enum_iterator(current - n);
 		}
-		size_enum_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR size_enum_iterator& operator+=(difference_type n) {
 			size_enum_iterator temp(current + n);
 			temp.swap(*this);
 			return *this;
 		}
-		size_enum_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR size_enum_iterator& operator-=(difference_type n) {
 			size_enum_iterator temp(current - n);
 			temp.swap(*this);
 			return *this;
@@ -120,7 +122,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR size_enum_iterator prev() const {
 			return size_enum_iterator(sprout::prev(current));
 		}
-		void swap(size_enum_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(size_enum_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(sprout::swap(current, other.current)))
 		{
 			sprout::swap(current, other.current);
@@ -160,7 +162,9 @@ namespace sprout {
 		value_type sep_size;
 		bool is_sep;
 	public:
-		size_enum_iterator() = default;
+		SPROUT_CONSTEXPR size_enum_iterator()
+			: current(), sep_size(), is_sep()
+		{}
 		size_enum_iterator(size_enum_iterator const&) = default;
 		explicit SPROUT_CONSTEXPR size_enum_iterator(iterator_type it, value_type size = 0, bool sep = false)
 			: current(it)
@@ -194,7 +198,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &(is_sep ? sep_size : sprout::size(*current));
 		}
-		size_enum_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR size_enum_iterator& operator++() {
 			if (is_sep) {
 				++current;
 				is_sep = false;
@@ -203,7 +207,7 @@ namespace sprout {
 			}
 			return *this;
 		}
-		size_enum_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR size_enum_iterator operator++(int) {
 			size_enum_iterator result(*this);
 			if (is_sep) {
 				++current;
@@ -213,7 +217,7 @@ namespace sprout {
 			}
 			return result;
 		}
-		size_enum_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR size_enum_iterator& operator--() {
 			if (is_sep) {
 				is_sep = false;
 			} else {
@@ -222,7 +226,7 @@ namespace sprout {
 			}
 			return *this;
 		}
-		size_enum_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR size_enum_iterator operator--(int) {
 			size_enum_iterator temp(*this);
 			if (is_sep) {
 				is_sep = false;
@@ -238,12 +242,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR size_enum_iterator operator-(difference_type n) const {
 			return size_enum_iterator(current - (n - is_sep) / 2, sep_size, (n - is_sep) % 2);
 		}
-		size_enum_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR size_enum_iterator& operator+=(difference_type n) {
 			size_enum_iterator temp(current + (n + is_sep) / 2, sep_size, (n + is_sep) % 2);
 			temp.swap(*this);
 			return *this;
 		}
-		size_enum_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR size_enum_iterator& operator-=(difference_type n) {
 			size_enum_iterator temp(current - (n - is_sep) / 2, sep_size, (n - is_sep) % 2);
 			temp.swap(*this);
 			return *this;
@@ -263,7 +267,7 @@ namespace sprout {
 				: size_enum_iterator(sprout::prev(current), sep_size, true)
 				;
 		}
-		void swap(size_enum_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(size_enum_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(sprout::swap(current, other.current)))
 		{
 			sprout::swap(current, other.current);
@@ -402,7 +406,8 @@ namespace sprout {
 	// swap
 	//
 	template<typename Iterator, bool Separated>
-	void swap(sprout::size_enum_iterator<Iterator, Separated>& lhs, sprout::size_enum_iterator<Iterator, Separated>& rhs)
+	inline SPROUT_CXX14_CONSTEXPR void
+	swap(sprout::size_enum_iterator<Iterator, Separated>& lhs, sprout::size_enum_iterator<Iterator, Separated>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
 		lhs.swap(rhs);
diff --git a/sprout/iterator/square_iterator.hpp b/sprout/iterator/square_iterator.hpp
index ba36c5d2..30c98175 100644
--- a/sprout/iterator/square_iterator.hpp
+++ b/sprout/iterator/square_iterator.hpp
@@ -84,7 +84,7 @@ namespace sprout {
 			, duty_(it.duty_)
 		{}
 		template<typename U>
-		square_iterator& operator=(square_iterator<U> const& it) {
+		SPROUT_CXX14_CONSTEXPR square_iterator& operator=(square_iterator<U> const& it) {
 			square_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -112,20 +112,20 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &operator*()();
 		}
-		square_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR square_iterator& operator++() {
 			++index_;
 			return *this;
 		}
-		square_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR square_iterator operator++(int) {
 			square_iterator result(*this);
 			++index_;
 			return result;
 		}
-		square_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR square_iterator& operator--() {
 			--index_;
 			return *this;
 		}
-		square_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR square_iterator operator--(int) {
 			square_iterator temp(*this);
 			--index_;
 			return temp;
@@ -136,12 +136,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR square_iterator operator-(difference_type n) const {
 			return square_iterator(*this, index_ - n);
 		}
-		square_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR square_iterator& operator+=(difference_type n) {
 			square_iterator temp(*this, index_ + n);
 			temp.swap(*this);
 			return *this;
 		}
-		square_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR square_iterator& operator-=(difference_type n) {
 			square_iterator temp(*this, index_ - n);
 			temp.swap(*this);
 			return *this;
@@ -157,7 +157,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR square_iterator prev() const {
 			return square_iterator(*this, index_ - 1);
 		}
-		void swap(square_iterator& other) SPROUT_NOEXCEPT {
+		SPROUT_CXX14_CONSTEXPR void swap(square_iterator& other) SPROUT_NOEXCEPT {
 			sprout::swap(index_, other.index_);
 			sprout::swap(frequency_, other.frequency_);
 			sprout::swap(amplitude_, other.amplitude_);
@@ -211,7 +211,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename Value>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::square_iterator<Value>& lhs, sprout::square_iterator<Value>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
diff --git a/sprout/iterator/step_iterator.hpp b/sprout/iterator/step_iterator.hpp
index bbbf9dda..c61d1e02 100644
--- a/sprout/iterator/step_iterator.hpp
+++ b/sprout/iterator/step_iterator.hpp
@@ -79,7 +79,7 @@ namespace sprout {
 			, back(get_back(it.base(), it.width(), it.end())), is_last(it.is_end())
 		{}
 		template<typename U>
-		step_iterator& operator=(step_iterator<U> const& it) {
+		SPROUT_CXX14_CONSTEXPR step_iterator& operator=(step_iterator<U> const& it) {
 			step_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -102,14 +102,14 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &*current;
 		}
-		step_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR step_iterator& operator++() {
 			if (current == back) {
 				is_last = true;
 			}
 			current += next_distance(*this, 1);
 			return *this;
 		}
-		step_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR step_iterator operator++(int) {
 			step_iterator result(*this);
 			if (current == back) {
 				is_last = true;
@@ -117,14 +117,14 @@ namespace sprout {
 			current += next_distance(*this, 1);
 			return result;
 		}
-		step_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR step_iterator& operator--() {
 			current += next_distance(*this, -1);
 			if (current != back) {
 				is_last = false;
 			}
 			return *this;
 		}
-		step_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR step_iterator operator--(int) {
 			step_iterator temp(*this);
 			current += next_distance(*this, -1);
 			if (current != back) {
@@ -138,12 +138,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR step_iterator operator-(difference_type n) const {
 			return step_iterator(*this, -n);
 		}
-		step_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR step_iterator& operator+=(difference_type n) {
 			step_iterator temp(*this, n);
 			temp.swap(*this);
 			return *this;
 		}
-		step_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR step_iterator& operator-=(difference_type n) {
 			step_iterator temp(*this, -n);
 			temp.swap(*this);
 			return *this;
@@ -157,7 +157,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR step_iterator prev() const {
 			return step_iterator(*this, -1);
 		}
-		void swap(step_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(step_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(swap(current, other.current))
 			&& SPROUT_NOEXCEPT_EXPR(swap(last, other.last))
@@ -233,7 +233,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename Iterator>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::step_iterator<Iterator>& lhs, sprout::step_iterator<Iterator>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
diff --git a/sprout/iterator/transform_iterator.hpp b/sprout/iterator/transform_iterator.hpp
index aef5128a..010a47e6 100644
--- a/sprout/iterator/transform_iterator.hpp
+++ b/sprout/iterator/transform_iterator.hpp
@@ -70,7 +70,9 @@ namespace sprout {
 		iterator2_type current2;
 		BinaryFunction func;
 	public:
-		transform_iterator() = default;
+		SPROUT_CONSTEXPR transform_iterator()
+			: current(), current2(), func()
+		{}
 		transform_iterator(transform_iterator const&) = default;
 		SPROUT_CONSTEXPR transform_iterator(iterator_type it, iterator2_type it2)
 			: current(it)
@@ -88,7 +90,7 @@ namespace sprout {
 			, func(it.func)
 		{}
 		template<typename U, typename V, typename W>
-		transform_iterator& operator=(transform_iterator<U, V, W> const& it) {
+		SPROUT_CXX14_CONSTEXPR transform_iterator& operator=(transform_iterator<U, V, W> const& it) {
 			transform_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -108,23 +110,23 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &func(*current, *current2);
 		}
-		transform_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR transform_iterator& operator++() {
 			++current;
 			++current2;
 			return *this;
 		}
-		transform_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR transform_iterator operator++(int) {
 			transform_iterator result(*this);
 			++current;
 			++current2;
 			return result;
 		}
-		transform_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR transform_iterator& operator--() {
 			--current;
 			--current2;
 			return *this;
 		}
-		transform_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR transform_iterator operator--(int) {
 			transform_iterator temp(*this);
 			--current;
 			--current2;
@@ -136,12 +138,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR transform_iterator operator-(difference_type n) const {
 			return transform_iterator(current - n, current2 - n, func);
 		}
-		transform_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR transform_iterator& operator+=(difference_type n) {
 			transform_iterator temp(current + n, current2 + n, func);
 			temp.swap(*this);
 			return *this;
 		}
-		transform_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR transform_iterator& operator-=(difference_type n) {
 			transform_iterator temp(current - n, current2 - n, func);
 			temp.swap(*this);
 			return *this;
@@ -155,7 +157,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR transform_iterator prev() const {
 			return transform_iterator(sprout::prev(current), sprout::prev(current2), func);
 		}
-		void swap(transform_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(transform_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(sprout::swap(current, other.current))
 			&& SPROUT_NOEXCEPT_EXPR(sprout::swap(current2, other.current2))
@@ -205,7 +207,9 @@ namespace sprout {
 		iterator_type current;
 		UnaryFunction func;
 	public:
-		transform_iterator() = default;
+		SPROUT_CONSTEXPR transform_iterator()
+			: current(), func()
+		{}
 		transform_iterator(transform_iterator const&) = default;
 		explicit SPROUT_CONSTEXPR transform_iterator(iterator_type it)
 			: current(it)
@@ -220,7 +224,7 @@ namespace sprout {
 			, func(it.func)
 		{}
 		template<typename U, typename V>
-		transform_iterator& operator=(transform_iterator<U, V> const& it) {
+		SPROUT_CXX14_CONSTEXPR transform_iterator& operator=(transform_iterator<U, V> const& it) {
 			transform_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -237,20 +241,20 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &func(*current);
 		}
-		transform_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR transform_iterator& operator++() {
 			++current;
 			return *this;
 		}
-		transform_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR transform_iterator operator++(int) {
 			transform_iterator result(*this);
 			++current;
 			return result;
 		}
-		transform_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR transform_iterator& operator--() {
 			--current;
 			return *this;
 		}
-		transform_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR transform_iterator operator--(int) {
 			transform_iterator temp(*this);
 			--current;
 			return temp;
@@ -261,12 +265,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR transform_iterator operator-(difference_type n) const {
 			return transform_iterator(current - n, func);
 		}
-		transform_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR transform_iterator& operator+=(difference_type n) {
 			transform_iterator temp(current + n, func);
 			temp.swap(*this);
 			return *this;
 		}
-		transform_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR transform_iterator& operator-=(difference_type n) {
 			transform_iterator temp(current - n, func);
 			temp.swap(*this);
 			return *this;
@@ -280,7 +284,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR transform_iterator prev() const {
 			return transform_iterator(sprout::prev(current), func);
 		}
-		void swap(transform_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(transform_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(sprout::swap(current, other.current))
 			&& SPROUT_NOEXCEPT_EXPR(sprout::swap(func, other.func))
@@ -395,7 +399,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename UnaryOrBinaryFunction, typename LIterator, typename RIterator>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(
 		sprout::transform_iterator<UnaryOrBinaryFunction, LIterator, RIterator>& lhs,
 		sprout::transform_iterator<UnaryOrBinaryFunction, LIterator, RIterator>& rhs
diff --git a/sprout/iterator/triangle_iterator.hpp b/sprout/iterator/triangle_iterator.hpp
index b2b621ea..b19b9c49 100644
--- a/sprout/iterator/triangle_iterator.hpp
+++ b/sprout/iterator/triangle_iterator.hpp
@@ -78,7 +78,7 @@ namespace sprout {
 			, phase_(it.phase_)
 		{}
 		template<typename U>
-		triangle_iterator& operator=(triangle_iterator<U> const& it) {
+		SPROUT_CXX14_CONSTEXPR triangle_iterator& operator=(triangle_iterator<U> const& it) {
 			triangle_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -103,20 +103,20 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &operator*()();
 		}
-		triangle_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR triangle_iterator& operator++() {
 			++index_;
 			return *this;
 		}
-		triangle_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR triangle_iterator operator++(int) {
 			triangle_iterator result(*this);
 			++index_;
 			return result;
 		}
-		triangle_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR triangle_iterator& operator--() {
 			--index_;
 			return *this;
 		}
-		triangle_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR triangle_iterator operator--(int) {
 			triangle_iterator temp(*this);
 			--index_;
 			return temp;
@@ -127,12 +127,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR triangle_iterator operator-(difference_type n) const {
 			return triangle_iterator(*this, index_ - n);
 		}
-		triangle_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR triangle_iterator& operator+=(difference_type n) {
 			triangle_iterator temp(*this, index_ + n);
 			temp.swap(*this);
 			return *this;
 		}
-		triangle_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR triangle_iterator& operator-=(difference_type n) {
 			triangle_iterator temp(*this, index_ - n);
 			temp.swap(*this);
 			return *this;
@@ -148,7 +148,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR triangle_iterator prev() const {
 			return triangle_iterator(*this, index_ - 1);
 		}
-		void swap(triangle_iterator& other) SPROUT_NOEXCEPT {
+		SPROUT_CXX14_CONSTEXPR void swap(triangle_iterator& other) SPROUT_NOEXCEPT {
 			sprout::swap(index_, other.index_);
 			sprout::swap(frequency_, other.frequency_);
 			sprout::swap(amplitude_, other.amplitude_);
@@ -225,7 +225,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename Value>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::triangle_iterator<Value>& lhs, sprout::triangle_iterator<Value>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
diff --git a/sprout/iterator/valued_iterator.hpp b/sprout/iterator/valued_iterator.hpp
index b1f27355..12d4c6b9 100644
--- a/sprout/iterator/valued_iterator.hpp
+++ b/sprout/iterator/valued_iterator.hpp
@@ -46,7 +46,9 @@ namespace sprout {
 		iterator_type current;
 		holder_type holder;
 	public:
-		valued_iterator() = default;
+		SPROUT_CONSTEXPR valued_iterator()
+			: current(), holder()
+		{}
 		SPROUT_CONSTEXPR valued_iterator(valued_iterator const& other)
 			: current(other.current)
 			, holder(other.holder)
@@ -69,7 +71,7 @@ namespace sprout {
 			, holder(it.get())
 		{}
 		template<typename U, typename V>
-		valued_iterator& operator=(valued_iterator<U, V> const& it) {
+		SPROUT_CXX14_CONSTEXPR valued_iterator& operator=(valued_iterator<U, V> const& it) {
 			valued_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -86,20 +88,20 @@ namespace sprout {
 		SPROUT_CONSTEXPR pointer operator->() const {
 			return &*current;
 		}
-		valued_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR valued_iterator& operator++() {
 			++current;
 			return *this;
 		}
-		valued_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR valued_iterator operator++(int) {
 			valued_iterator result(*this);
 			++current;
 			return result;
 		}
-		valued_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR valued_iterator& operator--() {
 			--current;
 			return *this;
 		}
-		valued_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR valued_iterator operator--(int) {
 			valued_iterator temp(*this);
 			--current;
 			return temp;
@@ -110,12 +112,12 @@ namespace sprout {
 		SPROUT_CONSTEXPR valued_iterator operator-(difference_type n) const {
 			return valued_iterator(current - n, holder);
 		}
-		valued_iterator& operator+=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR valued_iterator& operator+=(difference_type n) {
 			valued_iterator temp(current + n, holder);
 			temp.swap(*this);
 			return *this;
 		}
-		valued_iterator& operator-=(difference_type n) {
+		SPROUT_CXX14_CONSTEXPR valued_iterator& operator-=(difference_type n) {
 			valued_iterator temp(current - n, holder);
 			temp.swap(*this);
 			return *this;
@@ -129,7 +131,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR valued_iterator prev() const {
 			return valued_iterator(sprout::prev(current), holder);
 		}
-		void swap(valued_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(valued_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(swap(current, other.current))
 			&& SPROUT_NOEXCEPT_EXPR(swap(holder, other.holder))
@@ -198,7 +200,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename Iterator, typename T>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::valued_iterator<Iterator, T>& lhs, sprout::valued_iterator<Iterator, T>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{
diff --git a/sprout/iterator/while_iterator.hpp b/sprout/iterator/while_iterator.hpp
index 4ea53554..20289c1d 100644
--- a/sprout/iterator/while_iterator.hpp
+++ b/sprout/iterator/while_iterator.hpp
@@ -64,12 +64,12 @@ namespace sprout {
 		iterator_type last;
 		Predicate pred;
 	private:
-		void satisfy_predicate() {
+		SPROUT_CXX14_CONSTEXPR void satisfy_predicate() {
 			if (!pred(*current)) {
 				current = last;
 			}
 		}
-		void satisfy_predicate_backward() {
+		SPROUT_CXX14_CONSTEXPR void satisfy_predicate_backward() {
 			while (!pred(*current)) {
 				--current;
 			}
@@ -80,7 +80,9 @@ namespace sprout {
 			, pred(pred)
 		{}
 	public:
-		while_iterator() = default;
+		SPROUT_CONSTEXPR while_iterator()
+			: current(), last(), pred()
+		{}
 		while_iterator(while_iterator const&) = default;
 		SPROUT_CONSTEXPR while_iterator(Predicate pred, iterator_type it, iterator_type last = iterator_type())
 			: current(find_next(it, last, pred))
@@ -94,7 +96,7 @@ namespace sprout {
 			, pred(it.pred)
 		{}
 		template<typename U>
-		while_iterator& operator=(while_iterator<Predicate, U> const& it) {
+		SPROUT_CXX14_CONSTEXPR while_iterator& operator=(while_iterator<Predicate, U> const& it) {
 			while_iterator temp(it);
 			temp.swap(*this);
 			return *this;
@@ -115,23 +117,23 @@ namespace sprout {
 			return &*current;
 		}
 
-		while_iterator& operator++() {
+		SPROUT_CXX14_CONSTEXPR while_iterator& operator++() {
 			++current;
 			satisfy_predicate();
 			return *this;
 		}
-		while_iterator operator++(int) {
+		SPROUT_CXX14_CONSTEXPR while_iterator operator++(int) {
 			while_iterator result(*this);
 			++current;
 			satisfy_predicate();
 			return result;
 		}
-		while_iterator& operator--() {
+		SPROUT_CXX14_CONSTEXPR while_iterator& operator--() {
 			--current;
 			satisfy_predicate_backward();
 			return *this;
 		}
-		while_iterator operator--(int) {
+		SPROUT_CXX14_CONSTEXPR while_iterator operator--(int) {
 			while_iterator temp(*this);
 			--current;
 			satisfy_predicate_backward();
@@ -143,7 +145,7 @@ namespace sprout {
 		SPROUT_CONSTEXPR while_iterator prev() const {
 			return while_iterator(pred, find_prev(sprout::prev(current), pred), last, private_construct_t());
 		}
-		void swap(while_iterator& other)
+		SPROUT_CXX14_CONSTEXPR void swap(while_iterator& other)
 		SPROUT_NOEXCEPT_EXPR(
 			SPROUT_NOEXCEPT_EXPR(sprout::swap(current, other.current))
 			&& SPROUT_NOEXCEPT_EXPR(sprout::swap(last, other.last))
@@ -186,7 +188,7 @@ namespace sprout {
 	// swap
 	//
 	template<typename Predicate, typename Iterator>
-	inline void
+	inline SPROUT_CXX14_CONSTEXPR void
 	swap(sprout::while_iterator<Predicate, Iterator>& lhs, sprout::while_iterator<Predicate, Iterator>& rhs)
 	SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
 	{