diff --git a/sprout/algorithm/fixed/generate.hpp b/sprout/algorithm/fixed/generate.hpp
index d31d0651..ada409c3 100644
--- a/sprout/algorithm/fixed/generate.hpp
+++ b/sprout/algorithm/fixed/generate.hpp
@@ -6,7 +6,7 @@
 #include <sprout/config.hpp>
 #include <sprout/fixed_container/traits.hpp>
 #include <sprout/fixed_container/functions.hpp>
-#include <sprout/iterator/operation.hpp>
+#include <sprout/iterator/operation.hpp>
 #include <sprout/algorithm/fixed/result_of.hpp>
 
 namespace sprout {
@@ -82,7 +82,7 @@ namespace sprout {
 				Args const&... args
 				)
 			{
-				return sizeof...(Args) < offset
+				return sizeof...(Args) < static_cast<std::size_t>(offset)
 					? generate_impl_3<InitSize>(cont, gen, offset, args..., call_gen<InitSize, Container>(gen, args...))
 					: generate_impl_4(cont, args...)
 					;
@@ -161,7 +161,7 @@ namespace sprout {
 				Args const&... args
 				)
 			{
-				return sizeof...(Args) - InitSize < offset
+				return sizeof...(Args) - InitSize < static_cast<std::size_t>(offset)
 					? generate_impl_1<InitSize>(cont, gen, offset, size, args..., *sprout::next(sprout::fixed_begin(cont), sizeof...(Args) - InitSize))
 					: generate_impl_2<InitSize>(cont, gen, offset, size, InitSize, args...)
 					;
diff --git a/sprout/algorithm/string.hpp b/sprout/algorithm/string.hpp
new file mode 100644
index 00000000..44386251
--- /dev/null
+++ b/sprout/algorithm/string.hpp
@@ -0,0 +1,7 @@
+#ifndef SPROUT_ALGORITHM_STRING_HPP
+#define SPROUT_ALGORITHM_STRING_HPP
+
+#include <sprout/config.hpp>
+#include <sprout/algorithm/string/join.hpp>
+
+#endif	// #ifndef SPROUT_ALGORITHM_STRING_HPP
diff --git a/sprout/algorithm/string/join.hpp b/sprout/algorithm/string/join.hpp
new file mode 100644
index 00000000..6bf935a2
--- /dev/null
+++ b/sprout/algorithm/string/join.hpp
@@ -0,0 +1,108 @@
+#ifndef SPROUT_ALGORITHM_STRING_JOIN_HPP
+#define SPROUT_ALGORITHM_STRING_JOIN_HPP
+
+#include <type_traits>
+#include <sprout/config.hpp>
+#include <sprout/fixed_container/traits.hpp>
+#include <sprout/fixed_container/functions.hpp>
+#include <sprout/iterator/operation.hpp>
+#include <sprout/operation/fixed/append_back.hpp>
+
+namespace sprout {
+	namespace algorithm {
+		namespace result_of {
+			//
+			// join
+			//
+			template<typename ContainerContainer, typename Separator>
+			struct join {
+			public:
+				typedef typename sprout::rebind_fixed_size<
+					typename sprout::fixed_container_traits<ContainerContainer>::value_type
+				>::template apply<
+					sprout::fixed_container_traits<ContainerContainer>::fixed_size != 0
+						? (
+							sprout::fixed_container_traits<
+								typename sprout::fixed_container_traits<ContainerContainer>::value_type
+							>::fixed_size
+							+ (sprout::fixed_container_traits<ContainerContainer>::fixed_size - 1) * (
+								sprout::fixed_container_traits<Separator>::fixed_size
+								+ sprout::fixed_container_traits<
+									typename sprout::fixed_container_traits<ContainerContainer>::value_type
+								>::fixed_size
+								)
+							)
+						: 0
+				>::type type;
+			};
+		}	// namespace result_of
+
+		namespace detail {
+			template<typename Result, typename ContainerIterator, typename Separator, typename Container>
+			SPROUT_CONSTEXPR inline typename std::enable_if<
+				(sprout::fixed_container_traits<Container>::fixed_size == sprout::fixed_container_traits<Result>::fixed_size),
+				Result
+			>::type join_impl_1(
+				ContainerIterator first,
+				ContainerIterator last,
+				Separator const& separator,
+				Container const& current
+				)
+			{
+				return current;
+			}
+			template<typename Result, typename ContainerIterator, typename Separator, typename Container>
+			SPROUT_CONSTEXPR inline typename std::enable_if<
+				(sprout::fixed_container_traits<Container>::fixed_size < sprout::fixed_container_traits<Result>::fixed_size),
+				Result
+			>::type join_impl_1(
+				ContainerIterator first,
+				ContainerIterator last,
+				Separator const& separator,
+				Container const& current
+				)
+			{
+				return sprout::algorithm::detail::join_impl_1<Result>(
+					sprout::next(first),
+					last,
+					separator,
+					sprout::fixed::append_back(sprout::fixed::append_back(current, separator), *first)
+					);
+			}
+			template<typename Result, typename ContainerIterator, typename Separator>
+			SPROUT_CONSTEXPR inline Result join_impl(
+				ContainerIterator first,
+				ContainerIterator last,
+				Separator const& separator
+				)
+			{
+				return first != last
+					? sprout::algorithm::detail::join_impl_1<Result>(
+						sprout::next(first),
+						last,
+						separator,
+						*first
+						)
+					: sprout::make_clone<Result>()
+					;
+			}
+		}	// namespace detail
+		//
+		// join
+		//
+		template<typename ContainerContainer, typename Separator>
+		SPROUT_CONSTEXPR inline typename sprout::algorithm::result_of::join<ContainerContainer, Separator>::type join(
+			ContainerContainer const& cont_cont,
+			Separator const& separator
+			)
+		{
+			return sprout::algorithm::detail::join_impl<typename sprout::algorithm::result_of::join<ContainerContainer, Separator>::type>(
+				sprout::begin(cont_cont),
+				sprout::end(cont_cont),
+				separator
+				);
+		}
+	}	// namespace algorithm
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_ALGORITHM_STRING_JOIN_HPP
diff --git a/sprout/array.hpp b/sprout/array.hpp
index 6b85d320..ebaf7249 100644
--- a/sprout/array.hpp
+++ b/sprout/array.hpp
@@ -181,6 +181,7 @@ namespace sprout {
 	};
 
 	//
+	// operator==
 	// operator!=
 	// operator<
 	// operator>
@@ -267,7 +268,7 @@ namespace sprout {
 		template<typename T, typename Enable = void>
 		struct is_array_impl {
 		public:
-			typedef std::integral_constant<bool, false> type;
+			typedef std::false_type type;
 			SPROUT_STATIC_CONSTEXPR bool value = type::value;
 		};
 		template<typename T>
@@ -281,7 +282,7 @@ namespace sprout {
 			>::type
 		> {
 		public:
-			typedef std::integral_constant<bool, true> type;
+			typedef std::true_type type;
 			SPROUT_STATIC_CONSTEXPR bool value = type::value;
 		};
 	}	// namespace detail
diff --git a/sprout/null_array.hpp b/sprout/null_array.hpp
index bfcbaf1c..99dc88b0 100644
--- a/sprout/null_array.hpp
+++ b/sprout/null_array.hpp
@@ -126,6 +126,7 @@ namespace sprout {
 	};
 
 	//
+	// operator==
 	// operator!=
 	// operator<
 	// operator>
diff --git a/sprout/random.hpp b/sprout/random.hpp
index 60ec27c7..8e18490f 100644
--- a/sprout/random.hpp
+++ b/sprout/random.hpp
@@ -8,6 +8,7 @@
 #include <sprout/random/uniform_int_distribution.hpp>
 #include <sprout/random/uniform_01.hpp>
 #include <sprout/random/uniform_real_distribution.hpp>
+#include <sprout/random/bernoulli_distribution.hpp>
 #include <sprout/random/variate_generator.hpp>
 #include <sprout/random/random_result.hpp>
 #include <sprout/random/random_iterator.hpp>
diff --git a/sprout/random/bernoulli_distribution.hpp b/sprout/random/bernoulli_distribution.hpp
new file mode 100644
index 00000000..c94a7d09
--- /dev/null
+++ b/sprout/random/bernoulli_distribution.hpp
@@ -0,0 +1,142 @@
+#ifndef SPROUT_RANDOM_BERNOULLI_DISTRIBUTION_HPP
+#define SPROUT_RANDOM_BERNOULLI_DISTRIBUTION_HPP
+
+#include <iosfwd>
+#include <sprout/config.hpp>
+#include <sprout/random/random_result.hpp>
+
+namespace sprout {
+	namespace random {
+		//
+		// bernoulli_distribution
+		//
+		template<typename RealType = double>
+		class bernoulli_distribution {
+		public:
+			typedef int input_type;
+			typedef bool result_type;
+		private:
+			static SPROUT_CONSTEXPR RealType arg_check(RealType p_arg) {
+				return p_arg >= 0 && p_arg <= 1
+					? p_arg
+					: throw "assert(p_arg >= 0 && p_arg <= 1)"
+					;
+			}
+		public:
+			//
+			// param_type
+			//
+			class param_type {
+			public:
+				typedef bernoulli_distribution distribution_type;
+			private:
+				RealType p_;
+			public:
+				SPROUT_CONSTEXPR param_type()
+					: p_(RealType(0.5))
+				{}
+				SPROUT_CONSTEXPR explicit param_type(RealType p_arg = RealType(0.5))
+					: p_(arg_check(p_arg))
+				{}
+				SPROUT_CONSTEXPR RealType p() const {
+					return p_;
+				}
+				template<typename Elem, typename Traits>
+				friend std::basic_ostream<Elem, Traits>& operator>>(
+					std::basic_istream<Elem, Traits>& lhs,
+					param_type const& rhs
+					)
+				{
+					return lhs >> rhs.p_;
+				}
+				template<typename Elem, typename Traits>
+				friend std::basic_ostream<Elem, Traits>& operator<<(
+					std::basic_ostream<Elem, Traits>& lhs,
+					param_type const& rhs
+					)
+				{
+					return lhs << rhs.p_;
+				}
+				SPROUT_CONSTEXPR friend bool operator==(param_type const& lhs, param_type const& rhs) {
+					return lhs.p_ == rhs.p_;
+				}
+				SPROUT_CONSTEXPR friend bool operator!=(param_type const& lhs, param_type const& rhs) {
+					return !(lhs == rhs);
+				}
+			};
+		private:
+			RealType p_;
+		private:
+			template<typename Engine>
+			SPROUT_CONSTEXPR sprout::random::random_result<Engine, bernoulli_distribution> generate(
+				sprout::random::random_result<Engine> const& rnd
+				) const
+			{
+				return sprout::random::random_result<Engine, bernoulli_distribution>(
+					RealType(rnd.result() - rnd.engine().min()) <= p_ * RealType(rnd.engine().max() - rnd.engine().min()),
+					rnd.engine(),
+					*this
+					);
+			}
+		public:
+			SPROUT_CONSTEXPR bernoulli_distribution()
+				: p_(RealType(0.5))
+			{}
+			SPROUT_CONSTEXPR explicit bernoulli_distribution(RealType p_arg = RealType(0.5))
+				: p_(arg_check(p_arg))
+			{}
+			SPROUT_CONSTEXPR RealType p() const {
+				return p_;
+			}
+			SPROUT_CONSTEXPR result_type min() const {
+				return false;
+			}
+			SPROUT_CONSTEXPR result_type max() const {
+				return true;
+			}
+			SPROUT_CONSTEXPR param_type param() const {
+				return param_type(p_);
+			}
+			void param(param_type const& parm) {
+				p_ = parm.p();
+			}
+			template<typename Engine>
+			SPROUT_CONSTEXPR sprout::random::random_result<Engine, bernoulli_distribution> operator()(Engine const& eng) const {
+				return p_ == RealType(0)
+					? sprout::random::random_result<Engine, bernoulli_distribution>(false, eng, *this)
+					: generate(eng())
+					;
+			}
+			template<typename Elem, typename Traits>
+			friend std::basic_ostream<Elem, Traits>& operator>>(
+				std::basic_istream<Elem, Traits>& lhs,
+				bernoulli_distribution const& rhs
+				)
+			{
+				param_type parm;
+				return lhs >> parm;
+				param(parm);
+				return lhs;
+			}
+			template<typename Elem, typename Traits>
+			friend std::basic_ostream<Elem, Traits>& operator<<(
+				std::basic_ostream<Elem, Traits>& lhs,
+				bernoulli_distribution const& rhs
+				)
+			{
+				return lhs << param();
+			}
+			SPROUT_CONSTEXPR friend bool operator==(bernoulli_distribution const& lhs, bernoulli_distribution const& rhs) {
+				return lhs.param() == rhs.param();
+			}
+			SPROUT_CONSTEXPR friend bool operator!=(bernoulli_distribution const& lhs, bernoulli_distribution const& rhs) {
+				return !(lhs == rhs);
+			}
+		};
+	}	// namespace random
+
+	using sprout::random::bernoulli_distribution;
+}	// namespace sprout
+
+#endif // #ifndef SPROUT_RANDOM_BERNOULLI_DISTRIBUTION_HPP
+
diff --git a/sprout/random/uniform_01.hpp b/sprout/random/uniform_01.hpp
index 3adc08a6..64742980 100644
--- a/sprout/random/uniform_01.hpp
+++ b/sprout/random/uniform_01.hpp
@@ -2,6 +2,7 @@
 #define SPROUT_RANDOM_UNIFORM_01_HPP
 
 #include <iosfwd>
+#include <istream>
 #include <limits>
 #include <sprout/config.hpp>
 #include <sprout/random/random_result.hpp>
diff --git a/sprout/string.hpp b/sprout/string.hpp
index 164abd70..1fd4a70e 100644
--- a/sprout/string.hpp
+++ b/sprout/string.hpp
@@ -89,39 +89,55 @@ namespace sprout {
 			return impl_type::eof();
 		}
 #if SPROUT_USE_INDEX_ITERATOR_IMPLEMENTATION
-		template<typename CharIterator>
-		static SPROUT_CONSTEXPR int compare(CharIterator s1, CharIterator s2, std::size_t n) {
+		template<typename ConstIterator>
+		static SPROUT_CONSTEXPR int compare(char_type const* s1, ConstIterator s2, std::size_t n) {
 			return !n ? 0
 				: lt(*s1, *s2) ? -1
 				: lt(*s2, *s1) ? 1
 				: compare(s1 + 1, s2 + 1, n - 1)
 				;
 		}
-		template<typename CharIterator>
-		static SPROUT_CONSTEXPR std::size_t length(CharIterator s) {
+		template<typename ConstIterator>
+		static SPROUT_CONSTEXPR int compare(ConstIterator s1, char_type const* s2, std::size_t n) {
+			return !n ? 0
+				: lt(*s1, *s2) ? -1
+				: lt(*s2, *s1) ? 1
+				: compare(s1 + 1, s2 + 1, n - 1)
+				;
+		}
+		template<typename ConstIterator1, typename ConstIterator2>
+		static SPROUT_CONSTEXPR int compare(ConstIterator1 s1, ConstIterator2 s2, std::size_t n) {
+			return !n ? 0
+				: lt(*s1, *s2) ? -1
+				: lt(*s2, *s1) ? 1
+				: compare(s1 + 1, s2 + 1, n - 1)
+				;
+		}
+		template<typename ConstIterator>
+		static SPROUT_CONSTEXPR std::size_t length(ConstIterator s) {
     		return !*s ? 0
     			: 1 + length(s + 1)
     			;
 		}
-		template<typename CharIterator>
-		static SPROUT_CONSTEXPR CharIterator find(CharIterator s, std::size_t n, char_type const& a) {
+		template<typename ConstIterator>
+		static SPROUT_CONSTEXPR ConstIterator find(ConstIterator s, std::size_t n, char_type const& a) {
 			return !n ? nullptr
 				: eq(*s, a) ? s
 				: find(s + 1, n - 1, a)
 				;
 		}
-		template<typename CharIterator1, typename CharIterator2>
-		static CharIterator1 move(CharIterator1 s1, CharIterator2 s2, std::size_t n) {
+		template<typename Iterator, typename ConstIterator>
+		static Iterator move(Iterator s1, ConstIterator s2, std::size_t n) {
 			std::copy_backward(s2, s2 + n, s1);
 			return s1;
 		}
-		template<typename CharIterator1, typename CharIterator2>
-		static CharIterator1 copy(CharIterator1 s1, CharIterator2 s2, std::size_t n) {
+		template<typename Iterator, typename ConstIterator>
+		static Iterator copy(Iterator s1, ConstIterator s2, std::size_t n) {
 			std::copy(s2, s2 + n, s1);
 			return s1;
 		}
-		template<typename CharIterator>
-		static CharIterator assign(CharIterator s, std::size_t n, char_type a) {
+		template<typename Iterator>
+		static Iterator assign(Iterator s, std::size_t n, char_type a) {
 			std::fill(s, s + n, a);
 			return s;
 		}
@@ -151,6 +167,37 @@ namespace sprout {
 		typedef sprout::reverse_iterator<iterator> reverse_iterator;
 		typedef sprout::reverse_iterator<const_iterator> const_reverse_iterator;
 		typedef Traits traits_type;
+#if SPROUT_USE_INDEX_ITERATOR_IMPLEMENTATION
+	private:
+		template<typename U, typename Enable = void>
+		struct is_index_iterator_impl {
+		public:
+			typedef std::false_type type;
+			SPROUT_STATIC_CONSTEXPR bool value = type::value;
+		};
+		template<typename U>
+		struct is_index_iterator_impl<
+			U,
+			typename std::enable_if<
+				std::is_same<
+					U,
+					sprout::index_iterator<typename U::container_type>
+				>::value
+				&& std::is_same<
+					typename std::iterator_traits<U>::value_type,
+					value_type
+				>::value
+			>::type
+		> {
+		public:
+			typedef std::true_type type;
+			SPROUT_STATIC_CONSTEXPR bool value = type::value;
+		};
+		template<typename U>
+		struct is_index_iterator
+			: public is_index_iterator_impl<U>
+		{};
+#endif
 	public:
 		SPROUT_STATIC_CONSTEXPR size_type npos = -1;
 		SPROUT_STATIC_CONSTEXPR size_type static_size = N;
@@ -180,7 +227,29 @@ namespace sprout {
 			return sprout::basic_string<T, N, Traits>{{(Indexes < n ? s[Indexes] : T())...}, n};
 		}
 #if SPROUT_USE_INDEX_ITERATOR_IMPLEMENTATION
-		static SPROUT_CONSTEXPR int compare_impl_1(const_iterator dest, size_type pos1, size_type n1, const_iterator s, size_type n2) {
+		template<typename ConstIterator>
+		static SPROUT_CONSTEXPR typename std::enable_if<
+			is_index_iterator<ConstIterator>::value,
+			int
+		>::type compare_impl_1(value_type const* dest, size_type pos1, size_type n1, ConstIterator s, size_type n2) {
+			return compare_impl_2(
+				traits_type::compare(dest + pos1, s, NS_SSCRISK_CEL_OR_SPROUT_DETAIL::min(n1, n2)),
+				n1,
+				n2
+				);
+		}
+		static SPROUT_CONSTEXPR int compare_impl_1(const_iterator dest, size_type pos1, size_type n1, value_type const* s, size_type n2) {
+			return compare_impl_2(
+				traits_type::compare(dest + pos1, s, NS_SSCRISK_CEL_OR_SPROUT_DETAIL::min(n1, n2)),
+				n1,
+				n2
+				);
+		}
+		template<typename ConstIterator>
+		static SPROUT_CONSTEXPR typename std::enable_if<
+			is_index_iterator<ConstIterator>::value,
+			int
+		>::type compare_impl_1(const_iterator dest, size_type pos1, size_type n1, ConstIterator s, size_type n2) {
 			return compare_impl_2(
 				traits_type::compare(dest + pos1, s, NS_SSCRISK_CEL_OR_SPROUT_DETAIL::min(n1, n2)),
 				n1,
@@ -401,7 +470,7 @@ namespace sprout {
 		}
 		template<std::size_t N2>
 		SPROUT_CONSTEXPR int compare(basic_string<T, N2, Traits> const& str) const {
-			return compare(0, size(), str.c_str(), str.size());
+			return compare(0, size(), str.begin(), str.size());
 		}
 		SPROUT_CONSTEXPR int compare(value_type const* s) const {
 			return compare(0, size(), s, traits_type::length(s));
@@ -416,13 +485,13 @@ namespace sprout {
 		template<std::size_t N2>
 		SPROUT_CONSTEXPR int compare(size_type pos1, size_type n1, basic_string<T, N2, Traits> const& str, size_type pos2, size_type n2) const {
 			return !(str.size() < pos2)
-				? compare(pos1, n1, str.c_str() + pos2, NS_SSCRISK_CEL_OR_SPROUT_DETAIL::min(n2, str.size() - pos2))
+				? compare(pos1, n1, str.begin() + pos2, NS_SSCRISK_CEL_OR_SPROUT_DETAIL::min(n2, str.size() - pos2))
 				: throw "basic_string<>: index out of range"
 				;
 		}
 		SPROUT_CONSTEXPR int compare(size_type pos1, size_type n1, value_type const* s, size_type n2) const {
 			return !(size() < pos1)
-				? compare_impl_1(c_str(), pos1, NS_SSCRISK_CEL_OR_SPROUT_DETAIL::min(n1, size() - pos1), s, n2)
+				? compare_impl_1(begin(), pos1, NS_SSCRISK_CEL_OR_SPROUT_DETAIL::min(n1, size() - pos1), s, n2)
 				: throw "basic_string<>: index out of range"
 				;
 		}
@@ -441,7 +510,11 @@ namespace sprout {
 			}
 		}
 #if SPROUT_USE_INDEX_ITERATOR_IMPLEMENTATION
-		basic_string<T, N, Traits>& assign(const_iterator s, size_type n) {
+		template<typename ConstIterator>
+		typename std::enable_if<
+			is_index_iterator<ConstIterator>::value,
+			basic_string<T, N, Traits>&
+		>::type assign(ConstIterator s, size_type n) {
 			maxcheck(n);
 			for (size_type i = 0; i < n; ++i) {
 				traits_type::assign(elems[i], s[i]);
@@ -452,21 +525,41 @@ namespace sprout {
 			len = n;
 			return *this;
 		}
-		basic_string<T, N, Traits>& assign(const_iterator s) {
+		template<typename ConstIterator>
+		typename std::enable_if<
+			is_index_iterator<ConstIterator>::value,
+			basic_string<T, N, Traits>&
+		>::type assign(ConstIterator s) {
 			return assign(s, traits_type::length(s));
 		}
-		basic_string<T, N, Traits>& operator=(const_iterator rhs) {
+		template<typename ConstIterator>
+		typename std::enable_if<
+			is_index_iterator<ConstIterator>::value,
+			basic_string<T, N, Traits>&
+		>::type operator=(ConstIterator rhs) {
 			return assign(rhs);
 		}
-		SPROUT_CONSTEXPR int compare(const_iterator s) const {
+		template<typename ConstIterator>
+		SPROUT_CONSTEXPR typename std::enable_if<
+			is_index_iterator<ConstIterator>::value,
+			int
+		>::type compare(ConstIterator s) const {
 			return compare(0, size(), s, traits_type::length(s));
 		}
-		SPROUT_CONSTEXPR int compare(size_type pos1, size_type n1, const_iterator s) const {
+		template<typename ConstIterator>
+		SPROUT_CONSTEXPR typename std::enable_if<
+			is_index_iterator<ConstIterator>::value,
+			int
+		>::type compare(size_type pos1, size_type n1, ConstIterator s) const {
 			return compare(pos1, n1, s, traits_type::length(s));
 		}
-		SPROUT_CONSTEXPR int compare(size_type pos1, size_type n1, const_iterator s, size_type n2) const {
+		template<typename ConstIterator>
+		SPROUT_CONSTEXPR typename std::enable_if<
+			is_index_iterator<ConstIterator>::value,
+			int
+		>::type compare(size_type pos1, size_type n1, ConstIterator s, size_type n2) const {
 			return !(size() < pos1)
-				? compare_impl_1(c_str(), pos1, NS_SSCRISK_CEL_OR_SPROUT_DETAIL::min(n1, size() - pos1), s, n2)
+				? compare_impl_1(begin(), pos1, NS_SSCRISK_CEL_OR_SPROUT_DETAIL::min(n1, size() - pos1), s, n2)
 				: throw "basic_string<>: index out of range"
 				;
 		}
@@ -474,6 +567,7 @@ namespace sprout {
 	};
 
 	//
+	// operator==
 	// operator!=
 	// operator<
 	// operator>
diff --git a/sprout/sub_array.hpp b/sprout/sub_array.hpp
index da8600e5..8d7992d0 100644
--- a/sprout/sub_array.hpp
+++ b/sprout/sub_array.hpp
@@ -381,6 +381,7 @@ namespace sprout {
 	};
 
 	//
+	// operator==
 	// operator!=
 	// operator<
 	// operator>