diff --git a/sprout/generator.hpp b/sprout/generator.hpp
index 1eeb60b7..4ad56834 100644
--- a/sprout/generator.hpp
+++ b/sprout/generator.hpp
@@ -9,6 +9,7 @@
 #define SPROUT_GENERATOR_HPP
 
 #include <sprout/generator/functions.hpp>
+#include <sprout/generator/results.hpp>
 #include <sprout/generator/generator_access_traits.hpp>
 
 #endif	// #ifndef SPROUT_GENERATOR_HPP
diff --git a/sprout/generator/results.hpp b/sprout/generator/results.hpp
new file mode 100644
index 00000000..166a98c9
--- /dev/null
+++ b/sprout/generator/results.hpp
@@ -0,0 +1,44 @@
+/*=============================================================================
+  Copyright (c) 2011-2014 Bolero MURAKAMI
+  https://github.com/bolero-MURAKAMI/Sprout
+
+  Distributed under the Boost Software License, Version 1.0. (See accompanying
+  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+=============================================================================*/
+#ifndef SPROUT_GENERATOR_RESULTS_HPP
+#define SPROUT_GENERATOR_RESULTS_HPP
+
+#include <type_traits>
+#include <utility>
+#include <sprout/config.hpp>
+#include <sprout/generator/generated_value.hpp>
+#include <sprout/generator/next_generator.hpp>
+
+namespace sprout {
+	namespace generators {
+		namespace results {
+			//
+			// generated_value
+			//
+			template<typename Generator>
+			struct generated_value
+				: public std::decay<decltype(sprout::generators::generated_value(std::declval<Generator>()()))>
+			{};
+
+			//
+			// next_generator
+			//
+			template<typename Generator>
+			struct next_generator
+				: public std::decay<decltype(sprout::generators::next_generator(std::declval<Generator>()()))>
+			{};
+		}	// namespace results
+	}	// namespace generators
+
+	namespace results {
+		using sprout::generators::generated_value;
+		using sprout::generators::next_generator;
+	}	// namespace results
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_GENERATOR_RESULTS_HPP
diff --git a/sprout/random/generate_array.hpp b/sprout/random/generate_array.hpp
index 63aa79a1..b42216fe 100644
--- a/sprout/random/generate_array.hpp
+++ b/sprout/random/generate_array.hpp
@@ -12,16 +12,18 @@
 #include <sprout/config.hpp>
 #include <sprout/array/array.hpp>
 #include <sprout/utility/pair/pair.hpp>
+#include <sprout/generator/functions.hpp>
+#include <sprout/generator/results.hpp>
 
 namespace sprout {
 	namespace random {
 		//
 		// generate_array
 		//
-		template<std::size_t N, typename URNG>
-		inline SPROUT_CXX14_CONSTEXPR sprout::array<typename URNG::result_type, N>
-		generate_array(URNG& rng) {
-			sprout::array<typename URNG::result_type, N> result{{}};
+		template<std::size_t N, typename RandomNumberGenerator>
+		inline SPROUT_CXX14_CONSTEXPR sprout::array<typename RandomNumberGenerator::result_type, N>
+		generate_array(RandomNumberGenerator& rng) {
+			sprout::array<typename RandomNumberGenerator::result_type, N> result{{}};
 			for (std::size_t i = 0; i != N; ++i) {
 				result[i] = rng();
 			}
@@ -29,32 +31,47 @@ namespace sprout {
 		}
 
 		namespace detail {
-			template<std::size_t N, typename URNG, typename Random, typename... Args>
+			template<std::size_t N, typename RandomNumberGenerator, typename Random, typename... Args>
 			static SPROUT_CONSTEXPR typename std::enable_if<
 				(sizeof...(Args) + 1 == N),
-				sprout::pair<sprout::array<typename URNG::result_type, N>, URNG> const
+				sprout::pair<
+					sprout::array<typename sprout::generators::results::generated_value<RandomNumberGenerator const>::type, N>,
+					typename sprout::generators::results::next_generator<RandomNumberGenerator const>::type
+				> const
 			>::type generate_array_impl(Random const& rnd, Args const&... args) {
-				typedef sprout::pair<sprout::array<typename URNG::result_type, N>, URNG> const pair_type;
+				typedef sprout::pair<
+					sprout::array<typename sprout::generators::results::generated_value<RandomNumberGenerator const>::type, N>,
+					typename sprout::generators::results::next_generator<RandomNumberGenerator const>::type
+				> const pair_type;
 				return pair_type{
-					sprout::array<typename URNG::result_type, N>{{args..., rnd.result()}},
-					rnd.engine()
+					sprout::array<typename RandomNumberGenerator::result_type, N>{{args..., sprout::generators::generated_value(rnd)}},
+					sprout::generators::next_generator(rnd)
 					};
 			}
-			template<std::size_t N, typename URNG, typename Random, typename... Args>
+			template<std::size_t N, typename RandomNumberGenerator, typename Random, typename... Args>
 			static SPROUT_CONSTEXPR typename std::enable_if<
 				(sizeof...(Args) + 1 < N),
-				sprout::pair<sprout::array<typename URNG::result_type, N>, URNG> const
+				sprout::pair<
+					sprout::array<typename sprout::generators::results::generated_value<RandomNumberGenerator const>::type, N>,
+					typename sprout::generators::results::next_generator<RandomNumberGenerator const>::type
+				> const
 			>::type generate_array_impl(Random const& rnd, Args const&... args) {
-				return sprout::random::detail::generate_array_impl<N, URNG>(rnd(), args..., rnd.result());
+				return sprout::random::detail::generate_array_impl<N, RandomNumberGenerator>(
+					sprout::generators::next_generator(rnd)(),
+					args..., sprout::generators::generated_value(rnd)
+					);
 			}
 		}	// namespace detail
 		//
 		// generate_array
 		//
-		template<std::size_t N, typename URNG>
-		inline SPROUT_CONSTEXPR sprout::pair<sprout::array<typename URNG::result_type, N>, URNG> const
-		generate_array(URNG const& rng) {
-			return sprout::random::detail::generate_array_impl<N, URNG>(rng());
+		template<std::size_t N, typename RandomNumberGenerator>
+		inline SPROUT_CONSTEXPR sprout::pair<
+			sprout::array<typename sprout::generators::results::generated_value<RandomNumberGenerator const>::type, N>,
+			typename sprout::generators::results::next_generator<RandomNumberGenerator const>::type
+		> const
+		generate_array(RandomNumberGenerator const& rng) {
+			return sprout::random::detail::generate_array_impl<N, RandomNumberGenerator>(rng());
 		}
 	}	// namespace random
 }	// namespace sprout
diff --git a/sprout/random/generate_canonical.hpp b/sprout/random/generate_canonical.hpp
index 9ce07359..404fdce5 100644
--- a/sprout/random/generate_canonical.hpp
+++ b/sprout/random/generate_canonical.hpp
@@ -18,6 +18,7 @@
 #include <sprout/random/detail/const_mod.hpp>
 #include <sprout/random/detail/signed_unsigned_tools.hpp>
 #include <sprout/random/detail/generator_bits.hpp>
+#include <sprout/generator/functions.hpp>
 #include <sprout/utility/pair/pair.hpp>
 #include HDR_ALGORITHM_MIN_MAX_SSCRISK_CEL_OR_SPROUT
 
@@ -89,13 +90,23 @@ namespace sprout {
 				typedef sprout::pair<RealType, URNG> const pair_type;
 				return mult * r < limit ? sprout::random::detail::generate_canonical_impl_1_1<RealType, bits, URNG>(
 					r, limit,
-					s + RealType(sprout::random::detail::subtract<base_result>()(rnd.result(), rnd.engine().min())) * mult,
+					s + RealType(
+						sprout::random::detail::subtract<base_result>()(
+							sprout::generators::generated_value(rnd),
+							sprout::generators::next_generator(rnd).min()
+							)
+						) * mult,
 					mult * r,
 					rnd()
 					)
 					: pair_type(
-						(s + RealType(sprout::random::detail::subtract<base_result>()(rnd.result(), rnd.engine().min())) * mult) / (mult * r),
-						rnd.engine()
+						(s + RealType(
+							sprout::random::detail::subtract<base_result>()(
+								sprout::generators::generated_value(rnd),
+								sprout::generators::next_generator(rnd).min()
+								)
+							) * mult) / (mult * r),
+						sprout::generators::next_generator(rnd)
 						)
 					;
 			}
@@ -106,13 +117,23 @@ namespace sprout {
 				typedef sprout::pair<RealType, URNG> const pair_type;
 				return r < limit ? sprout::random::detail::generate_canonical_impl_1_1<RealType, bits, URNG>(
 						r, limit,
-						RealType(sprout::random::detail::subtract<base_result>()(rnd.result(), rnd.engine().min())),
+						RealType(
+							sprout::random::detail::subtract<base_result>()(
+								sprout::generators::generated_value(rnd),
+								sprout::generators::next_generator(rnd).min()
+								)
+							),
 						r,
 						rnd()
 						)
 					: pair_type(
-						RealType(sprout::random::detail::subtract<base_result>()(rnd.result(), rnd.engine().min())) / r,
-						rnd.engine()
+						RealType(
+							sprout::random::detail::subtract<base_result>()(
+								sprout::generators::generated_value(rnd),
+								sprout::generators::next_generator(rnd).min()
+								)
+							) / r,
+						sprout::generators::next_generator(rnd)
 						)
 					;
 			}
@@ -135,13 +156,17 @@ namespace sprout {
 				typedef sprout::pair<RealType, URNG> const pair_type;
 				return mult * r < limit ? sprout::random::detail::generate_canonical_impl_0_1<RealType, bits, URNG>(
 					r, limit,
-					s + sprout::math::floor((RealType(rnd.result()) - RealType(rnd.engine().min())) * r) * mult,
+					s + sprout::math::floor(
+						(RealType(sprout::generators::generated_value(rnd)) - RealType(sprout::generators::next_generator(rnd).min())) * r
+						) * mult,
 					mult * r,
 					rnd()
 					)
 					: pair_type(
-						(s + sprout::math::floor((RealType(rnd.result()) - RealType(rnd.engine().min())) * r) * mult) / (mult * r),
-						rnd.engine()
+						(s + sprout::math::floor(
+							(RealType(sprout::generators::generated_value(rnd)) - RealType(sprout::generators::next_generator(rnd).min())) * r
+							) * mult) / (mult * r),
+						sprout::generators::next_generator(rnd)
 						)
 					;
 			}
@@ -151,13 +176,13 @@ namespace sprout {
 				typedef sprout::pair<RealType, URNG> const pair_type;
 				return r < limit ? sprout::random::detail::generate_canonical_impl_0_1<RealType, bits, URNG>(
 						r, limit,
-						RealType(rnd.result() - rnd.engine().min()),
+						RealType(sprout::generators::generated_value(rnd) - sprout::generators::next_generator(rnd).min()),
 						r,
 						rnd()
 						)
 					: pair_type(
-						RealType(rnd.result() - rnd.engine().min()) / r,
-						rnd.engine()
+						RealType(sprout::generators::generated_value(rnd) - sprout::generators::next_generator(rnd).min()) / r,
+						sprout::generators::next_generator(rnd)
 						)
 					;
 			}
diff --git a/sprout/random/random_result.hpp b/sprout/random/random_result.hpp
index 4e44e424..8b678d2b 100644
--- a/sprout/random/random_result.hpp
+++ b/sprout/random/random_result.hpp
@@ -15,7 +15,9 @@
 #include <sprout/config.hpp>
 #include <sprout/iterator/next.hpp>
 #include <sprout/tuple/tuple.hpp>
-#include <sprout/generator.hpp>
+#include <sprout/generator/functions.hpp>
+#include <sprout/random/random_result_fwd.hpp>
+#include <sprout/random/variate_generator.hpp>
 #include <sprout/utility/swap.hpp>
 #include <sprout/utility/move.hpp>
 #include <sprout/type_traits/integral_constant.hpp>
@@ -25,9 +27,6 @@ namespace sprout {
 		//
 		// random_result
 		//
-		template<typename Engine, typename Distribution = void, typename Enable = void>
-		class random_result;
-
 		template<typename Engine, typename Distribution>
 		class random_result<
 			Engine,
@@ -46,6 +45,7 @@ namespace sprout {
 			typedef Engine engine_type;
 			typedef Distribution distribution_type;
 			typedef typename distribution_type::result_type result_type;
+			typedef sprout::random::variate_generator<engine_type, distribution_type> generator_type;
 		private:
 			typedef std::iterator<
 				std::input_iterator_tag,
@@ -62,31 +62,23 @@ namespace sprout {
 			typedef typename base_type::reference reference;
 		private:
 			result_type result_;
-			engine_type engine_;
-			distribution_type distribution_;
+			generator_type generator_;
 		public:
 			SPROUT_CONSTEXPR random_result()
 				: result_()
-				, engine_()
-				, distribution_()
+				, generator_()
 			{}
+			random_result(random_result const&) = default;
 			SPROUT_CONSTEXPR random_result(
 				result_type result,
 				engine_type const& engine,
 				distribution_type const& distribution
 				)
 				: result_(result)
-				, engine_(engine)
-				, distribution_(distribution)
+				, generator_(engine, distribution)
 			{}
 			SPROUT_CONSTEXPR random_result operator()() const {
-				return distribution_(engine_);
-			}
-			SPROUT_CXX14_CONSTEXPR result_type& result() SPROUT_NOEXCEPT {
-				return result_;
-			}
-			SPROUT_CONSTEXPR result_type const& result() const SPROUT_NOEXCEPT {
-				return result_;
+				return generator_();
 			}
 			SPROUT_CXX14_CONSTEXPR result_type& generated_value() SPROUT_NOEXCEPT {
 				return result_;
@@ -94,51 +86,54 @@ namespace sprout {
 			SPROUT_CONSTEXPR result_type const& generated_value() const SPROUT_NOEXCEPT {
 				return result_;
 			}
+			SPROUT_CXX14_CONSTEXPR generator_type& next_generator() SPROUT_NOEXCEPT {
+				return generator_;
+			}
+			SPROUT_CONSTEXPR generator_type const& next_generator() const SPROUT_NOEXCEPT {
+				return generator_;
+			}
+			SPROUT_CXX14_CONSTEXPR result_type& result() SPROUT_NOEXCEPT {
+				return result_;
+			}
+			SPROUT_CONSTEXPR result_type const& result() const SPROUT_NOEXCEPT {
+				return result_;
+			}
 			SPROUT_CXX14_CONSTEXPR engine_type& engine() SPROUT_NOEXCEPT {
-				return engine_;
+				return generator_.engine();
 			}
 			SPROUT_CONSTEXPR engine_type const& engine() const SPROUT_NOEXCEPT {
-				return engine_;
-			}
-			SPROUT_CXX14_CONSTEXPR random_result& next_generator() SPROUT_NOEXCEPT {
-				return *this;
-			}
-			SPROUT_CONSTEXPR random_result const& next_generator() const SPROUT_NOEXCEPT {
-				return *this;
+				return generator_.engine();
 			}
 			SPROUT_CXX14_CONSTEXPR distribution_type& distribution() SPROUT_NOEXCEPT {
-				return distribution_;
+				return generator_.distribution();
 			}
 			SPROUT_CONSTEXPR distribution_type const& distribution() const SPROUT_NOEXCEPT {
-				return distribution_;
+				return generator_.distribution();
 			}
 			SPROUT_CXX14_CONSTEXPR operator result_type&() SPROUT_NOEXCEPT {
-				return generated_value();
+				return result_;
 			}
 			SPROUT_CONSTEXPR operator result_type const&() const SPROUT_NOEXCEPT {
-				return generated_value();
+				return result_;
 			}
 			SPROUT_CONSTEXPR result_type min() const SPROUT_NOEXCEPT {
-				return distribution_.min();
+				return distribution().min();
 			}
 			SPROUT_CONSTEXPR result_type max() const SPROUT_NOEXCEPT {
-				return distribution_.max();
+				return distribution().max();
 			}
 			SPROUT_CXX14_CONSTEXPR void swap(random_result& other)
 			SPROUT_NOEXCEPT_EXPR(
 				SPROUT_NOEXCEPT_EXPR(sprout::swap(result_, other.result_))
-				&& SPROUT_NOEXCEPT_EXPR(sprout::swap(engine_, other.engine_))
-				&& SPROUT_NOEXCEPT_EXPR(sprout::swap(distribution_, other.distribution_))
+				&& SPROUT_NOEXCEPT_EXPR(sprout::swap(generator_, other.generator_))
 				)
 			{
 				sprout::swap(result_, other.result_);
-				sprout::swap(engine_, other.engine_);
-				sprout::swap(distribution_, other.distribution_);
+				sprout::swap(generator_, other.generator_);
 			}
 			friend SPROUT_CONSTEXPR bool operator==(random_result const& lhs, random_result const& rhs) SPROUT_NOEXCEPT {
 				return lhs.result_ == rhs.result_
-					&& lhs.engine_ == rhs.engine_
-					&& lhs.distribution_ == rhs.distribution_
+					&& lhs.generator_ == rhs.generator_
 					;
 			}
 			friend SPROUT_CONSTEXPR bool operator!=(random_result const& lhs, random_result const& rhs) SPROUT_NOEXCEPT {
@@ -178,6 +173,7 @@ namespace sprout {
 		public:
 			typedef Engine engine_type;
 			typedef typename engine_type::result_type result_type;
+			typedef engine_type generator_type;
 		private:
 			typedef std::iterator<
 				std::input_iterator_tag,
@@ -194,27 +190,22 @@ namespace sprout {
 			typedef typename base_type::reference reference;
 		private:
 			result_type result_;
-			engine_type engine_;
+			generator_type generator_;
 		public:
 			SPROUT_CONSTEXPR random_result()
 				: result_()
-				, engine_()
+				, generator_()
 			{}
+			random_result(random_result const&) = default;
 			SPROUT_CONSTEXPR random_result(
 				result_type result,
 				engine_type const& engine
 				)
 				: result_(result)
-				, engine_(engine)
+				, generator_(engine)
 			{}
 			SPROUT_CONSTEXPR random_result operator()() const {
-				return engine_();
-			}
-			SPROUT_CXX14_CONSTEXPR result_type& result() SPROUT_NOEXCEPT {
-				return result_;
-			}
-			SPROUT_CONSTEXPR result_type const& result() const SPROUT_NOEXCEPT {
-				return result_;
+				return generator_();
 			}
 			SPROUT_CXX14_CONSTEXPR result_type& generated_value() SPROUT_NOEXCEPT {
 				return result_;
@@ -222,33 +213,39 @@ namespace sprout {
 			SPROUT_CONSTEXPR result_type const& generated_value() const SPROUT_NOEXCEPT {
 				return result_;
 			}
+			SPROUT_CXX14_CONSTEXPR generator_type& next_generator() SPROUT_NOEXCEPT {
+				return generator_;
+			}
+			SPROUT_CONSTEXPR generator_type const& next_generator() const SPROUT_NOEXCEPT {
+				return generator_;
+			}
+			SPROUT_CXX14_CONSTEXPR result_type& result() SPROUT_NOEXCEPT {
+				return result_;
+			}
+			SPROUT_CONSTEXPR result_type const& result() const SPROUT_NOEXCEPT {
+				return result_;
+			}
 			SPROUT_CXX14_CONSTEXPR engine_type& engine() SPROUT_NOEXCEPT {
-				return engine_;
+				return generator_;
 			}
 			SPROUT_CONSTEXPR engine_type const& engine() const SPROUT_NOEXCEPT {
-				return engine_;
-			}
-			SPROUT_CXX14_CONSTEXPR random_result& next_generator() SPROUT_NOEXCEPT {
-				return *this;
-			}
-			SPROUT_CONSTEXPR random_result const& next_generator() const SPROUT_NOEXCEPT {
-				return *this;
+				return generator_;
 			}
 			SPROUT_CXX14_CONSTEXPR operator result_type&() SPROUT_NOEXCEPT {
-				return generated_value();
+				return result_;
 			}
 			SPROUT_CONSTEXPR operator result_type const&() const SPROUT_NOEXCEPT {
-				return generated_value();
+				return result_;
 			}
 			SPROUT_CONSTEXPR result_type min() const SPROUT_NOEXCEPT {
-				return engine_.min();
+				return engine().min();
 			}
 			SPROUT_CONSTEXPR result_type max() const SPROUT_NOEXCEPT {
-				return engine_.max();
+				return engine().max();
 			}
 			friend SPROUT_CONSTEXPR bool operator==(random_result const& lhs, random_result const& rhs) SPROUT_NOEXCEPT {
 				return lhs.result_ == rhs.result_
-					&& lhs.engine_ == rhs.engine_
+					&& lhs.generator_ == rhs.generator_
 					;
 			}
 			friend SPROUT_CONSTEXPR bool operator!=(random_result const& lhs, random_result const& rhs) SPROUT_NOEXCEPT {
@@ -257,11 +254,11 @@ namespace sprout {
 			SPROUT_CXX14_CONSTEXPR void swap(random_result& other)
 			SPROUT_NOEXCEPT_EXPR(
 				SPROUT_NOEXCEPT_EXPR(sprout::swap(result_, other.result_))
-				&& SPROUT_NOEXCEPT_EXPR(sprout::swap(engine_, other.engine_))
+				&& SPROUT_NOEXCEPT_EXPR(sprout::swap(generator_, other.generator_))
 				)
 			{
 				sprout::swap(result_, other.result_);
-				sprout::swap(engine_, other.engine_);
+				sprout::swap(generator_, other.generator_);
 			}
 			SPROUT_CONSTEXPR reference operator*() const SPROUT_NOEXCEPT {
 				return result_;
@@ -303,8 +300,6 @@ namespace sprout {
 		}
 	}	// namespace random
 
-	using sprout::random::random_result;
-
 	namespace tuples {
 		namespace detail {
 			template<std::size_t I, typename T>
@@ -317,7 +312,7 @@ namespace sprout {
 			template<typename Engine, typename Distribution>
 			struct tuple_element_impl<1, sprout::random::random_result<Engine, Distribution> > {
 			public:
-				typedef sprout::random::random_result<Engine, Distribution> type;
+				typedef typename sprout::random::random_result<Engine, Distribution>::generator_type type;
 			};
 
 			template<std::size_t I, typename T>
@@ -337,11 +332,11 @@ namespace sprout {
 			template<typename Engine, typename Distribution>
 			struct get_impl<1, sprout::random::random_result<Engine, Distribution> > {
 			public:
-				SPROUT_CONSTEXPR sprout::random::random_result<Engine, Distribution>&
+				SPROUT_CONSTEXPR typename sprout::random::random_result<Engine, Distribution>::generator_type&
 				operator()(sprout::random::random_result<Engine, Distribution>& t) const {
 					return t.next_generator();
 				}
-				SPROUT_CONSTEXPR sprout::random::random_result<Engine, Distribution> const&
+				SPROUT_CONSTEXPR typename sprout::random::random_result<Engine, Distribution>::generator_type const&
 				operator()(sprout::random::random_result<Engine, Distribution> const& t) const {
 					return t.next_generator();
 				}
diff --git a/sprout/random/random_result_fwd.hpp b/sprout/random/random_result_fwd.hpp
new file mode 100644
index 00000000..f925bc7d
--- /dev/null
+++ b/sprout/random/random_result_fwd.hpp
@@ -0,0 +1,25 @@
+/*=============================================================================
+  Copyright (c) 2011-2014 Bolero MURAKAMI
+  https://github.com/bolero-MURAKAMI/Sprout
+
+  Distributed under the Boost Software License, Version 1.0. (See accompanying
+  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+=============================================================================*/
+#ifndef SPROUT_RANDOM_RANDOM_RESULT_FWD_HPP
+#define SPROUT_RANDOM_RANDOM_RESULT_FWD_HPP
+
+#include <sprout/config.hpp>
+
+namespace sprout {
+	namespace random {
+		//
+		// random_result
+		//
+		template<typename Engine, typename Distribution = void, typename Enable = void>
+		class random_result;
+	}	// namespace random
+
+	using sprout::random::random_result;
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_RANDOM_RANDOM_RESULT_FWD_HPP
diff --git a/sprout/random/utility.hpp b/sprout/random/utility.hpp
index 1261e58d..fa414aab 100644
--- a/sprout/random/utility.hpp
+++ b/sprout/random/utility.hpp
@@ -9,10 +9,11 @@
 #define SPROUT_RANDOM_UTILITY_HPP
 
 #include <sprout/config.hpp>
+#include <sprout/random/random_result_fwd.hpp>
 #include <sprout/random/random_result.hpp>
+#include <sprout/random/variate_generator.hpp>
 #include <sprout/random/generate_canonical.hpp>
 #include <sprout/random/generate_array.hpp>
-#include <sprout/random/variate_generator.hpp>
 #include <sprout/random/iterator.hpp>
 #include <sprout/random/range.hpp>
 
diff --git a/sprout/random/variate_generator.hpp b/sprout/random/variate_generator.hpp
index e297a79d..2c6442d0 100644
--- a/sprout/random/variate_generator.hpp
+++ b/sprout/random/variate_generator.hpp
@@ -11,7 +11,8 @@
 #include <type_traits>
 #include <sprout/config.hpp>
 #include <sprout/random/detail/ptr_helper.hpp>
-#include <sprout/random/random_result.hpp>
+#include <sprout/random/random_result_fwd.hpp>
+#include <sprout/utility/swap.hpp>
 
 namespace sprout {
 	namespace random {
@@ -41,6 +42,11 @@ namespace sprout {
 			engine_type engine_;
 			distribution_type distribution_;
 		public:
+			SPROUT_CONSTEXPR variate_generator()
+				: engine_()
+				, distribution_()
+			{}
+			variate_generator(variate_generator const&) = default;
 			SPROUT_CONSTEXPR variate_generator(
 				engine_param_type engine,
 				distribution_param_type distribution
@@ -48,7 +54,7 @@ namespace sprout {
 				: engine_(engine)
 				, distribution_(distribution)
 			{}
-			SPROUT_CONSTEXPR random_result_type operator()() const {
+			SPROUT_CONSTEXPR random_result_type const operator()() const {
 				return distribution_(engine_);
 			}
 			engine_reference_type engine() SPROUT_NOEXCEPT {
@@ -69,8 +75,36 @@ namespace sprout {
 			SPROUT_CONSTEXPR result_type max() const SPROUT_NOEXCEPT {
 				return distribution_.max();
 			}
+			SPROUT_CXX14_CONSTEXPR void swap(variate_generator& other)
+			SPROUT_NOEXCEPT_EXPR(
+				SPROUT_NOEXCEPT_EXPR(sprout::swap(engine_, other.engine_))
+				&& SPROUT_NOEXCEPT_EXPR(sprout::swap(distribution_, other.distribution_))
+				)
+			{
+				sprout::swap(engine_, other.engine_);
+				sprout::swap(distribution_, other.distribution_);
+			}
+			friend SPROUT_CONSTEXPR bool operator==(variate_generator const& lhs, variate_generator const& rhs) SPROUT_NOEXCEPT {
+				return lhs.engine_ == rhs.engine_
+					&& lhs.distribution_ == rhs.distribution_
+					;
+			}
+			friend SPROUT_CONSTEXPR bool operator!=(variate_generator const& lhs, variate_generator const& rhs) SPROUT_NOEXCEPT {
+				return !(lhs == rhs);
+			}
 		};
 
+		//
+		// swap
+		//
+		template<typename Engine, typename Distribution>
+		inline SPROUT_CXX14_CONSTEXPR void
+		swap(sprout::random::variate_generator<Engine, Distribution>& lhs, sprout::random::variate_generator<Engine, Distribution>& rhs)
+		SPROUT_NOEXCEPT_EXPR(SPROUT_NOEXCEPT_EXPR(lhs.swap(rhs)))
+		{
+			lhs.swap(rhs);
+		}
+
 		//
 		// combine
 		//
@@ -93,4 +127,6 @@ namespace sprout {
 	using sprout::random::variate_generator;
 }	// namespace sprout
 
+#include <sprout/random/random_result.hpp>
+
 #endif	// #ifndef SPROUT_RANDOM_VARIATE_GENERATOR_HPP