diff --git a/sprout/functional/hash/hash.hpp b/sprout/functional/hash/hash.hpp
index 3adb75c9..d10bddaf 100644
--- a/sprout/functional/hash/hash.hpp
+++ b/sprout/functional/hash/hash.hpp
@@ -11,7 +11,7 @@ namespace sprout {
 	//
 	// hash
 	//
-	template<typename T>
+	template<typename T = void>
 	struct hash {
 	public:
 		typedef T argument_type;
diff --git a/sprout/iterator/amplitude_spectrum_iterator.hpp b/sprout/iterator/amplitude_spectrum_iterator.hpp
index 58af95c0..8cbbf5dd 100644
--- a/sprout/iterator/amplitude_spectrum_iterator.hpp
+++ b/sprout/iterator/amplitude_spectrum_iterator.hpp
@@ -10,14 +10,23 @@ namespace sprout {
 	//
 	// amplitude_value
 	//
-	template<typename T>
+	template<typename T = void>
 	class amplitude_value {
 	public:
 		typedef typename T::value_type result_type;
 		typedef T argument_type;
 	public:
-		SPROUT_CONSTEXPR amplitude_value() {}
-		SPROUT_CONSTEXPR typename T::value_type operator()(T const& value) const {
+		SPROUT_CONSTEXPR typename T::value_type
+		operator()(T const& value) const {
+			return sprout::amplitude_spectrum_value(value);
+		}
+	};
+	template<>
+	class amplitude_value<void> {
+	public:
+		template<typename T>
+		SPROUT_CONSTEXPR typename T::value_type
+		operator()(T const& value) const {
 			return sprout::amplitude_spectrum_value(value);
 		}
 	};
diff --git a/sprout/iterator/phase_spectrum_iterator.hpp b/sprout/iterator/phase_spectrum_iterator.hpp
index 189bf5da..11fc18b3 100644
--- a/sprout/iterator/phase_spectrum_iterator.hpp
+++ b/sprout/iterator/phase_spectrum_iterator.hpp
@@ -10,14 +10,23 @@ namespace sprout {
 	//
 	// phase_value
 	//
-	template<typename T>
+	template<typename T = void>
 	class phase_value {
 	public:
 		typedef typename T::value_type result_type;
 		typedef T argument_type;
 	public:
-		SPROUT_CONSTEXPR phase_value() {}
-		SPROUT_CONSTEXPR typename T::value_type operator()(T const& value) const {
+		SPROUT_CONSTEXPR typename T::value_type
+		operator()(T const& value) const {
+			return sprout::phase_spectrum_value(value);
+		}
+	};
+	template<>
+	class phase_value<void> {
+	public:
+		template<typename T>
+		SPROUT_CONSTEXPR typename T::value_type
+		operator()(T const& value) const {
 			return sprout::phase_spectrum_value(value);
 		}
 	};
diff --git a/sprout/iterator/replace_if_iterator.hpp b/sprout/iterator/replace_if_iterator.hpp
index a1cc3a72..720c1a9d 100644
--- a/sprout/iterator/replace_if_iterator.hpp
+++ b/sprout/iterator/replace_if_iterator.hpp
@@ -19,8 +19,7 @@ namespace sprout {
 		T new_;
 	public:
 		SPROUT_CONSTEXPR replace_value_if(Predicate pred, T const& new_value)
-			: pred_(pred)
-			, new_(new_value)
+			: pred_(pred), new_(new_value)
 		{}
 		SPROUT_CONSTEXPR T operator()(T const& value) const {
 			return pred_(value) ? new_ : value;
diff --git a/sprout/iterator/replace_iterator.hpp b/sprout/iterator/replace_iterator.hpp
index 927012ee..f80da170 100644
--- a/sprout/iterator/replace_iterator.hpp
+++ b/sprout/iterator/replace_iterator.hpp
@@ -12,16 +12,16 @@ namespace sprout {
 	class replace_value {
 	public:
 		typedef T result_type;
-		typedef T const& argument_type;
+		typedef T argument_type;
 	private:
 		T old_;
 		T new_;
 	public:
 		SPROUT_CONSTEXPR replace_value(T const& old_value, T const& new_value)
-			: old_(old_value)
-			, new_(new_value)
+			: old_(old_value), new_(new_value)
 		{}
-		SPROUT_CONSTEXPR T operator()(T const& value) const {
+		SPROUT_CONSTEXPR T
+		operator()(T const& value) const {
 			return (value == old_) ? new_ : value;
 		}
 	};
diff --git a/sprout/math/gcd.hpp b/sprout/math/gcd.hpp
index 515e10ea..db5c6801 100644
--- a/sprout/math/gcd.hpp
+++ b/sprout/math/gcd.hpp
@@ -215,15 +215,24 @@ namespace sprout {
 		//
 		// gcd_evaluator
 		//
-		template<typename IntType>
+		template<typename IntType = void>
 		class gcd_evaluator {
 		public:
 			typedef IntType result_type;
 			typedef IntType first_argument_type;
 			typedef IntType second_argument_type;
 		public:
-			SPROUT_CONSTEXPR result_type
-			operator()(first_argument_type const& a, second_argument_type const& b) const {
+			SPROUT_CONSTEXPR IntType
+			operator()(IntType const& a, IntType const& b) const {
+				return sprout::math::detail::gcd_optimal(a, b);
+			}
+		};
+		template<>
+		class gcd_evaluator<void> {
+		public:
+			template<typename IntType>
+			SPROUT_CONSTEXPR IntType
+			operator()(IntType const& a, IntType const& b) const {
 				return sprout::math::detail::gcd_optimal(a, b);
 			}
 		};
diff --git a/sprout/math/lcm.hpp b/sprout/math/lcm.hpp
index 16efdb11..a40eb1f7 100644
--- a/sprout/math/lcm.hpp
+++ b/sprout/math/lcm.hpp
@@ -74,15 +74,24 @@ namespace sprout {
 		//
 		// lcm_evaluator
 		//
-		template<typename IntType>
+		template<typename IntType = void>
 		class lcm_evaluator {
 		public:
 			typedef IntType result_type;
 			typedef IntType first_argument_type;
 			typedef IntType second_argument_type;
 		public:
-			SPROUT_CONSTEXPR result_type
-			operator()(first_argument_type const& a, second_argument_type const& b) const {
+			SPROUT_CONSTEXPR IntType
+			operator()(IntType const& a, IntType const& b) const {
+				return sprout::math::detail::lcm_optimal(a, b);
+			}
+		};
+		template<>
+		class lcm_evaluator<void> {
+		public:
+			template<typename IntType>
+			SPROUT_CONSTEXPR IntType
+			operator()(IntType const& a, IntType const& b) const {
 				return sprout::math::detail::lcm_optimal(a, b);
 			}
 		};
diff --git a/sprout/range/adaptor/amplitude_spectrum.hpp b/sprout/range/adaptor/amplitude_spectrum.hpp
index d3fe7929..ad1d205e 100644
--- a/sprout/range/adaptor/amplitude_spectrum.hpp
+++ b/sprout/range/adaptor/amplitude_spectrum.hpp
@@ -6,6 +6,7 @@
 #include <sprout/container/traits.hpp>
 #include <sprout/container/functions.hpp>
 #include <sprout/iterator/transform_iterator.hpp>
+#include <sprout/iterator/amplitude_spectrum_iterator.hpp>
 #include <sprout/range/adaptor/detail/adapted_range_default.hpp>
 #include <sprout/type_traits/lvalue_reference.hpp>
 #include <sprout/utility/forward.hpp>
@@ -14,18 +15,6 @@
 
 namespace sprout {
 	namespace adaptors {
-		namespace detail {
-			template<typename T>
-			class amplitude_spectrum_value {
-			public:
-				typedef typename T::value_type result_type;
-				typedef T argument_type;
-			public:
-				SPROUT_CONSTEXPR result_type operator()(T const& value) const {
-					return sprout::amplitude_spectrum_value(value);
-				}
-			};
-		}	// namespace detail
 		//
 		// amplitude_spectrum_range
 		//
@@ -34,7 +23,7 @@ namespace sprout {
 			: public sprout::adaptors::detail::adapted_range_default<
 				Range,
 				sprout::transform_iterator<
-					sprout::adaptors::detail::amplitude_spectrum_value<typename sprout::container_traits<Range>::value_type>,
+					sprout::amplitude_value<typename sprout::container_traits<Range>::value_type>,
 					typename sprout::container_traits<Range>::iterator
 				>
 			>
@@ -43,7 +32,7 @@ namespace sprout {
 			typedef sprout::adaptors::detail::adapted_range_default<
 				Range,
 				sprout::transform_iterator<
-					sprout::adaptors::detail::amplitude_spectrum_value<typename sprout::container_traits<Range>::value_type>,
+					sprout::amplitude_value<typename sprout::container_traits<Range>::value_type>,
 					typename sprout::container_traits<Range>::iterator
 				>
 			> base_type;
diff --git a/sprout/range/adaptor/phase_spectrum.hpp b/sprout/range/adaptor/phase_spectrum.hpp
index a1fd79a8..287868c5 100644
--- a/sprout/range/adaptor/phase_spectrum.hpp
+++ b/sprout/range/adaptor/phase_spectrum.hpp
@@ -6,6 +6,7 @@
 #include <sprout/container/traits.hpp>
 #include <sprout/container/functions.hpp>
 #include <sprout/iterator/transform_iterator.hpp>
+#include <sprout/iterator/phase_spectrum_iterator.hpp>
 #include <sprout/range/adaptor/detail/adapted_range_default.hpp>
 #include <sprout/type_traits/lvalue_reference.hpp>
 #include <sprout/utility/forward.hpp>
@@ -14,18 +15,6 @@
 
 namespace sprout {
 	namespace adaptors {
-		namespace detail {
-			template<typename T>
-			class phase_spectrum_value {
-			public:
-				typedef typename T::value_type result_type;
-				typedef T argument_type;
-			public:
-				SPROUT_CONSTEXPR result_type operator()(T const& value) const {
-					return sprout::phase_spectrum_value(value);
-				}
-			};
-		}	// namespace detail
 		//
 		// phase_spectrum_range
 		//
@@ -34,7 +23,7 @@ namespace sprout {
 			: public sprout::adaptors::detail::adapted_range_default<
 				Range,
 				sprout::transform_iterator<
-					sprout::adaptors::detail::phase_spectrum_value<typename sprout::container_traits<Range>::value_type>,
+					sprout::phase_value<typename sprout::container_traits<Range>::value_type>,
 					typename sprout::container_traits<Range>::iterator
 				>
 			>
@@ -43,7 +32,7 @@ namespace sprout {
 			typedef sprout::adaptors::detail::adapted_range_default<
 				Range,
 				sprout::transform_iterator<
-					sprout::adaptors::detail::phase_spectrum_value<typename sprout::container_traits<Range>::value_type>,
+					sprout::phase_value<typename sprout::container_traits<Range>::value_type>,
 					typename sprout::container_traits<Range>::iterator
 				>
 			> base_type;