diff --git a/sprout/array/hash.hpp b/sprout/array/hash.hpp
index a0c2ff53..03bb3fd7 100644
--- a/sprout/array/hash.hpp
+++ b/sprout/array/hash.hpp
@@ -3,8 +3,8 @@
 
 #include <cstddef>
 #include <sprout/config.hpp>
-#include <sprout/functional/hash/hash.hpp>
 #include <sprout/array/array.hpp>
+#include <sprout/functional/hash.hpp>
 
 namespace sprout {
 	//
diff --git a/sprout/complex/hash.hpp b/sprout/complex/hash.hpp
index dd93a7a4..dcfc4f89 100644
--- a/sprout/complex/hash.hpp
+++ b/sprout/complex/hash.hpp
@@ -4,7 +4,7 @@
 #include <cstddef>
 #include <sprout/config.hpp>
 #include <sprout/complex/complex.hpp>
-#include <sprout/functional/hash/hash.hpp>
+#include <sprout/functional/hash.hpp>
 
 namespace sprout {
 	//
diff --git a/sprout/functional/hash.hpp b/sprout/functional/hash.hpp
index f7f3c8c3..2d6de228 100644
--- a/sprout/functional/hash.hpp
+++ b/sprout/functional/hash.hpp
@@ -2,6 +2,13 @@
 #define SPROUT_FUNCTIONAL_HASH_HPP
 
 #include <sprout/config.hpp>
+#include <sprout/functional/hash/hash_fwd.hpp>
+#include <sprout/functional/hash/hash_value.hpp>
+#include <sprout/functional/hash/to_hash.hpp>
 #include <sprout/functional/hash/hash.hpp>
+#include <sprout/functional/hash/hash_combine.hpp>
+#include <sprout/functional/hash/hash_range.hpp>
+#include <sprout/functional/hash/hash_values_combine.hpp>
+#include <sprout/functional/hash/hash_values.hpp>
 
 #endif	// #ifndef SPROUT_FUNCTIONAL_HASH_HPP
diff --git a/sprout/functional/hash/hash.hpp b/sprout/functional/hash/hash.hpp
index 29e00293..e8d27df4 100644
--- a/sprout/functional/hash/hash.hpp
+++ b/sprout/functional/hash/hash.hpp
@@ -2,212 +2,11 @@
 #define SPROUT_FUNCTIONAL_HASH_HASH_HPP
 
 #include <cstddef>
-#include <limits>
-#include <type_traits>
 #include <sprout/config.hpp>
 #include <sprout/functional/hash/hash_fwd.hpp>
-#include <sprout/iterator/operation.hpp>
-#include <sprout/type_traits/enabler_if.hpp>
+#include <sprout/functional/hash/to_hash.hpp>
 
 namespace sprout {
-	namespace hash_detail {
-		template <typename T>
-		struct is_basic_number
-			: public std::integral_constant<
-				bool,
-				std::is_integral<T>::value
-					&& (sizeof(T) <= sizeof(std::size_t))
-			>
-		{};
-		template <typename T>
-		struct is_long_number
-			: public std::integral_constant<
-				bool,
-				std::is_integral<T>::value
-					&& (sizeof(T) > sizeof(std::size_t))
-					&& std::is_signed<T>::value
-			>
-		{};
-		template <typename T>
-		struct is_ulong_number
-			: public std::integral_constant<
-				bool,
-				std::is_integral<T>::value
-					&& (sizeof(T) > sizeof(std::size_t))
-					&& std::is_unsigned<T>::value
-			>
-		{};
-
-		template<typename T>
-		inline SPROUT_CONSTEXPR std::size_t
-		hash_value_signed_2(T val, int length, std::size_t seed, T positive, std::size_t i) {
-			return i > 0
-				? hash_value_signed_2(
-					val,
-					length,
-					seed ^ static_cast<std::size_t>((positive >> i) + (seed << 6) + (seed >> 2)),
-					positive,
-					i - std::numeric_limits<std::size_t>::digits
-					)
-				: seed ^ static_cast<std::size_t>(val + (seed << 6) + (seed >> 2))
-				;
-		}
-		template<typename T>
-		inline SPROUT_CONSTEXPR std::size_t
-		hash_value_signed_1(T val, int length, std::size_t seed, T positive) {
-			return hash_value_signed_2(val, length, seed, positive, length * std::numeric_limits<std::size_t>::digits);
-		}
-		template<typename T>
-		inline SPROUT_CONSTEXPR std::size_t
-		hash_value_signed(T val) {
-			return sprout::hash_detail::hash_value_signed_1(
-				val,
-				(std::numeric_limits<T>::digits - 1) / std::numeric_limits<std::size_t>::digits,
-				0,
-				val < 0 ? -1 - val : val
-				);
-		}
-
-		template<typename T>
-		inline SPROUT_CONSTEXPR std::size_t
-		hash_value_unsigned_2(T val, int length, std::size_t seed, std::size_t i) {
-			return i > 0
-				? hash_value_unsigned_2(
-					val,
-					length,
-					seed ^ static_cast<std::size_t>((val >> i) + (seed << 6) + (seed >> 2)),
-					i - std::numeric_limits<std::size_t>::digits
-					)
-				: seed ^ static_cast<std::size_t>(val + (seed << 6) + (seed >> 2))
-				;
-		}
-		template<typename T>
-		inline SPROUT_CONSTEXPR std::size_t
-		hash_value_unsigned_1(T val, int length, std::size_t seed) {
-			return hash_value_unsigned_2(val, length, seed, length * std::numeric_limits<std::size_t>::digits);
-		}
-		template<typename T>
-		inline SPROUT_CONSTEXPR std::size_t
-		hash_value_unsigned(T val) {
-			return sprout::hash_detail::hash_value_unsigned_1(
-				val,
-				(std::numeric_limits<T>::digits - 1) / std::numeric_limits<std::size_t>::digits,
-				0
-				);
-		}
-
-		inline std::size_t
-		hash_value_pointer_1(std::size_t x) {
-			return x + (x >> 3);
-		}
-		template<typename T>
-		std::size_t
-		hash_value_pointer(T const* v) {
-			return sprout::hash_detail::hash_value_pointer_1(static_cast<std::size_t>(reinterpret_cast<std::ptrdiff_t>(v)));
-		}
-	}	// namespace hash_detail
-
-	//
-	// hash_value
-	//
-	template<typename T>
-	inline SPROUT_CONSTEXPR typename std::enable_if<sprout::hash_detail::is_basic_number<T>::value, std::size_t>::type
-	hash_value(T v) {
-		return static_cast<std::size_t>(v);
-	}
-	template<typename T>
-	inline SPROUT_CONSTEXPR typename std::enable_if<sprout::hash_detail::is_long_number<T>::value, std::size_t>::type
-	hash_value(T v) {
-		return sprout::hash_detail::hash_value_signed(v);
-	}
-	template<typename T>
-	inline SPROUT_CONSTEXPR typename std::enable_if<sprout::hash_detail::is_ulong_number<T>::value, std::size_t>::type
-	hash_value(T v) {
-		return sprout::hash_detail::hash_value_unsigned(v);
-	}
-	template<typename T>
-	inline SPROUT_CONSTEXPR typename std::enable_if<std::is_enum<T>::value, std::size_t>::type
-	hash_value(T v) {
-		return sprout::hash_value(static_cast<typename std::underlying_type<T>::type>(v));
-	}
-	template<typename T>
-	inline SPROUT_CONSTEXPR typename std::enable_if<std::is_pointer<typename std::remove_reference<T>::type>::value, std::size_t>::type
-	hash_value(T&& v) {
-		return sprout::hash_detail::hash_value_pointer(v);
-	}
-	template<typename T, std::size_t N>
-	inline SPROUT_CONSTEXPR std::size_t
-	hash_value(T const (&v)[N]) {
-		return sprout::hash_range(&v[0], &v[0] + N);
-	}
-
-	//
-	// to_hash
-	//
-	template<typename T>
-	inline SPROUT_CONSTEXPR std::size_t
-	to_hash(T const& v) {
-		using sprout::hash_value;
-		return hash_value(v);
-	}
-
-	//
-	// hash_combine
-	//
-	template<typename T>
-	inline SPROUT_CONSTEXPR std::size_t
-	hash_combine(std::size_t seed, T const& v) {
-		return seed ^ (sprout::to_hash(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2));
-	}
-
-	//
-	// hash_range
-	//
-	template<typename Iterator>
-	inline SPROUT_CONSTEXPR std::size_t
-	hash_range(std::size_t seed, Iterator first, Iterator last) {
-		return first != last
-			? sprout::hash_range(sprout::hash_combine(seed, *first), sprout::next(first), last)
-			: seed
-			;
-	}
-	template<typename Iterator>
-	inline SPROUT_CONSTEXPR std::size_t
-	hash_range(Iterator first, Iterator last) {
-		return sprout::hash_range(0, first, last);
-	}
-
-	namespace detail {
-		template<typename T>
-		inline SPROUT_CONSTEXPR std::size_t
-		hash_values_combine_impl(std::size_t seed, T const& v) {
-			return sprout::hash_combine(seed, v);
-		}
-		template<typename Head, typename... Tail>
-		inline SPROUT_CONSTEXPR std::size_t
-		hash_values_combine_impl(std::size_t seed, Head const& head, Tail const&... tail) {
-			return sprout::detail::hash_values_combine_impl(sprout::hash_combine(seed, head), tail...);
-		}
-	}	// namespace detail
-
-	//
-	// hash_values_combine
-	//
-	template<typename... Args>
-	inline SPROUT_CONSTEXPR std::size_t
-	hash_values_combine(std::size_t seed, Args const&... args) {
-		return sprout::detail::hash_values_combine_impl(seed, args...);
-	}
-
-	//
-	// hash_values
-	//
-	template<typename... Args>
-	inline SPROUT_CONSTEXPR std::size_t
-	hash_values(Args const&... args) {
-		return sprout::hash_values_combine(0, args...);
-	}
-
 	//
 	// hash
 	//
diff --git a/sprout/functional/hash/hash_combine.hpp b/sprout/functional/hash/hash_combine.hpp
new file mode 100644
index 00000000..0cd8f1f4
--- /dev/null
+++ b/sprout/functional/hash/hash_combine.hpp
@@ -0,0 +1,20 @@
+#ifndef SPROUT_FUNCTIONAL_HASH_HASH_COMBINE_HPP
+#define SPROUT_FUNCTIONAL_HASH_HASH_COMBINE_HPP
+
+#include <cstddef>
+#include <sprout/config.hpp>
+#include <sprout/functional/hash/hash_fwd.hpp>
+#include <sprout/functional/hash/to_hash.hpp>
+
+namespace sprout {
+	//
+	// hash_combine
+	//
+	template<typename T>
+	inline SPROUT_CONSTEXPR std::size_t
+	hash_combine(std::size_t seed, T const& v) {
+		return seed ^ (sprout::to_hash(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2));
+	}
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_FUNCTIONAL_HASH_HASH_COMBINE_HPP
diff --git a/sprout/functional/hash/hash_range.hpp b/sprout/functional/hash/hash_range.hpp
new file mode 100644
index 00000000..6048d1db
--- /dev/null
+++ b/sprout/functional/hash/hash_range.hpp
@@ -0,0 +1,29 @@
+#ifndef SPROUT_FUNCTIONAL_HASH_HASH_RANGE_HPP
+#define SPROUT_FUNCTIONAL_HASH_HASH_RANGE_HPP
+
+#include <cstddef>
+#include <sprout/config.hpp>
+#include <sprout/functional/hash/hash_fwd.hpp>
+#include <sprout/functional/hash/hash_combine.hpp>
+#include <sprout/iterator/next.hpp>
+
+namespace sprout {
+	//
+	// hash_range
+	//
+	template<typename InputIterator>
+	inline SPROUT_CONSTEXPR std::size_t
+	hash_range(std::size_t seed, InputIterator first, InputIterator last) {
+		return first != last
+			? sprout::hash_range(sprout::hash_combine(seed, *first), sprout::next(first), last)
+			: seed
+			;
+	}
+	template<typename InputIterator>
+	inline SPROUT_CONSTEXPR std::size_t
+	hash_range(InputIterator first, InputIterator last) {
+		return sprout::hash_range(0, first, last);
+	}
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_FUNCTIONAL_HASH_HASH_RANGE_HPP
diff --git a/sprout/functional/hash/hash_value.hpp b/sprout/functional/hash/hash_value.hpp
new file mode 100644
index 00000000..67d3efda
--- /dev/null
+++ b/sprout/functional/hash/hash_value.hpp
@@ -0,0 +1,143 @@
+#ifndef SPROUT_FUNCTIONAL_HASH_HASH_VALUE_HPP
+#define SPROUT_FUNCTIONAL_HASH_HASH_VALUE_HPP
+
+#include <cstddef>
+#include <limits>
+#include <type_traits>
+#include <sprout/config.hpp>
+#include <sprout/functional/hash/hash_fwd.hpp>
+
+namespace sprout {
+	namespace hash_detail {
+		template <typename T>
+		struct is_basic_number
+			: public std::integral_constant<
+				bool,
+				std::is_integral<T>::value
+					&& (sizeof(T) <= sizeof(std::size_t))
+			>
+		{};
+		template <typename T>
+		struct is_long_number
+			: public std::integral_constant<
+				bool,
+				std::is_integral<T>::value
+					&& (sizeof(T) > sizeof(std::size_t))
+					&& std::is_signed<T>::value
+			>
+		{};
+		template <typename T>
+		struct is_ulong_number
+			: public std::integral_constant<
+				bool,
+				std::is_integral<T>::value
+					&& (sizeof(T) > sizeof(std::size_t))
+					&& std::is_unsigned<T>::value
+			>
+		{};
+
+		template<typename T>
+		inline SPROUT_CONSTEXPR std::size_t
+		hash_value_signed_2(T val, int length, std::size_t seed, T positive, std::size_t i) {
+			return i > 0
+				? hash_value_signed_2(
+					val,
+					length,
+					seed ^ static_cast<std::size_t>((positive >> i) + (seed << 6) + (seed >> 2)),
+					positive,
+					i - std::numeric_limits<std::size_t>::digits
+					)
+				: seed ^ static_cast<std::size_t>(val + (seed << 6) + (seed >> 2))
+				;
+		}
+		template<typename T>
+		inline SPROUT_CONSTEXPR std::size_t
+		hash_value_signed_1(T val, int length, std::size_t seed, T positive) {
+			return hash_value_signed_2(val, length, seed, positive, length * std::numeric_limits<std::size_t>::digits);
+		}
+		template<typename T>
+		inline SPROUT_CONSTEXPR std::size_t
+		hash_value_signed(T val) {
+			return sprout::hash_detail::hash_value_signed_1(
+				val,
+				(std::numeric_limits<T>::digits - 1) / std::numeric_limits<std::size_t>::digits,
+				0,
+				val < 0 ? -1 - val : val
+				);
+		}
+
+		template<typename T>
+		inline SPROUT_CONSTEXPR std::size_t
+		hash_value_unsigned_2(T val, int length, std::size_t seed, std::size_t i) {
+			return i > 0
+				? hash_value_unsigned_2(
+					val,
+					length,
+					seed ^ static_cast<std::size_t>((val >> i) + (seed << 6) + (seed >> 2)),
+					i - std::numeric_limits<std::size_t>::digits
+					)
+				: seed ^ static_cast<std::size_t>(val + (seed << 6) + (seed >> 2))
+				;
+		}
+		template<typename T>
+		inline SPROUT_CONSTEXPR std::size_t
+		hash_value_unsigned_1(T val, int length, std::size_t seed) {
+			return hash_value_unsigned_2(val, length, seed, length * std::numeric_limits<std::size_t>::digits);
+		}
+		template<typename T>
+		inline SPROUT_CONSTEXPR std::size_t
+		hash_value_unsigned(T val) {
+			return sprout::hash_detail::hash_value_unsigned_1(
+				val,
+				(std::numeric_limits<T>::digits - 1) / std::numeric_limits<std::size_t>::digits,
+				0
+				);
+		}
+
+		inline std::size_t
+		hash_value_pointer_1(std::size_t x) {
+			return x + (x >> 3);
+		}
+		template<typename T>
+		std::size_t
+		hash_value_pointer(T const* v) {
+			return sprout::hash_detail::hash_value_pointer_1(static_cast<std::size_t>(reinterpret_cast<std::ptrdiff_t>(v)));
+		}
+	}	// namespace hash_detail
+
+	//
+	// hash_value
+	//
+	template<typename T>
+	inline SPROUT_CONSTEXPR typename std::enable_if<sprout::hash_detail::is_basic_number<T>::value, std::size_t>::type
+	hash_value(T v) {
+		return static_cast<std::size_t>(v);
+	}
+	template<typename T>
+	inline SPROUT_CONSTEXPR typename std::enable_if<sprout::hash_detail::is_long_number<T>::value, std::size_t>::type
+	hash_value(T v) {
+		return sprout::hash_detail::hash_value_signed(v);
+	}
+	template<typename T>
+	inline SPROUT_CONSTEXPR typename std::enable_if<sprout::hash_detail::is_ulong_number<T>::value, std::size_t>::type
+	hash_value(T v) {
+		return sprout::hash_detail::hash_value_unsigned(v);
+	}
+	template<typename T>
+	inline SPROUT_CONSTEXPR typename std::enable_if<std::is_enum<T>::value, std::size_t>::type
+	hash_value(T v) {
+		return sprout::hash_value(static_cast<typename std::underlying_type<T>::type>(v));
+	}
+	template<typename T>
+	inline SPROUT_CONSTEXPR typename std::enable_if<std::is_pointer<typename std::remove_reference<T>::type>::value, std::size_t>::type
+	hash_value(T&& v) {
+		return sprout::hash_detail::hash_value_pointer(v);
+	}
+	template<typename T, std::size_t N>
+	inline SPROUT_CONSTEXPR std::size_t
+	hash_value(T const (&v)[N]) {
+		return sprout::hash_range(&v[0], &v[0] + N);
+	}
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_FUNCTIONAL_HASH_HASH_VALUE_HPP
diff --git a/sprout/functional/hash/hash_values.hpp b/sprout/functional/hash/hash_values.hpp
new file mode 100644
index 00000000..81bcf1cc
--- /dev/null
+++ b/sprout/functional/hash/hash_values.hpp
@@ -0,0 +1,20 @@
+#ifndef SPROUT_FUNCTIONAL_HASH_HASH_VALUES_HPP
+#define SPROUT_FUNCTIONAL_HASH_HASH_VALUES_HPP
+
+#include <cstddef>
+#include <sprout/config.hpp>
+#include <sprout/functional/hash/hash_fwd.hpp>
+#include <sprout/functional/hash/hash_values_combine.hpp>
+
+namespace sprout {
+	//
+	// hash_values
+	//
+	template<typename... Args>
+	inline SPROUT_CONSTEXPR std::size_t
+	hash_values(Args const&... args) {
+		return sprout::hash_values_combine(0, args...);
+	}
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_FUNCTIONAL_HASH_HASH_VALUES_HPP
diff --git a/sprout/functional/hash/hash_values_combine.hpp b/sprout/functional/hash/hash_values_combine.hpp
new file mode 100644
index 00000000..5c6d1c11
--- /dev/null
+++ b/sprout/functional/hash/hash_values_combine.hpp
@@ -0,0 +1,33 @@
+#ifndef SPROUT_FUNCTIONAL_HASH_HASH_VALUES_COMBINE_HPP
+#define SPROUT_FUNCTIONAL_HASH_HASH_VALUES_COMBINE_HPP
+
+#include <cstddef>
+#include <sprout/config.hpp>
+#include <sprout/functional/hash/hash_fwd.hpp>
+#include <sprout/functional/hash/hash_combine.hpp>
+
+namespace sprout {
+	namespace detail {
+		template<typename T>
+		inline SPROUT_CONSTEXPR std::size_t
+		hash_values_combine_impl(std::size_t seed, T const& v) {
+			return sprout::hash_combine(seed, v);
+		}
+		template<typename Head, typename... Tail>
+		inline SPROUT_CONSTEXPR std::size_t
+		hash_values_combine_impl(std::size_t seed, Head const& head, Tail const&... tail) {
+			return sprout::detail::hash_values_combine_impl(sprout::hash_combine(seed, head), tail...);
+		}
+	}	// namespace detail
+
+	//
+	// hash_values_combine
+	//
+	template<typename... Args>
+	inline SPROUT_CONSTEXPR std::size_t
+	hash_values_combine(std::size_t seed, Args const&... args) {
+		return sprout::detail::hash_values_combine_impl(seed, args...);
+	}
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_FUNCTIONAL_HASH_HASH_VALUES_COMBINE_HPP
diff --git a/sprout/functional/hash/sscrisk/cel/utility.hpp b/sprout/functional/hash/sscrisk/cel/utility.hpp
index 8b39d424..9faa8ea6 100644
--- a/sprout/functional/hash/sscrisk/cel/utility.hpp
+++ b/sprout/functional/hash/sscrisk/cel/utility.hpp
@@ -13,7 +13,7 @@ namespace sprout {
 	template<typename T1, typename T2>
 	inline SPROUT_CONSTEXPR std::size_t
 	hash_value(sscrisk::cel::pair<T1, T2> const& v) {
-		return sprout::hash_combine(sprout::hash_combine(0, v.first), v.second);
+		return sprout::hash_values(v.first, v.second);
 	}
 }	// namespace sprout
 
diff --git a/sprout/functional/hash/to_hash.hpp b/sprout/functional/hash/to_hash.hpp
new file mode 100644
index 00000000..c9a6fc84
--- /dev/null
+++ b/sprout/functional/hash/to_hash.hpp
@@ -0,0 +1,145 @@
+#ifndef SPROUT_FUNCTIONAL_HASH_TO_HASH_HPP
+#define SPROUT_FUNCTIONAL_HASH_TO_HASH_HPP
+
+#include <cstddef>
+#include <utility>
+#include <type_traits>
+#include <sprout/config.hpp>
+#include <sprout/functional/hash/hash_fwd.hpp>
+#include <sprout/functional/hash/hash_value.hpp>
+#include <sprout/utility/forward.hpp>
+#include <sprout/type_traits/enabler_if.hpp>
+#include <sprout/adl/not_found.hpp>
+
+namespace sprout_adl {
+	sprout::not_found_via_adl hash_value(...);
+}	// namespace sprout_adl
+
+namespace sprout_hash_detail {
+	using sprout::hash_value;
+	using sprout_adl::hash_value;
+
+	template<typename T>
+	struct has_adl_hash_value_test {
+	public:
+		template<
+			typename U = T,
+			typename sprout::enabler_if<
+				sprout::is_found_via_adl<decltype(hash_value(std::declval<U>()))>::value
+			>::type = sprout::enabler
+		>
+		static std::true_type test(int);
+		static std::false_type test(...);
+	};
+#if defined(_MSC_VER)
+	template<typename T, typename Base_ = decltype(sprout_hash_detail::has_adl_hash_value_test<T>::test(0))>
+	struct has_adl_hash_value
+		: public Base_
+	{};
+#else
+	template<typename T>
+	struct has_adl_hash_value
+		: public decltype(sprout_hash_detail::has_adl_hash_value_test<T>::test(0))
+	{};
+#endif
+
+	template<typename T, typename Enable = void>
+	struct select_adl_hash_value;
+	template<typename T>
+	struct select_adl_hash_value<
+		T,
+		typename std::enable_if<
+			sprout_hash_detail::has_adl_hash_value<T>::value
+		>::type
+	>
+		: public std::true_type
+	{};
+	template<typename T>
+	struct select_adl_hash_value<
+		T,
+		typename std::enable_if<!(
+			sprout_hash_detail::has_adl_hash_value<T>::value
+		)>::type
+	>
+		: public std::false_type
+	{};
+
+	template<typename T, typename Enable = void>
+	struct select_std_hash;
+	template<typename T>
+	struct select_std_hash<
+		T,
+		typename std::enable_if<
+			!sprout_hash_detail::has_adl_hash_value<T>::value
+		>::type
+	>
+		: public std::true_type
+	{};
+	template<typename T>
+	struct select_std_hash<
+		T,
+		typename std::enable_if<!(
+			!sprout_hash_detail::has_adl_hash_value<T>::value
+		)>::type
+	>
+		: public std::false_type
+	{};
+
+	template<typename T, typename = void>
+	struct noexcept_to_hash;
+	template<typename T>
+	struct noexcept_to_hash<T, typename std::enable_if<sprout_hash_detail::select_adl_hash_value<T>::value>::type>
+		: public std::integral_constant<bool, SPROUT_NOEXCEPT_EXPR_OR_DEFAULT(hash_value(std::declval<T>()), false)>
+	{};
+	template<typename T>
+	struct noexcept_to_hash<T, typename std::enable_if<sprout_hash_detail::select_std_hash<T>::value>::type>
+		: public std::integral_constant<bool, SPROUT_NOEXCEPT_EXPR_OR_DEFAULT(std::hash<typename std::decay<T>::type>()(std::declval<T>()), false)>
+	{};
+
+	template<typename T, typename = void>
+	struct to_hash_result;
+	template<typename T>
+	struct to_hash_result<T, typename std::enable_if<sprout_hash_detail::select_adl_hash_value<T>::value>::type> {
+	public:
+		typedef decltype(hash_value(std::declval<T>())) type;
+	};
+	template<typename T>
+	struct to_hash_result<T, typename std::enable_if<sprout_hash_detail::select_std_hash<T>::value>::type> {
+	public:
+		typedef decltype(std::hash<typename std::decay<T>::type>()(std::declval<T>())) type;
+	};
+
+	template<
+		typename T,
+		typename sprout::enabler_if<sprout_hash_detail::select_adl_hash_value<T>::value>::type = sprout::enabler
+	>
+	inline SPROUT_CONSTEXPR typename sprout_hash_detail::to_hash_result<T>::type
+	to_hash_impl(T&& t)
+	SPROUT_NOEXCEPT_EXPR((sprout_hash_detail::noexcept_to_hash<T>::value))
+	{
+		return hash_value(sprout::forward<T>(t));
+	}
+	template<
+		typename T,
+		typename sprout::enabler_if<sprout_hash_detail::select_std_hash<T>::value>::type = sprout::enabler
+	>
+	inline SPROUT_CONSTEXPR typename sprout_hash_detail::to_hash_result<T>::type
+	to_hash_impl(T&& t)
+	SPROUT_NOEXCEPT_EXPR((sprout_hash_detail::noexcept_to_hash<T>::value))
+	{
+		return std::hash<typename std::decay<T>::type>()(sprout::forward<T>(t));
+	}
+}	// namespace sprout_hash_detail
+
+namespace sprout {
+	//
+	// to_hash
+	//
+	template<typename T>
+	inline SPROUT_CONSTEXPR std::size_t
+	to_hash(T const& v) {
+		return sprout_hash_detail::to_hash_impl(v);
+	}
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_FUNCTIONAL_HASH_TO_HASH_HPP
diff --git a/sprout/logic/tribool/hash.hpp b/sprout/logic/tribool/hash.hpp
index 74635deb..66119f8a 100644
--- a/sprout/logic/tribool/hash.hpp
+++ b/sprout/logic/tribool/hash.hpp
@@ -3,8 +3,8 @@
 
 #include <cstddef>
 #include <sprout/config.hpp>
-#include <sprout/functional/hash/hash.hpp>
 #include <sprout/logic/tribool/tribool.hpp>
+#include <sprout/functional/hash.hpp>
 
 namespace sprout {
 	//
diff --git a/sprout/optional/hash.hpp b/sprout/optional/hash.hpp
index 37bf9cbd..d20a8313 100644
--- a/sprout/optional/hash.hpp
+++ b/sprout/optional/hash.hpp
@@ -3,8 +3,8 @@
 
 #include <cstddef>
 #include <sprout/config.hpp>
-#include <sprout/functional/hash/hash.hpp>
 #include <sprout/optional/optional.hpp>
+#include <sprout/functional/hash.hpp>
 
 namespace sprout {
 	//
diff --git a/sprout/pit/hash.hpp b/sprout/pit/hash.hpp
index 426bacc4..5963844e 100644
--- a/sprout/pit/hash.hpp
+++ b/sprout/pit/hash.hpp
@@ -3,8 +3,8 @@
 
 #include <cstddef>
 #include <sprout/config.hpp>
-#include <sprout/functional/hash/hash.hpp>
 #include <sprout/pit/pit.hpp>
+#include <sprout/functional/hash.hpp>
 
 namespace sprout {
 	//
diff --git a/sprout/rational/hash.hpp b/sprout/rational/hash.hpp
index 6864917a..e9368f32 100644
--- a/sprout/rational/hash.hpp
+++ b/sprout/rational/hash.hpp
@@ -4,7 +4,7 @@
 #include <cstddef>
 #include <sprout/config.hpp>
 #include <sprout/rational/rational.hpp>
-#include <sprout/functional/hash/hash.hpp>
+#include <sprout/functional/hash.hpp>
 
 namespace sprout {
 	//
diff --git a/sprout/string/hash.hpp b/sprout/string/hash.hpp
index b0ee5354..9c1eb753 100644
--- a/sprout/string/hash.hpp
+++ b/sprout/string/hash.hpp
@@ -4,7 +4,7 @@
 #include <cstddef>
 #include <sprout/config.hpp>
 #include <sprout/string/string.hpp>
-#include <sprout/functional/hash/hash.hpp>
+#include <sprout/functional/hash.hpp>
 
 namespace sprout {
 	//
diff --git a/sprout/sub_array/hash.hpp b/sprout/sub_array/hash.hpp
index d56b9cf6..4cd656bf 100644
--- a/sprout/sub_array/hash.hpp
+++ b/sprout/sub_array/hash.hpp
@@ -2,8 +2,8 @@
 #define SPROUT_SUB_ARRAY_HASH_HPP
 
 #include <sprout/config.hpp>
-#include <sprout/functional/hash/hash.hpp>
 #include <sprout/sub_array/sub_array.hpp>
+#include <sprout/functional/hash.hpp>
 
 namespace sprout {
 	//
diff --git a/sprout/tuple/tuple/hash.hpp b/sprout/tuple/tuple/hash.hpp
index 3f2a83cd..39bb9bd2 100644
--- a/sprout/tuple/tuple/hash.hpp
+++ b/sprout/tuple/tuple/hash.hpp
@@ -4,7 +4,7 @@
 #include <cstddef>
 #include <sprout/config.hpp>
 #include <sprout/index_tuple.hpp>
-#include <sprout/functional/hash/hash.hpp>
+#include <sprout/functional/hash.hpp>
 #include <sprout/tuple/tuple/tuple.hpp>
 #include <sprout/tuple/tuple/get.hpp>
 
diff --git a/sprout/utility/pair/hash.hpp b/sprout/utility/pair/hash.hpp
index a29d922e..a3d94a8b 100644
--- a/sprout/utility/pair/hash.hpp
+++ b/sprout/utility/pair/hash.hpp
@@ -3,8 +3,8 @@
 
 #include <cstddef>
 #include <sprout/config.hpp>
-#include <sprout/functional/hash/hash.hpp>
 #include <sprout/utility/pair/pair.hpp>
+#include <sprout/functional/hash.hpp>
 
 namespace sprout {
 	//
diff --git a/sprout/utility/value_holder/hash.hpp b/sprout/utility/value_holder/hash.hpp
index ab6633b4..4bcd301a 100644
--- a/sprout/utility/value_holder/hash.hpp
+++ b/sprout/utility/value_holder/hash.hpp
@@ -3,8 +3,8 @@
 
 #include <cstddef>
 #include <sprout/config.hpp>
-#include <sprout/functional/hash/hash.hpp>
 #include <sprout/utility/value_holder/value_holder.hpp>
+#include <sprout/functional/hash.hpp>
 
 namespace sprout {
 	//
diff --git a/sprout/uuid/hash.hpp b/sprout/uuid/hash.hpp
index 08572aa6..b5332b35 100644
--- a/sprout/uuid/hash.hpp
+++ b/sprout/uuid/hash.hpp
@@ -3,8 +3,8 @@
 
 #include <cstddef>
 #include <sprout/config.hpp>
-#include <sprout/functional/hash/hash.hpp>
 #include <sprout/uuid/uuid.hpp>
+#include <sprout/functional/hash.hpp>
 
 namespace sprout {
 	//
diff --git a/sprout/variant/hash.hpp b/sprout/variant/hash.hpp
index 9e1c6bdb..66db3172 100644
--- a/sprout/variant/hash.hpp
+++ b/sprout/variant/hash.hpp
@@ -3,7 +3,7 @@
 
 #include <cstddef>
 #include <sprout/config.hpp>
-#include <sprout/functional/hash/hash.hpp>
+#include <sprout/functional/hash.hpp>
 #include <sprout/variant/variant.hpp>
 #include <sprout/variant/static_visitor.hpp>
 #include <sprout/variant/apply_visitor.hpp>