diff --git a/libs/algorithm/test/copy.cpp b/libs/algorithm/test/copy.cpp
index 07419a30..2db4c922 100644
--- a/libs/algorithm/test/copy.cpp
+++ b/libs/algorithm/test/copy.cpp
@@ -114,7 +114,7 @@ namespace testspr {
 					array<int, 10>{{3, 4, 5, 6, 7, 8, 0, 0, 0, 0}}
 					));
 			}
-			// !!!
+			// !!! BUG: sprout::fit::copy implementation requires ForwardIterator
 //			{
 //				SPROUT_STATIC_CONSTEXPR auto copied = sprout::fit::copy(
 //					testspr::reduct_input(sprout::begin(arr1) + 2),
@@ -139,7 +139,7 @@ namespace testspr {
 					array<int, 4>{{3, 4, 5, 6}}
 					));
 			}
-			// !!!
+			// !!! BUG: sprout::fit::copy implementation requires ForwardIterator
 //			{
 //				SPROUT_STATIC_CONSTEXPR auto copied = sprout::fit::copy(
 //					testspr::reduct_input(sprout::begin(arr1) + 2),
@@ -168,7 +168,7 @@ namespace testspr {
 					array<int, 10>{{0, 0, 3, 4, 5, 6, 7, 8, 0, 0}}
 					));
 			}
-			// !!!
+			// !!! BUG: sprout::fit::copy implementation requires ForwardIterator
 //			{
 //				SPROUT_STATIC_CONSTEXPR auto copied = sprout::fit::copy(
 //					testspr::reduct_input(sprout::begin(arr1) + 2),
diff --git a/sprout/cstdint.hpp b/sprout/cstdint.hpp
index a0f81d8f..c8d00683 100644
--- a/sprout/cstdint.hpp
+++ b/sprout/cstdint.hpp
@@ -17,7 +17,7 @@
 // SPROUT_INT[N]_C
 // SPROUT_UINT[N]_C
 //
-#if SPROUT_CLANG_BETWEEN(3, 0, 0, 3, 3, 0) && !defined(__STDC_CONSTANT_MACROS)
+#if SPROUT_CLANG_BETWEEN((3, 0, 0), (3, 3, 0)) && !defined(__STDC_CONSTANT_MACROS)
 #	define SPROUT_INT8_C(n) n
 #	define SPROUT_UINT8_C(n) n
 #	define SPROUT_INT16_C(n) n
diff --git a/sprout/detail/predef.hpp b/sprout/detail/predef.hpp
index 047b4fba..5bb2e117 100644
--- a/sprout/detail/predef.hpp
+++ b/sprout/detail/predef.hpp
@@ -11,12 +11,31 @@
 #include <sprout/config.hpp>
 
 //
-// SPROUT_IS_GCC
+// SPROUT_VERSION_NUMBER
+//
+#define SPROUT_VERSION_NUMBER(major, minor, patch) \
+	((((major) % 100) * 10000000) + (((minor) % 100) * 100000) + ((patch) % 100000))
+//
+// SPROUT_VERSION_NUMBER_ZERO
+//
+#define SPROUT_VERSION_NUMBER_ZERO \
+    SPROUT_VERSION_NUMBER(0, 0, 0)
+
+//
+// SPROUT_AVAILABLE_GCC
 //
 #if defined(__GNUC__)
-#	define SPROUT_IS_GCC (1)
+#	define SPROUT_AVAILABLE_GCC (1)
 #else
-#	define SPROUT_IS_GCC (0)
+#	define SPROUT_AVAILABLE_GCC (0)
+#endif
+//
+// SPROUT_VERSION_GCC
+//
+#if SPROUT_AVAILABLE_GCC
+#	define SPROUT_VERSION_GCC SPROUT_VERSION_NUMBER(__GNUC__, __GNUC_MINOR__, __GNUC_PATCHLEVEL__)
+#else
+#	define SPROUT_VERSION_GCC SPROUT_VERSION_NUMBER_ZERO
 #endif
 //
 // SPROUT_GCC_LESS
@@ -24,55 +43,56 @@
 // SPROUT_GCC_LESS_EQUAL
 // SPROUT_GCC_GREATER_EQUAL
 //
-#if SPROUT_IS_GCC
-#	define SPROUT_GCC_LESS(major, minor, patch) ( \
-		__GNUC__ < major \
-		|| (__GNUC__ == major && __GNUC_MINOR__ < minor) \
-		|| (__GNUC__ == major && __GNUC_MINOR__ == minor && __GNUC_PATCHLEVEL__ < patch) \
-		)
-#	define SPROUT_GCC_GREATER(major, minor, patch) ( \
-		__GNUC__ > major \
-		|| (__GNUC__ == major && __GNUC_MINOR__ > minor) \
-		|| (__GNUC__ == major && __GNUC_MINOR__ == minor && __GNUC_PATCHLEVEL__ > patch) \
-		)
-#	define SPROUT_GCC_LESS_EQUAL(major, minor, patch) ( \
-		__GNUC__ < major \
-		|| (__GNUC__ == major && __GNUC_MINOR__ < minor) \
-		|| (__GNUC__ == major && __GNUC_MINOR__ == minor && __GNUC_PATCHLEVEL__ <= patch) \
-		)
-#	define SPROUT_GCC_GREATER_EQUAL(major, minor, patch) ( \
-		__GNUC__ > major \
-		|| (__GNUC__ == major && __GNUC_MINOR__ > minor) \
-		|| (__GNUC__ == major && __GNUC_MINOR__ == minor && __GNUC_PATCHLEVEL__ >= patch) \
-		)
+#if SPROUT_AVAILABLE_GCC
+#	define SPROUT_GCC_LESS(major, minor, patch) \
+		(SPROUT_VERSION_GCC < SPROUT_VERSION_NUMBER(major, minor, patch))
+#	define SPROUT_GCC_GREATER(major, minor, patch) \
+		(SPROUT_VERSION_GCC > SPROUT_VERSION_NUMBER(major, minor, patch))
+#	define SPROUT_GCC_LESS_EQUAL(major, minor, patch) \
+		(SPROUT_VERSION_GCC <= SPROUT_VERSION_NUMBER(major, minor, patch))
+#	define SPROUT_GCC_GREATER_EQUAL(major, minor, patch) \
+		(SPROUT_VERSION_GCC >= SPROUT_VERSION_NUMBER(major, minor, patch))
 #else
-#	define SPROUT_GCC_LESS(major, minor, patch) (0)
-#	define SPROUT_GCC_GREATER(major, minor, patch) (0)
-#	define SPROUT_GCC_LESS_EQUAL(major, minor, patch) (0)
-#	define SPROUT_GCC_GREATER_EQUAL(major, minor, patch) (0)
+#	define SPROUT_GCC_LESS(major, minor, patch) \
+		(0)
+#	define SPROUT_GCC_GREATER(major, minor, patch) \
+		(0)
+#	define SPROUT_GCC_LESS_EQUAL(major, minor, patch) \
+		(0)
+#	define SPROUT_GCC_GREATER_EQUAL(major, minor, patch) \
+		(0)
 #endif
 //
 // SPROUT_GCC_BETWEEN
 //
-#if SPROUT_IS_GCC
-#	define SPROUT_GCC_BETWEEN(major1, minor1, patch1, major2, minor2, patch2) \
-		SPROUT_GCC_GREATER_EQUAL(major1, minor1, patch1) && SPROUT_GCC_LESS(major2, minor2, patch2)
+#if SPROUT_AVAILABLE_GCC
+#	define SPROUT_GCC_BETWEEN(first_version, last_version) \
+		(SPROUT_GCC_GREATER_EQUAL first_version && SPROUT_GCC_LESS last_version)
 #else
-#	define SPROUT_GCC_BETWEEN(major1, minor1, patch1, major2, minor2, patch2) (0)
+#	define SPROUT_GCC_BETWEEN(first_version, last_version) \
+		(0)
 #endif
 
 //
-// SPROUT_IS_CLANG
+// SPROUT_AVAILABLE_CLANG
 //
 #if defined(__clang__)
-#	define SPROUT_IS_CLANG (1)
+#	define SPROUT_AVAILABLE_CLANG (1)
 #else
-#	define SPROUT_IS_CLANG (0)
+#	define SPROUT_AVAILABLE_CLANG (0)
+#endif
+//
+// SPROUT_VERSION_CLANG
+//
+#if SPROUT_AVAILABLE_CLANG
+#	define SPROUT_VERSION_CLANG SPROUT_VERSION_NUMBER(__clang_major__, __clang_minor__, __clang_patchlevel__)
+#else
+#	define SPROUT_VERSION_CLANG SPROUT_VERSION_NUMBER_ZERO
 #endif
 //
 // SPROUT_CLANG_HAS_FUTURE
 //
-#if SPROUT_IS_CLANG
+#if SPROUT_AVAILABLE_CLANG
 #	define SPROUT_CLANG_HAS_FUTURE(future) (__has_feature(future))
 #else
 #	define SPROUT_CLANG_HAS_FUTURE(future) (0)
@@ -83,41 +103,34 @@
 // SPROUT_CLANG_LESS_EQUAL
 // SPROUT_CLANG_GREATER_EQUAL
 //
-#if SPROUT_IS_CLANG
-#	define SPROUT_CLANG_LESS(major, minor, patch) ( \
-		__clang_major__ < major \
-		|| (__clang_major__ == major && __clang_minor__ < minor) \
-		|| (__clang_major__ == major && __clang_minor__ == minor && __clang_patchlevel__ < patch) \
-		)
-#	define SPROUT_CLANG_GREATER(major, minor, patch) ( \
-		__clang_major__ > major \
-		|| (__clang_major__ == major && __clang_minor__ > minor) \
-		|| (__clang_major__ == major && __clang_minor__ == minor && __clang_patchlevel__ > patch) \
-		)
-#	define SPROUT_CLANG_LESS_EQUAL(major, minor, patch) ( \
-		__clang_major__ < major \
-		|| (__clang_major__ == major && __clang_minor__ < minor) \
-		|| (__clang_major__ == major && __clang_minor__ == minor && __clang_patchlevel__ <= patch) \
-		)
-#	define SPROUT_CLANG_GREATER_EQUAL(major, minor, patch) ( \
-		__clang_major__ > major \
-		|| (__clang_major__ == major && __clang_minor__ > minor) \
-		|| (__clang_major__ == major && __clang_minor__ == minor && __clang_patchlevel__ >= patch) \
-		)
+#if SPROUT_AVAILABLE_CLANG
+#	define SPROUT_CLANG_LESS(major, minor, patch) \
+		(SPROUT_VERSION_CLANG < SPROUT_VERSION_NUMBER(major, minor, patch))
+#	define SPROUT_CLANG_GREATER(major, minor, patch) \
+		(SPROUT_VERSION_CLANG > SPROUT_VERSION_NUMBER(major, minor, patch))
+#	define SPROUT_CLANG_LESS_EQUAL(major, minor, patch) \
+		(SPROUT_VERSION_CLANG <= SPROUT_VERSION_NUMBER(major, minor, patch))
+#	define SPROUT_CLANG_GREATER_EQUAL(major, minor, patch) \
+		(SPROUT_VERSION_CLANG >= SPROUT_VERSION_NUMBER(major, minor, patch))
 #else
-#	define SPROUT_CLANG_LESS(major, minor, patch) (0)
-#	define SPROUT_CLANG_GREATER(major, minor, patch) (0)
-#	define SPROUT_CLANG_LESS_EQUAL(major, minor, patch) (0)
-#	define SPROUT_CLANG_GREATER_EQUAL(major, minor, patch) (0)
+#	define SPROUT_CLANG_LESS(major, minor, patch) \
+		(0)
+#	define SPROUT_CLANG_GREATER(major, minor, patch) \
+		(0)
+#	define SPROUT_CLANG_LESS_EQUAL(major, minor, patch) \
+		(0)
+#	define SPROUT_CLANG_GREATER_EQUAL(major, minor, patch) \
+		(0)
 #endif
 //
 // SPROUT_CLANG_BETWEEN
 //
-#if SPROUT_IS_CLANG
-#	define SPROUT_CLANG_BETWEEN(major1, minor1, patch1, major2, minor2, patch2) \
-		SPROUT_CLANG_GREATER_EQUAL(major1, minor1, patch1) && SPROUT_CLANG_LESS(major2, minor2, patch2)
+#if SPROUT_AVAILABLE_CLANG
+#	define SPROUT_CLANG_BETWEEN(first_version, last_version) \
+		(SPROUT_CLANG_GREATER_EQUAL first_version && SPROUT_CLANG_LESS last_version)
 #else
-#	define SPROUT_CLANG_BETWEEN(major1, minor1, patch1, major2, minor2, patch2) (0)
+#	define SPROUT_CLANG_BETWEEN(first_version, last_version) \
+		(0)
 #endif
 
 #endif	// #ifndef SPROUT_DETAIL_PREDEF_HPP
diff --git a/sprout/optional/optional.hpp b/sprout/optional/optional.hpp
index 33b1f286..9a6556f4 100644
--- a/sprout/optional/optional.hpp
+++ b/sprout/optional/optional.hpp
@@ -107,7 +107,7 @@ namespace sprout {
 			: init(v.init)
 			, val(v.is_initialized() ? holder_type(*v) : holder_type())
 		{}
-#if SPROUT_GCC_BETWEEN(4, 8, 0, 4, 8, 2)
+#if SPROUT_GCC_BETWEEN((4, 8, 0), (4, 8, 2))
 		optional(optional&&) = default;
 #else
 		SPROUT_CONSTEXPR optional(optional&& v)
diff --git a/sprout/tuple/tuple/tuple_decl.hpp b/sprout/tuple/tuple/tuple_decl.hpp
index d5c2868b..31e39ac4 100644
--- a/sprout/tuple/tuple/tuple_decl.hpp
+++ b/sprout/tuple/tuple/tuple_decl.hpp
@@ -189,7 +189,7 @@ namespace sprout {
 					, base_type(sprout::forward<UHead>(h))
 				{}
 				tuple_impl(tuple_impl const&) = default;
-#if SPROUT_GCC_BETWEEN(4, 8, 0, 4, 8, 2)
+#if SPROUT_GCC_BETWEEN((4, 8, 0), (4, 8, 2))
 				tuple_impl(tuple_impl&&) = default;
 #else
 				SPROUT_CONSTEXPR tuple_impl(tuple_impl&& t)