From ffb876c930df2c5acc2afa4f0d2cfa3f629654e6 Mon Sep 17 00:00:00 2001
From: bolero-MURAKAMI <bolero.murakami@gmail.com>
Date: Mon, 29 Apr 2013 10:56:46 +0900
Subject: [PATCH] fix math functions

---
 sprout/math.hpp             |  1 +
 sprout/math/acos.hpp        |  6 ++++--
 sprout/math/acosh.hpp       |  4 +++-
 sprout/math/asin.hpp        |  4 +++-
 sprout/math/asinh.hpp       |  4 +++-
 sprout/math/atan.hpp        |  4 +++-
 sprout/math/atan2.hpp       | 15 +++++++++++++--
 sprout/math/atanh.hpp       |  6 ++++--
 sprout/math/constants.hpp   |  5 +++++
 sprout/math/copysign.hpp    | 19 ++++++++++++++-----
 sprout/math/cos.hpp         |  9 +++++----
 sprout/math/cosh.hpp        |  5 +++--
 sprout/math/isfinite.hpp    |  2 +-
 sprout/math/isinf.hpp       |  2 +-
 sprout/math/isnan.hpp       |  2 +-
 sprout/math/isnormal.hpp    |  2 +-
 sprout/math/issubnormal.hpp |  4 ++--
 sprout/math/iszero.hpp      |  2 +-
 sprout/math/signbit.hpp     |  3 ++-
 sprout/math/sin.hpp         |  7 ++++---
 sprout/math/sinh.hpp        |  4 +++-
 sprout/math/tan.hpp         |  8 +++++---
 sprout/math/tanh.hpp        |  4 +++-
 23 files changed, 85 insertions(+), 37 deletions(-)

diff --git a/sprout/math.hpp b/sprout/math.hpp
index b6ea1eba..05c8ba2f 100644
--- a/sprout/math.hpp
+++ b/sprout/math.hpp
@@ -3,5 +3,6 @@
 
 #include <sprout/config.hpp>
 #include <sprout/math/functions.hpp>
+#include <sprout/math/constants.hpp>
 
 #endif	// #ifndef SPROUT_MATH_HPP
diff --git a/sprout/math/acos.hpp b/sprout/math/acos.hpp
index dc5c71fe..84cddb41 100644
--- a/sprout/math/acos.hpp
+++ b/sprout/math/acos.hpp
@@ -6,9 +6,10 @@
 #include <sprout/config.hpp>
 #include <sprout/math/detail/config.hpp>
 #include <sprout/math/detail/float_compute.hpp>
+#include <sprout/math/constants.hpp>
+#include <sprout/math/isnan.hpp>
 #include <sprout/math/asin.hpp>
 #include <sprout/math/fabs.hpp>
-#include <sprout/math/constants.hpp>
 #include <sprout/type_traits/enabler_if.hpp>
 
 namespace sprout {
@@ -26,7 +27,8 @@ namespace sprout {
 			>
 			inline SPROUT_CONSTEXPR FloatType
 			acos(FloatType x) {
-				return sprout::math::fabs(x) > 1 ? std::numeric_limits<FloatType>::quiet_NaN()
+				return sprout::math::isnan(x) ? x
+					: sprout::math::fabs(x) > 1 ? std::numeric_limits<FloatType>::quiet_NaN()
 #if SPROUT_USE_BUILTIN_CMATH_FUNCTION
 					: std::acos(x)
 #else
diff --git a/sprout/math/acosh.hpp b/sprout/math/acosh.hpp
index 38423d86..0fb5f546 100644
--- a/sprout/math/acosh.hpp
+++ b/sprout/math/acosh.hpp
@@ -6,6 +6,7 @@
 #include <sprout/config.hpp>
 #include <sprout/math/detail/config.hpp>
 #include <sprout/math/detail/float_compute.hpp>
+#include <sprout/math/isnan.hpp>
 #include <sprout/math/log.hpp>
 #include <sprout/math/sqrt.hpp>
 #include <sprout/type_traits/enabler_if.hpp>
@@ -25,7 +26,8 @@ namespace sprout {
 			>
 			inline SPROUT_CONSTEXPR FloatType
 			acosh(FloatType x) {
-				return x < 1 ? std::numeric_limits<FloatType>::quiet_NaN()
+				return sprout::math::isnan(x) ? x
+					: x < 1 ? -std::numeric_limits<FloatType>::quiet_NaN()
 					: x == std::numeric_limits<FloatType>::infinity() ? std::numeric_limits<FloatType>::infinity()
 #if SPROUT_USE_BUILTIN_CMATH_FUNCTION
 					: std::acosh(x)
diff --git a/sprout/math/asin.hpp b/sprout/math/asin.hpp
index b01070a3..14304e06 100644
--- a/sprout/math/asin.hpp
+++ b/sprout/math/asin.hpp
@@ -10,6 +10,7 @@
 #include <sprout/math/detail/float_compute.hpp>
 #include <sprout/math/constants.hpp>
 #include <sprout/math/factorial.hpp>
+#include <sprout/math/isnan.hpp>
 #include <sprout/math/fabs.hpp>
 #include <sprout/math/sqrt.hpp>
 #include <sprout/type_traits/enabler_if.hpp>
@@ -43,7 +44,8 @@ namespace sprout {
 			>
 			inline SPROUT_CONSTEXPR FloatType
 			asin(FloatType x) {
-				return sprout::math::fabs(x) > 1 ? std::numeric_limits<FloatType>::quiet_NaN()
+				return sprout::math::isnan(x) ? x
+					: sprout::math::fabs(x) > 1 ? std::numeric_limits<FloatType>::quiet_NaN()
 #if SPROUT_USE_BUILTIN_CMATH_FUNCTION
 					: std::asin(x)
 #else
diff --git a/sprout/math/asinh.hpp b/sprout/math/asinh.hpp
index 16782d6c..673f4ffd 100644
--- a/sprout/math/asinh.hpp
+++ b/sprout/math/asinh.hpp
@@ -6,6 +6,7 @@
 #include <sprout/config.hpp>
 #include <sprout/math/detail/config.hpp>
 #include <sprout/math/detail/float_compute.hpp>
+#include <sprout/math/isnan.hpp>
 #include <sprout/math/log.hpp>
 #include <sprout/math/sqrt.hpp>
 #include <sprout/type_traits/enabler_if.hpp>
@@ -25,7 +26,8 @@ namespace sprout {
 			>
 			inline SPROUT_CONSTEXPR FloatType
 			asinh(FloatType x) {
-				return x == std::numeric_limits<FloatType>::infinity() ? std::numeric_limits<FloatType>::infinity()
+				return sprout::math::isnan(x) ? x
+					: x == std::numeric_limits<FloatType>::infinity() ? std::numeric_limits<FloatType>::infinity()
 					: x == -std::numeric_limits<FloatType>::infinity() ? -std::numeric_limits<FloatType>::infinity()
 #if SPROUT_USE_BUILTIN_CMATH_FUNCTION
 					: std::asinh(x)
diff --git a/sprout/math/atan.hpp b/sprout/math/atan.hpp
index 3177e69f..c68cf2f8 100644
--- a/sprout/math/atan.hpp
+++ b/sprout/math/atan.hpp
@@ -10,6 +10,7 @@
 #include <sprout/math/detail/float_compute.hpp>
 #include <sprout/math/constants.hpp>
 #include <sprout/math/factorial.hpp>
+#include <sprout/math/isnan.hpp>
 #include <sprout/type_traits/enabler_if.hpp>
 
 namespace sprout {
@@ -41,7 +42,8 @@ namespace sprout {
 			>
 			inline SPROUT_CONSTEXPR FloatType
 			atan(FloatType x) {
-				return x == std::numeric_limits<FloatType>::infinity() ? sprout::math::half_pi<FloatType>()
+				return sprout::math::isnan(x) ? x
+					: x == std::numeric_limits<FloatType>::infinity() ? sprout::math::half_pi<FloatType>()
 					: x == -std::numeric_limits<FloatType>::infinity() ? -sprout::math::half_pi<FloatType>()
 #if SPROUT_USE_BUILTIN_CMATH_FUNCTION
 					: std::atan(x)
diff --git a/sprout/math/atan2.hpp b/sprout/math/atan2.hpp
index 41cbba9e..1faef1ff 100644
--- a/sprout/math/atan2.hpp
+++ b/sprout/math/atan2.hpp
@@ -7,6 +7,8 @@
 #include <sprout/math/detail/config.hpp>
 #include <sprout/math/detail/float_compute.hpp>
 #include <sprout/math/constants.hpp>
+#include <sprout/math/isnan.hpp>
+#include <sprout/math/signbit.hpp>
 #include <sprout/math/copysign.hpp>
 #include <sprout/math/signbit.hpp>
 #include <sprout/math/atan.hpp>
@@ -33,7 +35,13 @@ namespace sprout {
 			>
 			inline SPROUT_CONSTEXPR FloatType
 			atan2(FloatType y, FloatType x) {
-				return x == -std::numeric_limits<FloatType>::infinity()
+				return sprout::math::isnan(y)
+						? sprout::math::isnan(x)
+							? sprout::math::signbit(y) && sprout::math::signbit(x) ? -std::numeric_limits<double>::quiet_NaN()
+								: std::numeric_limits<double>::quiet_NaN()
+							: y
+					: sprout::math::isnan(x) ? x
+					: x == -std::numeric_limits<FloatType>::infinity()
 						? y == std::numeric_limits<FloatType>::infinity() ? sprout::math::three_quarters_pi<FloatType>()
 							: y == -std::numeric_limits<FloatType>::infinity() ? -sprout::math::three_quarters_pi<FloatType>()
 							: sprout::math::copysign(sprout::math::pi<FloatType>(), y)
@@ -77,11 +85,14 @@ namespace sprout {
 			}
 		}	// namespace detail
 		//
-		// bug:
+		// issue:
+		//	[ !SPROUT_USE_BUILTIN_CMATH_FUNCTION ]
 		//	atan2(�}0, -0) returns �}�� .
 		//		# returns �}0 . ( same as atan2(�}0, +0) )
 		//	atan2(-0, x) returns -�� for x < 0.
 		//		# returns +�� . ( same as atan2(+0, x) )
+		//	atan2(-NaN, -NaN) returns -NaN .
+		//		# returns +NaN . ( same as atan2(+NaN, +NaN) )
 		//
 		using sprout::math::detail::atan2;
 	}	// namespace math
diff --git a/sprout/math/atanh.hpp b/sprout/math/atanh.hpp
index d1280dac..ad85ebfd 100644
--- a/sprout/math/atanh.hpp
+++ b/sprout/math/atanh.hpp
@@ -6,6 +6,7 @@
 #include <sprout/config.hpp>
 #include <sprout/math/detail/config.hpp>
 #include <sprout/math/detail/float_compute.hpp>
+#include <sprout/math/isnan.hpp>
 #include <sprout/math/log.hpp>
 #include <sprout/math/fabs.hpp>
 #include <sprout/type_traits/enabler_if.hpp>
@@ -25,9 +26,10 @@ namespace sprout {
 			>
 			inline SPROUT_CONSTEXPR FloatType
 			atanh(FloatType x) {
-				return x == 1 ? std::numeric_limits<FloatType>::infinity()
+				return sprout::math::isnan(x) ? x
+					: x == 1 ? std::numeric_limits<FloatType>::infinity()
 					: x == -1 ? -std::numeric_limits<FloatType>::infinity()
-					: sprout::math::fabs(x) > 1 ? std::numeric_limits<FloatType>::quiet_NaN()
+					: sprout::math::fabs(x) > 1 ? -std::numeric_limits<FloatType>::quiet_NaN()
 #if SPROUT_USE_BUILTIN_CMATH_FUNCTION
 					: std::atanh(x)
 #else
diff --git a/sprout/math/constants.hpp b/sprout/math/constants.hpp
index 77af9ebb..86f824b7 100644
--- a/sprout/math/constants.hpp
+++ b/sprout/math/constants.hpp
@@ -91,6 +91,7 @@ namespace sprout {
 		}
 		//
 		// half
+		// quarter
 		// third
 		// twothirds
 		//
@@ -99,6 +100,10 @@ namespace sprout {
 			return 0.5L;
 		}
 		template<typename T>
+		inline SPROUT_CONSTEXPR T quarter() {
+			return 0.25L;
+		}
+		template<typename T>
 		inline SPROUT_CONSTEXPR T third() {
 			return 0.33333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333L;
 		}
diff --git a/sprout/math/copysign.hpp b/sprout/math/copysign.hpp
index 5abbe557..5df0a45a 100644
--- a/sprout/math/copysign.hpp
+++ b/sprout/math/copysign.hpp
@@ -1,9 +1,11 @@
 #ifndef SPROUT_MATH_COPYSIGN_HPP
 #define SPROUT_MATH_COPYSIGN_HPP
 
+#include <limits>
 #include <type_traits>
 #include <sprout/config.hpp>
 #include <sprout/math/detail/config.hpp>
+#include <sprout/math/isnan.hpp>
 #include <sprout/math/signbit.hpp>
 #include <sprout/type_traits/float_promote.hpp>
 #include <sprout/type_traits/enabler_if.hpp>
@@ -18,9 +20,13 @@ namespace sprout {
 			inline SPROUT_CONSTEXPR FloatType
 			copysign(FloatType x, FloatType y) {
 				return x == 0
-					? y == 0 ? y
-						: sprout::math::signbit(y) ? -FloatType(0)
-						: FloatType(0)
+						? y == 0 ? y
+							: sprout::math::signbit(y) ? -FloatType(0)
+							: FloatType(0)
+					: sprout::math::isnan(x)
+						? sprout::math::isnan(y) ? y
+							: sprout::math::signbit(y) ? -std::numeric_limits<FloatType>::quiet_NaN()
+							: std::numeric_limits<FloatType>::quiet_NaN()
 					: sprout::math::signbit(y) != sprout::math::signbit(x) ? -x
 					: x
 					;
@@ -39,9 +45,12 @@ namespace sprout {
 			}
 		}	// namespace detail
 		//
-		// bug:
-		//	copysign(�}x, -0) returns -x for |x| > 0 .
+		// issue:
+		//	[ !SPROUT_USE_BUILTIN_CMATH_FUNCTION ]
+		//	copysign(�}x, -0) returns -x for |x| is not 0 .
 		//		# returns +x . ( same as copysign(�}x, +0) )
+		//	copysign(�}x, -NaN) returns -x for |x| is not NaN .
+		//		# returns +x . ( same as copysign(�}x, +NaN) )
 		//
 		using NS_SPROUT_MATH_DETAIL::copysign;
 	}	// namespace math
diff --git a/sprout/math/cos.hpp b/sprout/math/cos.hpp
index 114962b4..a1389c8f 100644
--- a/sprout/math/cos.hpp
+++ b/sprout/math/cos.hpp
@@ -8,8 +8,9 @@
 #include <sprout/detail/pow.hpp>
 #include <sprout/math/detail/config.hpp>
 #include <sprout/math/detail/float_compute.hpp>
-#include <sprout/math/factorial.hpp>
 #include <sprout/math/constants.hpp>
+#include <sprout/math/isnan.hpp>
+#include <sprout/math/factorial.hpp>
 #include <sprout/math/fmod.hpp>
 #include <sprout/type_traits/enabler_if.hpp>
 
@@ -40,9 +41,9 @@ namespace sprout {
 			>
 			inline SPROUT_CONSTEXPR FloatType
 			cos(FloatType x) {
-				return x == std::numeric_limits<FloatType>::infinity()
-					|| x == -std::numeric_limits<FloatType>::infinity()
-						? std::numeric_limits<FloatType>::quiet_NaN()
+				return sprout::math::isnan(x) ? x
+					: x == std::numeric_limits<FloatType>::infinity() || x == -std::numeric_limits<FloatType>::infinity()
+						? -std::numeric_limits<FloatType>::quiet_NaN()
 #if SPROUT_USE_BUILTIN_CMATH_FUNCTION
 					: std::cos(x)
 #else
diff --git a/sprout/math/cosh.hpp b/sprout/math/cosh.hpp
index 8ad25913..af8e0c20 100644
--- a/sprout/math/cosh.hpp
+++ b/sprout/math/cosh.hpp
@@ -8,6 +8,7 @@
 #include <sprout/detail/pow.hpp>
 #include <sprout/math/detail/config.hpp>
 #include <sprout/math/detail/float_compute.hpp>
+#include <sprout/math/isnan.hpp>
 #include <sprout/math/factorial.hpp>
 #include <sprout/type_traits/enabler_if.hpp>
 
@@ -38,8 +39,8 @@ namespace sprout {
 			>
 			inline SPROUT_CONSTEXPR FloatType
 			cosh(FloatType x) {
-				return x == std::numeric_limits<FloatType>::infinity()
-					|| x == -std::numeric_limits<FloatType>::infinity()
+				return sprout::math::isnan(x) ? x
+					: x == std::numeric_limits<FloatType>::infinity() || x == -std::numeric_limits<FloatType>::infinity()
 						? std::numeric_limits<FloatType>::infinity()
 #if SPROUT_USE_BUILTIN_CMATH_FUNCTION
 					: std::cosh(x)
diff --git a/sprout/math/isfinite.hpp b/sprout/math/isfinite.hpp
index 0228ce8e..7b7cc544 100644
--- a/sprout/math/isfinite.hpp
+++ b/sprout/math/isfinite.hpp
@@ -15,7 +15,7 @@ namespace sprout {
 				typename FloatType,
 				typename sprout::enabler_if<std::is_floating_point<FloatType>::value>::type = sprout::enabler
 			>
-			inline SPROUT_CONSTEXPR int
+			inline SPROUT_CONSTEXPR bool
 			isfinite(FloatType x) {
 				return !sprout::math::isnan(x)
 					&& !sprout::math::isinf(x)
diff --git a/sprout/math/isinf.hpp b/sprout/math/isinf.hpp
index de6f7d87..81db067a 100644
--- a/sprout/math/isinf.hpp
+++ b/sprout/math/isinf.hpp
@@ -14,7 +14,7 @@ namespace sprout {
 				typename FloatType,
 				typename sprout::enabler_if<std::is_floating_point<FloatType>::value>::type = sprout::enabler
 			>
-			inline SPROUT_CONSTEXPR int
+			inline SPROUT_CONSTEXPR bool
 			isinf(FloatType x) {
 				return x == std::numeric_limits<FloatType>::infinity()
 					|| x == -std::numeric_limits<FloatType>::infinity()
diff --git a/sprout/math/isnan.hpp b/sprout/math/isnan.hpp
index 892f9f71..e4e235c8 100644
--- a/sprout/math/isnan.hpp
+++ b/sprout/math/isnan.hpp
@@ -13,7 +13,7 @@ namespace sprout {
 				typename FloatType,
 				typename sprout::enabler_if<std::is_floating_point<FloatType>::value>::type = sprout::enabler
 			>
-			inline SPROUT_CONSTEXPR int
+			inline SPROUT_CONSTEXPR bool
 			isnan(FloatType x) {
 				return !(x == x);
 			}
diff --git a/sprout/math/isnormal.hpp b/sprout/math/isnormal.hpp
index 315674c7..b4f78b2d 100644
--- a/sprout/math/isnormal.hpp
+++ b/sprout/math/isnormal.hpp
@@ -16,7 +16,7 @@ namespace sprout {
 				typename FloatType,
 				typename sprout::enabler_if<std::is_floating_point<FloatType>::value>::type = sprout::enabler
 			>
-			inline SPROUT_CONSTEXPR int
+			inline SPROUT_CONSTEXPR bool
 			isnormal(FloatType x) {
 				return !sprout::math::isnan(x)
 					&& !sprout::math::isinf(x)
diff --git a/sprout/math/issubnormal.hpp b/sprout/math/issubnormal.hpp
index 5a687ff4..c1cd0d16 100644
--- a/sprout/math/issubnormal.hpp
+++ b/sprout/math/issubnormal.hpp
@@ -15,7 +15,7 @@ namespace sprout {
 				typename FloatType,
 				typename sprout::enabler_if<std::is_floating_point<FloatType>::value>::type = sprout::enabler
 			>
-			inline SPROUT_CONSTEXPR int
+			inline SPROUT_CONSTEXPR bool
 			issubnormal_or_zero(FloatType x) {
 				return x > 0
 					? x < std::numeric_limits<double>::min()
@@ -27,7 +27,7 @@ namespace sprout {
 				typename FloatType,
 				typename sprout::enabler_if<std::is_floating_point<FloatType>::value>::type = sprout::enabler
 			>
-			inline SPROUT_CONSTEXPR int
+			inline SPROUT_CONSTEXPR bool
 			issubnormal(FloatType x) {
 				return !sprout::math::isnan(x)
 					&& !sprout::math::iszero(x)
diff --git a/sprout/math/iszero.hpp b/sprout/math/iszero.hpp
index db708834..b653ebd5 100644
--- a/sprout/math/iszero.hpp
+++ b/sprout/math/iszero.hpp
@@ -12,7 +12,7 @@ namespace sprout {
 				typename FloatType,
 				typename sprout::enabler_if<std::is_floating_point<FloatType>::value>::type = sprout::enabler
 			>
-			inline SPROUT_CONSTEXPR int
+			inline SPROUT_CONSTEXPR bool
 			iszero(FloatType x) {
 				return x == 0;
 			}
diff --git a/sprout/math/signbit.hpp b/sprout/math/signbit.hpp
index 40de7814..afda7937 100644
--- a/sprout/math/signbit.hpp
+++ b/sprout/math/signbit.hpp
@@ -20,7 +20,8 @@ namespace sprout {
 			}
 		}	// namespace detail
 		//
-		// bug:
+		// issue:
+		//	[ !SPROUT_USE_BUILTIN_CMATH_FUNCTION ]
 		//	signbit(-0) returns false .
 		//		# returns true . ( same as signbit(+0) )
 		//	signbit(-NaN) returns false .
diff --git a/sprout/math/sin.hpp b/sprout/math/sin.hpp
index 9d4ef31b..e65ae171 100644
--- a/sprout/math/sin.hpp
+++ b/sprout/math/sin.hpp
@@ -7,6 +7,7 @@
 #include <sprout/math/detail/config.hpp>
 #include <sprout/math/detail/float_compute.hpp>
 #include <sprout/math/constants.hpp>
+#include <sprout/math/isnan.hpp>
 #include <sprout/math/cos.hpp>
 #include <sprout/type_traits/enabler_if.hpp>
 
@@ -25,9 +26,9 @@ namespace sprout {
 			>
 			inline SPROUT_CONSTEXPR FloatType
 			sin(FloatType x) {
-				return x == std::numeric_limits<FloatType>::infinity()
-					|| x == -std::numeric_limits<FloatType>::infinity()
-						? std::numeric_limits<FloatType>::quiet_NaN()
+				return sprout::math::isnan(x) ? x
+					: x == std::numeric_limits<FloatType>::infinity() || x == -std::numeric_limits<FloatType>::infinity()
+						? -std::numeric_limits<FloatType>::quiet_NaN()
 #if SPROUT_USE_BUILTIN_CMATH_FUNCTION
 					: std::sin(x)
 #else
diff --git a/sprout/math/sinh.hpp b/sprout/math/sinh.hpp
index e6e06738..adf355ab 100644
--- a/sprout/math/sinh.hpp
+++ b/sprout/math/sinh.hpp
@@ -8,6 +8,7 @@
 #include <sprout/detail/pow.hpp>
 #include <sprout/math/detail/config.hpp>
 #include <sprout/math/detail/float_compute.hpp>
+#include <sprout/math/isnan.hpp>
 #include <sprout/math/factorial.hpp>
 #include <sprout/type_traits/enabler_if.hpp>
 
@@ -38,7 +39,8 @@ namespace sprout {
 			>
 			inline SPROUT_CONSTEXPR FloatType
 			sinh(FloatType x) {
-				return x == std::numeric_limits<FloatType>::infinity() ? std::numeric_limits<FloatType>::infinity()
+				return sprout::math::isnan(x) ? x
+					: x == std::numeric_limits<FloatType>::infinity() ? std::numeric_limits<FloatType>::infinity()
 					: x == -std::numeric_limits<FloatType>::infinity() ? -std::numeric_limits<FloatType>::infinity()
 #if SPROUT_USE_BUILTIN_CMATH_FUNCTION
 					: std::sinh(x)
diff --git a/sprout/math/tan.hpp b/sprout/math/tan.hpp
index c007949e..a95432e2 100644
--- a/sprout/math/tan.hpp
+++ b/sprout/math/tan.hpp
@@ -6,6 +6,7 @@
 #include <sprout/config.hpp>
 #include <sprout/math/detail/config.hpp>
 #include <sprout/math/detail/float_compute.hpp>
+#include <sprout/math/isnan.hpp>
 #include <sprout/math/cos.hpp>
 #include <sprout/math/sin.hpp>
 #include <sprout/type_traits/enabler_if.hpp>
@@ -25,10 +26,11 @@ namespace sprout {
 			>
 			inline SPROUT_CONSTEXPR FloatType
 			tan(FloatType x) {
-				return x == std::numeric_limits<FloatType>::infinity() || x == -std::numeric_limits<FloatType>::infinity()
-						? std::numeric_limits<FloatType>::quiet_NaN()
+				return sprout::math::isnan(x) ? x
+					: x == std::numeric_limits<FloatType>::infinity() || x == -std::numeric_limits<FloatType>::infinity()
+						? -std::numeric_limits<FloatType>::quiet_NaN()
 #if SPROUT_USE_BUILTIN_CMATH_FUNCTION
-					: std::sin(x)
+					: std::tan(x)
 #else
 					: x == 0 ? x
 					: static_cast<FloatType>(sprout::math::detail::tan_impl(static_cast<typename sprout::math::detail::float_compute<FloatType>::type>(x)))
diff --git a/sprout/math/tanh.hpp b/sprout/math/tanh.hpp
index 6d28063d..0bd1d9db 100644
--- a/sprout/math/tanh.hpp
+++ b/sprout/math/tanh.hpp
@@ -6,6 +6,7 @@
 #include <sprout/config.hpp>
 #include <sprout/math/detail/config.hpp>
 #include <sprout/math/detail/float_compute.hpp>
+#include <sprout/math/isnan.hpp>
 #include <sprout/math/sinh.hpp>
 #include <sprout/math/cosh.hpp>
 #include <sprout/type_traits/enabler_if.hpp>
@@ -25,7 +26,8 @@ namespace sprout {
 			>
 			inline SPROUT_CONSTEXPR FloatType
 			tanh(FloatType x) {
-				return x == std::numeric_limits<FloatType>::infinity() ? FloatType(1)
+				return sprout::math::isnan(x) ? x
+					: x == std::numeric_limits<FloatType>::infinity() ? FloatType(1)
 					: x == -std::numeric_limits<FloatType>::infinity() ? FloatType(-1)
 #if SPROUT_USE_BUILTIN_CMATH_FUNCTION
 					: std::tanh(x)