fix math::log implementation

support std::hash

sprout/math/scalbn.hpp

@@ -0,0 +1,39 @@
+#ifndef SPROUT_MATH_SCALBN_HPP
+#define SPROUT_MATH_SCALBN_HPP
+
+#include <cfloat>
+#include <type_traits>
+#include <sprout/config.hpp>
+#include <sprout/math/detail/config.hpp>
+#include <sprout/detail/pow.hpp>
+#include <sprout/type_traits/enabler_if.hpp>
+
+namespace sprout {
+	namespace math {
+		namespace detail {
+			template<
+				typename FloatType,
+				typename sprout::enabler_if<std::is_floating_point<FloatType>::value>::type = sprout::enabler
+			>
+			inline SPROUT_CONSTEXPR FloatType
+			scalbn(FloatType x, int exp) {
+				return static_cast<FloatType>(x * sprout::detail::pow_n(FloatType(FLT_RADIX), exp));
+			}
+
+			template<
+				typename IntType,
+				typename sprout::enabler_if<std::is_integral<IntType>::value>::type = sprout::enabler
+			>
+			inline SPROUT_CONSTEXPR double
+			scalbn(IntType x, int exp) {
+				return sprout::math::detail::scalbn(static_cast<double>(x), exp);
+			}
+		}	// namespace detail
+
+		using NS_SPROUT_MATH_DETAIL::scalbn;
+	}	// namespace math
+
+	using sprout::math::scalbn;
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_MATH_SCALBN_HPP