add floor, ceil, trunc, round

sprout/math/floor.hpp

@@ -0,0 +1,53 @@
+#ifndef SPROUT_MATH_FLOOR_HPP
+#define SPROUT_MATH_FLOOR_HPP
+
+#include <cstdint>
+#include <limits>
+#include <type_traits>
+#include <stdexcept>
+#include <sprout/config.hpp>
+#include <sprout/math/detail/config.hpp>
+#include <sprout/type_traits/enabler_if.hpp>
+
+namespace sprout {
+	namespace math {
+		namespace detail {
+			template<typename FloatType>
+			inline SPROUT_CONSTEXPR FloatType
+			floor_impl(FloatType x, FloatType x0) {
+				return x0 - x < std::numeric_limits<FloatType>::epsilon()
+					? x0
+					: x0 - 1
+					;
+			}
+			template<
+				typename FloatType,
+				typename sprout::enabler_if<std::is_floating_point<FloatType>::value>::type = sprout::enabler
+			>
+			inline SPROUT_CONSTEXPR FloatType
+			floor(FloatType x) {
+				return std::numeric_limits<std::uintmax_t>::max() < x || std::numeric_limits<std::uintmax_t>::max() < -x
+					? throw std::domain_error("floor: Sorry, not implemented.")
+					: x < 0
+						? sprout::math::detail::floor_impl(x, -static_cast<FloatType>(static_cast<std::uintmax_t>(-x)))
+						: static_cast<FloatType>(static_cast<std::uintmax_t>(x))
+					;
+			}
+
+			template<
+				typename IntType,
+				typename sprout::enabler_if<std::is_integral<IntType>::value>::type = sprout::enabler
+			>
+			inline SPROUT_CONSTEXPR double
+			floor(IntType x) {
+				return sprout::math::detail::floor(static_cast<double>(x));
+			}
+		}	// namespacedetailmath
+
+		using NS_SPROUT_MATH_DETAIL::floor;
+	}	// namespace math
+
+	using sprout::math::floor;
+}	// namespace sprout
+
+#endif	// #ifndef SPROUT_MATH_FLOOR_HPP