Add Horner's method for polynomial evaluation

src/math/polynomial.hpp

@@ -0,0 +1,49 @@
+/*
+ * Copyright (C) 2021  Christopher J. Howard
+ *
+ * This file is part of Antkeeper source code.
+ *
+ * Antkeeper source code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Antkeeper source code is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Antkeeper source code.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef ANTKEEPER_MATH_POLYNOMIAL_HPP
+#define ANTKEEPER_MATH_POLYNOMIAL_HPP
+
+namespace math {
+
+/// Polynomial evaluation functions.
+namespace polynomial {
+
+/**
+ * Evaluates a polynomial using Horner's method.
+ *
+ * @param first,last Range of polynomial coefficients, in descending order of degree.
+ * @param x Variable value.
+ * @return Evaluation of P(x).
+ *
+ * @see https://en.wikipedia.org/wiki/Horner%27s_method
+ */
+template <class InputIt, class T>
+T horner(InputIt first, InputIt last, T x)
+{
+	T sum = *first;
+	for (++first; first != last; ++first)
+		sum = sum * x + *first;
+	return sum;
+}
+
+} // namespace polynomial
+} // namespace math
+
+#endif // ANTKEEPER_MATH_POLYNOMIAL_HPP