Added MathUtil

Author: gistrec

src/MathUtil.hpp

@@ -0,0 +1,116 @@
+//******************************************************************************
+// Copyright 2013 Google Inc.
+// https://github.com/googlemaps/android-maps-utils/blob/master/library/src/com/google/maps/android/MathUtil.java
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// This software and the related documents are provided  as is,  with no express
+// or implied  warranties,  other than  those that are  expressly stated  in the
+// License.
+//******************************************************************************
+
+#ifndef GEOMETRY_LIBRARY_MATH_UTIL
+#define GEOMETRY_LIBRARY_MATH_UTIL
+
+#include <cmath>
+
+#define M_PI 3.14159265358979323846
+
+
+class MathUtil {
+public:
+    /**
+     * The earth's radius, in meters.
+     * Mean radius as defined by IUGG.
+     */
+    const size_t EARTH_RADIUS = 6371009;
+
+    /**
+     * Restrict x to the range [low, high].
+     */
+    static inline double clamp(double x, double low, double high) {
+        return x < low ? low : (x > high ? high : x);
+    }
+
+    /**
+     * Wraps the given value into the inclusive-exclusive interval between min and max.
+     * @param n   The value to wrap.
+     * @param min The minimum.
+     * @param max The maximum.
+     */
+    static inline double wrap(double n, double min, double max) {
+        return (n >= min && n < max) ? n : (MathUtil::mod(n - min, max - min) + min);
+    }
+
+    /**
+     * Returns the non-negative remainder of x / m.
+     * @param x The operand.
+     * @param m The modulus.
+     */
+    static inline double mod(size_t x, size_t m) {
+        return ((x % m) + m) % m;
+    }
+
+    /**
+     * Returns mercator Y corresponding to latitude.
+     * See http://en.wikipedia.org/wiki/Mercator_projection .
+     */
+    static inline double mercator(double lat) {
+        return log(tan(lat * 0.5 + M_PI / 4.0));
+    }
+
+    /**
+     * Returns latitude from mercator Y.
+     */
+    static inline double inverseMercator(double y) {
+        return 2.0 * atan(exp(y)) - M_PI / 2.0;
+    }
+
+    /**
+     * Returns haversine(angle-in-radians).
+     * hav(x) == (1 - cos(x)) / 2 == sin(x / 2)^2.
+     */
+    static inline double hav(double x) {
+        double sinHalf = sin(x * 0.5);
+        return sinHalf * sinHalf;
+    }
+
+    /**
+     * Computes inverse haversine. Has good numerical stability around 0.
+     * arcHav(x) == acos(1 - 2 * x) == 2 * asin(sqrt(x)).
+     * The argument must be in [0, 1], and the result is positive.
+     */
+    static inline double arcHav(double x) {
+        return 2.0 * asin(sqrt(x));
+    }
+
+    // Given h==hav(x), returns sin(abs(x)).
+    static inline double sinFromHav(double h) {
+        return 2.0 * sqrt(h * (1.0 - h));
+    }
+
+    // Returns hav(asin(x)).
+    static inline double havFromSin(double x) {
+        double x2 = x * x;
+        return x2 / (1.0 + sqrt(1.0 - x2)) * 0.5;
+    }
+
+    // Returns sin(arcHav(x) + arcHav(y)).
+    static inline double sinSumFromHav(double x, double y) {
+        double a = sqrt(x * (1 - x));
+        double b = sqrt(y * (1 - y));
+        return 2.0 * (a + b - 2 * (a * y + b * x));
+    }
+
+    /**
+     * Returns hav() of distance from (lat1, lng1) to (lat2, lng2) on the unit sphere.
+     */
+    static inline double havDistance(double lat1, double lat2, double dLng) {
+        return MathUtil::hav(lat1 - lat2) + MathUtil::hav(dLng) * cos(lat1) * cos(lat2);
+    }
+};
+
+#endif // GEOMETRY_LIBRARY_MATH_UTIL