java - Java 数学库的 Objective-C 等效项是什么？

Question

什么库/头文件/类相当于 Java Math 类？

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背景和奖励问题:

我正在尝试将此函数从 Java 移植到 Objective-C。我应该重写它，还是可以复制粘贴并仅重写语法不同的部分？ (换句话说，如果 Java 作为 Objective-C 或 C 运行，其行为是否会相同？)

这是Java中的怪物函数。它本质上是 Vincinty Formula :

private double vincentyFormula(GeoLocation location, int formula) {
    double a = 6378137;
    double b = 6356752.3142;
    double f = 1 / 298.257223563; // WGS-84 ellipsiod
    double L = Math.toRadians(location.getLongitude() - getLongitude());
    double U1 = Math
            .atan((1 - f) * Math.tan(Math.toRadians(getLatitude())));
    double U2 = Math.atan((1 - f)
            * Math.tan(Math.toRadians(location.getLatitude())));
    double sinU1 = Math.sin(U1), cosU1 = Math.cos(U1);
    double sinU2 = Math.sin(U2), cosU2 = Math.cos(U2);

    double lambda = L;
    double lambdaP = 2 * Math.PI;
    double iterLimit = 20;
    double sinLambda = 0;
    double cosLambda = 0;
    double sinSigma = 0;
    double cosSigma = 0;
    double sigma = 0;
    double sinAlpha = 0;
    double cosSqAlpha = 0;
    double cos2SigmaM = 0;
    double C;
    while (Math.abs(lambda - lambdaP) > 1e-12 && --iterLimit > 0) {
        sinLambda = Math.sin(lambda);
        cosLambda = Math.cos(lambda);
        sinSigma = Math.sqrt((cosU2 * sinLambda) * (cosU2 * sinLambda)
                + (cosU1 * sinU2 - sinU1 * cosU2 * cosLambda)
                * (cosU1 * sinU2 - sinU1 * cosU2 * cosLambda));
        if (sinSigma == 0)
            return 0; // co-incident points
        cosSigma = sinU1 * sinU2 + cosU1 * cosU2 * cosLambda;
        sigma = Math.atan2(sinSigma, cosSigma);
        sinAlpha = cosU1 * cosU2 * sinLambda / sinSigma;
        cosSqAlpha = 1 - sinAlpha * sinAlpha;
        cos2SigmaM = cosSigma - 2 * sinU1 * sinU2 / cosSqAlpha;
        if (Double.isNaN(cos2SigmaM))
            cos2SigmaM = 0; // equatorial line: cosSqAlpha=0 (ß6)
        C = f / 16 * cosSqAlpha * (4 + f * (4 - 3 * cosSqAlpha));
        lambdaP = lambda;
        lambda = L
                + (1 - C)
                * f
                * sinAlpha
                * (sigma + C
                        * sinSigma
                        * (cos2SigmaM + C * cosSigma
                                * (-1 + 2 * cos2SigmaM * cos2SigmaM)));
    }
    if (iterLimit == 0)
        return Double.NaN; // formula failed to converge

    double uSq = cosSqAlpha * (a * a - b * b) / (b * b);
    double A = 1 + uSq / 16384
            * (4096 + uSq * (-768 + uSq * (320 - 175 * uSq)));
    double B = uSq / 1024 * (256 + uSq * (-128 + uSq * (74 - 47 * uSq)));
    double deltaSigma = B
            * sinSigma
            * (cos2SigmaM + B
                    / 4
                    * (cosSigma * (-1 + 2 * cos2SigmaM * cos2SigmaM) - B
                            / 6 * cos2SigmaM
                            * (-3 + 4 * sinSigma * sinSigma)
                            * (-3 + 4 * cos2SigmaM * cos2SigmaM)));
    double distance = b * A * (sigma - deltaSigma);

    // initial bearing
    double fwdAz = Math.toDegrees(Math.atan2(cosU2 * sinLambda, cosU1
            * sinU2 - sinU1 * cosU2 * cosLambda));
    // final bearing
    double revAz = Math.toDegrees(Math.atan2(cosU1 * sinLambda, -sinU1
            * cosU2 + cosU1 * sinU2 * cosLambda));
    if (formula == DISTANCE) {
        return distance;
    } else if (formula == INITIAL_BEARING) {
        return fwdAz;
    } else if (formula == FINAL_BEARING) {
        return revAz;
    } else { // should never happpen
        return Double.NaN;
    }
  }

Answer 1

Java 的 Math 类很大程度上基于标准 C math.h ，所以你可以使用那个。