c++ - 如何提高代码的精度

Question

我怎样才能提高以下的准确性(精确度)？

struct Degree_Minutes { signed int degrees; signed int minutes; double seconds; };
Degree_Minutes geo_dec_to_deg (double dec)
{
    Degree_Minutes degrees_minutes;
    signed int degrees, minutes;
    double remainder, temp, seconds;

    remainder = fmod(dec, 1);
    degrees_minutes.degrees = dec - remainder;
    temp = remainder*60;
    remainder = fmod(temp,1);
    degrees_minutes.minutes = temp-remainder;
    degrees_minutes.seconds = remainder*60;

    return degrees_minutes;
}

    double geo_deg_to_dec (Degree_Minutes degrees)
{
    double decimal = degrees.degrees + (degrees.minutes/60) + (degrees.seconds/60);
    return decimal;
}

int main(int argc, char **argv)
{
    Degree_Minutes deg;
    double decimal = 38.898556;

    deg = geo_dec_to_deg(decimal);
    cout << "Results of geo_dec_to_deg function: \n" << decimal << " was converted to " << deg.degrees << " degrees, " << deg.minutes << " minutes, " << deg.seconds << " seconds.\n";
    decimal = geo_deg_to_dec(deg);
    cout << "Results of geo_dec_to_deg function: \n" << deg.degrees << " degrees, " << deg.minutes << " minutes, " << deg.seconds << " seconds was converted to " << decimal << "\n";

    return EXIT_SUCCESS;
}

编辑:忘记添加这里有一个结构:

struct Degree_Minutes { signed int degrees; signed int minutes; double seconds; };

当您从十进制转换为度/分/秒，然后再转换回十进制时，您最终得到的是 38.9134，而原来的是 38.898556。

Answer 1

由于意外的整数除法，您遇到了舍入/截断错误。要获得正确的 double ，您需要将 degrees.minutes 和 degrees.seconds 隐式转换为 double，如下所示:

double decimal = degrees.degrees + (degrees.minutes/60.0) + (degrees.seconds/3600.0);

注意 60 -> 60.0 以及在秒字段中将 60 更正为 3600。