如何提高代碼的精確度

如何提高以下的準確度（精度）？如何提高代碼的精確度

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; 
}

編輯：忘了補充，這裏有一個結構：

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

通過你從十進制轉換爲度/分/秒的時間，然後回十進制你風與38.9134當原來是38.898556。

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2012-10-23 Joey Huggins

哦，順便說一句我忘記注意結構：struct Degree_Minutes {signed int degrees;簽名int分鐘;雙秒; }; –

請編輯帖子以包含此新信息。 –

沒有必要包含Degree_Minutes聲明，因爲它可以從所提供的信息中推導出來。（如果'minutes'已被聲明爲浮點數或'seconds'已被聲明爲整數，則將獲得不同的結果。） –

由於意外的整數除法，您正在經歷舍入/截斷錯誤。爲了得到你需要隱式轉換degrees.minutes和degrees.seconds到double，像這樣適當的雙精度：

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

注60 - >60.0和60秒字段校正至3600。

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2012-10-23 20:07:56

有一個編譯器選項可以警告你這樣的錯誤，如果我沒有弄錯，gcc和clang的''WConversion''。「牆」更好。 :-) – Florian

有3600秒的學位。 –

啊，我明白了......因爲我使用了signed int（不知道爲什麼我爲分鐘簽名）。所以，通過使用雙重它應該將其轉換.... 好吧，試過這個，但是，它現在是從原來的進一步。一旦轉換回來，它變成39.7967與38.8985 –

#include <stdlib.h> 
#include <iostream> 
#include <math.h> 

using namespace std; 

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*60.0; 
    remainder = fmod(temp,1); 
    degrees_minutes.minutes = temp-remainder; 
    degrees_minutes.seconds = remainder*60.0; 

    return degrees_minutes; 
} 

double geo_deg_to_dec (Degree_Minutes degrees) 
{ 
    double decimal = degrees.degrees + (degrees.minutes/60.0) + (degrees.seconds/60.0/60.0); 
    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"; 
    cout << "This should be: 38deg 53' 54.801\"" << endl; 
    cout << endl; 
    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"; 
    cout << "This should be: 38.898556" << endl; 

    return EXIT_SUCCESS; 
}

你已經差不多了。您需要通過明確指定小數（如其他答案中所示）進行強制雙重除法，但您還需要將秒數除以60兩次。在實踐中，我可能會將其更改爲degrees.seconds/3600，但我已將其留在原地進行說明。

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2012-10-23 20:16:05 jedwards

有兩個問題。

首先，Degree_Minutes結構的minutes成員被聲明爲整數類型，因此degrees.minutes/60將整數除以整數，從而生成截斷整數結果。將其更改爲degrees.minutes/60.會產生浮點結果。

二，degrees.seconds/60不正確。或者這應該是degrees.seconds/3600或degrees.seconds/60應該加上degree.minutes和總和，然後除以60.

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2012-10-23 20:16:33

如何提高代碼的精確度

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