为什么这会一直打印圆的宽度？

Question

    #include "stdafx.h"
#include <iostream>
#include <string>
#include <cmath>


using namespace std;

const double PI = 3.141592653589793238463;

enum Figur {DREIECK, RECHTECK, KREIS};

struct Geo {
    mutable Figur figur;
    mutable double a, b, c;
};

Geo createGeo(Figur f, double a, double b, double c)
{
    Geo d;
    d.figur = f;
    d.a = a;
    d.b = b;
    d.c = c;
    return d;
}

Geo getGeo() {
    double a=0.0, b=0.0, c=0.0;
n:
    cout << "Please insert which geometrical object you want to create:" << endl;
    cout << "0 for triangle" << endl << "1 for rectangle" << endl << "2 for circle" << endl;
    Figur f;
    int p = 3;
    cin >> p;
    if (p == 0)
    {
        f = DREIECK;

        cout << "Please insert the length: ";
        cin >> a;

        cout << endl << "Please insert the width: ";
        cin >> b;

        {   m:
                cout << endl << "Please set the angle >0 and <180°: ";
                cin >> c;
                if (c <= 0 || c >= 180)
                {
                    cout << endl << "Invalid value! Please try again" << endl;
                    goto m;
                }
        }
        cout << endl << "Your figure is now going to be created" << endl;
        Geo geo = createGeo(f, a, b, c);
        return geo;
    }
    else if (p == 1)
    {
        f = RECHTECK;
        cout << "Please insert the length: ";
        cin >> a;
        cout << endl << "Please insert the width: ";
        cin >> b;
        cout << endl << "Your figure is now going to be created" << endl;
        Geo geo = createGeo(f, a, b ,0);
        return geo;
    }
    else if (p == 2)
    {
        f = KREIS;
        cout << "Please insert the radius: ";
        cin >> a;
        cout << endl << "Your figure is now going to be created" << endl;
        Geo geo = createGeo(f, a,0,0);
        return geo;
    }
    else
    {
        cout << "Invalid value. Please try again." << endl;
        goto n;
    }


}


double flaeche(Geo const &g)
{
    double flaeche;
    if(g.figur = DREIECK) 
    {
        flaeche = 0.5 * g.a*g.b;
    }
    else if (g.figur = RECHTECK)
    {
        flaeche = g.a*g.b;
    }

    else if(g.figur = KREIS)
    {
        flaeche = PI * pow(g.a, 2);
    }

    return flaeche;
}

void putGeo(double a, Geo &g)
{
    string typ;
    if (g.figur == DREIECK) typ = "triangle";
    else if (g.figur == RECHTECK) typ = "rectangle";
    else typ = "circle";
    cout << "Type of figure: " << typ << endl;
    if (g.figur == DREIECK) {
        cout << "Length: " << g.a << endl;
        cout << "Height: " << g.b << endl;
        cout << "Angle: " << g.a << endl;
        cout << "Area: " << a << endl;
    }
    else if (g.figur == RECHTECK) {
        cout << "Length: " << g.a << endl;
        cout << "Width: " << g.b << endl;
        cout << "Area: " << a << endl;
    }
    else if(g.figur == KREIS){
        cout << "Radius: " << g.a << endl;
        cout << "Area: " << a << endl;
    }
}

int main()
{
    Geo g1 = getGeo();

    double a = flaeche(g1);

    putGeo(a, g1);

    return 0;
}

您好，

希望此代码示例易于您理解。我想创建一个程序，用户必须在其中通过控制台创建一个几何对象。

目前矩形和三角形的效果很好，但是圆形有点问题。

每次当我创建一个圆并调用 putGeo() 方法时，宽度也会被打印出来，面积被计算为零。

有人可能知道为什么会这样吗？

这是我课程中的一个练习，现在我真的不知道了。

程序完全是德语，但我翻译了输出。对于枚举 DREIECK 是三角形，RECHTECK 是矩形，KREIS 是圆形。

感谢您的帮助。

编辑输出问题

如果我创建半径为 5 的圆

我想通过 putGeo() 进行打印

半径：5 地区：78.5398163397

但我实际上得到了

半径：5 宽度：0 面积：0

Answer 1

看这里：

if(g.figur = DREIECK)

您打算进行 测试， 但这是一个 作业。 这会将 g.figur 的值设置为 DREIECK.之后，面积会计算错误。

当您以这种方式使用赋值时，一个好的编译器会警告您。（如果抑制或忽略编译器警告，会给自己带来麻烦。）

正确的形式是

if(g.figur == DREIECK)

为什么这会一直打印圆的宽度？

Why does this print the width all the time for the circle?

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