爲什麼這不起作用？ （C++）

Question

我有這段代碼來計算形狀的面積。我不明白爲什麼我得到的錯誤「預期不合格的ID之前‘雙’」和「預期（前雙」關於「類三角::三角（雙S1，S2雙，雙S3）線44：多邊形（S1， S2，S3，0.0）{}「任何幫助將是非常讚賞謝謝你在前進

#include "Polygon.h" 
    #include <iostream> 
    #include <cmath> 
    using namespace std; 

    //Polygon constructor 
    Polygon :: Polygon(double side1, double side2, double side3, double side4) 
    { 
     s1 = side1; 
     s2 = side2; 
     s3 = side3; 
     s4 = side4; 
    } 
    //get area method 
    double Polygon :: getArea() 
    { 
     float length, width, area; 

     if (s1 == s2) 
      { 
       length = s1; 
       width = s3; 
      } 
     else if (s1 == s3) 
      { 
       length = s1; 
       width = s2; 
      } 
     else if (s1 == s4) 
      { 
       length = s1; 
       width = s3; 
      } 
     area = length * width; 
     return area; 
    } 
    //Triangle class 
    class Triangle :: Triangle(double s1, double s2, double s3) : Polygon(s1,  s2, s3, 0.0) {} 

    double Triangle :: getArea() 
    { 
     float s, area; 

      s = (s1 + s2 + s3)/2; 
      area = sqrt(s * (s - s1) * (s - s2) * (s - s3)); 

      return area; 
    } 

Answer 1

您需要刪除單詞class這裏：。

class Triangle :: Triangle 

當然你需要確保class Triangle是之前宣佈。

Answer 2

使用此弗洛翼代碼片段。

#include "Polygon.h" 
    #include <iostream> 
    #include <cmath> 
    using namespace std; 

    //Polygon constructor 
    Polygon :: Polygon(double side1, double side2, double side3, double side4) 
    { 
     s1 = side1; 
     s2 = side2; 
     s3 = side3; 
     s4 = side4; 
    } 
    //get area method 
    double Polygon :: getArea() 
    { 
     float length, width, area; 

     if (s1 == s2) 
      { 
       length = s1; 
       width = s3; 
      } 
     else if (s1 == s3) 
      { 
       length = s1; 
       width = s2; 
      } 
     else if (s1 == s4) 
      { 
       length = s1; 
       width = s3; 
      } 
     area = length * width; 
     return area; 
    } 
    //Triangle class 
    Triangle :: Triangle(double s1, double s2, double s3) : Polygon(s1,  s2, s3, 0.0) {} 

    double Triangle :: getArea() 
    { 
     float s, area; 

      s = (s1 + s2 + s3)/2; 
      area = sqrt(s * (s - s1) * (s - s2) * (s - s3)); 

      return area; 
    }