static關鍵字錯誤

Question

我有以下代碼

#include<math.h> 
class complex 
{ 

public: 
    double getRe(); 
    double gerIm(); 
    void setRe(double value); 
    void setIm(double value); 
    explicit complex(double=0.0,double=0.0); 
    static complex fromPolar(double radius,double angle); 
    complex operator+(complex rhs); 
    complex operator-(complex rhhs); 
    complex operator*(complex rhs); 
    complex operator+(double rhs); 
    complex operator-(double rhs); 
    complex operator*(double rhs); 
    complex conjugate(); 
    double norm(); 
    complex operator/(double rhs); 
    complex operator/(complex rhs); 

private: 
    double real; 
    double img; 

}; 
complex operator+(double lhs,complex rhs); 
complex operator-(double lhs,complex rhs); 
complex operator*(double lhs,complex rhs); 
complex operator/(double lhs,complex rhs); 
complex exp(complex c); 
inline double complex::getRe(){return real;} 
inline double complex::gerIm(){ return img;} 
inline void complex::setRe(double value) { real=value;} 
inline void complex::setIm(double value) { img=value;} 
inline complex::complex(double re,double im) :real(re),img(im){} 
inline static complex complex::fromPolar(double radius,double angle){ 

    return complex(radius*cos(angle),radius*sin(angle)); 

} 
inline complex complex::operator+(complex rhs) 
{ 
    return complex(this->real+rhs.real,this->img+rhs.img); 

} 
inline complex complex::operator-(complex rhs) 
{ 
    return complex(this->real-rhs.real,this->img-rhs.img); 

} 
inline complex complex::operator*(complex rhs) 
{ 
    return complex(this->real*rhs.real-this->img*rhs.img,this->real*rhs.img+this->img*rhs.real); 

} 
inline complex complex::operator+(double rhs) 
{ 
    return complex(this->real+rhs,this->img); 

} 

inline complex complex::operator-(double rhs) 
{ 
    return complex(this->real-rhs,this->img); 

} 
inline complex complex::operator*(double rhs) 
{ 
    return complex(this->real*rhs,this->img*rhs); 

} 
inline complex complex::operator/(double rhs) 
{ 
    return complex(this->real/rhs,this->img/rhs); 

} 
inline complex complex::operator/(complex rhs) 
{ 

    return (*this)*rhs.conjugate()/rhs.norm(); 


} 

inline double complex::norm() 
{ 
return (this->real*this->real+this->img*this->img); 
} 

inline complex complex::conjugate() 
{ 

    return complex(this->real,-this->img); 
} 


inline complex operator+(double lhs,complex rhs) 
{ 
    return rhs+lhs; 
} 

inline complex operator-(double lhs,complex rhs) 
{ 
    return complex(lhs-rhs.getRe(),rhs.gerIm()); 

} 
inline complex operator*(double lhs,complex rhs) 
{ 
    rhs*lhs; 

} 

inline complex operator/(double lhs,complex rhs) 
{ 
    return rhs.conjugate()*lhs/rhs.norm(); 

} 

而是說，

1>c:\users\daviti\documents\visual studio 2010\projects\complex_number\complex_number\complex.h(38): error C2724: 'complex::fromPolar' : 'static' should not be used on member functions defined at file scope 

如果我刪除static關鍵字，它編譯罰款，但我已經使用這個static關鍵字類定義，所以如果我刪除它，不會是錯誤？

Answer 1

static只需要出現在類定義中，而不是您實現該方法的地方。

class complex 
{ 
    //...... 
    static complex fromPolar(double radius,double angle); 
    //..... 
}; 

inline complex complex::fromPolar(double radius,double angle){ 
    return complex(radius*cos(angle),radius*sin(angle)); 
} 

Answer 2

@Luchian已經很好地回答了這個問題。我將討論fromPolar的替代方案。

也許你已經知道，你不能這樣寫：

class complex 
{ 
    //.. 
    explicit complex(double real, double imaginary); 
    explicit complex(double radius, double angle); //same as above 
}; 

第二個構造函數作爲第一個基本相同（參數不同的名稱沒有任何區別），所以你不能做到這一點，這就是爲什麼你想出了fromPolar解決方案。

但是一個微妙的問題仍然存在，即使在fromPolar解決方案：什麼是角度參數的單位？它是弧度，程度還是什麼？

所以我會建議下面的類，它解決了上面討論的兩個問題，你不需要fromPolar函數了。

class complex 
{ 
    //.. 
    explicit complex(double real, double imaginary); 
    explicit complex(double radius, Angle angle); //now it is different 
}; 

其中Angle是被定義爲另一個類：使你的類更好一點

class Angle 
{ 
    double m_value; //always maintain this in radian 

public: 
    Angle(double value, bool isradian = true); 

    double radian(){ return m_value; } 
    double degree(){ return m_value * 180/PI; }//or maybe M_PI is the symbol 
}; 

希望。