C++：使用非成員函數(non-member)處理函數的所有參數都需要類型轉換

有些函數, 所有參數都需要使用類型轉換, 比如乘法, 寫一個有理數類Rational, 需要執行乘法操作:

函數滿足: Rational = Rational*double; Rational = double*Rational; 則需要使用非成員函數(non-member);

成員函數的發起者必須是類, 因為可能出現double類型在前的情況, 則無法執行乘法, 所以應使用非成員函數;

執行時: 即Rational = Rational*Rational(double); Rational = Rational(double)*Rational, 發生了隱式轉換.

代碼:

/* 
 * test.cpp 
 * 
 *  Created on: 2014.04.22 
 *      Author: Spike 
 */
      
/*eclipse cdt, gcc 4.8.1*/
      
#include <iostream>  
      
//有理數  
class Rational {  
public:  
    Rational(double numerator = 0, double denominator = 1) :  
        m_n(numerator), m_d(denominator) {}  
    double numerator() const {return m_n;};  
    double denominator() const {return m_d;};  
    double value() {return (m_n/m_d);}  
private:  
    double m_n;  
    double m_d;  
};  
      
const Rational operator* (const Rational& lhs,  
        const Rational& rhs) {  
    return Rational(lhs.numerator()*rhs.numerator(),  
            lhs.denominator()*rhs.denominator());  
}  
      
int main(void) {  
    Rational oneFourth(1, 4);  
    Rational result;  
    result = oneFourth * 3.5;  
    result = 3.5 * oneFourth;  
    std::cout << "result = " << result.value() << std::endl;  
      
    return 0;  
}

輸出:

result = 0.875

作者：csdn博客 Spike_King