c++ - C++ 重载 + 运算符友元函数

Question

我正在尝试创建一个重载的朋友函数，它将添加两个分数。到目前为止，我有以下解决方案，但我在第 17 行和第 19 行有错误。我相信问题出在参数（分数数量 1，分数数量 2）上，但我无法完全确定它。任何人都可以帮忙吗？这需要在 Visual Studio 2010 上编译。

#include <iostream>

using namespace std;

class fraction
{
public:
fraction(); //constructor for initialize
void read(); //read 3 int from keyboard for the fraction
void print(); //print the fraction on screen
friend fraction operator +(fraction, fraction); //fraction add
private:
int integral, numerator, denominator;
}


int main(){

return 0;
}

fraction operator +(fraction amount1, fraction amount2)
{
fraction temp;
temp.integral = amount1.integral + amount2.integral;
temp.numerator = amount1.numerator + amount2.numerator;
temp.denominator = amount1.denominator + amount2.denominator;
return temp;
}


void fraction::read()
{
cin >> integral >> numerator >> denominator;
}

编辑：我已将我的加法算法更正为

friend fraction operator +(const fraction&, const fraction&); //fraction add

和

fraction operator +(const fraction& amount1, const fraction& amount2)
{
fraction temp;
temp.integral = amount1.integral + amount2.integral;
temp.numerator = (amount1.numerator)*(amount2.denominator) + (amount2.numerator)*(amount1.denominator);
temp.denominator = (amount1.denominator)*(amount2.denominator);
return temp;
}

然而，在测试这一点时，我为分子和分母变量输出零。有人能帮忙吗？

Answer 1

这是在经过多次更改后编译的：

• 您需要在类定义后添加一个分号，并且
• 您需要定义您已声明的构造函数，即

这个构造函数

fraction(); //constructor for initialize

应该有一个内联或在单独文件中定义的正文。

此外，您应该将您的签名更改operator为

friend fraction operator +(const fraction&, const fraction&)

Answer 2

#include <iostream>

using namespace std;

class fraction
{
public:
//fraction(); //constructor for initialize
void read(); //read 3 int from keyboard for the fraction
void print(); //print the fraction on screen
friend fraction operator +(fraction, fraction); //fraction add
private:
int integral, numerator, denominator;
};


int main(){
fraction f1, f2, f3;
cout<<"\n Enter first fraction: ";
f1.read();
cout<<"\n Enter second fraction: ";
f2.read();
cout<<"\n result: ";

f3 = f1 + f2;
f3.print();
return 0;
}

fraction operator +(fraction amount1, fraction amount2)
{
fraction temp;
temp.integral = amount1.integral + amount2.integral;
temp.numerator = amount1.numerator + amount2.numerator;
temp.denominator = amount1.denominator + amount2.denominator;
return temp;
}


void fraction::read()
{
cin >> integral >> numerator >> denominator;
}

void fraction::print()
{
cout << integral<<" "<< numerator <<" "<< denominator <<std::endl;
}

Answer 3

如果在类块之外定义，则需要在运算符之前使用类名：

fraction fraction::operator +(fraction amount1, fraction amount2);