c++的运算符重载题目

Question

定义分数类:
//fraction.h
#include <iostream.h>
class fraction{
private:
int above;
int below;
public:
//…
};
//使用以下代码编程:
#include "fraction.h"
#include <iostream.h>
int main()
{
fraction f1(-2,-3),f2,f3,f4,f5(6);
cin>>f2; //input: -2 3
cout << "f1=" << f1 << endl;
cout << "f2=" << f2 << endl;
f3=f1+f2;
f4=f1+1;
f5=3+f2;
cout << "f3=" << f3 << endl;
cout << "f4=" << f4 << endl;
cout << "f5=" << f5 << endl;
return 0;
}
//运行程序，输入: -2 3 将得到以下结果：:
f1=2/3
f2=-2/3
f3=0
f4=5/3
f5=7/3
请您把答案写的详细点，尽量通俗易懂，最好是有注释啦~~~~~

Answer 1

//fraction.h
#include <iostream.h>
class fraction{
private:
int above;
int below;
public:
friend fraction operator+(fraction &a , fraction &b){
int x,y;
x=(a.above)*(b.below)+(a.below)*(b.above);
y=(a.below)*(b.below);

return fraction(x,y);
}
fraction &operator=(fraction &a){
this->above=a.above;
this->below=a.below;

return *this;
}
friend fraction operator+(fraction &a , int b){
int x,y;
x=a.above+b*a.below;
y=a.below;

return fraction(x,y);
}

friend fraction operator+(int a , fraction &b){
int x,y;
x=a*b.below+b.above;
y=b.below;

return fraction(x,y);
}

friend ostream &operator<<(ostream &out ,const fraction a){
out<<a.above<<"/"<<a.below;

return out;
}
friend istream &operator>>(istream &in , fraction &a){
in>>a.above>>a.below;

return in;
}
fraction(int a=0,int b=1){
above=a;
below=b;
}
};

//test.cpp
#include "fraction.h"
#include <iostream.h>
int main()
{
fraction f1(-2,-3),f2,f3,f4,f5(6);
cin>>f2; //input: -2 3
cout << "f1=" << f1 << endl;
cout << "f2=" << f2 << endl;
f3=f1+f2;
f4=f1+1;
f5=3+f2;
cout << "f3=" << f3 << endl;
cout << "f4=" << f4 << endl;
cout << "f5=" << f5 << endl;
return 0;
}

Answer 2

看不明结果，代码仅供参考。
class fraction
{
private:
int above;
int below;
public:
fraction(int a = 0, int b = 1) { above = a; below = b; } // 构造函数
friend istream &operator>>(istream &in, fraction &f) // 重载输入操作符
{
in >> f.above >> f.below;
return in;
}
friend ostream &operator<<(ostream &out, const fraction &f) // 重载输出操作符
{
if (f.below != 0)
{
if (f.above < 0 && f.below < 0)
out << -f.above << "/" << -f.below;
else
out << f.above << "/" << f.below;
}
else
out << 0;
return out;
}
friend fraction operator+(int num, const fraction &f) // 3 + f2
{
return fraction(f.above+num, f.below);
}
fraction operator+(const fraction &f) // f1 + f2 或者 f1 + 1;
{
return fraction(above + f.above, below + f.below);
}

};

Answer 3

题目挺有意思。不过这个题目不太完美，分数的运算只要求了加法。略略看了两位师兄的答案，似乎不尽如人意，一楼的师兄没有进行约分，出来的结果可能是假分数，其余的代码我没看。二楼的师兄那个加法的重载也有问题，剩下的代码也没看。最近课业比较紧张，楼主要是不急的话，我可以做一个。有问题的话可以讨论，452032545