分数の加減乗除(C++の有理数クラス)

#include <iostream>
#include <cstdio>
using namespace std;
class Number{
	int numerator,denominator;
public:
	void input(int a,int b)
	{
	   numerator=a;
	   denominator=b;
	}
	void output(int &a,int &b)
	{
		a=numerator;
		b=denominator;
	}

};
int fun(int a,int b)
{
    int temp;
    if(a<b)
    {
        temp=a;
        a=b;
        b=temp;
    }
    while(b)
    {
        temp=a;
        a=b;
        b=temp%b;
    }
    return a;
}


void add(Number num1,Number num2)
{
    int num_num1,num_num2,num_den1,num_den2;
    int temp,temp1,temp2;
    num1.output(num_num1,num_den1);
    num2.output(num_num2,num_den2);
    temp=num_den2*num_den1;
    temp1=num_num1*num_den2;
    temp2=num_num2*num_den1;
    temp1=temp1+temp2;
    int index=fun(temp1,temp);

    temp1=temp1/index;
    temp=temp/index;

    printf("%d/%d + %d/%d = %d/%d
",num_num1,num_den1,num_num2,num_den2,temp1,temp);
}
void subtract(Number num1,Number num2)
{
    int num_num1,num_num2,num_den1,num_den2;
    int temp,temp1,temp2;
    num1.output(num_num1,num_den1);
    num2.output(num_num2,num_den2);
    temp=num_den2*num_den1;
    temp1=num_num1*num_den2;
    temp2=num_num2*num_den1;
    temp1=temp1-temp2;
    int index=fun(temp1,temp);

    temp1=temp1/index;
    temp=temp/index;

    printf("%d/%d + %d/%d = %d/%d
",num_num1,num_den1,num_num2,num_den2,temp1,temp);
}
void multiply(Number num1,Number num2)
{
    int num_num1,num_num2,num_den1,num_den2;
    int temp1,temp2;
    num1.output(num_num1,num_den1);
    num2.output(num_num2,num_den2);
    temp1=num_num1*num_num2;
    temp2=num_den1*num_den2;
    int index=fun(temp1,temp2);

    temp1=temp1/index;
    temp2=temp2/index;

    printf("%d/%d * %d/%d = %d/%d
",num_num1,num_den1,num_num2,num_den2,temp1,temp2);
}

void divide(Number num1,Number num2)
{
    int num_num1,num_num2,num_den1,num_den2;
    int temp1,temp2;
    num1.output(num_num1,num_den1);
    num2.output(num_num2,num_den2);
    temp1=num_num1*num_den2;
    temp2=num_den1*num_num2;
    int index=fun(temp1,temp2);

    temp1=temp1/index;
    temp2=temp2/index;

    printf("%d/%d / %d/%d = %d/%d
",num_num1,num_den1,num_num2,num_den2,temp1,temp2);
}

int main()
{
	Number num1,num2;
	int n,a,b,peace=0;
	cout<<"please input numerator and denominator.
";
	cout<<"first number:";
    cin>>a>>b;
    num1.input(a,b);
    cout<<"last number:";
    cin>>a>>b;
    num2.input(a,b);
	while(1)
    {
        cout<<"         1.Change numerator and denominator.
";
        cout<<"         2.Add
";
        cout<<"         3.Subtract
";
        cout<<"         4.Multiply
";
        cout<<"         5.Divide
";
        cout<<"         6.end
";
        cout<<"Please input a choose:";
        cin>>n;
        switch(n)
        {
            case 1:
                cout<<"first number:";
                cin>>a>>b;
                num1.input(a,b);
                cout<<"last number:";
                cin>>a>>b;
                num2.input(a,b);
                break;
            case 2:
                add(num1,num2);
                break;
            case 3:
                subtract(num1,num2);
                break;
            case 4:
                multiply(num1,num2);
                break;
            case 5:
                divide(num1,num2);
                break;
            case 6:
                peace=1;
                break;
        }
        if(peace)
            break;
    }

	return 0;
}