Cтруктуры

#include <iostream>
using namespace std;
struct rational
{
    double a;
    double b;
};

int gcd(int a, int b)
{
    a = abs(a), b = abs(b);
    if (b == 0)return a;
    else return gcd(b, a%b);
}
void sokrdrob(int a, int b)
{
    int x = gcd(a, b);
    a /= x;
    b /= x;
    cout << a << " " << b;
}
/////////////
rational create_rational()
{
    rational p;
    cout << "enter 4islitel=";
    cin >> p.a;
    cout << "enter znamenatel=";
    cin >> p.b;
    return p;
}
//////////////////
void show(rational p)
{
    cout << p.a << "/ " << p.b << endl;
}
///////////////////////////////////
rational add(rational p, rational q)
{
    rational temp;
    if (p.b != q.b)
    {
        temp.b = p.b * q.b;
        temp.a = p.a*q.b + q.a*p.b;
    }
    else
    {
        temp.a = p.a + q.a;
        temp.b = p.a;
    }
    return temp;
}
//////////////////////////
rational subtr(rational p, rational q)
{
    rational temp;
    if (p.b != q.b)
    {
        temp.b = p.b * q.b;
        temp.a = p.a*q.b - q.a*p.b;
    }
    else
    {
        temp.a = p.a - q.a;
        temp.b = p.a;
    }
    return temp;
}
//////////////////////////
rational  mult(rational p, rational q)
{
    rational temp;
    temp.a = p.a*q.a;
    temp.b = p.b*q.b;
    return temp;
}
////////////////////////////


//////////////////////////////
rational div(rational p, rational q)
{
    rational temp;
    temp.a = p.a*q.b;
    temp.b = p.b*q.a;
    return temp;
}

////////////////////
void main()
{
    rational p, q;
    cout << " enter rational p:" << endl;
    p = create_rational();
    cout << " enter rational q:" << endl;
    q = create_rational();
    cout << "  rational number p:   ";
    show(p);
    cout << "  rational number q:   ";
    show(q);
    rational u = add(p, q);
    cout << "  rational number u=p+q u:   ";
    show(u);
    u = subtr(p, q);
    cout << "  rational number u=p-q u:   ";
    show(u);
    u = mult(p,q);
    cout << "  rational number u=p*q u:   ";
    show(u);
    u = div(p,q);
    cout << "  rational number u=(p/q) u:   ";
    show(u);
    system("pause");
}