libreria - pilas y colas con array

#include <array>
#include <iostream>

using namespace std;

struct pila {
    array<int,10> arr;
    int count = 0;
};

struct cola {
    array <int,5> arr;
    int front = 0;
    int rear = 0;
    int cant = 0;
};

pila& push (pila& p, int v)
{
    p.arr.at(p.count) = v;
    p.count++;
    return p;
}

pila& pop (pila& p, int& v)
{
    v = p.arr.at(p.count - 1);
    p.count--;
    return p;
}

cola& enqueue (cola& q, int v)
{
    if (q.cant == 5)
    {
        cout << "Cola llena." << endl;
        return q;
    }
    else
    {
        q.arr.at(q.rear) = v;
        q.rear = (q.rear+1)%5;
        q.cant++;
        return q;
    }
}

cola& dequeue (cola& q, int& v)
{
    if (q.cant == 0)
    {
        cout << "Cola vacia." << endl;
        return q;
    }
    else
    {
        v = q.arr.at(q.front);
        q.front = (q.front+1)%5;
        q.cant--;
        return q;
    }
}

void mostrar_cola (cola& q)
{
    cout << "F a R: ";
    for (int i=0; i<q.cant; i++)
        cout << q.arr.at((q.front+i)%5) << ' ';
    cout << endl;
}