using System.Collections.Generic;

interface IEatable
{
    Eat() : void;
}

class FoodBox[T] : IEnumerable[T]
  where T : IEatable
{
    private _foods : list[T] = [];

    public this() {}

    public this(items : IEnumerable[T])
    {
        this._foods = $[food | food in items];
    }

    public Add(food : T) : FoodBox[T]
    {
        FoodBox(food::_foods);
    }

    public GetEnumerator() : IEnumerator[T]
    {
        _foods.GetEnumerator();
    }
}

class Apple : IEatable
{
    public this() {}

    public Eat() : void
    {
        System.Console.WriteLine("nom..nom..nom");
    }
}

mutable appleBox = FoodBox();
repeat(3) {
    appleBox = appleBox.Add(Apple());
}

foreach (apple in appleBox) apple.Eat();