abstract class Iterator
{
public abstract object First();
public abstract object Next();
public abstract bool IsDone();
public abstract object CurrentItem();
}
abstract class Aggregate
{
public abstract Iterator CreateIterator();
}
class ConcreteIterator : Iterator
{
private ConcreteAggregate aggregate;
private int current = 0;
public ConcreteIterator(ConcreteAggregate agg)
{
this.aggregate = agg;
}
public override object First()
{
return this.aggregate[0];
}
public override object Next()
{
object ret = null;
current++;
if (current < aggregate.Count)
ret = aggregate[current];
return ret;
}
public override bool IsDone()
{
return current > aggregate.Count ? true : false;
}
public override object CurrentItem()
{
return this.aggregate[current];
}
}
class ConcreteAggregate : Aggregate
{
private IList<object> items = new List<object>();
public override Iterator CreateIterator()
{
return new ConcreteIterator(this);
}
public int Count
{
get { return items.Count; }
}
public object this[int index]
{
get { return items[index]; }
set { items.Insert(index, value); }
}
}