public class IntInterval: IntSequence{

  private int from, to;

  public IntInterval(int from, int to){
    this.from = from;
    this.to = to;
  }

  public override int Min{
    get {return Math.Min(from,to);}
  }

  public override int Max{
    get {return Math.Max(from,to);}
  }
    
  public override IEnumerator GetEnumerator (){
    return new IntervalEnumerator(this);
  }

  private class IntervalEnumerator: IEnumerator{
 
    private readonly IntInterval interval; 
    private int idx;

    public IntervalEnumerator (IntInterval i){
      this.interval = i;
      idx = -1;   // position enumerator outside range
    }
 
    public Object Current{ 
         get {return (interval.from < interval.to) ? 
                       interval.from + idx :
                       interval.from - idx;}
    }

    public bool MoveNext (){
      if ( idx < Math.Abs(interval.to - interval.from))
         {idx++; return true;}
      else
         {return false;}
    }

    public void Reset(){
      idx = -1;         
    }
  }

}