def pair_distance(cluster_list, idx1, idx2):
    """
    Helper function to compute Euclidean distance between two clusters
    in cluster_list with indices idx1 and idx2
    
    Returns tuple (dist, idx1, idx2) with idx1 < idx2 where dist is distance between
    cluster_list[idx1] and cluster_list[idx2]
    """
    return (cluster_list[idx1].distance(cluster_list[idx2]),
            min(idx1, idx2), max(idx1, idx2))