def full_diff_left(l1, l2):
    """
    Computes which elements are in l1 but not in l2
    :param l1: Array
    :param l2: Array
    :return: diff -> Array
    """
    diff = l1.copy()
    for e2 in l2:
        for e1 in l1:
            if e1.full_diff(e2):
                diff.remove(e1)

    return diff