def p_indice(p):
    """indice : lbracket expresion rbracket
              | lbracket expresion rbracket lbracket expresion rbracket
              | empty
    """
    if len(p) > 4:
        p[0] = p[2], p[5]
    elif len(p) > 2:
        p[0] = 0, p[2]
