private boolean r_Step_4() {
            int among_var;
            int v_1;
                    // (, line 140
                    // [, line 141
                    ket = cursor;
                    // substring, line 141
                    among_var = find_among_b(a_7, 18);
                    if (among_var == 0)
                    {
                        return false;
                    }
                    // ], line 141
                    bra = cursor;
                    // call R2, line 141
                    if (!r_R2())
                    {
                        return false;
                    }
                    switch(among_var) {
                        case 0:
                            return false;
                        case 1:
                            // (, line 144
                            // delete, line 144
                            slice_del();
                            break;
                        case 2:
                            // (, line 145
                            // or, line 145
                            lab0: do {
                                v_1 = limit - cursor;
                                lab1: do {
                                    // literal, line 145
                                    if (!(eq_s_b(1, "s")))
                                    {
                                        break lab1;
                                    }
                                    break lab0;
                                } while (false);
                                cursor = limit - v_1;
                                // literal, line 145
                                if (!(eq_s_b(1, "t")))
                                {
                                    return false;
                                }
                            } while (false);
                            // delete, line 145
                            slice_del();
                            break;
                    }
                    return true;
                }