| 529 | |
| 530 | |
| 531 | void set_nullable() |
| 532 | { |
| 533 | register int i, j; |
| 534 | register int empty; |
| 535 | int done; |
| 536 | |
| 537 | nullable = MALLOC(nsyms); |
| 538 | if (nullable == 0) no_space(); |
| 539 | |
| 540 | for (i = 0; i < nsyms; ++i) |
| 541 | nullable[i] = 0; |
| 542 | |
| 543 | done = 0; |
| 544 | while (!done) |
| 545 | { |
| 546 | done = 1; |
| 547 | for (i = 1; i < nitems; i++) |
| 548 | { |
| 549 | empty = 1; |
| 550 | while ((j = ritem[i]) >= 0) |
| 551 | { |
| 552 | if (!nullable[j]) |
| 553 | empty = 0; |
| 554 | ++i; |
| 555 | } |
| 556 | if (empty) |
| 557 | { |
| 558 | j = rlhs[-j]; |
| 559 | if (!nullable[j]) |
| 560 | { |
| 561 | nullable[j] = 1; |
| 562 | done = 0; |
| 563 | } |
| 564 | } |
| 565 | } |
| 566 | } |
| 567 | |
| 568 | #ifdef DEBUG |
| 569 | for (i = 0; i < nsyms; i++) |
| 570 | { |
| 571 | if (nullable[i]) |
| 572 | printf("%s is nullable\n", symbol_name[i]); |
| 573 | else |
| 574 | printf("%s is not nullable\n", symbol_name[i]); |
| 575 | } |
| 576 | #endif |
| 577 | } |
| 578 | |
| 579 | |
| 580 | void free_nullable() |