summaryrefslogtreecommitdiff
path: root/Build/source/texk/web2c/weave.web
blob: 4981570e9b62ab20c4a11bcfa29d17498ad1beec (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453
3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539
3540
3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
3559
3560
3561
3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
3586
3587
3588
3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
3604
3605
3606
3607
3608
3609
3610
3611
3612
3613
3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
3625
3626
3627
3628
3629
3630
3631
3632
3633
3634
3635
3636
3637
3638
3639
3640
3641
3642
3643
3644
3645
3646
3647
3648
3649
3650
3651
3652
3653
3654
3655
3656
3657
3658
3659
3660
3661
3662
3663
3664
3665
3666
3667
3668
3669
3670
3671
3672
3673
3674
3675
3676
3677
3678
3679
3680
3681
3682
3683
3684
3685
3686
3687
3688
3689
3690
3691
3692
3693
3694
3695
3696
3697
3698
3699
3700
3701
3702
3703
3704
3705
3706
3707
3708
3709
3710
3711
3712
3713
3714
3715
3716
3717
3718
3719
3720
3721
3722
3723
3724
3725
3726
3727
3728
3729
3730
3731
3732
3733
3734
3735
3736
3737
3738
3739
3740
3741
3742
3743
3744
3745
3746
3747
3748
3749
3750
3751
3752
3753
3754
3755
3756
3757
3758
3759
3760
3761
3762
3763
3764
3765
3766
3767
3768
3769
3770
3771
3772
3773
3774
3775
3776
3777
3778
3779
3780
3781
3782
3783
3784
3785
3786
3787
3788
3789
3790
3791
3792
3793
3794
3795
3796
3797
3798
3799
3800
3801
3802
3803
3804
3805
3806
3807
3808
3809
3810
3811
3812
3813
3814
3815
3816
3817
3818
3819
3820
3821
3822
3823
3824
3825
3826
3827
3828
3829
3830
3831
3832
3833
3834
3835
3836
3837
3838
3839
3840
3841
3842
3843
3844
3845
3846
3847
3848
3849
3850
3851
3852
3853
3854
3855
3856
3857
3858
3859
3860
3861
3862
3863
3864
3865
3866
3867
3868
3869
3870
3871
3872
3873
3874
3875
3876
3877
3878
3879
3880
3881
3882
3883
3884
3885
3886
3887
3888
3889
3890
3891
3892
3893
3894
3895
3896
3897
3898
3899
3900
3901
3902
3903
3904
3905
3906
3907
3908
3909
3910
3911
3912
3913
3914
3915
3916
3917
3918
3919
3920
3921
3922
3923
3924
3925
3926
3927
3928
3929
3930
3931
3932
3933
3934
3935
3936
3937
3938
3939
3940
3941
3942
3943
3944
3945
3946
3947
3948
3949
3950
3951
3952
3953
3954
3955
3956
3957
3958
3959
3960
3961
3962
3963
3964
3965
3966
3967
3968
3969
3970
3971
3972
3973
3974
3975
3976
3977
3978
3979
3980
3981
3982
3983
3984
3985
3986
3987
3988
3989
3990
3991
3992
3993
3994
3995
3996
3997
3998
3999
4000
4001
4002
4003
4004
4005
4006
4007
4008
4009
4010
4011
4012
4013
4014
4015
4016
4017
4018
4019
4020
4021
4022
4023
4024
4025
4026
4027
4028
4029
4030
4031
4032
4033
4034
4035
4036
4037
4038
4039
4040
4041
4042
4043
4044
4045
4046
4047
4048
4049
4050
4051
4052
4053
4054
4055
4056
4057
4058
4059
4060
4061
4062
4063
4064
4065
4066
4067
4068
4069
4070
4071
4072
4073
4074
4075
4076
4077
4078
4079
4080
4081
4082
4083
4084
4085
4086
4087
4088
4089
4090
4091
4092
4093
4094
4095
4096
4097
4098
4099
4100
4101
4102
4103
4104
4105
4106
4107
4108
4109
4110
4111
4112
4113
4114
4115
4116
4117
4118
4119
4120
4121
4122
4123
4124
4125
4126
4127
4128
4129
4130
4131
4132
4133
4134
4135
4136
4137
4138
4139
4140
4141
4142
4143
4144
4145
4146
4147
4148
4149
4150
4151
4152
4153
4154
4155
4156
4157
4158
4159
4160
4161
4162
4163
4164
4165
4166
4167
4168
4169
4170
4171
4172
4173
4174
4175
4176
4177
4178
4179
4180
4181
4182
4183
4184
4185
4186
4187
4188
4189
4190
4191
4192
4193
4194
4195
4196
4197
4198
4199
4200
4201
4202
4203
4204
4205
4206
4207
4208
4209
4210
4211
4212
4213
4214
4215
4216
4217
4218
4219
4220
4221
4222
4223
4224
4225
4226
4227
4228
4229
4230
4231
4232
4233
4234
4235
4236
4237
4238
4239
4240
4241
4242
4243
4244
4245
4246
4247
4248
4249
4250
4251
4252
4253
4254
4255
4256
4257
4258
4259
4260
4261
4262
4263
4264
4265
4266
4267
4268
4269
4270
4271
4272
4273
4274
4275
4276
4277
4278
4279
4280
4281
4282
4283
4284
4285
4286
4287
4288
4289
4290
4291
4292
4293
4294
4295
4296
4297
4298
4299
4300
4301
4302
4303
4304
4305
4306
4307
4308
4309
4310
4311
4312
4313
4314
4315
4316
4317
4318
4319
4320
4321
4322
4323
4324
4325
4326
4327
4328
4329
4330
4331
4332
4333
4334
4335
4336
4337
4338
4339
4340
4341
4342
4343
4344
4345
4346
4347
4348
4349
4350
4351
4352
4353
4354
4355
4356
4357
4358
4359
4360
4361
4362
4363
4364
4365
4366
4367
4368
4369
4370
4371
4372
4373
4374
4375
4376
4377
4378
4379
4380
4381
4382
4383
4384
4385
4386
4387
4388
4389
4390
4391
4392
4393
4394
4395
4396
4397
4398
4399
4400
4401
4402
4403
4404
4405
4406
4407
4408
4409
4410
4411
4412
4413
4414
4415
4416
4417
4418
4419
4420
4421
4422
4423
4424
4425
4426
4427
4428
4429
4430
4431
4432
4433
4434
4435
4436
4437
4438
4439
4440
4441
4442
4443
4444
4445
4446
4447
4448
4449
4450
4451
4452
4453
4454
4455
4456
4457
4458
4459
4460
4461
4462
4463
4464
4465
4466
4467
4468
4469
4470
4471
4472
4473
4474
4475
4476
4477
4478
4479
4480
4481
4482
4483
4484
4485
4486
4487
4488
4489
4490
4491
4492
4493
4494
4495
4496
4497
4498
4499
4500
4501
4502
4503
4504
4505
4506
4507
4508
4509
4510
4511
4512
4513
4514
4515
4516
4517
4518
4519
4520
4521
4522
4523
4524
4525
4526
4527
4528
4529
4530
4531
4532
4533
4534
4535
4536
4537
4538
4539
4540
4541
4542
4543
4544
4545
4546
4547
4548
4549
4550
4551
4552
4553
4554
4555
4556
4557
4558
4559
4560
4561
4562
4563
4564
4565
4566
4567
4568
4569
4570
4571
4572
4573
4574
4575
4576
4577
4578
4579
4580
4581
4582
4583
4584
4585
4586
4587
4588
4589
4590
4591
4592
4593
4594
4595
4596
4597
4598
4599
4600
4601
4602
4603
4604
4605
4606
4607
4608
4609
4610
4611
4612
4613
4614
4615
4616
4617
4618
4619
4620
4621
4622
4623
4624
4625
4626
4627
4628
4629
4630
4631
4632
4633
4634
4635
4636
4637
4638
4639
4640
4641
4642
4643
4644
4645
4646
4647
4648
4649
4650
4651
4652
4653
4654
4655
4656
4657
4658
4659
4660
4661
4662
4663
4664
4665
4666
4667
4668
4669
4670
4671
4672
4673
4674
4675
4676
4677
4678
4679
4680
4681
4682
4683
4684
4685
4686
4687
4688
4689
4690
4691
4692
4693
4694
4695
4696
4697
4698
4699
4700
4701
4702
4703
4704
4705
4706
4707
4708
4709
4710
4711
4712
4713
4714
4715
4716
4717
4718
4719
4720
4721
4722
4723
4724
4725
4726
4727
4728
4729
4730
4731
4732
4733
4734
4735
4736
4737
4738
4739
4740
4741
4742
4743
4744
4745
4746
4747
4748
4749
4750
4751
4752
4753
4754
4755
4756
4757
4758
4759
4760
4761
4762
4763
4764
4765
4766
4767
4768
4769
4770
4771
4772
4773
4774
4775
4776
4777
4778
4779
4780
4781
4782
4783
4784
4785
4786
4787
4788
4789
4790
4791
4792
4793
4794
4795
4796
4797
4798
4799
4800
4801
4802
4803
4804
4805
4806
4807
4808
4809
4810
4811
4812
4813
4814
4815
4816
4817
4818
4819
4820
4821
4822
4823
4824
4825
4826
4827
4828
4829
4830
4831
4832
4833
4834
4835
4836
4837
4838
4839
4840
4841
4842
4843
4844
4845
4846
4847
4848
4849
4850
4851
4852
4853
4854
4855
4856
4857
4858
4859
4860
4861
4862
4863
4864
4865
4866
4867
4868
4869
4870
4871
4872
4873
4874
4875
4876
4877
4878
4879
4880
4881
4882
4883
4884
4885
4886
4887
4888
4889
4890
4891
4892
4893
4894
4895
4896
4897
4898
4899
4900
4901
4902
4903
% This program by D. E. Knuth is not copyrighted and can be used freely.
% Version 0 was released in December, 1981.
% Version 1 was released in September, 1982, with version 0 of TeX.
% Slight changes were made in October, 1982, for version 0.6 of TeX.
% Version 1.1 changed "_" to "\_" if not within an identifier (November, 1982).
% Version 1.2 added @@= and @@\ and marked changed modules (December, 1982).
% Version 1.3 marked and indexed changed modules better (January, 1983).
% Version 1.4 added "history" (February, 1983).
% Version 1.5 conformed to TeX version 0.96 (March, 1983).
% Version 1.6 conformed to TeX version 0.98 (May, 1983).
% Version 1.7 introduced the new change file format (June, 1983).
% Version 2 was released in July, 1983, with version 0.999 of TeX.
% Version 2.1 corrected a bug in changed_module reckoning (August, 1983).
% Version 2.2 corrected it better (August, 1983).
% Version 2.3 starts the output with \input webmac (August, 1983).
% Version 2.4 fixed a bug in compress(#) (September, 1983).
% Version 2.5 cleared xrefswitch after module names (November, 1983).
% Version 2.6 fixed a bug in declaration of trans array (January, 1984).
% Version 2.7 fixed a bug in real constants (August, 1984).
% Version 2.8 fixed a bug in change_buffer movement (August, 1985).
% Version 2.9 increased max_refs and max_toks to 30000 each (January, 1987).
% Version 3, for Sewell's book, fixed long-line bug in input_ln (March, 1989).
% Version 3.1 fixed a bug for programs with only one module (April, 1989).
% Version 4 was major change to allow 8-bit input (September, 1989).
% Version 4.1, for Breitenlohner, avoids English-only output (March, 1990).
% Version 4.2 conforms to ANSI standard for-loop rules (September, 1990).
% Version 4.3 catches extra } in input (Breitenlohner, September, 1991).
% Version 4.4 corrects changed_module logic, %-overflow (January, 1992).
% Version 4.5 corrects archaic @@z logic and empty change file (January, 2021).

% Here is TeX material that gets inserted after \input webmac
\def\hang{\hangindent 3em\indent\ignorespaces}
\font\ninerm=cmr9
\let\mc=\ninerm % medium caps for names like SAIL
\def\PASCAL{Pascal}
\def\pb{$\.|\ldots\.|$} % Pascal brackets (|...|)
\def\v{\.{\char'174}} % vertical (|) in typewriter font
\def\dleft{[\![} \def\dright{]\!]} % double brackets
\mathchardef\RA="3221 % right arrow
\mathchardef\BA="3224 % double arrow
\def\({} % kludge for alphabetizing certain module names

\def\title{WEAVE}
\def\contentspagenumber{15} % should be odd
\def\topofcontents{\null\vfill
  \titlefalse % include headline on the contents page
  \def\rheader{\mainfont Appendix D\hfil \contentspagenumber}
  \centerline{\titlefont The {\ttitlefont WEAVE} processor}
  \vskip 15pt
  \centerline{(Version 4.5)}
  \vfill}
\pageno=\contentspagenumber \advance\pageno by 1

@* Introduction.
This program converts a \.{WEB} file to a \TeX\ file. It was written
by D. E. Knuth in October, 1981; a somewhat similar {\mc SAIL} program had
been developed in March, 1979, although the earlier program used a top-down
parsing method that is quite different from the present scheme.

The code uses a few features of the local \PASCAL\ compiler that may need
to be changed in other installations:

\yskip\item{1)} Case statements have a default.
\item{2)} Input-output routines may need to be adapted for use with a particular
character set and/or for printing messages on the user's terminal.

\yskip\noindent
These features are also present in the \PASCAL\ version of \TeX, where they
are used in a similar (but more complex) way. System-dependent portions
of \.{WEAVE} can be identified by looking at the entries for `system
dependencies' in the index below.
@!@^system dependencies@>

The ``banner line'' defined here should be changed whenever \.{WEAVE}
is modified.

@d banner=='This is WEAVE, Version 4.5'

@ The program begins with a fairly normal header, made up of pieces that
@^system dependencies@>
will mostly be filled in later. The \.{WEB} input comes from files |web_file|
and |change_file|, and the \TeX\ output goes to file |tex_file|.

If it is necessary to abort the job because of a fatal error, the program
calls the `|jump_out|' procedure, which goes to the label |end_of_WEAVE|.

@d end_of_WEAVE = 9999 {go here to wrap it up}

@p @t\4@>@<Compiler directives@>@/
program WEAVE(@!web_file,@!change_file,@!tex_file);
label end_of_WEAVE; {go here to finish}
const @<Constants in the outer block@>@/
type @<Types in the outer block@>@/
var @<Globals in the outer block@>@/
@<Error handling procedures@>@/
procedure initialize;
  var @<Local variables for initialization@>@/
  begin @<Set initial values@>@/
  end;

@ Some of this code is optional for use when debugging only;
such material is enclosed between the delimiters |debug| and $|gubed|$.
Other parts, delimited by |stat| and $|tats|$, are optionally included
if statistics about \.{WEAVE}'s memory usage are desired.

@d debug==@{ {change this to `$\\{debug}\equiv\null$' when debugging}
@d gubed==@t@>@} {change this to `$\\{gubed}\equiv\null$' when debugging}
@f debug==begin
@f gubed==end
@#
@d stat==@{ {change this to `$\\{stat}\equiv\null$'
  when gathering usage statistics}
@d tats==@t@>@} {change this to `$\\{tats}\equiv\null$'
  when gathering usage statistics}
@f stat==begin
@f tats==end

@ The \PASCAL\ compiler used to develop this system has ``compiler
directives'' that can appear in comments whose first character is a dollar sign.
In production versions of \.{WEAVE} these directives tell the compiler that
@^system dependencies@>
it is safe to avoid range checks and to leave out the extra code it inserts
for the \PASCAL\ debugger's benefit, although interrupts will occur if
there is arithmetic overflow.

@<Compiler directives@>=
@{@&$C-,A+,D-@} {no range check, catch arithmetic overflow, no debug overhead}
@!debug @{@&$C+,D+@}@+ gubed {but turn everything on when debugging}

@ Labels are given symbolic names by the following definitions. We insert
the label `|exit|:' just before the `\ignorespaces|end|\unskip' of a
procedure in which we have used the `|return|' statement defined below;
the label `|restart|' is occasionally used at the very beginning of a
procedure; and the label `|reswitch|' is occasionally used just prior to
a \&{case} statement in which some cases change the conditions and we wish to
branch to the newly applicable case.
Loops that are set up with the \&{loop} construction defined below are
commonly exited by going to `|done|' or to `|found|' or to `|not_found|',
and they are sometimes repeated by going to `|continue|'.

@d exit=10 {go here to leave a procedure}
@d restart=20 {go here to start a procedure again}
@d reswitch=21 {go here to start a case statement again}
@d continue=22 {go here to resume a loop}
@d done=30 {go here to exit a loop}
@d found=31 {go here when you've found it}
@d not_found=32 {go here when you've found something else}

@ Here are some macros for common programming idioms.

@d incr(#) == #:=#+1 {increase a variable by unity}
@d decr(#) == #:=#-1 {decrease a variable by unity}
@d loop == @+ while true do@+ {repeat over and over until a |goto| happens}
@d do_nothing == {empty statement}
@d return == goto exit {terminate a procedure call}
@f return == nil
@f loop == xclause

@ We assume that |case| statements may include a default case that applies
if no matching label is found. Thus, we shall use constructions like
@^system dependencies@>
$$\vbox{\halign{#\hfil\cr
|case x of|\cr
1: $\langle\,$code for $x=1\,\rangle$;\cr
3: $\langle\,$code for $x=3\,\rangle$;\cr
|othercases| $\langle\,$code for |x<>1| and |x<>3|$\,\rangle$\cr
|endcases|\cr}}$$
since most \PASCAL\ compilers have plugged this hole in the language by
incorporating some sort of default mechanism. For example, the compiler
used to develop \.{WEB} and \TeX\ allows `|others|:' as a default label,
and other \PASCAL s allow syntaxes like `\ignorespaces|else|\unskip' or
`\&{otherwise}' or `\\{otherwise}:', etc. The definitions of |othercases|
and |endcases| should be changed to agree with local conventions.
(Of course, if no default mechanism is available, the |case| statements of
this program must be extended by listing all remaining cases.)

@d othercases == others: {default for cases not listed explicitly}
@d endcases == @+end {follows the default case in an extended |case| statement}
@f othercases == else
@f endcases == end

@ The following parameters are set big enough to handle \TeX, so they
should be sufficient for most applications of \.{WEAVE}.

@<Constants...@>=
@!max_bytes=45000; {|1/ww| times the number of bytes in identifiers,
  index entries, and module names; must be less than 65536}
@!max_names=5000; {number of identifiers, index entries, and module names;
  must be less than 10240}
@!max_modules=2000;{greater than the total number of modules}
@!hash_size=353; {should be prime}
@!buf_size=100; {maximum length of input line}
@!longest_name=400; {module names shouldn't be longer than this}
@!long_buf_size=500; {|buf_size+longest_name|}
@!line_length=80; {lines of \TeX\ output have at most this many characters,
  should be less than 256}
@!max_refs=30000; {number of cross references; must be less than 65536}
@!max_toks=30000; {number of symbols in \PASCAL\ texts being parsed;
  must be less than 65536}
@!max_texts=2000; {number of phrases in \PASCAL\ texts being parsed;
  must be less than 10240}
@!max_scraps=1000; {number of tokens in \PASCAL\ texts being parsed}
@!stack_size=200; {number of simultaneous output levels}

@ A global variable called |history| will contain one of four values
at the end of every run: |spotless| means that no unusual messages were
printed; |harmless_message| means that a message of possible interest
was printed but no serious errors were detected; |error_message| means that
at least one error was found; |fatal_message| means that the program
terminated abnormally. The value of |history| does not influence the
behavior of the program; it is simply computed for the convenience
of systems that might want to use such information.

@d spotless=0 {|history| value for normal jobs}
@d harmless_message=1 {|history| value when non-serious info was printed}
@d error_message=2 {|history| value when an error was noted}
@d fatal_message=3 {|history| value when we had to stop prematurely}
@#
@d mark_harmless==@t@>@+if history=spotless then history:=harmless_message
@d mark_error==history:=error_message
@d mark_fatal==history:=fatal_message

@<Glob...@>=@!history:spotless..fatal_message; {how bad was this run?}

@ @<Set init...@>=history:=spotless;

@* The character set.
One of the main goals in the design of \.{WEB} has been to make it readily
portable between a wide variety of computers. Yet \.{WEB} by its very
nature must use a greater variety of characters than most computer
programs deal with, and character encoding is one of the areas in which
existing machines differ most widely from each other.

To resolve this problem, all input to \.{WEAVE} and \.{TANGLE} is
converted to an internal eight-bit code that is essentially standard
ASCII, the ``American Standard Code for Information Interchange.''
The conversion is done immediately when each character is read in.
Conversely, characters are converted from ASCII to the user's external
representation just before they are output. (The original ASCII code
was seven bits only; \.{WEB} now allows eight bits in an attempt to
keep up with modern times.)

Such an internal code is relevant to users of \.{WEB} only because it is
the code used for preprocessed constants like \.{"A"}. If you are writing
a program in \.{WEB} that makes use of such one-character constants, you
should convert your input to ASCII form, like \.{WEAVE} and \.{TANGLE} do.
Otherwise \.{WEB}'s internal coding scheme does not affect you.
@^ASCII code@>

Here is a table of the standard visible ASCII codes:
$$\def\:{\char\count255\global\advance\count255 by 1}
\count255='40
\vbox{
\hbox{\hbox to 40pt{\it\hfill0\/\hfill}%
\hbox to 40pt{\it\hfill1\/\hfill}%
\hbox to 40pt{\it\hfill2\/\hfill}%
\hbox to 40pt{\it\hfill3\/\hfill}%
\hbox to 40pt{\it\hfill4\/\hfill}%
\hbox to 40pt{\it\hfill5\/\hfill}%
\hbox to 40pt{\it\hfill6\/\hfill}%
\hbox to 40pt{\it\hfill7\/\hfill}}
\vskip 4pt
\hrule
\def\^{\vrule height 10.5pt depth 4.5pt}
\halign{\hbox to 0pt{\hskip -24pt\O{#0}\hfill}&\^
\hbox to 40pt{\tt\hfill#\hfill\^}&
&\hbox to 40pt{\tt\hfill#\hfill\^}\cr
04&\:&\:&\:&\:&\:&\:&\:&\:\cr\noalign{\hrule}
05&\:&\:&\:&\:&\:&\:&\:&\:\cr\noalign{\hrule}
06&\:&\:&\:&\:&\:&\:&\:&\:\cr\noalign{\hrule}
07&\:&\:&\:&\:&\:&\:&\:&\:\cr\noalign{\hrule}
10&\:&\:&\:&\:&\:&\:&\:&\:\cr\noalign{\hrule}
11&\:&\:&\:&\:&\:&\:&\:&\:\cr\noalign{\hrule}
12&\:&\:&\:&\:&\:&\:&\:&\:\cr\noalign{\hrule}
13&\:&\:&\:&\:&\:&\:&\:&\:\cr\noalign{\hrule}
14&\:&\:&\:&\:&\:&\:&\:&\:\cr\noalign{\hrule}
15&\:&\:&\:&\:&\:&\:&\:&\:\cr\noalign{\hrule}
16&\:&\:&\:&\:&\:&\:&\:&\:\cr\noalign{\hrule}
17&\:&\:&\:&\:&\:&\:&\:\cr}
\hrule width 280pt}$$
(Actually, of course, code @'040 is an invisible blank space.)  Code @'136
was once an upward arrow (\.{\char'13}), and code @'137 was
once a left arrow (\.^^X), in olden times when the first draft
of ASCII code was prepared; but \.{WEB} works with today's standard
ASCII in which those codes represent circumflex and underline as shown.

@<Types...@>=
@!ASCII_code=0..255; {eight-bit numbers, a subrange of the integers}

@ The original \PASCAL\ compiler was designed in the late 60s, when six-bit
character sets were common, so it did not make provision for lowercase
letters. Nowadays, of course, we need to deal with both capital and small
letters in a convenient way, so \.{WEB} assumes that it is being used
with a \PASCAL\ whose character set contains at least the characters of
standard ASCII as listed above. Some \PASCAL\ compilers use the original
name |char| for the data type associated with the characters in text files,
while other \PASCAL s consider |char| to be a 64-element subrange of a larger
data type that has some other name.

In order to accommodate this difference, we shall use the name |text_char|
to stand for the data type of the characters in the input and output
files.  We shall also assume that |text_char| consists of the elements
|chr(first_text_char)| through |chr(last_text_char)|, inclusive. The
following definitions should be adjusted if necessary.
@^system dependencies@>

@d text_char == char {the data type of characters in text files}
@d first_text_char=0 {ordinal number of the smallest element of |text_char|}
@d last_text_char=255 {ordinal number of the largest element of |text_char|}

@<Types...@>=
@!text_file=packed file of text_char;

@ The \.{WEAVE} and \.{TANGLE} processors convert between ASCII code and
the user's external character set by means of arrays |xord| and |xchr|
that are analogous to \PASCAL's |ord| and |chr| functions.

@<Globals...@>=
@!xord: array [text_char] of ASCII_code;
  {specifies conversion of input characters}
@!xchr: array [ASCII_code] of text_char;
  {specifies conversion of output characters}

@ If we assume that every system using \.{WEB} is able to read and write the
visible characters of standard ASCII (although not necessarily using the
ASCII codes to represent them), the following assignment statements initialize
most of the |xchr| array properly, without needing any system-dependent
changes. For example, the statement \.{xchr[@@\'101]:=\'A\'} that appears
in the present \.{WEB} file might be encoded in, say, {\mc EBCDIC} code
on the external medium on which it resides, but \.{TANGLE} will convert from
this external code to ASCII and back again. Therefore the assignment
statement \.{XCHR[65]:=\'A\'} will appear in the corresponding \PASCAL\ file,
and \PASCAL\ will compile this statement so that |xchr[65]| receives the
character \.A in the external (|char|) code. Note that it would be quite
incorrect to say \.{xchr[@@\'101]:="A"}, because |"A"| is a constant of
type |integer|, not |char|, and because we have $|"A"|=65$ regardless of
the external character set.

@<Set init...@>=
xchr[@'40]:=' ';
xchr[@'41]:='!';
xchr[@'42]:='"';
xchr[@'43]:='#';
xchr[@'44]:='$';
xchr[@'45]:='%';
xchr[@'46]:='&';
xchr[@'47]:='''';@/
xchr[@'50]:='(';
xchr[@'51]:=')';
xchr[@'52]:='*';
xchr[@'53]:='+';
xchr[@'54]:=',';
xchr[@'55]:='-';
xchr[@'56]:='.';
xchr[@'57]:='/';@/
xchr[@'60]:='0';
xchr[@'61]:='1';
xchr[@'62]:='2';
xchr[@'63]:='3';
xchr[@'64]:='4';
xchr[@'65]:='5';
xchr[@'66]:='6';
xchr[@'67]:='7';@/
xchr[@'70]:='8';
xchr[@'71]:='9';
xchr[@'72]:=':';
xchr[@'73]:=';';
xchr[@'74]:='<';
xchr[@'75]:='=';
xchr[@'76]:='>';
xchr[@'77]:='?';@/
xchr[@'100]:='@@';
xchr[@'101]:='A';
xchr[@'102]:='B';
xchr[@'103]:='C';
xchr[@'104]:='D';
xchr[@'105]:='E';
xchr[@'106]:='F';
xchr[@'107]:='G';@/
xchr[@'110]:='H';
xchr[@'111]:='I';
xchr[@'112]:='J';
xchr[@'113]:='K';
xchr[@'114]:='L';
xchr[@'115]:='M';
xchr[@'116]:='N';
xchr[@'117]:='O';@/
xchr[@'120]:='P';
xchr[@'121]:='Q';
xchr[@'122]:='R';
xchr[@'123]:='S';
xchr[@'124]:='T';
xchr[@'125]:='U';
xchr[@'126]:='V';
xchr[@'127]:='W';@/
xchr[@'130]:='X';
xchr[@'131]:='Y';
xchr[@'132]:='Z';
xchr[@'133]:='[';
xchr[@'134]:='\';
xchr[@'135]:=']';
xchr[@'136]:='^';
xchr[@'137]:='_';@/
xchr[@'140]:='`';
xchr[@'141]:='a';
xchr[@'142]:='b';
xchr[@'143]:='c';
xchr[@'144]:='d';
xchr[@'145]:='e';
xchr[@'146]:='f';
xchr[@'147]:='g';@/
xchr[@'150]:='h';
xchr[@'151]:='i';
xchr[@'152]:='j';
xchr[@'153]:='k';
xchr[@'154]:='l';
xchr[@'155]:='m';
xchr[@'156]:='n';
xchr[@'157]:='o';@/
xchr[@'160]:='p';
xchr[@'161]:='q';
xchr[@'162]:='r';
xchr[@'163]:='s';
xchr[@'164]:='t';
xchr[@'165]:='u';
xchr[@'166]:='v';
xchr[@'167]:='w';@/
xchr[@'170]:='x';
xchr[@'171]:='y';
xchr[@'172]:='z';
xchr[@'173]:='{';
xchr[@'174]:='|';
xchr[@'175]:='}';
xchr[@'176]:='~';@/
xchr[0]:=' '; xchr[@'177]:=' '; {these ASCII codes are not used}

@ Some of the ASCII codes below @'40 have been given symbolic names in
\.{WEAVE} and \.{TANGLE} because they are used with a special meaning.

@d and_sign=@'4 {equivalent to `\.{and}'}
@d not_sign=@'5 {equivalent to `\.{not}'}
@d set_element_sign=@'6 {equivalent to `\.{in}'}
@d tab_mark=@'11 {ASCII code used as tab-skip}
@d line_feed=@'12 {ASCII code thrown away at end of line}
@d form_feed=@'14 {ASCII code used at end of page}
@d carriage_return=@'15 {ASCII code used at end of line}
@d left_arrow=@'30 {equivalent to `\.{:=}'}
@d not_equal=@'32 {equivalent to `\.{<>}'}
@d less_or_equal=@'34 {equivalent to `\.{<=}'}
@d greater_or_equal=@'35 {equivalent to `\.{>=}'}
@d equivalence_sign=@'36 {equivalent to `\.{==}'}
@d or_sign=@'37 {equivalent to `\.{or}'}

@ When we initialize the |xord| array and the remaining parts of |xchr|,
it will be convenient to make use of an index variable, |i|.

@<Local variables for init...@>=
@!i:0..255;

@ Here now is the system-dependent part of the character set.
If \.{WEB} is being implemented on a garden-variety \PASCAL\ for which
only standard ASCII codes will appear in the input and output files, you
don't need to make any changes here. But if you have, for example, an extended
character set like the one in Appendix~C of {\sl The \TeX book}, the first
line of code in this module should be changed to
$$\hbox{|for i:=1 to @'37 do xchr[i]:=chr(i);|}$$
\.{WEB}'s character set is essentially identical to \TeX's, even with respect to
characters less than @'40.
@^system dependencies@>

Changes to the present module will make \.{WEB} more friendly on computers
that have an extended character set, so that one can type things like
\.^^Z\ instead of \.{<>}. If you have an extended set of characters that
are easily incorporated into text files, you can assign codes arbitrarily
here, giving an |xchr| equivalent to whatever characters the users of
\.{WEB} are allowed to have in their input files, provided that unsuitable
characters do not correspond to special codes like |carriage_return|
that are listed above.

(The present file \.{WEAVE.WEB} does not contain any of the non-ASCII
characters, because it is intended to be used with all implementations of
\.{WEB}.  It was originally created on a Stanford system that has a
convenient extended character set, then ``sanitized'' by applying another
program that transliterated all of the non-standard characters into
standard equivalents.)

@<Set init...@>=
for i:=1 to @'37 do xchr[i]:=' ';
for i:=@'200 to @'377 do xchr[i]:=' ';

@ The following system-independent code makes the |xord| array contain a
suitable inverse to the information in |xchr|.

@<Set init...@>=
for i:=first_text_char to last_text_char do xord[chr(i)]:=" ";
for i:=1 to @'377 do xord[xchr[i]]:=i;
xord[' ']:=" ";

@* Input and output.
The input conventions of this program are intended to be very much like those
of \TeX\ (except, of course, that they are much simpler, because much less
needs to be done). Furthermore they are identical to those of \.{TANGLE}.
Therefore people who need to make modifications to all three systems
should be able to do so without too many headaches.

We use the standard \PASCAL\ input/output procedures in several places that
\TeX\ cannot, since \.{WEAVE} does not have to deal with files that are named
dynamically by the user, and since there is no input from the terminal.

@ Terminal output is done by writing on file |term_out|, which is assumed to
consist of characters of type |text_char|:
@^system dependencies@>

@d print(#)==write(term_out,#) {`|print|' means write on the terminal}
@d print_ln(#)==write_ln(term_out,#) {`|print|' and then start new line}
@d new_line==write_ln(term_out) {start new line}
@d print_nl(#)==  {print information starting on a new line}
  begin new_line; print(#);
  end

@<Globals...@>=
@!term_out:text_file; {the terminal as an output file}

@ Different systems have different ways of specifying that the output on a
certain file will appear on the user's terminal. Here is one way to do this
on the \PASCAL\ system that was used in \.{TANGLE}'s initial development:
@^system dependencies@>

@<Set init...@>=
rewrite(term_out,'TTY:'); {send |term_out| output to the terminal}

@ The |update_terminal| procedure is called when we want
to make sure that everything we have output to the terminal so far has
actually left the computer's internal buffers and been sent.
@^system dependencies@>

@d update_terminal == break(term_out) {empty the terminal output buffer}

@ The main input comes from |web_file|; this input may be overridden
by changes in |change_file|. (If |change_file| is empty, there are no changes.)

@<Globals...@>=
@!web_file:text_file; {primary input}
@!change_file:text_file; {updates}

@ The following code opens the input files.  Since these files were listed
in the program header, we assume that the \PASCAL\ runtime system has
already checked that suitable file names have been given; therefore no
additional error checking needs to be done. We will see below that
\.{WEAVE} reads through the entire input twice.
@^system dependencies@>

@p procedure open_input; {prepare to read |web_file| and |change_file|}
begin reset(web_file); reset(change_file);
end;

@ The main output goes to |tex_file|.

@<Globals...@>=
@!tex_file: text_file;

@ The following code opens |tex_file|.
Since this file was listed in the program header, we assume that the
\PASCAL\ runtime system has checked that a suitable external file name has
been given.
@^system dependencies@>

@<Set init...@>=
rewrite(tex_file);

@ Input goes into an array called |buffer|.

@<Globals...@>=@!buffer: array[0..long_buf_size] of ASCII_code;

@ The |input_ln| procedure brings the next line of input from the specified
file into the |buffer| array and returns the value |true|, unless the file has
already been entirely read, in which case it returns |false|. The conventions
of \TeX\ are followed; i.e., |ASCII_code| numbers representing the next line
of the file are input into |buffer[0]|, |buffer[1]|, \dots,
|buffer[limit-1]|; trailing blanks are ignored;
and the global variable |limit| is set to the length of the
@^system dependencies@>
line. The value of |limit| must be strictly less than |buf_size|.

We assume that none of the |ASCII_code| values
of |buffer[j]| for |0<=j<limit| is equal to 0, @'177, |line_feed|, |form_feed|,
or |carriage_return|. Since |buf_size| is strictly less than |long_buf_size|,
some of \.{WEAVE}'s routines use the fact that it is safe to refer to
|buffer[limit+2]| without overstepping the bounds of the array.

@p function input_ln(var f:text_file):boolean;
  {inputs a line or returns |false|}
var final_limit:0..buf_size; {|limit| without trailing blanks}
begin limit:=0; final_limit:=0;
if eof(f) then input_ln:=false
else  begin while not eoln(f) do
    begin buffer[limit]:=xord[f^]; get(f);
    incr(limit);
    if buffer[limit-1]<>" " then final_limit:=limit;
    if limit=buf_size then
      begin while not eoln(f) do get(f);
      decr(limit); {keep |buffer[buf_size]| empty}
      if final_limit>limit then final_limit:=limit;
      print_nl('! Input line too long'); loc:=0; error;
@.Input line too long@>
      end;
    end;
  read_ln(f); limit:=final_limit; input_ln:=true;
  end;
end;

@* Reporting errors to the user.
The \.{WEAVE} processor operates in three phases: first it inputs the source
file and stores cross-reference data, then it inputs the source once again and
produces the \TeX\ output file, and finally it sorts and outputs the index.

The global variables |phase_one| and |phase_three| tell which Phase we are in.

@<Globals...@>=
@!phase_one: boolean; {|true| in Phase I, |false| in Phases II and III}
@!phase_three: boolean; {|true| in Phase III, |false| in Phases I and II}

@ If an error is detected while we are debugging,
we usually want to look at the contents of memory.
A special procedure will be declared later for this purpose.

@<Error handling...@>=
@!debug@+ procedure debug_help; forward;@+gubed

@ The command `|err_print('! Error message')|' will report a syntax error to
the user, by printing the error message at the beginning of a new line and
then giving an indication of where the error was spotted in the source file.
Note that no period follows the error message, since the error routine
will automatically supply a period.

The actual error indications are provided by a procedure called |error|.
However, error messages are not actually reported during phase one,
since errors detected on the first pass will be detected again
during the second.

@d err_print(#)==
  begin if not phase_one then
    begin new_line; print(#); error;
    end;
  end

@<Error handling...@>=
procedure error; {prints `\..' and location of error message}
var@!k,@!l: 0..long_buf_size; {indices into |buffer|}
begin @<Print error location based on input buffer@>;
update_terminal; mark_error;
@!debug debug_skipped:=debug_cycle;debug_help;@+gubed
end;

@ The error locations can be indicated by using the global variables
|loc|, |line|, and |changing|, which tell respectively the first
unlooked-at position in |buffer|, the current line number, and whether or not
the current line is from |change_file| or |web_file|.
This routine should be modified on systems whose standard text editor
has special line-numbering conventions.
@^system dependencies@>

@<Print error location based on input buffer@>=
begin if changing then print('. (change file ')@+else print('. (');
print_ln('l.', line:1, ')');
if loc>=limit then l:=limit else l:=loc;
for k:=1 to l do
  if buffer[k-1]=tab_mark then print(' ')
  else print(xchr[buffer[k-1]]); {print the characters already read}
new_line;
for k:=1 to l do print(' '); {space out the next line}
for k:=l+1 to limit do print(xchr[buffer[k-1]]); {print the part not yet read}
if buffer[limit]="|" then print(xchr["|"]);
  {end of \PASCAL\ text in module names}
print(' '); {this space separates the message from future asterisks}
end

@ The |jump_out| procedure just cuts across all active procedure levels
and jumps out of the program. This is the only non-local \&{goto} statement
in \.{WEAVE}. It is used when no recovery from a particular error has
been provided.

Some \PASCAL\ compilers do not implement non-local |goto| statements.
@^system dependencies@>
In such cases the code that appears at label |end_of_WEAVE| should be
copied into the |jump_out| procedure, followed by a call to a system procedure
that terminates the program.

@d fatal_error(#)==begin new_line; print(#); error; mark_fatal; jump_out;
  end

@<Error handling...@>=
procedure jump_out;
begin goto end_of_WEAVE;
end;

@ Sometimes the program's behavior is far different from what it should be,
and \.{WEAVE} prints an error message that is really for the \.{WEAVE}
maintenance person, not the user. In such cases the program says
|confusion('indication of where we are')|.

@d confusion(#)==fatal_error('! This can''t happen (',#,')')
@.This can't happen@>

@ An overflow stop occurs if \.{WEAVE}'s tables aren't large enough.

@d overflow(#)==fatal_error('! Sorry, ',#,' capacity exceeded')
@.Sorry, x capacity exceeded@>

@* Data structures.
During the first phase of its processing, \.{WEAVE} puts identifier names,
index entries, and module names into the large |byte_mem| array, which is
packed with eight-bit integers. Allocation is sequential, since names are
never deleted.

An auxiliary array |byte_start| is used as a directory for |byte_mem|,
and the |link|, |ilk|, and |xref| arrays give further information about names.
These auxiliary arrays consist of sixteen-bit items.

@<Types...@>=
@!eight_bits=0..255; {unsigned one-byte quantity}
@!sixteen_bits=0..65535; {unsigned two-byte quantity}

@ \.{WEAVE} has been designed to avoid the need for indices that are more
than sixteen bits wide, so that it can be used on most computers. But
there are programs that need more than 65536 bytes; \TeX\ is one of these.
To get around this problem, a slight complication has been added to the
data structures:  |byte_mem| is a two-dimensional array, whose first index
is either 0 or 1. (For generality, the first index is actually allowed to
run between 0 and |ww-1|, where |ww| is defined to be 2; the program will
work for any positive value of |ww|, and it can be simplified in obvious
ways if |ww=1|.)

@d ww=2 {we multiply the byte capacity by approximately this amount}

@<Globals...@>=
@!byte_mem: packed array [0..ww-1,0..max_bytes] of ASCII_code;
  {characters of names}
@!byte_start: array [0..max_names] of sixteen_bits; {directory into |byte_mem|}
@!link: array [0..max_names] of sixteen_bits; {hash table or tree links}
@!ilk: array [0..max_names] of sixteen_bits; {type codes or tree links}
@!xref: array [0..max_names] of sixteen_bits; {heads of cross-reference lists}

@ The names of identifiers are found by computing a hash address |h| and
then looking at strings of bytes signified by |hash[h]|, |link[hash[h]]|,
|link[link[hash[h]]]|, \dots, until either finding the desired name
or encountering a zero.

A `|name_pointer|' variable, which signifies a name, is an index into
|byte_start|. The actual sequence of characters in the name pointed to by
|p| appears in positions |byte_start[p]| to |byte_start[p+ww]-1|, inclusive,
in the segment of |byte_mem| whose first index is |p mod ww|. Thus, when
|ww=2| the even-numbered name bytes appear in |byte_mem[0,@t$*$@>]|
and the odd-numbered ones appear in |byte_mem[1,@t$*$@>]|.
The pointer 0 is used for undefined module names; we don't
want to use it for the names of identifiers, since 0 stands for a null
pointer in a linked list.

We usually have |byte_start[name_ptr+w]=byte_ptr[(name_ptr+w) mod ww]|
for |0<=w<ww|, since these are the starting positions for the next |ww|
names to be stored in |byte_mem|.

@d length(#)==byte_start[#+ww]-byte_start[#] {the length of a name}

@<Types...@>=
@!name_pointer=0..max_names; {identifies a name}

@ @<Global...@>=
@!name_ptr:name_pointer; {first unused position in |byte_start|}
@!byte_ptr:array [0..ww-1] of 0..max_bytes;
  {first unused position in |byte_mem|}

@ @<Local variables for init...@>=
@!wi: 0..ww-1; {to initialize the |byte_mem| indices}

@ @<Set init...@>=
for wi:=0 to ww-1 do
  begin byte_start[wi]:=0; byte_ptr[wi]:=0;
  end;
byte_start[ww]:=0; {this makes name 0 of length zero}
name_ptr:=1;

@ Several types of identifiers are distinguished by their |ilk|:

\yskip\hang |normal| identifiers are part of the \PASCAL\ program and
will appear in italic type.

\yskip\hang |roman| identifiers are index entries that appear after
\.{@@\^} in the \.{WEB} file.

\yskip\hang |wildcard| identifiers are index entries that appear after
\.{@@:} in the \.{WEB} file.

\yskip\hang |typewriter| identifiers are index entries that appear after
\.{@@.} in the \.{WEB} file.

\yskip\hang |array_like|, |begin_like|, \dots, |var_like|
identifiers are \PASCAL\ reserved words whose |ilk| explains how they are
to be treated when \PASCAL\ code is being formatted.

\yskip\hang Finally, if |c| is an ASCII code, an |ilk| equal to
|char_like+c| denotes a reserved word that will be converted to character
|c|.

@d normal=0 {ordinary identifiers have |normal| ilk}
@d roman=1 {normal index entries have |roman| ilk}
@d wildcard=2 {user-formatted index entries have |wildcard| ilk}
@d typewriter=3 {`typewriter type' entries have |typewriter| ilk}
@d reserved(#)==(ilk[#]>typewriter) {tells if a name is a reserved word}
@d array_like=4 {\&{array}, \&{file}, \&{set}}
@d begin_like=5 {\&{begin}}
@d case_like=6 {\&{case}}
@d const_like=7 {\&{const}, \&{label}, \&{type}}
@d div_like=8 {\&{div}, \&{mod}}
@d do_like=9 {\&{do}, \&{of}, \&{then}}
@d else_like=10 {\&{else}}
@d end_like=11 {\&{end}}
@d for_like=12 {\&{for}, \&{while}, \&{with}}
@d goto_like=13 {\&{goto}, \&{packed}}
@d if_like=14 {\&{if}}
@d intercal_like=15 {not used}
@d nil_like=16 {\&{nil}}
@d proc_like=17 {\&{function}, \&{procedure}, \&{program}}
@d record_like=18 {\&{record}}
@d repeat_like=19 {\&{repeat}}
@d to_like=20 {\&{downto}, \&{to}}
@d until_like=21 {\&{until}}
@d var_like=22 {\&{var}}
@d loop_like=23 {\&{loop}, \&{xclause}}
@d char_like=24 {\&{and}, \&{or}, \&{not}, \&{in}}

@ The names of modules are stored in |byte_mem| together
with the identifier names, but a hash table is not used for them because
\.{WEAVE} needs to be able to recognize a module name when given a prefix of
that name. A conventional binary search tree is used to retrieve module names,
with fields called |llink| and |rlink| in place of |link| and |ilk|. The
root of this tree is |rlink[0]|.

@d llink==link {left link in binary search tree for module names}
@d rlink==ilk {right link in binary search tree for module names}
@d root==rlink[0] {the root of the binary search tree for module names}

@<Set init...@>=
root:=0; {the binary search tree starts out with nothing in it}

@ Here is a little procedure that prints the text of a given name on the
user's terminal.

@p procedure print_id(@!p:name_pointer); {print identifier or module name}
var k:0..max_bytes; {index into |byte_mem|}
@!w:0..ww-1; {row of |byte_mem|}
begin if p>=name_ptr then print('IMPOSSIBLE')
else  begin w:=p mod ww;
  for k:=byte_start[p] to byte_start[p+ww]-1 do
    print(xchr[byte_mem[w,k]]);
  end;
end;

@ We keep track of the current module number in
|module_count|, which is the total number of modules that have started.
Modules which have been altered by a change file entry
have their |changed_module| flag turned on during the first phase.

@<Globals...@>=
@!module_count:0..max_modules; {the current module number}
@!changed_module: packed array [0..max_modules] of boolean; {is it changed?}
@!change_exists: boolean; {has any module changed?}

@ The other large memory area in \.{WEAVE} keeps the cross-reference data.
All uses of the name |p| are recorded in a linked list beginning at
|xref[p]|, which points into the |xmem| array. Entries in |xmem| consist
of two sixteen-bit items per word, called the |num| and |xlink| fields.
If |x| is an index into |xmem|, reached from name |p|, the value of |num(x)|
is either a module number where |p| is used, or it is |def_flag| plus a
module number where |p| is defined; and |xlink(x)| points to the next such
cross reference for |p|, if any. This list of cross references is in
decreasing order by module number. The current number of cross references
is |xref_ptr|.

The global variable |xref_switch| is set either to |def_flag| or to zero,
depending on whether the next cross reference to an identifier is to be
underlined or not in the index. This switch is set to |def_flag| when
\.{@@!} or \.{@@d} or \.{@@f} is scanned, and it is cleared to zero when
the next identifier or index entry cross reference has been made. Similarly,
the global variable |mod_xref_switch| is either |def_flag| or zero, depending
on whether a module name is being defined or used.

@d num(#)==xmem[#].num_field
@d xlink(#)==xmem[#].xlink_field
@d def_flag=10240 {must be strictly larger than |max_modules|}

@ @<Types...@>=
@!xref_number=0..max_refs;

@ @<Globals...@>=
@!xmem:array[xref_number] of packed record@t@>@/
  @!num_field: sixteen_bits; {module number plus zero or |def_flag|}
  @!xlink_field: sixteen_bits; {pointer to the previous cross reference}
  end;
@!xref_ptr:xref_number; {the largest occupied position in |xmem|}
@!xref_switch,@!mod_xref_switch:0..def_flag; {either zero or |def_flag|}

@ @<Set init...@>=xref_ptr:=0; xref_switch:=0; mod_xref_switch:=0; num(0):=0;
xref[0]:=0; {cross references to undefined modules}

@ A new cross reference for an identifier is formed by calling |new_xref|,
which discards duplicate entries and ignores non-underlined references
to one-letter identifiers or \PASCAL's reserved words.

@d append_xref(#)==if xref_ptr=max_refs then overflow('cross reference')
  else  begin incr(xref_ptr); num(xref_ptr):=#;
    end

@p procedure new_xref(@!p:name_pointer);
label exit;
var q:xref_number; {pointer to previous cross reference}
@!m,@!n: sixteen_bits; {new and previous cross-reference value}
begin if (reserved(p)or(byte_start[p]+1=byte_start[p+ww]))and
  (xref_switch=0) then return;
m:=module_count+xref_switch; xref_switch:=0; q:=xref[p];
if q>0 then
  begin n:=num(q);
  if (n=m)or(n=m+def_flag) then return
  else if m=n+def_flag then
    begin num(q):=m; return;
    end;
  end;
append_xref(m); xlink(xref_ptr):=q; xref[p]:=xref_ptr;
exit: end;

@ The cross reference lists for module names are slightly different. Suppose
that a module name is defined in modules $m_1$, \dots, $m_k$ and used in
modules $n_1$, \dots, $n_l$. Then its list will contain $m_1+|def_flag|$,
$m_k+|def_flag|$, \dots, $m_2+|def_flag|$, $n_l$, \dots, $n_1$, in
this order.  After Phase II, however, the order will be
$m_1+|def_flag|$, \dots, $m_k+|def_flag|$, $n_1$, \dots, $n_l$.

@p procedure new_mod_xref(@!p:name_pointer);
var q,@!r:xref_number; {pointers to previous cross references}
begin q:=xref[p]; r:=0;
if q>0 then
  begin if mod_xref_switch=0 then while num(q)>=def_flag do
    begin r:=q; q:=xlink(q);
    end
  else if num(q)>=def_flag then
    begin r:=q; q:=xlink(q);
    end;
  end;
append_xref(module_count+mod_xref_switch); xlink(xref_ptr):=q;
mod_xref_switch:=0;
if r=0 then xref[p]:=xref_ptr
else xlink(r):=xref_ptr;
end;

@ A third large area of memory is used for sixteen-bit `tokens', which appear
in short lists similar to the strings of characters in |byte_mem|. Token lists
are used to contain the result of \PASCAL\ code translated into \TeX\ form;
further details about them will be explained later. A |text_pointer| variable
is an index into |tok_start|.

@<Types...@>=
@!text_pointer=0..max_texts; {identifies a token list}

@ The first position of |tok_mem|
that is unoccupied by replacement text is called |tok_ptr|, and the first
unused location of |tok_start| is called |text_ptr|.
Thus, we usually have |tok_start[text_ptr]=tok_ptr|.

@<Glob...@>=
@t\hskip1em@>@!tok_mem: packed array [0..max_toks] of sixteen_bits; {tokens}
@t\hskip1em@>@!tok_start: array [text_pointer] of sixteen_bits;
  {directory into |tok_mem|}
@t\hskip1em@>@!text_ptr:text_pointer; {first unused position in |tok_start|}
@t\hskip1em@>@!tok_ptr:0..max_toks; {first unused position in |tok_mem|}
stat@!max_tok_ptr,@!max_txt_ptr:0..max_toks; {largest values occurring}
tats

@ @<Set init...@>=
tok_ptr:=1; text_ptr:=1; tok_start[0]:=1; tok_start[1]:=1;
stat max_tok_ptr:=1; max_txt_ptr:=1;@+tats

@* Searching for identifiers.
The hash table described above is updated by the |id_lookup| procedure,
which finds a given identifier and returns a pointer to its index in
|byte_start|. The identifier is supposed to match character by character
and it is also supposed to have a given |ilk| code; the same name may be
present more than once if it is supposed to appear in the index with
different typesetting conventions.
If the identifier was not already present, it is inserted into the table.

Because of the way \.{WEAVE}'s scanning mechanism works, it is most convenient
to let |id_lookup| search for an identifier that is present in the |buffer|
array. Two other global variables specify its position in the buffer: the
first character is |buffer[id_first]|, and the last is |buffer[id_loc-1]|.

@<Glob...@>=
@!id_first:0..long_buf_size; {where the current identifier begins in the buffer}
@!id_loc:0..long_buf_size; {just after the current identifier in the buffer}
@#
@!hash:array [0..hash_size] of sixteen_bits; {heads of hash lists}

@ Initially all the hash lists are empty.

@<Local variables for init...@>=
@!h:0..hash_size; {index into hash-head array}

@ @<Set init...@>=
for h:=0 to hash_size-1 do hash[h]:=0;

@ Here now is the main procedure for finding identifiers (and index
entries).  The parameter |t| is set to the desired |ilk| code. The
identifier must either have |ilk=t|, or we must have
|t=normal| and the identifier must be a reserved word.

@p function id_lookup(@!t:eight_bits):name_pointer; {finds current identifier}
label found;
var i:0..long_buf_size; {index into |buffer|}
@!h:0..hash_size; {hash code}
@!k:0..max_bytes; {index into |byte_mem|}
@!w:0..ww-1; {row of |byte_mem|}
@!l:0..long_buf_size; {length of the given identifier}
@!p:name_pointer; {where the identifier is being sought}
begin l:=id_loc-id_first; {compute the length}
@<Compute the hash code |h|@>;
@<Compute the name location |p|@>;
if p=name_ptr then @<Enter a new name into the table at position |p|@>;
id_lookup:=p;
end;

@ A simple hash code is used: If the sequence of
ASCII codes is $c_1c_2\ldots c_n$, its hash value will be
$$(2^{n-1}c_1+2^{n-2}c_2+\cdots+c_n)\,\bmod\,|hash_size|.$$

@<Compute the hash...@>=
h:=buffer[id_first]; i:=id_first+1;
while i<id_loc do
  begin h:=(h+h+buffer[i]) mod hash_size; incr(i);
  end

@ If the identifier is new, it will be placed in position |p=name_ptr|,
otherwise |p| will point to its existing location.

@<Compute the name location...@>=
p:=hash[h];
while p<>0 do
  begin if (length(p)=l)and((ilk[p]=t)or((t=normal)and reserved(p))) then
    @<Compare name |p| with current identifier,
      |goto found| if equal@>;
  p:=link[p];
  end;
p:=name_ptr; {the current identifier is new}
link[p]:=hash[h]; hash[h]:=p; {insert |p| at beginning of hash list}
found:

@ @<Compare name |p|...@>=
begin i:=id_first; k:=byte_start[p]; w:=p mod ww;
while (i<id_loc)and(buffer[i]=byte_mem[w,k]) do
  begin incr(i); incr(k);
  end;
if i=id_loc then goto found; {all characters agree}
end

@ When we begin the following segment of the program, |p=name_ptr|.

@<Enter a new name...@>=
begin w:=name_ptr mod ww;
if byte_ptr[w]+l>max_bytes then overflow('byte memory');
if name_ptr+ww>max_names then overflow('name');
i:=id_first; k:=byte_ptr[w]; {get ready to move the identifier into |byte_mem|}
while i<id_loc do
  begin byte_mem[w,k]:=buffer[i]; incr(k); incr(i);
  end;
byte_ptr[w]:=k; byte_start[name_ptr+ww]:=k; incr(name_ptr);
ilk[p]:=t; xref[p]:=0;
end

@* Initializing the table of reserved words.
We have to get \PASCAL's reserved words into the hash table, and the
simplest way to do this is to insert them every time \.{WEAVE} is run.
A few macros permit us to do the initialization with a compact program.

@d sid9(#)==buffer[9]:=#;cur_name:=id_lookup
@d sid8(#)==buffer[8]:=#;sid9
@d sid7(#)==buffer[7]:=#;sid8
@d sid6(#)==buffer[6]:=#;sid7
@d sid5(#)==buffer[5]:=#;sid6
@d sid4(#)==buffer[4]:=#;sid5
@d sid3(#)==buffer[3]:=#;sid4
@d sid2(#)==buffer[2]:=#;sid3
@d sid1(#)==buffer[1]:=#;sid2
@d id2==id_first:=8; sid8
@d id3==id_first:=7; sid7
@d id4==id_first:=6; sid6
@d id5==id_first:=5; sid5
@d id6==id_first:=4; sid4
@d id7==id_first:=3; sid3
@d id8==id_first:=2; sid2
@d id9==id_first:=1; sid1

@<Globals...@>=
@!cur_name:name_pointer; {points to the identifier just inserted}

@ The intended use of the macros above might not be immediately obvious,
but the riddle is answered by the following:

@<Store all the reserved words@>=
id_loc:=10;@/
id3("a")("n")("d")(char_like+and_sign);@/
id5("a")("r")("r")("a")("y")(array_like);@/
id5("b")("e")("g")("i")("n")(begin_like);@/
id4("c")("a")("s")("e")(case_like);@/
id5("c")("o")("n")("s")("t")(const_like);@/
id3("d")("i")("v")(div_like);@/
id2("d")("o")(do_like);@/
id6("d")("o")("w")("n")("t")("o")(to_like);@/
id4("e")("l")("s")("e")(else_like);@/
id3("e")("n")("d")(end_like);@/
id4("f")("i")("l")("e")(array_like);@/
id3("f")("o")("r")(for_like);@/
id8("f")("u")("n")("c")("t")("i")("o")("n")(proc_like);@/
id4("g")("o")("t")("o")(goto_like);@/
id2("i")("f")(if_like);@/
id2("i")("n")(char_like+set_element_sign);@/
id5("l")("a")("b")("e")("l")(const_like);@/
id3("m")("o")("d")(div_like);@/
id3("n")("i")("l")(nil_like);@/
id3("n")("o")("t")(char_like+not_sign);@/
id2("o")("f")(do_like);@/
id2("o")("r")(char_like+or_sign);@/
id6("p")("a")("c")("k")("e")("d")(goto_like);@/
id9("p")("r")("o")("c")("e")("d")("u")("r")("e")(proc_like);@/
id7("p")("r")("o")("g")("r")("a")("m")(proc_like);@/
id6("r")("e")("c")("o")("r")("d")(record_like);@/
id6("r")("e")("p")("e")("a")("t")(repeat_like);@/
id3("s")("e")("t")(array_like);@/
id4("t")("h")("e")("n")(do_like);@/
id2("t")("o")(to_like);@/
id4("t")("y")("p")("e")(const_like);@/
id5("u")("n")("t")("i")("l")(until_like);@/
id3("v")("a")("r")(var_like);@/
id5("w")("h")("i")("l")("e")(for_like);@/
id4("w")("i")("t")("h")(for_like);@/
id7("x")("c")("l")("a")("u")("s")("e")(loop_like);@/

@* Searching for module names.
The |mod_lookup| procedure finds the module name |mod_text[1..l]| in the
search tree, after inserting it if necessary, and returns a pointer to
where it was found.

@<Glob...@>=
@!mod_text:array [0..longest_name] of ASCII_code; {name being sought for}

@ According to the rules of \.{WEB}, no module name
should be a proper prefix of another, so a ``clean'' comparison should
occur between any two names. The result of |mod_lookup| is 0 if this
prefix condition is violated. An error message is printed when such violations
are detected during phase two of \.{WEAVE}.

@d less=0 {the first name is lexicographically less than the second}
@d equal=1 {the first name is equal to the second}
@d greater=2 {the first name is lexicographically greater than the second}
@d prefix=3 {the first name is a proper prefix of the second}
@d extension=4 {the first name is a proper extension of the second}

@p function mod_lookup(@!l:sixteen_bits):name_pointer; {finds module name}
label found;
var c:less..extension; {comparison between two names}
@!j:0..longest_name; {index into |mod_text|}
@!k:0..max_bytes; {index into |byte_mem|}
@!w:0..ww-1; {row of |byte_mem|}
@!p:name_pointer; {current node of the search tree}
@!q:name_pointer; {father of node |p|}
begin c:=greater; q:=0; p:=root;
while p<>0 do
  begin @<Set variable |c| to the result of comparing the given name
    to name |p|@>;
  q:=p;
  if c=less then p:=llink[q]
  else if c=greater then p:=rlink[q]
  else goto found;
  end;
@<Enter a new module name into the tree@>;
found: if c<>equal then
  begin err_print('! Incompatible section names'); p:=0;
@.Incompatible section names@>
  end;
mod_lookup:=p;
end;

@ @<Enter a new module name...@>=
w:=name_ptr mod ww; k:=byte_ptr[w];
if k+l>max_bytes then overflow('byte memory');
if name_ptr>max_names-ww then overflow('name');
p:=name_ptr;
if c=less then llink[q]:=p else rlink[q]:=p;
llink[p]:=0; rlink[p]:=0; xref[p]:=0; c:=equal;
for j:=1 to l do byte_mem[w,k+j-1]:=mod_text[j];
byte_ptr[w]:=k+l; byte_start[name_ptr+ww]:=k+l; incr(name_ptr);

@ @<Set variable |c|...@>=
begin k:=byte_start[p]; w:=p mod ww; c:=equal; j:=1;
while (k<byte_start[p+ww]) and (j<=l) and (mod_text[j]=byte_mem[w,k]) do
  begin incr(k); incr(j);
  end;
if k=byte_start[p+ww] then
  if j>l then c:=equal
  else c:=extension
else if j>l then c:=prefix
else if mod_text[j]<byte_mem[w,k] then c:=less
else c:=greater;
end

@ The |prefix_lookup| procedure is supposed to find exactly one module
name that has |mod_text[1..l]| as a prefix. Actually the algorithm
silently accepts also the situation that some module name is a prefix of
|mod_text[1..l]|, because the user who painstakingly typed in more than
necessary probably doesn't want to be told about the wasted effort.

Recall that error messages are not printed during phase one. It is
possible that the |prefix_lookup| procedure will fail on the first pass,
because there is no match, yet the second pass might detect no error if a
matching module name has occurred after the offending prefix. In such a
case the cross-reference information will be incorrect and \.{WEAVE} will
report no error. However, such a mistake will be detected by the
\.{TANGLE} processor.

@p function prefix_lookup(@!l:sixteen_bits):name_pointer; {finds name extension}
var c:less..extension; {comparison between two names}
@!count:0..max_names; {the number of hits}
@!j:0..longest_name; {index into |mod_text|}
@!k:0..max_bytes; {index into |byte_mem|}
@!w:0..ww-1; {row of |byte_mem|}
@!p:name_pointer; {current node of the search tree}
@!q:name_pointer; {another place to resume the search after one branch is done}
@!r:name_pointer; {extension found}
begin q:=0; p:=root; count:=0; r:=0; {begin search at root of tree}
while p<>0 do
  begin @<Set variable |c| to the result of comparing...@>;
  if c=less then p:=llink[p]
  else if c=greater then p:=rlink[p]
  else  begin r:=p; incr(count); q:=rlink[p]; p:=llink[p];
    end;
  if p=0 then
    begin p:=q; q:=0;
    end;
  end;
if count<>1 then
  if count=0 then err_print('! Name does not match')
@.Name does not match@>
  else err_print('! Ambiguous prefix');
@.Ambiguous prefix@>
prefix_lookup:=r; {the result will be 0 if there was no match}
end;

@* Lexical scanning.
Let us now consider the subroutines that read the \.{WEB} source file
and break it into meaningful units. There are four such procedures:
One simply skips to the next `\.{@@\ }' or `\.{@@*}' that begins a
module; another passes over the \TeX\ text at the beginning of a
module; the third passes over the \TeX\ text in a \PASCAL\ comment;
and the last, which is the most interesting, gets the next token of
a \PASCAL\ text.

@ But first we need to consider the low-level routine |get_line|
that takes care of merging |change_file| into |web_file|. The |get_line|
procedure also updates the line numbers for error messages.

@<Globals...@>=
@!ii:integer; {general purpose |for| loop variable in the outer block}
@!line:integer; {the number of the current line in the current file}
@!other_line:integer; {the number of the current line in the input file that
  is not currently being read}
@!temp_line:integer; {used when interchanging |line| with |other_line|}
@!limit:0..long_buf_size; {the last character position occupied in the buffer}
@!loc:0..long_buf_size; {the next character position to be read from the buffer}
@!input_has_ended: boolean; {if |true|, there is no more input}
@!changing: boolean; {if |true|, the current line is from |change_file|}
@!change_pending: boolean; {if |true|, the current change is not yet
  recorded in |changed_module[module_count]|}

@ As we change |changing| from |true| to |false| and back again, we must
remember to swap the values of |line| and |other_line| so that the |err_print|
routine will be sure to report the correct line number.

@d change_changing==
  changing := not changing;
  temp_line:=other_line; other_line:=line; line:=temp_line
    {|line @t$\null\BA\null$@> other_line|}

@ When |changing| is |false|, the next line of |change_file| is kept in
|change_buffer[0..change_limit]|, for purposes of comparison with the next
line of |web_file|. After the change file has been completely input, we
set |change_limit:=0|, so that no further matches will be made.

@<Globals...@>=
@!change_buffer:array[0..buf_size] of ASCII_code;
@!change_limit:0..buf_size; {the last position occupied in |change_buffer|}

@ Here's a simple function that checks if the two buffers are different.

@p function lines_dont_match:boolean;
label exit;
var k:0..buf_size; {index into the buffers}
begin lines_dont_match:=true;
if change_limit<>limit then return;
if limit>0 then
  for k:=0 to limit-1 do if change_buffer[k]<>buffer[k] then return;
lines_dont_match:=false;
exit: end;

@ Procedure |prime_the_change_buffer| sets |change_buffer| in preparation
for the next matching operation. Since blank lines in the change file are
not used for matching, we have |(change_limit=0)and not changing| if and
only if the change file is exhausted. This procedure is called only
when |changing| is true; hence error messages will be reported correctly.

@p procedure prime_the_change_buffer;
label continue, done, exit;
var k:0..buf_size; {index into the buffers}
begin change_limit:=0; {this value will be used if the change file ends}
@<Skip over comment lines in the change file; |return| if end of file@>;
@<Skip to the next nonblank line; |return| if end of file@>;
@<Move |buffer| and |limit| to |change_buffer| and |change_limit|@>;
exit: end;

@ While looking for a line that begins with \.{@@x} in the change file,
we allow lines that begin with \.{@@}, as long as they don't begin with
\.{@@y} or \.{@@z} (which would probably indicate that the change file is
fouled up).

@<Skip over comment lines in the change file...@>=
loop@+  begin incr(line);
  if not input_ln(change_file) then return;
  if limit<2 then goto continue;
  if buffer[0]<>"@@" then goto continue;
  if (buffer[1]>="X")and(buffer[1]<="Z") then
    buffer[1]:=buffer[1]+"z"-"Z"; {lowercasify}
  if buffer[1]="x" then goto done;
  if (buffer[1]="y")or(buffer[1]="z") then
    begin loc:=2; err_print('! Where is the matching @@x?');
@.Where is the match...@>
    end;
continue: end;
done:

@ Here we are looking at lines following the \.{@@x}.

@<Skip to the next nonblank line...@>=
repeat incr(line);
  if not input_ln(change_file) then
    begin err_print('! Change file ended after @@x');
@.Change file ended...@>
    return;
    end;
until limit>0;

@ @<Move |buffer| and |limit| to |change_buffer| and |change_limit|@>=
begin change_limit:=limit;
if limit>0 then for k:=0 to limit-1 do change_buffer[k]:=buffer[k];
end

@ The following procedure is used to see if the next change entry should
go into effect; it is called only when |changing| is false.
The idea is to test whether or not the current
contents of |buffer| matches the current contents of |change_buffer|.
If not, there's nothing more to do; but if so, a change is called for:
All of the text down to the \.{@@y} is supposed to match. An error
message is issued if any discrepancy is found. Then the procedure
prepares to read the next line from |change_file|.

When a match is found, the current module is marked as changed unless
the first line after the \.{@@x} and after the \.{@@y} both start with
either |'@@*'| or |'@@ '| (possibly preceded by whitespace).

@d if_module_start_then_make_change_pending(#)==
  loc:=0; buffer[limit]:="!";
  while (buffer[loc]=" ")or(buffer[loc]=tab_mark) do incr(loc);
  buffer[limit]:=" ";
  if buffer[loc]="@@" then
    if (buffer[loc+1]="*") or
       (buffer[loc+1]=" ") or (buffer[loc+1]=tab_mark) then
      change_pending:=#

@p procedure check_change; {switches to |change_file| if the buffers match}
label exit;
var n:integer; {the number of discrepancies found}
@!k:0..buf_size; {index into the buffers}
begin if lines_dont_match then return;
change_pending:=false;
if not changed_module[module_count] then
  begin if_module_start_then_make_change_pending(true);
  if not change_pending then changed_module[module_count]:=true;
  end;
n:=0;
loop@+  begin change_changing; {now it's |true|}
  incr(line);
  if not input_ln(change_file) then
    begin err_print('! Change file ended before @@y');
@.Change file ended...@>
    change_limit:=0;  change_changing; {|false| again}
    return;
    end;
  @<If the current line starts with \.{@@y},
    report any discrepancies and |return|@>;
  @<Move |buffer| and |limit|...@>;
  change_changing; {now it's |false|}
  incr(line);
  if not input_ln(web_file) then
    begin err_print('! WEB file ended during a change');
@.WEB file ended...@>
    input_has_ended:=true; return;
    end;
  if lines_dont_match then incr(n);
  end;
exit: end;

@ @<If the current line starts with \.{@@y}...@>=
if limit>1 then if buffer[0]="@@" then
  begin if (buffer[1]>="X")and(buffer[1]<="Z") then
    buffer[1]:=buffer[1]+"z"-"Z"; {lowercasify}
  if (buffer[1]="x")or(buffer[1]="z") then
    begin loc:=2; err_print('! Where is the matching @@y?');
@.Where is the match...@>
    end
  else if buffer[1]="y" then
    begin if n>0 then
      begin loc:=2; err_print('! Hmm... ',n:1,
        ' of the preceding lines failed to match');
@.Hmm... n of the preceding...@>
      end;
    return;
    end;
  end

@ The |reset_input| procedure, which gets \.{WEAVE} ready to read the
user's \.{WEB} input, is used at the beginning of phases one and two.

@p procedure reset_input;
begin open_input; line:=0; other_line:=0;@/
changing:=true; prime_the_change_buffer; change_changing;@/
limit:=0; loc:=1; buffer[0]:=" "; input_has_ended:=false;
end;

@ The |get_line| procedure is called when |loc>limit|; it puts the next
line of merged input into the buffer and updates the other variables
appropriately. A space is placed at the right end of the line.

@p procedure get_line; {inputs the next line}
label restart;
begin restart:if changing then
  @<Read from |change_file| and maybe turn off |changing|@>;
if not changing then
  begin @<Read from |web_file| and maybe turn on |changing|@>;
  if changing then goto restart;
  end;
loc:=0; buffer[limit]:=" ";
end;

@ @<Read from |web_file|...@>=
begin incr(line);
if not input_ln(web_file) then input_has_ended:=true
else if change_limit>0 then check_change;
end

@ @<Read from |change_file|...@>=
begin incr(line);
if not input_ln(change_file) then
  begin err_print('! Change file ended without @@z');
@.Change file ended...@>
  buffer[0]:="@@"; buffer[1]:="z"; limit:=2;
  end;
if limit>0 then {check if the change has ended}
  begin if change_pending then
    begin if_module_start_then_make_change_pending(false);
    if change_pending then
      begin changed_module[module_count]:=true; change_pending:=false;
      end;
    end;
  buffer[limit]:=" ";
  if buffer[0]="@@" then
    begin if (buffer[1]>="X")and(buffer[1]<="Z") then
      buffer[1]:=buffer[1]+"z"-"Z"; {lowercasify}
    if (buffer[1]="x")or(buffer[1]="y") then
      begin loc:=2; err_print('! Where is the matching @@z?');
@.Where is the match...@>
      end
    else if buffer[1]="z" then
      begin prime_the_change_buffer; change_changing;
      end;
    end;
  end;
end

@ At the end of the program, we will tell the user if the change file
had a line that didn't match any relevant line in |web_file|.

@<Check that all changes have been read@>=
if change_limit<>0 then {|changing| is false}
  begin for ii:=0 to change_limit-1 do buffer[ii]:=change_buffer[ii];
  limit:=change_limit; changing:=true; line:=other_line; loc:=change_limit;
  err_print('! Change file entry did not match');
@.Change file entry did not match@>
  end

@ Control codes in \.{WEB}, which begin with `\.{@@}', are converted
into a numeric code designed to simplify \.{WEAVE}'s logic; for example,
larger numbers are given to the control codes that denote more significant
milestones, and the code of |new_module| should be the largest of
all. Some of these numeric control codes take the place of ASCII
control codes that will not otherwise appear in the output of the
scanning routines.
@^ASCII code@>

@d ignore=0 {control code of no interest to \.{WEAVE}}
@d verbatim=@'2 {extended ASCII alpha will not appear}
@d force_line=@'3 {extended ASCII beta will not appear}
@d begin_comment=@'11 {ASCII tab mark will not appear}
@d end_comment=@'12 {ASCII line feed will not appear}
@d octal=@'14 {ASCII form feed will not appear}
@d hex=@'15 {ASCII carriage return will not appear}
@d double_dot=@'40 {ASCII space will not appear except in strings}
@d no_underline=@'175 {this code will be intercepted without confusion}
@d underline=@'176 {this code will be intercepted without confusion}
@d param=@'177 {ASCII delete will not appear}
@d xref_roman=@'203 {control code for `\.{@@\^}'}
@d xref_wildcard=@'204 {control code for `\.{@@:}'}
@d xref_typewriter=@'205 {control code for `\.{@@.}'}
@d TeX_string=@'206 {control code for `\.{@@t}'}
@d check_sum=@'207 {control code for `\.{@@\$}'}
@d join=@'210 {control code for `\.{@@\&}'}
@d thin_space=@'211 {control code for `\.{@@,}'}
@d math_break=@'212 {control code for `\.{@@\char'174}'}
@d line_break=@'213 {control code for `\.{@@/}'}
@d big_line_break=@'214 {control code for `\.{@@\#}'}
@d no_line_break=@'215 {control code for `\.{@@+}'}
@d pseudo_semi=@'216 {control code for `\.{@@;}'}
@d format=@'217 {control code for `\.{@@f}'}
@d definition=@'220 {control code for `\.{@@d}'}
@d begin_Pascal=@'221 {control code for `\.{@@p}'}
@d module_name=@'222 {control code for `\.{@@<}'}
@d new_module=@'223 {control code for `\.{@@\ }' and `\.{@@*}'}

@ Control codes are converted from ASCII to \.{WEAVE}'s internal
representation by the |control_code| routine.

@p function control_code(@!c:ASCII_code):eight_bits; {convert |c|
  after \.{@@}}
begin case c of
"@@": control_code:="@@"; {`quoted' at sign}
"'": control_code:=octal; {precedes octal constant}
"""": control_code:=hex; {precedes hexadecimal constant}
"$": control_code:=check_sum; {precedes check sum constant}
" ",tab_mark,"*": control_code:=new_module; {beginning of a new module}
"=": control_code:=verbatim;
"\": control_code:=force_line;
"D","d": control_code:=definition; {macro definition}
"F","f": control_code:=format; {format definition}
"{": control_code:=begin_comment; {begin-comment delimiter}
"}": control_code:=end_comment; {end-comment delimiter}
"P","p": control_code:=begin_Pascal; {\PASCAL\ text in unnamed module}
"&": control_code:=join; {concatenate two tokens}
"<": control_code:=module_name; {beginning of a module name}
">": begin err_print('! Extra @@>'); control_code:=ignore;
@.Extra \AT!>@>
  end; {end of module name should not be discovered in this way}
"T","t": control_code:=TeX_string; {\TeX\ box within \PASCAL}
"!": control_code:=underline; {set definition flag}
"?": control_code:=no_underline; {reset definition flag}
"^": control_code:=xref_roman; {index entry to be typeset normally}
":": control_code:=xref_wildcard; {index entry to be in user format}
".": control_code:=xref_typewriter; {index entry to be in typewriter type}
",": control_code:=thin_space; {puts extra space in \PASCAL\ format}
"|": control_code:=math_break; {allows a break in a formula}
"/": control_code:=line_break; {forces end-of-line in \PASCAL\ format}
"#": control_code:=big_line_break; {forces end-of-line and some space besides}
"+": control_code:=no_line_break; {cancels end-of-line down to single space}
";": control_code:=pseudo_semi; {acts like a semicolon, but is invisible}
@t\4@>@<Special control codes allowed only when debugging@>@;
othercases begin err_print('! Unknown control code'); control_code:=ignore;
@.Unknown control code@>
  end
endcases;
end;

@ If \.{WEAVE} is compiled with debugging commands, one can write
\.{@@2}, \.{@@1}, and \.{@@0} to turn tracing fully on, partly on,
and off, respectively.
@.\AT!2@>
@.\AT!1@>

@<Special control codes...@>=
@!debug@t@>@/
"0","1","2": begin tracing:=c-"0"; control_code:=ignore;
  end;
gubed

@ The |skip_limbo| routine is used on the first pass to skip through
portions of the input that are not in any modules, i.e., that precede
the first module. After this procedure has been called, the value of
|input_has_ended| will tell whether or not a new module has
actually been found.

@p procedure skip_limbo; {skip to next module}
label exit;
var c:ASCII_code; {character following \.{@@}}
begin loop if loc>limit then
    begin get_line;
    if input_has_ended then return;
    end
  else  begin buffer[limit+1]:="@@";
    while buffer[loc]<>"@@" do incr(loc);
    if loc<=limit then
      begin loc:=loc+2; c:=buffer[loc-1];
      if (c=" ")or(c=tab_mark)or(c="*") then return;
      end;
    end;
exit: end;

@ The |skip_TeX| routine is used on the first pass to skip through
the \TeX\ code at the beginning of a module. It returns the next
control code or `\v' found in the input. A |new_module| is
assumed to exist at the very end of the file.

@p function skip_TeX: eight_bits; {skip past pure \TeX\ code}
label done;
var c:eight_bits; {control code found}
begin loop begin if loc>limit then
    begin get_line;
    if input_has_ended then
      begin c:=new_module; goto done;
      end;
    end;
  buffer[limit+1]:="@@";
  repeat c:=buffer[loc]; incr(loc);
  if c="|" then goto done;
  until c="@@";
  if loc<=limit then
    begin c:=control_code(buffer[loc]); incr(loc); goto done;
    end;
  end;
done:skip_TeX:=c;
end;

@ The |skip_comment| routine is used on the first pass to skip
through \TeX\ code in \PASCAL\ comments. The |bal| parameter
tells how many left braces are assumed to have been scanned when
this routine is called, and the procedure returns a corresponding
value of |bal| at the point that scanning has stopped. Scanning
stops either at a `\v' that introduces \PASCAL\ text,
in which case the returned value is positive, or it stops at the
end of the comment, in which case the returned value is zero.
The scanning also stops in anomalous situations when the comment
doesn't end or when it contains an illegal use of \.{@@}.
One should call |skip_comment(1)| when beginning to scan a comment.

@p function skip_comment(@!bal:eight_bits):eight_bits; {skips \TeX\
  code in comments}
label done;
var c:ASCII_code; {the current character}
begin loop begin if loc>limit then
    begin get_line;
    if input_has_ended then
      begin bal:=0; goto done;
      end; {an error message will occur in phase two}
    end;
  c:=buffer[loc]; incr(loc);
  if c="|" then goto done;
  @<Do special things when |c="@@", "\", "{", "}"|; |goto done| at end@>;
  end;
done: skip_comment:=bal;
end;

@ @<Do special things when |c="@@"...@>=
if c="@@" then
  begin c:=buffer[loc];
  if (c<>" ")and(c<>tab_mark)and(c<>"*") then incr(loc)
  else  begin decr(loc); bal:=0; goto done;
    end {an error message will occur in phase two}
  end
else if (c="\")and(buffer[loc]<>"@@") then incr(loc)
else if c="{" then incr(bal)
else if c="}" then
  begin decr(bal);
  if bal=0 then goto done;
  end

@* Inputting the next token.
As stated above, \.{WEAVE}'s most interesting lexical scanning routine is the
|get_next| function that inputs the next token of \PASCAL\ input. However,
|get_next| is not especially complicated.

The result of |get_next| is either an ASCII code for some special character,
or it is a special code representing a pair of characters (e.g., `\.{:=}'
or `\.{..}'), or it is the numeric value computed by the |control_code|
procedure, or it is one of the following special codes:

\yskip\hang |exponent|: The `\.E' in a real constant.

\yskip\hang |identifier|: In this case the global variables |id_first|
and |id_loc| will have been set to the appropriate values needed by the
|id_lookup| routine.

\yskip\hang |string|: In this case the global variables |id_first| and
|id_loc| will have been set to the beginning and ending-plus-one locations
in the buffer.  The string ends with the first reappearance of its initial
delimiter; thus, for example, $$\.{\'This isn\'\'t a single string\'}$$
will be treated as two consecutive strings, the first being \.{\'This
isn\'}.

\yskip\noindent Furthermore, some of the control codes cause
|get_next| to take additional actions:

\yskip\hang |xref_roman|, |xref_wildcard|,
|xref_typewriter|, |TeX_string|: The values of
|id_first| and |id_loc| will be set so that the string in question appears
in |buffer[id_first..(id_loc-1)]|.

\yskip\hang |module_name|: In this case the global variable |cur_module| will
point to the |byte_start| entry for the module name that has just been scanned.

\yskip\noindent If |get_next| sees `\.{@@!}' or `\.{@@?}',
it sets |xref_switch| to |def_flag| or zero and goes on to the next token.

A global variable called |scanning_hex| is set |true| during the time that
the letters \.A through \.F should be treated as if they were digits.

@d exponent=@'200 {\.E or \.e following a digit}
@d string=@'201 {\PASCAL\ string or \.{WEB} precomputed string}
@d identifier=@'202 {\PASCAL\ identifier or reserved word}

@<Globals...@>=
@!cur_module: name_pointer; {name of module just scanned}
@!scanning_hex: boolean; {are we scanning a hexadecimal constant?}

@ @<Set init...@>=
scanning_hex:=false;

@ As one might expect, |get_next| consists mostly of a big switch
that branches to the various special cases that can arise.

@d up_to(#)==#-24,#-23,#-22,#-21,#-20,#-19,#-18,#-17,#-16,#-15,#-14,
  #-13,#-12,#-11,#-10,#-9,#-8,#-7,#-6,#-5,#-4,#-3,#-2,#-1,#

@p function get_next:eight_bits; {produces the next input token}
label restart,done,found;
var c:eight_bits; {the current character}
@!d:eight_bits; {the next character}
@!j,@!k:0..longest_name; {indices into |mod_text|}
begin restart: if loc>limit then
  begin get_line;
  if input_has_ended then
    begin c:=new_module; goto found;
    end;
  end;
c:=buffer[loc]; incr(loc);
if scanning_hex then @<Go to |found| if |c| is a hexadecimal digit,
  otherwise set |scanning_hex:=false|@>;
case c of
"A",up_to("Z"),"a",up_to("z"): @<Get an identifier@>;
"'","""": @<Get a string@>;
"@@": @<Get control code and possible module name@>;
@t\4@>@<Compress two-symbol combinations like `\.{:=}'@>@;
" ",tab_mark: goto restart; {ignore spaces and tabs}
"}": begin err_print('! Extra }'); goto restart;
@.Extra \}@>
  end;
othercases if c>=128 then goto restart {ignore nonstandard characters}
  else do_nothing
endcases;
found:@!debug if trouble_shooting then debug_help;@;@+gubed@/
get_next:=c;
end;

@ @<Go to |found| if |c| is a hexadecimal digit...@>=
if ((c>="0")and(c<="9"))or((c>="A")and(c<="F")) then goto found
else scanning_hex:=false

@ Note that the following code substitutes \.{@@\{} and \.{@@\}} for the
respective combinations `\.{(*}' and `\.{*)}'. Explicit braces should be used
for \TeX\ comments in \PASCAL\ text.

@d compress(#)==begin if loc<=limit then begin c:=#; incr(loc); end; end

@<Compress two-symbol...@>=
".": if buffer[loc]="." then compress(double_dot)
  else if buffer[loc]=")" then compress("]");
":": if buffer[loc]="=" then compress(left_arrow);
"=": if buffer[loc]="=" then compress(equivalence_sign);
">": if buffer[loc]="=" then compress(greater_or_equal);
"<": if buffer[loc]="=" then compress(less_or_equal)
  else if buffer[loc]=">" then compress(not_equal);
"(": if buffer[loc]="*" then compress(begin_comment)
  else if buffer[loc]="." then compress("[");
"*": if buffer[loc]=")" then compress(end_comment);

@ @<Get an identifier@>=
begin if ((c="E")or(c="e"))and(loc>1) then
  if (buffer[loc-2]<="9")and(buffer[loc-2]>="0") then c:=exponent;
if c<>exponent then
  begin decr(loc); id_first:=loc;
  repeat incr(loc); d:=buffer[loc];
  until ((d<"0")or((d>"9")and(d<"A"))or((d>"Z")and(d<"a"))or(d>"z"))and(d<>"_");
  c:=identifier; id_loc:=loc;
  end;
end

@ A string that starts and ends with single or double quote marks is
scanned by the following piece of the program.

@<Get a string@>=
begin id_first:=loc-1;
repeat d:=buffer[loc]; incr(loc);
if loc>limit then
  begin err_print('! String constant didn''t end');
@.String constant didn't end@>
  loc:=limit; d:=c;
  end;
until d=c;
id_loc:=loc; c:=string;
end

@ After an \.{@@} sign has been scanned, the next character tells us
whether there is more work to do.

@<Get control code and possible module name@>=
begin c:=control_code(buffer[loc]); incr(loc);
if c=underline then
  begin xref_switch:=def_flag; goto restart;
  end
else if c=no_underline then
  begin xref_switch:=0; goto restart;
  end
else if (c<=TeX_string)and(c>=xref_roman) then
  @<Scan to the next \.{@@>}@>
else if c=hex then scanning_hex:=true
else if c=module_name then
  @<Scan the module name and make |cur_module| point to it@>
else if c=verbatim then @<Scan a verbatim string@>;
end

@ The occurrence of a module name sets |xref_switch| to zero,
because the module name might (for example) follow \&{var}.

@<Scan the module name...@>=
begin @<Put module name into |mod_text[1..k]|@>;
if k>3 then
  begin if (mod_text[k]=".")and(mod_text[k-1]=".")and(mod_text[k-2]=".") then
    cur_module:=prefix_lookup(k-3)
  else cur_module:=mod_lookup(k);
  end
else cur_module:=mod_lookup(k);
xref_switch:=0;
end

@ Module names are placed into the |mod_text| array with consecutive spaces,
tabs, and carriage-returns replaced by single spaces. There will be no
spaces at the beginning or the end. (We set |mod_text[0]:=" "| to facilitate
this, since the |mod_lookup| routine uses |mod_text[1]| as the first
character of the name.)

@<Set init...@>=mod_text[0]:=" ";

@ @<Put module name...@>=
k:=0;
loop@+  begin if loc>limit then
    begin get_line;
    if input_has_ended then
      begin err_print('! Input ended in section name');
@.Input ended in section name@>
      loc:=1; goto done;
      end;
    end;
  d:=buffer[loc];
  @<If end of name, |goto done|@>;
  incr(loc); if k<longest_name-1 then incr(k);
  if (d=" ")or(d=tab_mark) then
    begin d:=" "; if mod_text[k-1]=" " then decr(k);
    end;
  mod_text[k]:=d;
  end;
done: @<Check for overlong name@>;
if (mod_text[k]=" ")and(k>0) then decr(k)

@ @<If end of name,...@>=
if d="@@" then
  begin d:=buffer[loc+1];
  if d=">" then
    begin loc:=loc+2; goto done;
    end;
  if (d=" ")or(d=tab_mark)or(d="*") then
    begin err_print('! Section name didn''t end'); goto done;
@.Section name didn't end@>
    end;
  incr(k); mod_text[k]:="@@"; incr(loc); {now |d=buffer[loc]| again}
  end

@ @<Check for overlong name@>=
if k>=longest_name-2 then
  begin print_nl('! Section name too long: ');
@.Section name too long@>
  for j:=1 to 25 do print(xchr[mod_text[j]]);
  print('...'); mark_harmless;
  end

@ @<Scan to the next...@>=
begin id_first:=loc; buffer[limit+1]:="@@";
while buffer[loc]<>"@@" do incr(loc);
id_loc:=loc;
if loc>limit then
  begin err_print('! Control text didn''t end'); loc:=limit;
@.Control text didn't end@>
  end
else  begin loc:=loc+2;
  if buffer[loc-1]<>">" then
    err_print('! Control codes are forbidden in control text');
@.Control codes are forbidden...@>
  end;
end

@ A verbatim \PASCAL\ string will be treated like ordinary strings, but
with no surrounding delimiters.  At the present point in the program we
have |buffer[loc-1]=verbatim|; we must set |id_first| to the beginning
of the string itself, and |id_loc| to its ending-plus-one location in the
buffer.  We also set |loc| to the position just after the ending delimiter.

@<Scan a verbatim string@>=
begin id_first:=loc; incr(loc);
buffer[limit+1]:="@@"; buffer[limit+2]:=">";
while (buffer[loc]<>"@@")or(buffer[loc+1]<>">") do incr(loc);
if loc>=limit then err_print('! Verbatim string didn''t end');
@.Verbatim string didn't end@>
id_loc:=loc; loc:=loc+2;
end

@* Phase one processing.
We now have accumulated enough subroutines to make it possible to carry out
\.{WEAVE}'s first pass over the source file. If everything works right,
both phase one and phase two of \.{WEAVE} will assign the same numbers to
modules, and these numbers will agree with what \.{TANGLE} does.

The global variable |next_control| often contains the most recent output of
|get_next|; in interesting cases, this will be the control code that
ended a module or part of a module.

@<Glob...@>=@!next_control:eight_bits; {control code waiting to be acting upon}

@ The overall processing strategy in phase one has the following
straightforward outline.

@<Phase I: Read all the user's text and store the cross references@>=
phase_one:=true; phase_three:=false;
reset_input;
module_count:=0; changed_module[0]:=false;
skip_limbo; change_exists:=false;
while not input_has_ended do
  @<Store cross reference data for the current module@>;
changed_module[module_count]:=change_exists;
  {the index changes if anything does}
phase_one:=false; {prepare for second phase}
@<Print error messages about unused or undefined module names@>;

@ @<Store cross reference data...@>=
begin incr(module_count);
if module_count=max_modules then overflow('section number');
changed_module[module_count]:=changing;
 {it will become |true| if any line changes}
if buffer[loc-1]="*" then
  begin print('*',module_count:1);
  update_terminal; {print a progress report}
  end;
@<Store cross references in the \TeX\ part of a module@>;
@<Store cross references in the \(definition part of a module@>;
@<Store cross references in the \PASCAL\ part of a module@>;
if changed_module[module_count] then change_exists:=true;
end

@ The |Pascal_xref| subroutine stores references to identifiers in
\PASCAL\ text material beginning with the current value of |next_control|
and continuing until |next_control| is `\.\{' or `\v', or until the next
``milestone'' is passed (i.e., |next_control>=format|). If
|next_control>=format| when |Pascal_xref| is called, nothing will happen;
but if |next_control="|"| upon entry, the procedure assumes that this is
the `\v' preceding \PASCAL\ text that is to be processed.

The program uses the fact that our internal code numbers satisfy
the relations |xref_roman=identifier+roman| and |xref_wildcard=identifier
+wildcard| and |xref_typewriter=identifier+
typewriter| and |normal=0|. An implied `\.{@@!}' is inserted after
\&{function}, \&{procedure}, \&{program}, and \&{var}.

@p procedure Pascal_xref; {makes cross references for \PASCAL\ identifiers}
label exit;
var p:name_pointer; {a referenced name}
begin while next_control<format do
  begin if (next_control>=identifier)and
      (next_control<=xref_typewriter) then
    begin p:=id_lookup(next_control-identifier); new_xref(p);
    if (ilk[p]=proc_like)or(ilk[p]=var_like) then
      xref_switch:=def_flag; {implied `\.{@@!}'}
    end;
  next_control:=get_next;
  if (next_control="|")or(next_control="{") then return;
  end;
exit:end;

@ The |outer_xref| subroutine is like |Pascal_xref| but it begins
with |next_control<>"|"| and ends with |next_control>=format|. Thus, it
handles \PASCAL\ text with embedded comments.

@p procedure outer_xref; {extension of |Pascal_xref|}
var bal:eight_bits; {brace level in comment}
begin while next_control<format do
  if next_control<>"{" then Pascal_xref
  else  begin bal:=skip_comment(1); next_control:="|";
    while bal>0 do
      begin Pascal_xref;
      if next_control="|" then bal:=skip_comment(bal)
      else bal:=0; {an error will be reported in phase two}
      end;
    end;
end;

@ In the \TeX\ part of a module, cross reference entries are made only for
the identifiers in \PASCAL\ texts enclosed in \pb, or for control texts
enclosed in \.{@@\^}$\,\ldots\,$\.{@@>} or \.{@@.}$\,\ldots\,$\.{@@>}
or \.{@@:}$\,\ldots\,$\.{@@>}.

@<Store cross references in the \T...@>=
repeat next_control:=skip_TeX;
case next_control of
underline: xref_switch:=def_flag;
no_underline: xref_switch:=0;
"|": Pascal_xref;
xref_roman, xref_wildcard, xref_typewriter, module_name:
  begin loc:=loc-2; next_control:=get_next; {scan to \.{@@>}}
  if next_control<>module_name then
    new_xref(id_lookup(next_control-identifier));
  end;
othercases do_nothing
endcases;
until next_control>=format

@ During the definition and \PASCAL\ parts of a module, cross references
are made for all identifiers except reserved words; however, the
identifiers in a format definition are referenced even if they are
reserved. The \TeX\ code in comments is, of course, ignored, except for
\PASCAL\ portions enclosed in \pb; the text of a module name is skipped
entirely, even if it contains \pb\ constructions.

The variables |lhs| and |rhs| point to the respective identifiers involved
in a format definition.

@<Global...@>=
@!lhs,@!rhs:name_pointer; {indices into |byte_start| for format identifiers}

@ When we get to the following code we have |next_control>=format|.

@<Store cross references in the \(d...@>=
while next_control<=definition do {|format| or |definition|}
  begin xref_switch:=def_flag; {implied \.{@@!}}
  if next_control=definition then next_control:=get_next
  else @<Process a format definition@>;
  outer_xref;
  end

@ Error messages for improper format definitions will be issued in phase
two. Our job in phase one is to define the |ilk| of a properly formatted
identifier, and to fool the |new_xref| routine into thinking that the
identifier on the right-hand side of the format definition is not a
reserved word.

@<Process a form...@>=
begin next_control:=get_next;
if next_control=identifier then
  begin lhs:=id_lookup(normal); ilk[lhs]:=normal; new_xref(lhs);
  next_control:=get_next;
  if next_control=equivalence_sign then
    begin next_control:=get_next;
    if next_control=identifier then
      begin rhs:=id_lookup(normal);
      ilk[lhs]:=ilk[rhs]; ilk[rhs]:=normal; new_xref(rhs);
      ilk[rhs]:=ilk[lhs]; next_control:=get_next;
      end;
    end;
  end;
end

@ Finally, when the \TeX\ and definition parts have been treated, we have
|next_control>=begin_Pascal|.

@<Store cross references in the \P...@>=
if next_control<=module_name then {|begin_Pascal| or |module_name|}
  begin if next_control=begin_Pascal then mod_xref_switch:=0
  else mod_xref_switch:=def_flag;
  repeat if next_control=module_name then new_mod_xref(cur_module);
    next_control:=get_next; outer_xref;
  until next_control>module_name;
  end

@ After phase one has looked at everything, we want to check that each
module name was both defined and used.
The variable |cur_xref| will point to cross references for the
current module name of interest.

@<Glob...@>=@!cur_xref:xref_number; {temporary cross reference pointer}

@ The following recursive procedure
walks through the tree of module names and prints out anomalies.
@^recursion@>

@p procedure mod_check(@!p:name_pointer); {print anomalies in subtree |p|}
begin if p>0 then
  begin mod_check(llink[p]);@/
  cur_xref:=xref[p];
  if num(cur_xref)<def_flag then
    begin print_nl('! Never defined: <'); print_id(p);
@.Never defined: <section name>@>
    print('>'); mark_harmless;
    end;
  while num(cur_xref)>=def_flag do cur_xref:=xlink(cur_xref);
  if cur_xref=0 then
    begin print_nl('! Never used: <'); print_id(p); print('>');
@.Never used: <section name>@>
    mark_harmless;
    end;
  mod_check(rlink[p]);
  end;
end;

@ @<Print error messages about un...@>=@+mod_check(root)

@* Low-level output routines.
The \TeX\ output is supposed to appear in lines at most |line_length|
characters long, so we place it into an output buffer. During the output
process, |out_line| will hold the current line number of the line about to
be output.

@<Glo...@>=
@!out_buf:array[0..line_length] of ASCII_code; {assembled characters}
@!out_ptr:0..line_length; {number of characters in |out_buf|}
@!out_line: integer; {coordinates of next line to be output}

@ The |flush_buffer| routine empties the buffer up to a given breakpoint,
and moves any remaining characters to the beginning of the next line.
If the |per_cent| parameter is |true|, a |"%"| is appended to the line
that is being output; in this case the breakpoint |b| should be strictly
less than |line_length|. If the |per_cent| parameter is |false|,
trailing blanks are suppressed.
The characters emptied from the buffer form a new line of output;
if the |carryover| parameter is true, a |"%"| in that line will be
carried over to the next line (so that \TeX\ will ignore the completion
of commented-out text).

@p procedure flush_buffer(@!b:eight_bits;@!per_cent,@!carryover:boolean);
  {outputs |out_buf[1..b]|, where |b<=out_ptr|}
label done,found;
var j,@!k:0..line_length;
begin j:=b;
if not per_cent then {remove trailing blanks}
  loop@+  begin if j=0 then goto done;
    if out_buf[j]<>" " then goto done;
    decr(j);
    end;
done: for k:=1 to j do write(tex_file,xchr[out_buf[k]]);
if per_cent then write(tex_file,xchr["%"]);
write_ln(tex_file); incr(out_line);
if carryover then
  for k:=1 to j do
    if out_buf[k]="%" then
      if (k=1)or(out_buf[k-1]<>"\") then {comment mode should be preserved}
        begin out_buf[b]:="%"; decr(b); goto found;
        end;
found: if (b<out_ptr) then
  for k:=b+1 to out_ptr do out_buf[k-b]:=out_buf[k];
out_ptr:=out_ptr-b;
end;

@ When we are copying \TeX\ source material, we retain line breaks
that occur in the input, except that an empty line is not
output when the \TeX\ source line was nonempty. For example, a line
of the \TeX\ file that contains only an index cross-reference entry
will not be copied. The |finish_line| routine is called just before
|get_line| inputs a new line, and just after a line break token has
been emitted during the output of translated \PASCAL\ text.

@p procedure finish_line; {do this at the end of a line}
label exit;
var k:0..buf_size; {index into |buffer|}
begin if out_ptr>0 then flush_buffer(out_ptr,false,false)
else  begin for k:=0 to limit do
    if (buffer[k]<>" ")and(buffer[k]<>tab_mark) then return;
  flush_buffer(0,false,false);
  end;
exit:end;

@ In particular, the |finish_line| procedure is called near the very
beginning of phase two. We initialize the output variables in a slightly
tricky way so that the first line of the output file will be
`\.{\\input webmac}'.
@.\\input webmac@>
@.webmac@>

@<Set init...@>=
out_ptr:=1; out_line:=1; out_buf[1]:="c"; write(tex_file,'\input webma');

@ When we wish to append the character |c| to the output buffer, we write
`$|out|(c)$'; this will cause the buffer to be emptied if it was already
full. Similarly, `$|out2|(c_1)(c_2)$' appends a pair of characters.
A line break will occur at a space or after a single-nonletter
\TeX\ control sequence.

@d oot(#)==@;@/
  if out_ptr=line_length then break_out;
  incr(out_ptr); out_buf[out_ptr]:=#;
@d oot1(#)==oot(#)@+end
@d oot2(#)==oot(#)@,oot1
@d oot3(#)==oot(#)@,oot2
@d oot4(#)==oot(#)@,oot3
@d oot5(#)==oot(#)@,oot4
@d out==@+begin oot1
@d out2==@+begin oot2
@d out3==@+begin oot3
@d out4==@+begin oot4
@d out5==@+begin oot5

@ The |break_out| routine is called just before the output buffer is about
to overflow. To make this routine a little faster, we initialize position
0 of the output buffer to `\.\\'; this character isn't really output.

@<Set init...@>=
out_buf[0]:="\";

@ A long line is broken at a blank space or just before a backslash that isn't
preceded by another backslash. In the latter case, a |"%"| is output at
the break.

@p procedure break_out; {finds a way to break the output line}
label exit;
var k:0..line_length; {index into |out_buf|}
@!d:ASCII_code; {character from the buffer}
begin k:=out_ptr;
loop@+  begin if k=0 then
    @<Print warning message, break the line, |return|@>;
  d:=out_buf[k];
  if d=" " then
    begin flush_buffer(k,false,true); return;
    end;
  if (d="\")and(out_buf[k-1]<>"\") then {in this case |k>1|}
    begin flush_buffer(k-1,true,true); return;
    end;
  decr(k);
  end;
exit:end;

@ We get to this module only in unusual cases that the entire output line
consists of a string of backslashes followed by a string of nonblank
non-backslashes. In such cases it is almost always safe to break the
line by putting a |"%"| just before the last character.

@<Print warning message...@>=
begin print_nl('! Line had to be broken (output l.',out_line:1);
@.Line had to be broken@>
print_ln('):');
for k:=1 to out_ptr-1 do print(xchr[out_buf[k]]);
new_line; mark_harmless;
flush_buffer(out_ptr-1,true,true); return;
end

@ Here is a procedure that outputs a module number in decimal notation.

@<Glob...@>=@!dig:array[0..4] of 0..9; {digits to output}

@ The number to be converted by |out_mod| is known to be less than
|def_flag|, so it cannot have more than five decimal digits.  If
the module is changed, we output `\.{\\*}' just after the number.

@p procedure out_mod(@!m:integer); {output a module number}
var k:0..5; {index into |dig|}
@!a:integer; {accumulator}
begin k:=0; a:=m;
repeat dig[k]:=a mod 10; a:=a div 10; incr(k);
until a=0;
repeat decr(k); out(dig[k]+"0");
until k=0;
if changed_module[m] then out2("\")("*");
@.\\*@>
end;

@ The |out_name| subroutine is used to output an identifier or index
entry, enclosing it in braces.

@p procedure out_name(@!p:name_pointer); {outputs a name}
var k:0..max_bytes; {index into |byte_mem|}
@!w:0..ww-1; {row of |byte_mem|}
begin out("{"); w:=p mod ww;
for k:=byte_start[p] to byte_start[p+ww]-1 do
  begin if byte_mem[w,k]="_" then out("\");
@.\\_@>
  out(byte_mem[w,k]);
  end;
out("}");
end;

@* Routines that copy \TeX\ material.
During phase two, we use the subroutines |copy_limbo|, |copy_TeX|, and
|copy_comment| in place of the analogous |skip_limbo|, |skip_TeX|, and
|skip_comment| that were used in phase one.

The |copy_limbo| routine, for example, takes \TeX\ material that is not
part of any module and transcribes it almost verbatim to the output file.
No `\.{@@}' signs should occur in such material except in `\.{@@@@}'
pairs; such pairs are replaced by singletons.

@p procedure copy_limbo; {copy \TeX\ code until the next module begins}
label exit;
var c:ASCII_code; {character following \.{@@} sign}
begin loop if loc>limit then
    begin finish_line; get_line;
    if input_has_ended then return;
    end
  else  begin buffer[limit+1]:="@@";
    @<Copy up to control code, |return| if finished@>;
    end;
exit:end;

@ @<Copy up to control...@>=
while buffer[loc]<>"@@" do
  begin out(buffer[loc]); incr(loc);
  end;
if loc<=limit then
  begin loc:=loc+2; c:=buffer[loc-1];
  if (c=" ")or(c=tab_mark)or(c="*") then return;
  out("@@");
  if c<>"@@" then err_print('! Double @@ required outside of sections');
@.Double \AT! required...@>
  end

@ The |copy_TeX| routine processes the \TeX\ code at the beginning of a
module; for example, the words you are now reading were copied in this
way. It returns the next control code or `\v' found in the input.

@p function copy_TeX:eight_bits; {copy pure \TeX\ material}
label done;
var c:eight_bits; {control code found}
begin loop begin if loc>limit then
    begin finish_line; get_line;
    if input_has_ended then
      begin c:=new_module; goto done;
      end;
    end;
  buffer[limit+1]:="@@";
  @<Copy up to `\v' or control code, |goto done| if finished@>;
  end;
done:copy_TeX:=c;
end;

@ We don't copy spaces or tab marks into the beginning of a line. This
makes the test for empty lines in |finish_line| work.

@<Copy up to `\v'...@>=
repeat c:=buffer[loc]; incr(loc);
if c="|" then goto done;
if c<>"@@" then
  begin out(c);
  if (out_ptr=1)and((c=" ")or(c=tab_mark)) then decr(out_ptr);
  end;
until c="@@";
if loc<=limit then
  begin c:=control_code(buffer[loc]); incr(loc);
  goto done;
  end

@ The |copy_comment| uses and returns a brace-balance value, following the
conventions of |skip_comment| above. Instead of copying the \TeX\ material
into the output buffer, this procedure copies it into the token memory.
The abbreviation |app_tok(t)| is used to append token |t| to the current
token list, and it also makes sure that it is possible to append at least
one further token without overflow.

@d app_tok(#)==begin if tok_ptr+2>max_toks then overflow('token');
  tok_mem[tok_ptr]:=#; incr(tok_ptr);
  end

@p function copy_comment(@!bal:eight_bits):eight_bits; {copies \TeX\ code in
  comments}
label done;
var c:ASCII_code; {current character being copied}
begin loop begin if loc>limit then
    begin get_line;
    if input_has_ended then
      begin err_print('! Input ended in mid-comment');
@.Input ended in mid-comment@>
      loc:=1; @<Clear |bal| and |goto done|@>;
      end;
    end;
  c:=buffer[loc]; incr(loc);
  if c="|" then goto done;
  app_tok(c);
  @<Copy special things when |c="@@", "\", "{", "}"|;
    |goto done| at end@>;
  end;
done: copy_comment:=bal;
end;

@ @<Copy special things when |c="@@"...@>=
if c="@@" then
  begin incr(loc);
  if buffer[loc-1]<>"@@" then
    begin err_print('! Illegal use of @@ in comment');
@.Illegal use of \AT!...@>
    loc:=loc-2; decr(tok_ptr); @<Clear |bal|...@>;
    end;
  end
else if (c="\")and(buffer[loc]<>"@@") then
  begin app_tok(buffer[loc]); incr(loc);
  end
else if c="{" then incr(bal)
else if c="}" then
  begin decr(bal);
  if bal=0 then goto done;
  end

@ When the comment has terminated abruptly due to an error, we output
enough right braces to keep \TeX\ happy.

@<Clear |bal|...@>=
app_tok(" "); {this is done in case the previous character was `\.\\'}
repeat app_tok("}"); decr(bal);
until bal=0;
goto done;

@* Parsing.
The most intricate part of \.{WEAVE} is its mechanism for converting
\PASCAL-like code into \TeX\ code, and we might as well plunge into this
aspect of the program now. A ``bottom up'' approach is used to parse the
\PASCAL-like material, since \.{WEAVE} must deal with fragmentary
constructions whose overall ``part of speech'' is not known.

At the lowest level, the input is represented as a sequence of entities
that we shall call {\it scraps}, where each scrap of information consists
of two parts, its {\it category} and its {\it translation}. The category
is essentially a syntactic class, and the translation is a token list that
represents \TeX\ code. Rules of syntax and semantics tell us how to
combine adjacent scraps into larger ones, and if we are lucky an entire
\PASCAL\ text that starts out as hundreds of small scraps will join
together into one gigantic scrap whose translation is the desired \TeX\
code. If we are unlucky, we will be left with several scraps that don't
combine; their translations will simply be output, one by one.

The combination rules are given as context-sensitive productions that are
applied from left to right. Suppose that we are currently working on the
sequence of scraps $s_1\,s_2\ldots s_n$. We try first to find the longest
production that applies to an initial substring $s_1\,s_2\ldots\,$; but if
no such productions exist, we try to find the longest production
applicable to the next substring $s_2\,s_3\ldots\,$; and if that fails, we
try to match $s_3\,s_4\ldots\,$, etc.

A production applies if the category codes have a given pattern. For
example, one of the productions is
$$|open|\;|math|\;|semi|\;\RA\;|open|\;|math|$$
and it means that three consecutive scraps whose respective categories are
|open|, |math|, and |semi| are con\-verted to two scraps whose categories
are |open| and |math|. This production also has an associated rule that
tells how to combine the translation parts:
$$\eqalign{O_2&=O_1\cr
M_2&=M_1\,S\,\.{\\,}\,\hbox{|opt|\thinspace\tt5}\cr}$$
This means that the |open| scrap has not changed, while the new |math| scrap
has a translation $M_2$ composed of the translation $M_1$ of the original
|math| scrap followed by the translation |S| of the |semi| scrap followed
by `\.{\\,}' followed by `|opt|' followed by `\.5'. (In the \TeX\ file,
this will specify an additional thin space after the semicolon, followed
by an optional line break with penalty 50.) Translation rules use subscripts
to distinguish between translations of scraps whose categories have the
same initial letter; these subscripts are assigned from left to right.

$\.{WEAVE}$ also has the production rule
$$|semi|\;\RA\;|terminator|$$
(meaning that a semicolon can terminate a \PASCAL\ statement). Since
productions are applied from left to right, this rule will be activated
only if the |semi| is not preceded by scraps that match other productions;
in particular, a |semi| that is preceded by `|open| |math|' will have
disappeared because of the production above, and such semicolons do not
act as statement terminators.  This incidentally is how \.{WEAVE} is able
to treat semicolons in two distinctly different ways, the first of which
is intended for semicolons in the parameter list of a procedure
declaration.

The translation rule corresponding to $|semi|\;\RA\;|terminator|$ is
$$T=S$$
but we shall not mention translation rules in the common case that the
translation of the new scrap on the right-hand side is simply the
concatenation of the disappearing scraps on the left-hand side.

@ Here is a list of the category codes that scraps can have.

@d simp=1 {the translation can be used both in horizontal mode
  and in math mode of \TeX}
@d math=2 {the translation should be used only in \TeX\ math mode}
@d intro=3 {a statement is expected to follow this, after a space and
  an optional break}
@d open=4 {denotes an incomplete parenthesized quantity to be used in
  math mode}
@d beginning=5 {denotes an incomplete compound statement to be used in
  horizontal mode}
@d close=6 {ends a parenthesis or compound statement}
@d alpha=7 {denotes the beginning of a clause}
@d omega=8 {denotes the ending of a clause and possible comment following}
@d semi=9 {denotes a semicolon and possible comment following it}
@d terminator=10 {something that ends a statement or declaration}
@d stmt=11 {denotes a statement or declaration including its terminator}
@d cond=12 {precedes an \&{if} clause that might have a matching \&{else}}
@d clause=13 {precedes a statement after which indentation ends}
@d colon=14 {denotes a colon}
@d exp=15 {stands for the E in a floating point constant}
@d proc=16 {denotes a procedure or program or function heading}
@d case_head=17 {denotes a case statement or record heading}
@d record_head=18 {denotes a record heading without indentation}
@d var_head=19 {denotes a variable declaration heading}
@d elsie=20 {\&{else}}
@d casey=21 {\&{case}}
@d mod_scrap=22 {denotes a module name}

@p @!debug procedure print_cat(@!c:eight_bits);
  {symbolic printout of a category}
begin case c of
simp: print('simp');
math: print('math');
intro: print('intro');
open: print('open');
beginning: print('beginning');
close: print('close');
alpha: print('alpha');
omega: print('omega');
semi: print('semi');
terminator: print('terminator');
stmt: print('stmt');
cond: print('cond');
clause: print('clause');
colon: print('colon');
exp: print('exp');
proc: print('proc');
case_head: print('casehead');
record_head: print('recordhead');
var_head: print('varhead');
elsie: print('elsie');
casey: print('casey');
mod_scrap: print('module');
othercases print('UNKNOWN')
endcases;
end;
gubed

@ The token lists for translated \TeX\ output contain some special control
symbols as well as ordinary characters. These control symbols are
interpreted by \.{WEAVE} before they are written to the output file.

\yskip\hang |break_space| denotes an optional line break or an en space;

\yskip\hang |force| denotes a line break;

\yskip\hang |big_force| denotes a line break with additional vertical space;

\yskip\hang |opt| denotes an optional line break (with the continuation
line indented two ems with respect to the normal starting position)---this
code is followed by an integer |n|, and the break will occur with penalty
$10n$;

\yskip\hang |backup| denotes a backspace of one em;

\yskip\hang |cancel| obliterates any |break_space| or |force| or |big_force|
tokens that immediately precede or follow it and also cancels any
|backup| tokens that follow it;

\yskip\hang |indent| causes future lines to be indented one more em;

\yskip\hang |outdent| causes future lines to be indented one less em.

\yskip\noindent All of these tokens are removed from the \TeX\ output that
comes from \PASCAL\ text between \pb\ signs; |break_space| and |force| and
|big_force| become single spaces in this mode. The translation of other
\PASCAL\ texts results in \TeX\ control sequences \.{\\1}, \.{\\2},
\.{\\3}, \.{\\4}, \.{\\5}, \.{\\6}, \.{\\7} corresponding respectively to
|indent|, |outdent|, |opt|, |backup|, |break_space|, |force|, and
|big_force|. However, a sequence of consecutive `\.\ ', |break_space|,
|force|, and/or |big_force| tokens is first replaced by a single token
(the maximum of the given ones).

The tokens |math_rel|, |math_bin|, |math_op| will be translated into
\.{\\mathrel\{}, \.{\\mathbin\{}, and \.{\\mathop\{}, respectively.
Other control sequences in the \TeX\ output will be `\.{\\\\\{}$\,\ldots\,$\.\}'
surrounding identifiers, `\.{\\\&\{}$\,\ldots\,$\.\}' surrounding
reserved words, `\.{\\.\{}$\,\ldots\,$\.\}' surrounding strings,
`\.{\\C\{}$\,\ldots\,$\.\}$\,$|force|' surrounding comments, and
`\.{\\X$n$:}$\,\ldots\,$\.{\\X}' surrounding module names, where
|n| is the module number.

@d math_bin=@'203
@d math_rel=@'204
@d math_op=@'205
@d big_cancel=@'206 {like |cancel|, also overrides spaces}
@d cancel=@'207 {overrides |backup|, |break_space|, |force|, |big_force|}
@d indent=cancel+1 {one more tab (\.{\\1})}
@d outdent=cancel+2 {one less tab (\.{\\2})}
@d opt=cancel+3 {optional break in mid-statement (\.{\\3})}
@d backup=cancel+4 {stick out one unit to the left (\.{\\4})}
@d break_space=cancel+5 {optional break between statements (\.{\\5})}
@d force=cancel+6 {forced break between statements (\.{\\6})}
@d big_force=cancel+7 {forced break with additional space (\.{\\7})}
@d end_translation=big_force+1 {special sentinel token at end of list}

@ The raw input is converted into scraps according to the following table,
which gives category codes followed by the translations. Sometimes a single
item of input produces more than one scrap.
\def\stars {\.{**}}%
(The symbol `\stars' stands for `\.{\\\&\{{\rm identifier}\}}',
i.e., the identifier itself treated as a reserved word. In a few cases the
category is given as `|@!comment|'; this is not an actual category code, it
means that the translation will be treated as a comment, as explained
below.)

\yskip\halign{\quad#\hfil&\quad#\hfil\cr
\.{<>}&|math:|\.{\\I}\cr
\.{<=}&|math:|\.{\\L}\cr
\.{>=}&|math:|\.{\\G}\cr
\.{:=}&|math:|\.{\\K}\cr
\.{==}&|math:|\.{\\S}\cr
\.{(*}&|math:|\.{\\B}\cr
\.{*)}&|math:|\.{\\T}\cr
\.{(.}&|open:|\.[\cr
\.{.)}&|close:|\.]\cr
\."$\,$string$\,$\."&|simp:|\.{\\.\{"{\rm$\,$modified string$\,$}"\}}\cr
\.\'$\,$string$\,$\.\'&|simp:|\.{\\.\{\\\'{\rm$\,$modified
  string$\,$}\\\'\}}\cr
\.{@@=}$\,$string$\,$\.{@@>}&|simp:|\.{\\=\{{\rm$\,$modified string$\,$}\}}\cr
\#&|math:|\.{\\\#}\cr
\.\$&|math:|\.{\\\$}\cr
\.\_&|math:|\.{\\\_}\cr
\.\%&|math:|\.{\\\%}\cr
\.\^&|math:|\.{\\\^}\cr
\.(&|open:|\.(\cr
\.)&|close:|\.)\cr
\.[&|open:|\.[\cr
\.]&|close:|\.]\cr
\.*&|math:|\.{\\ast}\cr
\.,&|math:|\.,|@,opt@,|\.9\cr
\.{..}&|math:|\.{\\to}\cr
\..&|simp:|\..\cr
\.:&|colon:|\.:\cr
\.;&|semi:|\.;\cr
identifier&|simp:|\.{\\\\\{{\rm$\,$identifier$\,$}\}}\cr
\.E in constant&|exp:|\.{\\E\{}\cr
digit $d$&|simp:|$d$\cr
other character $c$&|math:|$c$\cr
\.{and}&|math:|\.{\\W}\cr
\.{array}&|alpha:|\stars\cr
\.{begin}&|beginning:|$|force|\,\stars\,|cancel|$\qquad|intro:|\cr
\.{case}&|casey:|\qquad|alpha:|$|force|\,\stars$\cr
\.{const}&|intro:|$|force|\,|backup|\,\stars$\cr
\.{div}&|math:|$|math_bin|\,\stars\,\.\}$\cr
\.{do}&|omega:|\stars\cr
\.{downto}&|math:|$|math_rel|\,\stars\,\.\}$\cr
\.{else}&|terminator:|\qquad|elsie:|$|force|\,|backup|\,\stars$\cr
\.{end}&|terminator:|\qquad|close:|$|force|\,\stars$\cr
\.{file}&|alpha:|\stars\cr
\.{for}&|alpha:|$|force|\,\stars$\cr
\.{function}&|proc:|$|force|\,|backup|\,\stars\,|cancel|$\qquad
  |intro:|$|indent|\,\.{\\\ }$\cr
\.{goto}&|intro:|\stars\cr
\.{if}&|cond:|\qquad|alpha:|$|force|\,\stars$\cr
\.{in}&|math:|\.{\\in}\cr
\.{label}&|intro:|$|force|\,|backup|\,\stars$\cr
\.{mod}&|math:|$|math_bin|\,\stars\,\.\}$\cr
\.{nil}&|simp:|\stars\cr
\.{not}&|math:|\.{\\R}\cr
\.{of}&|omega:|\stars\cr
\.{or}&|math:|\.{\\V}\cr
\.{packed}&|intro:|\stars\cr
\.{procedure}&|proc:|$|force|\,|backup|\,\stars\,|cancel|$\qquad
  |intro:|$|indent|\,\.{\\\ }$\cr
\.{program}&|proc:|$|force|\,|backup|\,\stars\,|cancel|$\qquad
  |intro:|$|indent|\,\.{\\\ }$\cr
\.{record}&|record_head:|\stars\qquad|intro:|\cr
\.{repeat}&|beginning:|$|force|\,|indent|\,\stars\,|cancel|$\qquad|intro:|\cr
\.{set}&|alpha:|\stars\cr
\.{then}&|omega:|\stars\cr
\.{to}&|math:|$|math_rel|\,\stars\,\.\}$\cr
\.{type}&|intro:|$|force|\,|backup|\,\stars$\cr
\.{until}&|terminator:|\qquad|close:|$|force|\,|backup|\,\stars$\qquad
  |clause:|\cr
\.{var}&|var_head:|$|force|\,|backup|\,\stars\,|cancel|$\qquad|intro:|\cr
\.{while}&|alpha:|$|force|\,\stars$\cr
\.{with}&|alpha:|$|force|\,\stars$\cr
\.{xclause}&|alpha:|$|force|\,\.{\\\~}$\qquad|omega:|\stars\cr
\.{@@\'}$\,$const&|simp:|\.{\\O\{}\hbox{const}\.\}\cr
\.{@@"}$\,$const&|simp:|\.{\\H\{}\hbox{const}\.\}\cr
\.{@@\$}&|simp:|\.{\\)}\cr
\.{@@\\}&|simp:|\.{\\]}\cr
\.{@@,}&|math:|\.{\\,}\cr
\.{@@t}$\,$stuff$\,$\.{@@>}&|simp:|\.{\\hbox\{{\rm$\,$stuff$\,$}\}}\cr
\.{@@<}$\,$module$\,$\.{@@>}&|mod_scrap:|\.{\\X$n$:{\rm$\,$module$\,$}\\X}\cr
\.{@@\#}&|comment:||big_force|\cr
\.{@@/}&|comment:||force|\cr
\.{@@\char'174}&|simp:|$|opt|\,\.0$\cr
\.{@@+}&|comment:|$|big_cancel|\,\.{\\\ }\,|big_cancel|$\cr
\.{@@;}&|semi:|\cr
\.{@@\&}&|math:|\.{\\J}\cr
\.{@@\{}&|math:|\.{\\B}\cr
\.{@@\}}&|math:|\.{\\T}\cr}
\yskip\noindent When a string is output, certain characters are preceded by
`\.\\' signs so that they will print properly.

A comment in the input will be combined with the preceding
|omega| or |semi| scrap, or with the following |terminator| scrap, if
possible; otherwise it will be inserted as a separate |terminator| scrap.
An additional ``comment'' is effectively appended at the end of the
\PASCAL\ text, just before translation begins; this consists of a |cancel|
token in the case of \PASCAL\ text in \pb, otherwise it consists of a
|force| token.

From this table it is evident that \.{WEAVE} will parse a lot of non-\PASCAL\
programs. For example, the reserved words `\.{for}' and `\.{array}' are
treated in an identical way by \.{WEAVE} from a syntactic standpoint,
and semantically they are equivalent except that a forced line break occurs
just before `\&{for}'; \PASCAL\ programmers may well be surprised at this
similarity. The idea is to keep \.{WEAVE}'s rules as simple as possible,
consistent with doing a reasonable job on syntactically correct \PASCAL\
programs. The production rules below have been formulated in the same
spirit of ``almost anything goes.''

@ Here is a table of all the productions. The reader can best get a feel for
@^productions, table of@>
how they work by trying them out by hand on small examples; no amount of
explanation will be as effective as watching the rules in action.
Parsing can also be watched by debugging with `\.{@@2}'.

\def\[#1]{\quad$\dleft#1\dright$}
\def\sp{\.{\ }}
\yskip
\halign to\the\hsize{\hfil\it# &
  #\hfil\hskip-200pt\tabskip 0pt plus 100pt&
  #\hfil\tabskip0pt\cr
&Production categories\[\hbox{translations}]&Remarks\cr
\noalign{\yskip}
1&|alpha@,math@,colon| $\RA$ |alpha@,math|&e.g., |case v:boolean of|\cr
2&|alpha@,math@,omega| $\RA$ |clause|\[C=A\,\sp\,\.\$\,M\,\.\$\,\sp\,|indent|\,
O]&e.g., |while x>0 do|\cr
3&|alpha@,omega| $\RA$ |clause|\[C=A\,\sp\,|indent|\,O]&e.g., |file of|\cr
4&|alpha@,simp| $\RA$ |alpha@,math|&convert to math mode\cr
5&|beginning@,close@,(terminator@t or @>stmt)| $\RA$ |stmt|&compound statement
ends\cr
6&|beginning@,stmt| $\RA$ |beginning|\[B_2=B_1\,|break_space|\,S]&compound
statement grows\cr
7&|case_head@,casey@,clause| $\RA$ |case_head|\[C_4=C_1\,|outdent|\,C_2\,C_3]&
variant records\cr
8&|case_head@,close@,terminator| $\RA$ |stmt|\[S=C_1\,|cancel|\,|outdent|\,
C_2\,T]&end of case statement\cr
9&|case_head@,stmt| $\RA$ |case_head|\[C_2=C_1\,|force|\,S]&case statement
grows\cr
10&|casey@,clause| $\RA$ |case_head|&beginning of case statement\cr
11&|clause@,stmt| $\RA$ |stmt|\[S_2=C\,|break_space|\,S_1\,|cancel|\,|outdent|\,
|force|]&end of controlled statement\cr
12&|cond@,clause@,stmt@,elsie| $\RA$ |clause|\[C_3=C_1\,C_2\,|break_space|\,S\,
E\,\sp\,|cancel|]&complete conditional\cr
13&|cond@,clause@,stmt| $\RA$ |stmt|\cr
&\qquad\[S_2=C_1\,C_2\,|break_space|\,S_1\,
|cancel|\,|outdent|\,|force|]&incomplete conditional\cr
14&|elsie| $\RA$ |intro|&unmatched else\cr
15&|exp@,math@,simp|* $\RA$ |math|\[M_2=E\,M_1\,S\,\.\}]&signed exponent\cr
16&|exp@,simp|* $\RA$ |math|\[M=E\,S\,\.\}]&unsigned exponent\cr
17&|intro@,stmt| $\RA$ |stmt|\[S_2=I\,\sp\,|opt|\,\.7\,|cancel|\,S_1]&labeled
statement, etc.\cr
18&|math@,close| $\RA$ |stmt@,close|\[S=\.\$\,M\,\.\$]&end of field list\cr
19&|math@,colon| $\RA$ |intro|\[I=|force|\,|backup|\,\.\$\,M\,\.\$\,C]&compound
label\cr
20&|math@,math| $\RA$ |math|&simple concatenation\cr
21&|math@,simp| $\RA$ |math|&simple concatenation\cr
22&|math@,stmt| $\RA$ |stmt|\cr
&\qquad\[S_2=\.\$\,M\,\.\$\,|indent|\,|break_space|\,
S_1\,|cancel|\,|outdent|\,|force|]&macro or type definition\cr
23&|math@,terminator| $\RA$ |stmt|\[S=\.\$\,M\,\.\$\,T]&statement involving
math\cr
24&|mod_scrap@,(terminator@t or @>semi)| $\RA$ |stmt|\[S=M\,T\,|force|]&module
like a statement\cr
25&|mod_scrap| $\RA$ |simp|&module unlike a statement\cr
26&|open@,case_head@,close| $\RA$ |math|\[M=O\,\.\$\,|cancel|\,C_1\,
|cancel|\,|outdent|\,\.\$\,C_2]&case in field list\cr
27&|open@,close| $\RA$ |math|\[M=O\,\.\\\,\.,\,C]&empty set |[]|\cr
28&|open@,math@,case_head@,close| $\RA$ |math|\cr
&\qquad\[M_2=O\,M_1\,\.\$\,|cancel|\,
C_1\,|cancel|\,|outdent|\,\.\$\,C_2]&case in field list\cr
29&|open@,math@,close| $\RA$ |math|&parenthesized group\cr
30&|open@,math@,colon| $\RA$ |open@,math|&colon in parentheses\cr
31&|open@,math@,proc@,intro| $\RA$ |open@,math|\[M_2=M_1\,|math_op|\,|cancel|\,
P\,\.\}]&|procedure| in parentheses\cr
32&|open@,math@,semi| $\RA$ |open@,math|\[M_2=M_1\,S\,\.\\\,\.,\,|opt|\,
\.5]&semicolon in parentheses\cr
33&|open@,math@,var_head@,intro| $\RA$ |open@,math|\[M_2=M_1\,|math_op|\,
|cancel|\,V\,\.\}]&|var| in parentheses\cr
34&|open@,proc@,intro| $\RA$ |open@,math|\[M=|math_op|\,|cancel|\,
P\,\.\}]&|procedure| in parentheses\cr
35&|open@,simp| $\RA$ |open@,math|&convert to math mode\cr
36&|open@,stmt@,close| $\RA$ |math|\[M=O\,\.\$\,|cancel|\,S\,|cancel|\,
\.\$\,C]&field list\cr
37&|open@,var_head@,intro| $\RA$ |open@,math|\[M=|math_op|\,|cancel|\,V\,
\.\}]&|var| in parentheses\cr
38&|proc@,beginning@,close@,terminator| $\RA$ |stmt|\[S=P\,|cancel|\,
|outdent|\,B\,C\,T]&end of procedure declaration\cr
39&|proc@,stmt| $\RA$ |proc|\[P_2=P_1\,|break_space|\,S]&procedure declaration
grows\cr
40&|record_head@,intro@,casey| $\RA$ |casey|\[C_2=R\,I\,\sp\,|cancel|\,C_1]&
\&{record case} $\ldots$\cr
41&|record_head| $\RA$ |case_head|\[C=|indent|\,R\,|cancel|]&other \&{record}
structures\cr
42&|semi| $\RA$ |terminator|&semicolon after statement\cr
43&|simp@,close| $\RA$ |stmt@,close|&end of field list\cr
44&|simp@,colon| $\RA$ |intro|\[I=|force|\,|backup|\,S\,C]&simple label\cr
45&|simp@,math| $\RA$ |math|&simple concatenation\cr
46&|simp@,mod_scrap| $\RA$ |mod_scrap|&in emergencies\cr
47&|simp@,simp| $\RA$ |simp|&simple concatenation\cr
48&|simp@,terminator| $\RA$ |stmt|&simple statement\cr
49&|stmt@,stmt| $\RA$ |stmt|\[S_3=S_1\,|break_space|\,S_2]&adjacent
statements\cr
50&|terminator| $\RA$ |stmt|&empty statement\cr
51&|var_head@,beginning| $\RA$ |stmt@,beginning|&end of variable
declarations\cr
52&|var_head@,math@,colon| $\RA$ |var_head@,intro|\[I=\.\$\,M\,\.\$\,C]&
variable declaration\cr
53&|var_head@,simp@,colon| $\RA$ |var_head@,intro|&variable declaration\cr
54&|var_head@,stmt| $\RA$ |var_head|\[V_2=V_1\,|break_space|\,S]&variable
declarations grow\cr}
\yskip\noindent
Translations are not specified here when they are simple concatenations
of the scraps that change. For example, the full translation of
`|open@,math@,colon| $\RA$ |open@,math|' is $O_2=O_1$, $M_2=M_1C$.

The notation `|simp|*', in the |exp|-related productions above,
stands for a |simp| scrap that isn't followed by another |simp|.

@* Implementing the productions.
When \PASCAL\ text is to be processed with the grammar above, we put its
initial scraps $s_1\ldots s_n$ into two arrays |cat[1..n]| and |trans[1..n]|.
The value of |cat[k]| is simply a category code from the list above; the
value of |trans[k]| is a text pointer, i.e., an index into |tok_start|.
Our production rules have the nice property that the right-hand side is never
longer than the left-hand side. Therefore it is convenient to use sequential
allocation for the current sequence of scraps. Five pointers are used to
manage the parsing:

\yskip\hang |pp| (the parsing pointer) is such that we are trying to match
the category codes |cat[pp]@,cat[pp+1]|$\,\ldots\,$ to the left-hand sides
of productions.

\yskip\hang |scrap_base|, |lo_ptr|, |hi_ptr|, and |scrap_ptr| are such that
the current sequence of scraps appears in positions |scrap_base| through
|lo_ptr| and |hi_ptr| through |scrap_ptr|, inclusive, in the |cat| and
|trans| arrays. Scraps located between |scrap_base| and |lo_ptr| have
been examined, while those in positions |>=hi_ptr| have not yet been
looked at by the parsing process.

\yskip\noindent Initially |scrap_ptr| is set to the position of the final
scrap to be parsed, and it doesn't change its value. The parsing process
makes sure that |lo_ptr>=pp+3|, since productions have as many as four terms,
by moving scraps from |hi_ptr| to |lo_ptr|. If there are
fewer than |pp+3| scraps left, the positions up to |pp+3| are filled with
blanks that will not match in any productions. Parsing stops when
|pp=lo_ptr+1| and |hi_ptr=scrap_ptr+1|.

The |trans| array elements are declared to be of type |0..10239| instead
of type |text_pointer|, because the final sorting phase of \.{WEAVE}
uses this array to contain elements of type |name_pointer|. Both
of these types are subranges of |0..10239|.

@<Glo...@>=
@!cat:array[0..max_scraps] of eight_bits; {category codes of scraps}
@!trans:array[0..max_scraps] of 0..10239; {translation texts of scraps}
@!pp:0..max_scraps; {current position for reducing productions}
@!scrap_base:0..max_scraps; {beginning of the current scrap sequence}
@!scrap_ptr:0..max_scraps; {ending of the current scrap sequence}
@!lo_ptr:0..max_scraps; {last scrap that has been examined}
@!hi_ptr:0..max_scraps; {first scrap that has not been examined}
stat@!max_scr_ptr:0..max_scraps; {largest value assumed by |scrap_ptr|}
tats

@ @<Set init...@>=
scrap_base:=1; scrap_ptr:=0;
stat max_scr_ptr:=0; @+tats

@ Token lists in |@!tok_mem| are composed of the following kinds of
items for \TeX\ output.

\yskip\item{$\bullet$}ASCII codes and special codes like |force| and
|math_rel| represent themselves;

\item{$\bullet$}|id_flag+p| represents \.{\\\\\{{\rm identifier $p$}\}};

\item{$\bullet$}|res_flag+p| represents \.{\\\&\{{\rm identifier $p$}\}};

\item{$\bullet$}|mod_flag+p| represents module name |p|;

\item{$\bullet$}|tok_flag+p| represents token list number |p|;

\item{$\bullet$}|inner_tok_flag+p| represents token list number |p|, to be
translated without line-break controls.

@d id_flag=10240 {signifies an identifier}
@d res_flag=id_flag+id_flag {signifies a reserved word}
@d mod_flag=res_flag+id_flag {signifies a module name}
@d tok_flag==mod_flag+id_flag {signifies a token list}
@d inner_tok_flag==tok_flag+id_flag {signifies a token list in `\pb'}
@#
@d lbrace==xchr["{"] {this avoids possible \PASCAL\ compiler confusion}
@d rbrace==xchr["}"] {because these braces might occur within comments}

@p @!debug procedure print_text(@!p:text_pointer); {prints a token list}
var j:0..max_toks; {index into |tok_mem|}
@!r:0..id_flag-1; {remainder of token after the flag has been stripped off}
begin if p>=text_ptr then print('BAD')
else for j:=tok_start[p] to tok_start[p+1]-1 do
  begin r:=tok_mem[j] mod id_flag;
  case tok_mem[j] div id_flag of
  1: begin print('\\',lbrace); print_id(r); print(rbrace);
    end; {|id_flag|}
  2: begin print('\&',lbrace); print_id(r); print(rbrace);
    end; {|res_flag|}
  3: begin print('<'); print_id(r); print('>');
    end; {|mod_flag|}
  4: print('[[',r:1,']]'); {|tok_flag|}
  5: print('|[[',r:1,']]|'); {|inner_tok_flag|}
  othercases @<Print token |r| in symbolic form@>
  endcases;
  end;
end;
gubed

@ @<Print token |r|...@>=
case r of
math_bin: print('\mathbin',lbrace);
math_rel: print('\mathrel',lbrace);
math_op: print('\mathop',lbrace);
big_cancel: print('[ccancel]');
cancel: print('[cancel]');
indent: print('[indent]');
outdent: print('[outdent]');
backup: print('[backup]');
opt: print('[opt]');
break_space: print('[break]');
force: print('[force]');
big_force: print('[fforce]');
end_translation: print('[quit]');
othercases print(xchr[r])
endcases

@ The production rules listed above are embedded directly into the \.{WEAVE}
program, since it is easier to do this than to write an interpretive system
that would handle production systems in general. Several macros are defined
here so that the program for each production is fairly short.

All of our productions conform to the general notion that some |k|
consecutive scraps starting at some position |j| are to be replaced by a
single scrap of some category |c| whose translation is composed from the
translations of the disappearing scraps. After this production has been
applied, the production pointer |pp| should change by an amount |d|. Such
a production can be represented by the quadruple $(j,k,c,d)$. For example,
the production `|simp@,math| $\RA$ |math|' would be represented by
`$(|pp|,2,|math|,-1)$'; in this case the pointer $pp$ should decrease by 1
after the production has been applied, because some productions with
|math| in their second positions might now match, but no productions have
|math| in the third or fourth position of their left-hand sides. Note that
the value of |d| is determined by the whole collection of productions, not
by an individual one. Consider the further example
`|var_head@,math@,colon| $\RA$ |var_head@,intro|', which is represented by
`$(|pp|+1,2,|intro|,+1)$'; the $+1$ here is deduced by looking at the
grammar and seeing that no matches could possibly occur at positions |<=pp|
after this production has been applied. The determination of |d| has been
done by hand in each case, based on the full set of productions but not on
the grammar of \PASCAL\ or on the rules for constructing the initial
scraps.

We also attach a serial number to each production, so that additional
information is available when debugging. For example, the program below
contains the statement `|reduce(pp+1,2,intro,+1)(52)|' when it implements
the production just mentioned.

Before calling |reduce|, the program should have appended the tokens of
the new translation to the |tok_mem| array. We commonly want to append
copies of several existing translations, and macros are defined to
simplify these common cases. For example, |app2(pp)| will append the
translations of two consecutive scraps, |trans[pp]| and |trans[pp+1]|, to
the current token list. If the entire new translation is formed in this
way, we write `$|squash|(j,k,c,d)$' instead of `$|reduce|(j,k,c,d)$'. For
example, `|squash(pp,2,math,-1)|' is an abbreviation for `|app2(pp);
reduce(pp,2,math,-1)|'.

The code below is an exact translation of the production rules into
\PASCAL, using such macros, and the reader should have no difficulty
understanding the format by comparing the code with the symbolic
productions as they were listed earlier.

{\sl Caution:\/} The macros |app|, |app1|, |app2|, and |app3| are
sequences of statements that are not enclosed with |begin| and $|end|$,
because such delimiters would make the \PASCAL\ program much longer. This
means that it is necessary to write |begin| and |end| explicitly when such
a macro is used as a single statement. Several mysterious bugs in the
original programming of \.{WEAVE} were caused by a failure to remember
this fact.  Next time the author will know better.

@d production(#)==@!debug prod(#) gubed; goto found
@d reduce(#)==red(#); production
@d production_end(#)==@!debug prod(#) gubed; goto found;
  end
@d squash(#)==begin sq(#); production_end
@d app(#)==tok_mem[tok_ptr]:=#; incr(tok_ptr) {this is like |app_tok|,
  but it doesn't test for overflow}
@d app1(#)==tok_mem[tok_ptr]:=tok_flag+trans[#]; incr(tok_ptr)
@d app2(#)==app1(#);app1(#+1)
@d app3(#)==app2(#);app1(#+2)

@ Let us consider the big case statement for productions now, before looking
at its context. We want to design the program so that this case statement
works, so we might as well not keep ourselves in suspense about exactly what
code needs to be provided with a proper environment.

The code here is more complicated than it need be, since some popular
\PASCAL\ compilers are unable to deal with procedures that contain a lot
of program text. The |translate| procedure, which incorporates the |case|
statement here, would become too long for those compilers if we did
not do something to split the cases into parts. Therefore
a separate procedure called |five_cases| has been introduced.
@^split procedures@>
This auxiliary procedure contains approximately half of the program text
that |translate| would otherwise have had. There's also a procedure
called |alpha_cases|, which turned out to be necessary because the best
two-way split wasn't good enough. The procedure could be split further
in an analogous manner, but the present scheme works on all compilers
known to the author.

@<Match a production at |pp|, or increase |pp| if there is no match@>=
if cat[pp]<=alpha then
  if cat[pp]<alpha then five_cases@+else alpha_cases
else  begin case cat[pp] of
  case_head: @<Cases for |case_head|@>;
  casey: @<Cases for |casey|@>;
  clause: @<Cases for |clause|@>;
  cond: @<Cases for |cond|@>;
  elsie: @<Cases for |elsie|@>;
  exp: @<Cases for |exp|@>;
  mod_scrap: @<Cases for |mod_scrap|@>;
  proc: @<Cases for |proc|@>;
  record_head: @<Cases for |record_head|@>;
  semi: @<Cases for |semi|@>;
  stmt: @<Cases for |stmt|@>;
  terminator: @<Cases for |terminator|@>;
  var_head: @<Cases for |var_head|@>;
  othercases do_nothing
  endcases;@/
  incr(pp); {if no match was found, we move to the right}
  found: end

@ Here are the procedures that need to be present for the reason just
explained.

@<Declaration of subprocedures for |translate|@>=
procedure five_cases; {handles almost half of the syntax}
label found;
begin case cat[pp] of
beginning: @<Cases for |beginning|@>;
intro: @<Cases for |intro|@>;
math: @<Cases for |math|@>;
open: @<Cases for |open|@>;
simp: @<Cases for |simp|@>;
othercases do_nothing
endcases;@/
incr(pp); {if no match was found, we move to the right}
found: end;
@#
procedure alpha_cases;
label found;
begin @<Cases for |alpha|@>;
incr(pp); {if no match was found, we move to the right}
found: end;

@ Now comes the code that tries to match each production starting
with a particular type of scrap. Whenever a match is discovered,
the |squash| or |reduce| macro will cause the appropriate action
to be performed, followed by |goto found|.

@<Cases for |alpha|@>=
if cat[pp+1]=math then
  begin if cat[pp+2]=colon then squash(pp+1,2,math,0)(1)
  else if cat[pp+2]=omega then
    begin app1(pp); app(" "); app("$"); app1(pp+1);
    app("$"); app(" "); app(indent); app1(pp+2);
    reduce(pp,3,clause,-2)(2);
    end;
  end
else if cat[pp+1]=omega then
  begin app1(pp); app(" "); app(indent); app1(pp+1);
  reduce(pp,2,clause,-2)(3);
  end
else if cat[pp+1]=simp then squash(pp+1,1,math,0)(4)

@ @<Cases for |beginning|@>=
if cat[pp+1]=close then
  begin if (cat[pp+2]=terminator)or(cat[pp+2]=stmt) then
    squash(pp,3,stmt,-2)(5);
  end
else if cat[pp+1]=stmt then
  begin app1(pp); app(break_space); app1(pp+1);
  reduce(pp,2,beginning,-1)(6);
  end

@ @<Cases for |case_head|@>=
if cat[pp+1]=casey then
  begin if cat[pp+2]=clause then
    begin app1(pp); app(outdent); app2(pp+1);
    reduce(pp,3,case_head,0)(7);
    end;
  end
else if cat[pp+1]=close then
  begin if cat[pp+2]=terminator then
    begin app1(pp); app(cancel); app(outdent); app2(pp+1);
    reduce(pp,3,stmt,-2)(8);
    end;
  end
else if cat[pp+1]=stmt then
  begin app1(pp); app(force); app1(pp+1);
  reduce(pp,2,case_head,0)(9);
  end

@ @<Cases for |casey|@>=
if cat[pp+1]=clause then squash(pp,2,case_head,0)(10)

@ @<Cases for |clause|@>=
if cat[pp+1]=stmt then
  begin app1(pp); app(break_space); app1(pp+1);
  app(cancel); app(outdent);
  app(force); reduce(pp,2,stmt,-2)(11);
  end

@ @<Cases for |cond|@>=
if (cat[pp+1]=clause)and(cat[pp+2]=stmt) then
  if cat[pp+3]=elsie then
    begin app2(pp); app(break_space); app2(pp+2); app(" ");
    app(cancel); reduce(pp,4,clause,-2)(12);
    end
  else  begin app2(pp); app(break_space); app1(pp+2); app(cancel);
    app(outdent); app(force); reduce(pp,3,stmt,-2)(13);
    end

@ @<Cases for |elsie|@>=
squash(pp,1,intro,-3)(14)

@ @<Cases for |exp|@>=
if cat[pp+1]=math then
  begin if cat[pp+2]=simp then if cat[pp+3]<>simp then
    begin app3(pp); app("}"); reduce(pp,3,math,-1)(15);
    end;
  end
else if cat[pp+1]=simp then if cat[pp+2]<>simp then
  begin app2(pp); app("}"); reduce(pp,2,math,-1)(16);
  end

@ @<Cases for |intro|@>=
if cat[pp+1]=stmt then
  begin app1(pp); app(" "); app(opt); app("7");
  app(cancel); app1(pp+1); reduce(pp,2,stmt,-2)(17);
  end

@ @<Cases for |math|@>=
if cat[pp+1]=close then
  begin app("$"); app1(pp); app("$"); reduce(pp,1,stmt,-2)(18);
  end
else if cat[pp+1]=colon then
  begin app(force); app(backup); app("$"); app1(pp);
  app("$"); app1(pp+1); reduce(pp,2,intro,-3)(19);
  end
else if cat[pp+1]=math then squash(pp,2,math,-1)(20)
else if cat[pp+1]=simp then squash(pp,2,math,-1)(21)
else if cat[pp+1]=stmt then
  begin app("$"); app1(pp); app("$"); app(indent);
  app(break_space); app1(pp+1); app(cancel); app(outdent);
  app(force); reduce(pp,2,stmt,-2)(22);
  end
else if cat[pp+1]=terminator then
  begin app("$"); app1(pp); app("$"); app1(pp+1);
  reduce(pp,2,stmt,-2)(23);
  end

@ @<Cases for |mod_scrap|@>=
if (cat[pp+1]=terminator)or(cat[pp+1]=semi) then
  begin app2(pp); app(force); reduce(pp,2,stmt,-2)(24);
  end
else squash(pp,1,simp,-2)(25)

@ @<Cases for |open|@>=
if (cat[pp+1]=case_head)and(cat[pp+2]=close) then
  begin app1(pp); app("$"); app(cancel); app1(pp+1); app(cancel);
  app(outdent); app("$"); app1(pp+2); reduce(pp,3,math,-1)(26);
  end
else if cat[pp+1]=close then
  begin app1(pp); app("\"); app(","); app1(pp+1);
@.\\,@>
  reduce(pp,2,math,-1)(27);
  end
else if cat[pp+1]=math then @<Cases for |open@,math|@>
else if cat[pp+1]=proc then
  begin if cat[pp+2]=intro then
    begin app(math_op); app(cancel); app1(pp+1); app("}");
    reduce(pp+1,2,math,0)(34);
    end;
  end
else if cat[pp+1]=simp then squash(pp+1,1,math,0)(35)
else if (cat[pp+1]=stmt)and(cat[pp+2]=close) then
  begin app1(pp); app("$"); app(cancel); app1(pp+1); app(cancel);
  app("$"); app1(pp+2); reduce(pp,3,math,-1)(36);
  end
else if cat[pp+1]=var_head then
  begin if cat[pp+2]=intro then
    begin app(math_op); app(cancel); app1(pp+1); app("}");
    reduce(pp+1,2,math,0)(37);
    end;
  end

@ @<Cases for |open@,math|@>=
begin if (cat[pp+2]=case_head)and(cat[pp+3]=close) then
  begin app2(pp); app("$"); app(cancel); app1(pp+2); app(cancel);
  app(outdent); app("$"); app1(pp+3); reduce(pp,4,math,-1)(28);
  end
else if cat[pp+2]=close then squash(pp,3,math,-1)(29)
else if cat[pp+2]=colon then squash(pp+1,2,math,0)(30)
else if cat[pp+2]=proc then
  begin if cat[pp+3]=intro then
    begin app1(pp+1); app(math_op); app(cancel);
    app1(pp+2); app("}"); reduce(pp+1,3,math,0)(31);
    end;
  end
else if cat[pp+2]=semi then
  begin app2(pp+1); app("\"); app(","); app(opt); app("5");
@.\\,@>
  reduce(pp+1,2,math,0)(32);
  end
else if cat[pp+2]=var_head then
  begin if cat[pp+3]=intro then
    begin app1(pp+1); app(math_op); app(cancel);
    app1(pp+2); app("}"); reduce(pp+1,3,math,0)(33);
    end;
  end;
end

@ @<Cases for |proc|@>=
if cat[pp+1]=beginning then
  begin if (cat[pp+2]=close)and(cat[pp+3]=terminator) then
    begin app1(pp); app(cancel); app(outdent); app3(pp+1);
    reduce(pp,4,stmt,-2)(38);
    end;
  end
else if cat[pp+1]=stmt then
  begin app1(pp); app(break_space); app1(pp+1);
  reduce(pp,2,proc,-2)(39);
  end

@ @<Cases for |record_head|@>=
if (cat[pp+1]=intro)and(cat[pp+2]=casey) then
  begin app2(pp); app(" "); app(cancel); app1(pp+2);
  reduce(pp,3,casey,-2)(40);
  end
else  begin app(indent); app1(pp); app(cancel);
  reduce(pp,1,case_head,0)(41);
  end

@ @<Cases for |semi|@>=
squash(pp,1,terminator,-3)(42)

@ @<Cases for |simp|@>=
if cat[pp+1]=close then squash(pp,1,stmt,-2)(43)
else if cat[pp+1]=colon then
  begin app(force); app(backup); app2(pp); reduce(pp,2,intro,-3)(44);
  end
else if cat[pp+1]=math then squash(pp,2,math,-1)(45)
else if cat[pp+1]=mod_scrap then squash(pp,2,mod_scrap,0)(46)
else if cat[pp+1]=simp then squash(pp,2,simp,-2)(47)
else if cat[pp+1]=terminator then squash(pp,2,stmt,-2)(48)

@ @<Cases for |stmt|@>=
if cat[pp+1]=stmt then
  begin app1(pp); app(break_space); app1(pp+1);
  reduce(pp,2,stmt,-2)(49);
  end

@ @<Cases for |terminator|@>=
squash(pp,1,stmt,-2)(50)

@ @<Cases for |var_head|@>=
if cat[pp+1]=beginning then squash(pp,1,stmt,-2)(51)
else if cat[pp+1]=math then
  begin if cat[pp+2]=colon then
    begin app("$"); app1(pp+1); app("$"); app1(pp+2);
    reduce(pp+1,2,intro,+1)(52);
    end;
  end
else if cat[pp+1]=simp then
  begin if cat[pp+2]=colon then squash(pp+1,2,intro,+1)(53);
  end
else if cat[pp+1]=stmt then
  begin app1(pp); app(break_space); app1(pp+1);
  reduce(pp,2,var_head,-2)(54);
  end

@ The `|freeze_text|' macro is used to give official status to a token list.
Before saying |freeze_text|, items are appended to the current token list,
and we know that the eventual number of this token list will be the current
value of |text_ptr|. But no list of that number really exists as yet,
because no ending point for the current list has been
stored in the |tok_start| array. After saying |freeze_text|, the
old current token list becomes legitimate, and its number is the current
value of |text_ptr-1| since |text_ptr| has been increased. The new
current token list is empty and ready to be appended to.
Note that |freeze_text| does not check to see that |text_ptr| hasn't gotten
too large, since it is assumed that this test was done beforehand.

@d freeze_text==incr(text_ptr); tok_start[text_ptr]:=tok_ptr

@ The `|reduce|' macro used in our code for productions actually calls on
a procedure named `|red|', which makes the appropriate changes to the
scrap list.

@p procedure red(@!j:sixteen_bits; @!k:eight_bits; @!c:eight_bits;
  @!d:integer);
var i:0..max_scraps; {index into scrap memory}
begin cat[j]:=c; trans[j]:=text_ptr; freeze_text;
if k>1 then
  begin for i:=j+k to lo_ptr do
    begin cat[i-k+1]:=cat[i]; trans[i-k+1]:=trans[i];
    end;
  lo_ptr:=lo_ptr-k+1;
  end;
@<Change |pp| to $\max(|scrap_base|,|pp+d|)$@>;
end;

@ @<Change |pp| to $\max(|scrap_base|,|pp+d|)$@>=
if pp+d>=scrap_base then pp:=pp+d
else pp:=scrap_base

@ Similarly, the `|squash|' macro invokes a procedure called `|sq|'. This
procedure takes advantage of the simplification that occurs when |k=1|.

@p procedure sq(@!j:sixteen_bits; @!k:eight_bits; @!c:eight_bits;
  @!d:integer);
var i:0..max_scraps; {index into scrap memory}
begin if k=1 then
  begin cat[j]:=c; @<Change |pp|...@>;
  end
else  begin for i:=j to j+k-1 do
    begin app1(i);
    end;
  red(j,k,c,d);
  end;
end;

@ Here now is the code that applies productions as long as possible. It
requires two local labels (|found| and |done|), as well as a local
variable (|i|).

@<Reduce the scraps using the productions until no more rules apply@>=
loop@+begin @<Make sure the entries |cat[pp..(pp+3)]| are defined@>;
  if (tok_ptr+8>max_toks)or(text_ptr+4>max_texts) then
    begin stat if tok_ptr>max_tok_ptr then max_tok_ptr:=tok_ptr;
    if text_ptr>max_txt_ptr then max_txt_ptr:=text_ptr;
    tats@;@/
    overflow('token/text');
    end;
  if pp>lo_ptr then goto done;
  @<Match a production...@>;
  end;
done:

@ If we get to the end of the scrap list, category codes equal to zero are
stored, since zero does not match anything in a production.

@<Make sure the entries...@>=
if lo_ptr<pp+3 then
  begin repeat if hi_ptr<=scrap_ptr then
    begin incr(lo_ptr);@/
    cat[lo_ptr]:=cat[hi_ptr]; trans[lo_ptr]:=trans[hi_ptr];@/
    incr(hi_ptr);
    end;
  until (hi_ptr>scrap_ptr)or(lo_ptr=pp+3);
  for i:=lo_ptr+1 to pp+3 do cat[i]:=0;
  end

@ If \.{WEAVE} is being run in debugging mode, the production numbers and
current stack categories will be printed out when |tracing| is set to 2;
a sequence of two or more irreducible scraps will be printed out when
|tracing| is set to 1.
@.\AT!2@>
@.\AT!1@>

@<Glo...@>=
@!debug@!tracing:0..2; {can be used to show parsing details}
gubed

@ The |prod| procedure is called in debugging mode just after |reduce| or
|squash|; its parameter is the number of the production that has just
been applied.

@p @!debug procedure prod(@!n:eight_bits); {shows current categories}
var k:1..max_scraps; {index into |cat|}
begin if tracing=2 then
  begin print_nl(n:1,':');
  for k:=scrap_base to lo_ptr do
    begin if k=pp then print('*') @+ else print(' ');
    print_cat(cat[k]);
    end;
  if hi_ptr<=scrap_ptr then print('...'); {indicate that more is coming}
  end;
end;
gubed

@ The |translate| function assumes that scraps have been stored in
positions |scrap_base| through |scrap_ptr| of |cat| and |trans|. It
appends a |terminator| scrap and begins to apply productions as much as
possible. The result is a token list containing the translation of
the given sequence of scraps.

After calling |translate|, we will have |text_ptr+3<=max_texts| and
|tok_ptr+6<=max_toks|, so it will be possible to create up to three token
lists with up to six tokens without checking for overflow. Before calling
|translate|, we should have |text_ptr<max_texts| and |scrap_ptr<max_scraps|,
since |translate| might add a new text and a new scrap before it checks
for overflow.

@p @<Declaration of subprocedures for |translate|@>@;
function translate:text_pointer; {converts a sequence of scraps}
label done,found;
var i: 1..max_scraps; {index into |cat|}
@!j:0..max_scraps; {runs through final scraps}
@!debug@!k:0..long_buf_size; {index into |buffer|}
gubed
begin pp:=scrap_base; lo_ptr:=pp-1; hi_ptr:=pp;
@<If tracing, print an indication of where we are@>;
@<Reduce the scraps...@>;
if (lo_ptr=scrap_base)and(cat[lo_ptr]<>math) then translate:=trans[lo_ptr]
else @<Combine the irreducible scraps that remain@>;
end;

@ If the initial sequence of scraps does not reduce to a single scrap,
we concatenate the translations of all remaining scraps, separated by
blank spaces, with dollar signs surrounding the translations of |math|
scraps.

@<Combine the irreducible...@>=
begin @<If semi-tracing, show the irreducible scraps@>;
for j:=scrap_base to lo_ptr do
  begin if j<>scrap_base then
    begin app(" ");
    end;
  if cat[j]=math then
    begin app("$");
    end;
  app1(j);
  if cat[j]=math then
    begin app("$");
    end;
  if tok_ptr+6>max_toks then overflow('token');
  end;
freeze_text; translate:=text_ptr-1;
end

@ @<If semi-tracing, show the irreducible scraps@>=
@!debug if (lo_ptr>scrap_base)and(tracing=1) then
  begin print_nl('Irreducible scrap sequence in section ',module_count:1);
  print_ln(':'); mark_harmless;
  for j:=scrap_base to lo_ptr do
    begin print(' '); print_cat(cat[j]);
    end;
  end;
gubed

@ @<If tracing,...@>=
@!debug if tracing=2 then
  begin print_nl('Tracing after l.',line:1,':'); mark_harmless;
  if loc>50 then
    begin print('...');
    for k:=loc-50 to loc do print(xchr[buffer[k-1]]);
    end
  else for k:=1 to loc do print(xchr[buffer[k-1]]);
  end
gubed

@* Initializing the scraps.
If we are going to use the powerful production mechanism just developed, we
must get the scraps set up in the first place, given a \PASCAL\ text. A table
of the initial scraps corresponding to \PASCAL\ tokens appeared above in the
section on parsing; our goal now is to implement that table. We shall do this
by implementing a subroutine called |Pascal_parse| that is analogous to the
|Pascal_xref| routine used during phase one.

Like |Pascal_xref|, the |Pascal_parse| procedure starts with the current
value of |next_control| and it uses the operation |next_control:=get_next|
repeatedly to read \PASCAL\ text until encountering the next `\v' or
`\.\{', or until |next_control>=format|. The scraps corresponding to what
it reads are appended into the |cat| and |trans| arrays, and |scrap_ptr|
is advanced.

Like |prod|, this procedure has to split into pieces so that each
part is short enough to be handled by \PASCAL\ compilers that discriminate
against long subroutines. This time there are two split-off routines,
called |easy_cases| and |sub_cases|.
@^split procedures@>

After studying |Pascal_parse|, we will look at the sub-procedures
|app_comment|, |app_octal|, and |app_hex| that are used in some of its
branches.

@p @<Declaration of the |app_comment| procedure@>@;
@<Declaration of the |app_octal| and |app_hex| procedures@>@;
@<Declaration of the |easy_cases| procedure@>@;
@<Declaration of the |sub_cases| procedure@>@;
procedure Pascal_parse; {creates scraps from \PASCAL\ tokens}
label reswitch, exit;
var j:0..long_buf_size; {index into |buffer|}
@!p:name_pointer; {identifier designator}
begin while next_control<format do
  begin @<Append the scrap appropriate to |next_control|@>;
  next_control:=get_next;
  if (next_control="|")or(next_control="{") then return;
  end;
exit:end;

@ The macros defined here are helpful abbreviations for the operations
needed when generating the scraps. A scrap of category |c| whose
translation has three tokens $t_1$, $t_2$, $t_3$ is generated by
|sc3|$(t_1)(t_2)(t_3)(c)$, etc.

@d s0(#)==incr(scrap_ptr); cat[scrap_ptr]:=#; trans[scrap_ptr]:=text_ptr;
  freeze_text;
  end
@d s1(#)==app(#);s0
@d s2(#)==app(#);s1
@d s3(#)==app(#);s2
@d s4(#)==app(#);s3
@d sc4==@+begin s4
@d sc3==@+begin s3
@d sc2==@+begin s2
@d sc1==@+begin s1
@d sc0(#)==begin incr(scrap_ptr); cat[scrap_ptr]:=#; trans[scrap_ptr]:=0;
  end
@d comment_scrap(#)==begin app(#); app_comment;
  end

@ @<Append the scr...@>=
@<Make sure that there is room for at least four more scraps, six more
tokens, and four more texts@>;
reswitch: case next_control of
string,verbatim: @<Append a \(string scrap@>;
identifier: @<Append an identifier scrap@>;
TeX_string: @<Append a \TeX\ string scrap@>;
othercases easy_cases
endcases

@ The |easy_cases| each result in straightforward scraps.

@<Declaration of the |easy_cases| procedure@>=
procedure easy_cases; {a subprocedure of |Pascal_parse|}
begin case next_control of
set_element_sign: sc3("\")("i")("n")(math);
@.\\in@>
double_dot: sc3("\")("t")("o")(math);
@.\\to@>
"#","$","%","^","_": sc2("\")(next_control)(math);
@.\\\#@>
@.\\\$@>
@.\\\%@>
@.\\\^@>
ignore,"|",xref_roman,xref_wildcard,xref_typewriter: do_nothing;
"(","[": sc1(next_control)(open);
")","]": sc1(next_control)(close);
"*": sc4("\")("a")("s")("t")(math);
@.\\ast@>
",": sc3(",")(opt)("9")(math);
".","0","1","2","3","4","5","6","7","8","9": sc1(next_control)(simp);
";": sc1(";")(semi);
":": sc1(":")(colon);
@t\4@>  @<Cases involving nonstandard ASCII characters@>@;
exponent: sc3("\")("E")("{")(exp);
@.\\E@>
begin_comment: sc2("\")("B")(math);
@.\\B@>
end_comment: sc2("\")("T")(math);
@.\\T@>
octal: app_octal;
hex: app_hex;
check_sum: sc2("\")(")")(simp);
@.\\)@>
force_line: sc2("\")("]")(simp);
@.\\]@>
thin_space: sc2("\")(",")(math);
@.\\,@>
math_break: sc2(opt)("0")(simp);
line_break: comment_scrap(force);
big_line_break: comment_scrap(big_force);
no_line_break: begin app(big_cancel); app("\"); app(" ");
@.\\\ @>
  comment_scrap(big_cancel);
  end;
pseudo_semi: sc0(semi);
join: sc2("\")("J")(math);
@.\\J@>
othercases sc1(next_control)(math)
endcases;
end;

@ @<Make sure that there is room for at least four...@>=
if (scrap_ptr+4>max_scraps)or(tok_ptr+6>max_toks)or(text_ptr+4>max_texts) then
  begin stat if scrap_ptr>max_scr_ptr then max_scr_ptr:=scrap_ptr;
  if tok_ptr>max_tok_ptr then max_tok_ptr:=tok_ptr;
  if text_ptr>max_txt_ptr then max_txt_ptr:=text_ptr;
  tats@;@/
  overflow('scrap/token/text');
  end

@ Some nonstandard ASCII characters may have entered \.{WEAVE} by means of
standard ones. They are converted to \TeX\ control sequences so that it is
possible to keep \.{WEAVE} from stepping beyond standard ASCII.

@<Cases involving nonstandard...@>=
not_equal: sc2("\")("I")(math);
@.\\I@>
less_or_equal: sc2("\")("L")(math);
@.\\L@>
greater_or_equal: sc2("\")("G")(math);
@.\\G@>
equivalence_sign: sc2("\")("S")(math);
@.\\S@>
and_sign: sc2("\")("W")(math);
@.\\W@>
or_sign: sc2("\")("V")(math);
@.\\V@>
not_sign: sc2("\")("R")(math);
@.\\R@>
left_arrow: sc2("\")("K")(math);
@.\\K@>

@ The following code must use |app_tok| instead of |app| in order to
protect against overflow. Note that |tok_ptr+1<=max_toks| after |app_tok|
has been used, so another |app| is legitimate before testing again.

Many of the special characters in a string must be prefixed by `\.\\' so that
\TeX\ will print them properly.
@^special string characters@>

@<Append a \(string scrap@>=
begin app("\");
if next_control=verbatim then
  begin app("=");
@.\\=@>
  end
else  begin app(".");
@.\\.@>
  end;
app("{"); j:=id_first;
while j<id_loc do
  begin case buffer[j] of
  " ","\","#","%","$","^","'","`","{","}","~","&","_":
      begin app("\");
      end;
@.\\\ @>
@.\\\\@>
@.\\\#@>
@.\\\%@>
@.\\\$@>
@.\\\^@>
@.\\\'@>
@.\\\`@>
@.\\\{@>
@.\\\}@>
@.\\\~@>
@.\\\&@>
@.\\_@>
  "@@": if buffer[j+1]="@@" then incr(j)
    else err_print('! Double @@ should be used in strings');
@.Double \AT! should be used...@>
  othercases do_nothing
  endcases;@/
  app_tok(buffer[j]); incr(j);
  end;
sc1("}")(simp);
end

@ @<Append a \TeX\ string scrap@>=
begin app("\"); app("h"); app("b"); app("o"); app("x");
app("{");
for j:=id_first to id_loc-1 do app_tok(buffer[j]);
sc1("}")(simp);
end

@ @<Append an identifier scrap@>=
begin p:=id_lookup(normal);
case ilk[p] of
normal,array_like,const_like,div_like,
  do_like,for_like,goto_like,nil_like,to_like: sub_cases(p);
@t\4@>@<Cases that generate more than one scrap@>@;
othercases begin next_control:=ilk[p]-char_like; goto reswitch;
  end {\&{and}, \&{in}, \&{not}, \&{or}}
endcases;
end

@ The |sub_cases| also result in straightforward scraps.

@<Declaration of the |sub_cases| procedure@>=
procedure sub_cases(@!p:name_pointer); {a subprocedure of |Pascal_parse|}
begin case ilk[p] of
normal: sc1(id_flag+p)(simp); {not a reserved word}
array_like: sc1(res_flag+p)(alpha); {\&{array}, \&{file}, \&{set}}
const_like: sc3(force)(backup)(res_flag+p)(intro);
  {\&{const}, \&{label}, \&{type}}
div_like: sc3(math_bin)(res_flag+p)("}")(math); {\&{div}, \&{mod}}
do_like: sc1(res_flag+p)(omega); {\&{do}, \&{of}, \&{then}}
for_like: sc2(force)(res_flag+p)(alpha); {\&{for}, \&{while}, \&{with}}
goto_like: sc1(res_flag+p)(intro); {\&{goto}, \&{packed}}
nil_like: sc1(res_flag+p)(simp); {\&{nil}}
to_like: sc3(math_rel)(res_flag+p)("}")(math); {\&{downto}, \&{to}}
end;
end;

@ @<Cases that generate more than one scrap@>=
begin_like: begin sc3(force)(res_flag+p)(cancel)(beginning); sc0(intro);
  end; {\&{begin}}
case_like: begin sc0(casey); sc2(force)(res_flag+p)(alpha);
  end; {\&{case}}
else_like: begin @<Append |terminator| if not already present@>;
  sc3(force)(backup)(res_flag+p)(elsie);
  end; {\&{else}}
end_like: begin @<Append |term...@>;
  sc2(force)(res_flag+p)(close);
  end; {\&{end}}
if_like: begin sc0(cond); sc2(force)(res_flag+p)(alpha);
  end; {\&{if}}
loop_like: begin sc3(force)("\")("~")(alpha);
@.\\\~@>
  sc1(res_flag+p)(omega);
  end; {\&{xclause}}
proc_like: begin sc4(force)(backup)(res_flag+p)(cancel)(proc);
  sc3(indent)("\")(" ")(intro);
@.\\\ @>
  end; {\&{function}, \&{procedure}, \&{program}}
record_like: begin sc1(res_flag+p)(record_head); sc0(intro);
  end; {\&{record}}
repeat_like: begin sc4(force)(indent)(res_flag+p)(cancel)(beginning);
  sc0(intro);
  end; {\&{repeat}}
until_like: begin @<Append |term...@>;
  sc3(force)(backup)(res_flag+p)(close); sc0(clause);
  end; {\&{until}}
var_like: begin sc4(force)(backup)(res_flag+p)(cancel)(var_head); sc0(intro);
  end; {\&{var}}

@ If a comment or semicolon appears before the reserved words \&{end},
\&{else}, or \&{until}, the |semi| or |terminator| scrap that is already
present overrides the |terminator| scrap belonging to this reserved word.

@<Append |termin...@>=
if (scrap_ptr<scrap_base)or((cat[scrap_ptr]<>terminator)and
    (cat[scrap_ptr]<>semi)) then sc0(terminator)

@ A comment is incorporated into the previous scrap if that scrap is of type
|omega| or |semi| or |terminator|. (These three categories have consecutive
category codes.) Otherwise the comment is entered as a separate scrap
of type |terminator|, and it will combine with a |terminator| scrap that
immediately follows~it.

The |app_comment| procedure takes care of placing a comment at the end of the
current scrap list. When |app_comment| is called, we assume that the current
token list is the translation of the comment involved.

@<Declaration of the |app_comment|...@>=
procedure app_comment; {append a comment to the scrap list}
begin freeze_text;
if (scrap_ptr<scrap_base)or(cat[scrap_ptr]<omega)or
    (cat[scrap_ptr]>terminator) then sc0(terminator)
else  begin app1(scrap_ptr); {|cat[scrap_ptr]| is
    |omega| or |semi| or |terminator|}
  end;
app(text_ptr-1+tok_flag); trans[scrap_ptr]:=text_ptr; freeze_text;
end;

@ We are now finished with |Pascal_parse|, except for two relatively
trivial subprocedures that convert constants into tokens.

@<Declaration of the |app_octal| and...@>=
procedure app_octal;
begin app("\"); app("O"); app("{");
@.\\O@>
while (buffer[loc]>="0")and(buffer[loc]<="7") do
  begin app_tok(buffer[loc]); incr(loc);
  end;
sc1("}")(simp);
end;
@#
procedure app_hex;
begin app("\"); app("H"); app("{");
@.\\H@>
while ((buffer[loc]>="0")and(buffer[loc]<="9"))or@|
    ((buffer[loc]>="A")and(buffer[loc]<="F")) do
  begin app_tok(buffer[loc]); incr(loc);
  end;
sc1("}")(simp);
end;


@ When the `\v' that introduces \PASCAL\ text is sensed, a call on
|Pascal_translate| will return a pointer to the \TeX\ translation of
that text. If scraps exist in the |cat| and |trans| arrays, they are
unaffected by this translation process.

@p function Pascal_translate: text_pointer;
var p:text_pointer; {points to the translation}
@!save_base:0..max_scraps; {holds original value of |scrap_base|}
begin save_base:=scrap_base; scrap_base:=scrap_ptr+1;
Pascal_parse; {get the scraps together}
if next_control<>"|" then err_print('! Missing "|" after Pascal text');
@.Missing "|"...@>
app_tok(cancel); app_comment; {place a |cancel| token as a final ``comment''}
p:=translate; {make the translation}
stat if scrap_ptr>max_scr_ptr then max_scr_ptr:=scrap_ptr;@;@+tats@;@/
scrap_ptr:=scrap_base-1; scrap_base:=save_base; {scrap the scraps}
Pascal_translate:=p;
end;

@ The |outer_parse| routine is to |Pascal_parse| as |outer_xref|
is to |Pascal_xref|: It constructs a sequence of scraps for \PASCAL\ text
until |next_control>=format|. Thus, it takes care of embedded comments.

@p procedure outer_parse; {makes scraps from \PASCAL\ tokens and comments}
var bal:eight_bits; {brace level in comment}
@!p,@!q:text_pointer; {partial comments}
begin while next_control<format do
  if next_control<>"{" then Pascal_parse
  else  begin @<Make sure that there is room for at least seven more
      tokens, three more texts, and one more scrap@>;
    app("\"); app("C"); app("{");
@.\\C@>
    bal:=copy_comment(1); next_control:="|";
    while bal>0 do
      begin p:=text_ptr; freeze_text; q:=Pascal_translate;
      {at this point we have |tok_ptr+6<=max_toks|}
      app(tok_flag+p); app(inner_tok_flag+q);
      if next_control="|" then bal:=copy_comment(bal)
      else bal:=0; {an error has been reported}
      end;
    app(force); app_comment; {the full comment becomes a scrap}
    end;
end;

@ @<Make sure that there is room for at least seven more...@>=
if (tok_ptr+7>max_toks)or(text_ptr+3>max_texts)or(scrap_ptr>=max_scraps) then
  begin stat if scrap_ptr>max_scr_ptr then max_scr_ptr:=scrap_ptr;
  if tok_ptr>max_tok_ptr then max_tok_ptr:=tok_ptr;
  if text_ptr>max_txt_ptr then max_txt_ptr:=text_ptr;
  tats@;@/
  overflow('token/text/scrap');
  end

@* Output of tokens.
So far our programs have only built up multi-layered token lists in
\.{WEAVE}'s internal memory; we have to figure out how to get them into
the desired final form. The job of converting token lists to characters in
the \TeX\ output file is not difficult, although it is an implicitly
recursive process. Four main considerations had to be kept in mind when
this part of \.{WEAVE} was designed.  (a) There are two modes of output:
|outer| mode, which translates tokens like |force| into line-breaking
control sequences, and |inner| mode, which ignores them except that blank
spaces take the place of line breaks. (b) The |cancel| instruction applies
to adjacent token or tokens that are output, and this cuts across levels
of recursion since `|cancel|' occurs at the beginning or end of a token
list on one level. (c) The \TeX\ output file will be semi-readable if line
breaks are inserted after the result of tokens like |break_space| and
|force|.  (d) The final line break should be suppressed, and there should
be no |force| token output immediately after `\.{\\Y\\P}'.

@ The output process uses a stack to keep track of what is going on at
different ``levels'' as the token lists are being written out. Entries on
this stack have three parts:

\yskip\hang |end_field| is the |tok_mem| location where the token list of a
particular level will end;

\yskip\hang |tok_field| is the |tok_mem| location from which the next token
on a particular level will be read;

\yskip\hang |mode_field| is the current mode, either |inner| or |outer|.

\yskip\noindent The current values of these quantities are referred to
quite frequently, so they are stored in a separate place instead of in the
|stack| array. We call the current values |cur_end|, |cur_tok|, and
|cur_mode|.

The global variable |stack_ptr| tells how many levels of output are
currently in progress. The end of output occurs when an |end_translation|
token is found, so the stack is never empty except when we first begin the
output process.

@d inner=0 {value of |mode| for \PASCAL\ texts within \TeX\ texts}
@d outer=1 {value of |mode| for \PASCAL\ texts in modules}

@<Types...@>=
@!mode=inner..outer;@/
@!output_state=record@!end_field:sixteen_bits; {ending location of token list}
  @!tok_field:sixteen_bits; {present location within token list}
  @!mode_field:mode; {interpretation of control tokens}
  end;

@ @d cur_end==cur_state.end_field {current ending location in |tok_mem|}
@d cur_tok==cur_state.tok_field {location of next output token in |tok_mem|}
@d cur_mode==cur_state.mode_field {current mode of interpretation}
@d init_stack==stack_ptr:=0;cur_mode:=outer {do this to initialize the stack}

@<Glob...@>=
@!cur_state:output_state; {|cur_end|, |cur_tok|, |cur_mode|}
@!stack:array[1..stack_size] of output_state; {info for non-current levels}
@!stack_ptr:0..stack_size; {first unused location in the output state stack}
stat@!max_stack_ptr:0..stack_size; {largest value assumed by |stack_ptr|}
tats

@ @<Set init...@>=stat max_stack_ptr:=0;@+tats

@ To insert token-list |p| into the output, the |push_level| subroutine
is called; it saves the old level of output and gets a new one going.
The value of |cur_mode| is not changed.

@p procedure push_level(@!p:text_pointer); {suspends the current level}
begin if stack_ptr=stack_size then overflow('stack')
else  begin if stack_ptr>0 then
    stack[stack_ptr]:=cur_state; {save |cur_end|$\,\ldots\,$|cur_mode|}
  incr(stack_ptr);
  stat if stack_ptr>max_stack_ptr then
    max_stack_ptr:=stack_ptr;@;@+tats@;@/
  cur_tok:=tok_start[p]; cur_end:=tok_start[p+1];
  end;
end;

@ Conversely, the |pop_level| routine restores the conditions that were in
force when the current level was begun. This subroutine will never be
called when |stack_ptr=1|. It is so simple, we declare it as a macro:

@d pop_level==begin decr(stack_ptr); cur_state:=stack[stack_ptr];
  end {do this when |cur_tok| reaches |cur_end|}

@ The |get_output| function returns the next byte of output that is not a
reference to a token list. It returns the values |identifier| or |res_word|
or |mod_name| if the next token is to be an identifier (typeset in
italics), a reserved word (typeset in boldface) or a module name (typeset
by a complex routine that might generate additional levels of output).
In these cases |cur_name| points to the identifier or module name in
question.

@d res_word=@'201 {returned by |get_output| for reserved words}
@d mod_name=@'200 {returned by |get_output| for module names}

@p function get_output:eight_bits; {returns the next token of output}
label restart;
var a:sixteen_bits; {current item read from |tok_mem|}
begin restart: while cur_tok=cur_end do pop_level;
a:=tok_mem[cur_tok]; incr(cur_tok);
if a>=@'400 then
  begin cur_name:=a mod id_flag;
  case a div id_flag of
  2: a:=res_word; {|a=res_flag+cur_name|}
  3: a:=mod_name; {|a=mod_flag+cur_name|}
  4: begin push_level(cur_name); goto restart;
    end; {|a=tok_flag+cur_name|}
  5: begin push_level(cur_name); cur_mode:=inner; goto restart;
    end; {|a=inner_tok_flag+cur_name|}
  othercases a:=identifier {|a=id_flag+cur_name|}
  endcases;
  end;
@!debug if trouble_shooting then debug_help; @+ gubed@/
get_output:=a;
end;

@ The real work associated with token output is done by |make_output|.
This procedure appends an |end_translation| token to the current token list,
and then it repeatedly calls |get_output| and feeds characters to the output
buffer until reaching the |end_translation| sentinel. It is possible for
|make_output| to
be called recursively, since a module name may include embedded \PASCAL\
text; however, the depth of recursion never exceeds one level, since
module names cannot be inside of module names.

A procedure called |output_Pascal| does the scanning, translation, and
output of \PASCAL\ text within `\pb' brackets, and this procedure uses
|make_output| to output the current token list. Thus, the recursive call
of |make_output| actually occurs when |make_output| calls |output_Pascal|
while outputting the name of a module.
@^recursion@>

@p procedure make_output; forward; @t\2@>@#
procedure output_Pascal; {outputs the current token list}
var save_tok_ptr,@!save_text_ptr,@!save_next_control:sixteen_bits;
  {values to be restored}
p:text_pointer; {translation of the \PASCAL\ text}
begin save_tok_ptr:=tok_ptr; save_text_ptr:=text_ptr;
save_next_control:=next_control; next_control:="|"; p:=Pascal_translate;
app(p+inner_tok_flag);
make_output; {output the list}
stat if text_ptr>max_txt_ptr then max_txt_ptr:=text_ptr;
if tok_ptr>max_tok_ptr then max_tok_ptr:=tok_ptr;@;@+tats@;@/
text_ptr:=save_text_ptr; tok_ptr:=save_tok_ptr; {forget the tokens}
next_control:=save_next_control; {restore |next_control| to original state}
end;

@ Here is \.{WEAVE}'s major output handler.

@p procedure make_output; {outputs the equivalents of tokens}
label reswitch,exit,found;
var a:eight_bits; {current output byte}
@!b:eight_bits; {next output byte}
@!k,@!k_limit:0..max_bytes; {indices into |byte_mem|}
@!w:0..ww-1; {row of |byte_mem|}
@!j:0..long_buf_size; {index into |buffer|}
@!string_delimiter:ASCII_code; {first and last character of
  string being copied}
@!save_loc,@!save_limit:0..long_buf_size; {|loc| and |limit| to be restored}
@!cur_mod_name:name_pointer; {name of module being output}
@!save_mode:mode; {value of |cur_mode| before a sequence of breaks}
begin app(end_translation); {append a sentinel}
freeze_text; push_level(text_ptr-1);
loop@+  begin a:=get_output;
reswitch: case a of
  end_translation: return;
  identifier,res_word:@<Output an identifier@>;
  mod_name:@<Output a module name@>;
  math_bin,math_op,math_rel:@<Output a \.{\\math} operator@>;
  cancel: begin repeat a:=get_output;
    until (a<backup)or(a>big_force);
    goto reswitch;
    end;
  big_cancel: begin repeat a:=get_output;
    until ((a<backup)and(a<>" "))or(a>big_force);
    goto reswitch;
    end;
  indent,outdent,opt,backup,break_space,force,big_force:@<Output a
    \(control, look ahead in case of line breaks,
    possibly |goto reswitch|@>;
  othercases out(a) {otherwise |a| is an ASCII character}
  endcases;
  end;
exit:end;

@ An identifier of length one does not have to be enclosed in braces, and it
looks slightly better if set in a math-italic font instead of a (slightly
narrower) text-italic font. Thus we output `\.{\\\char'174a}' but
`\.{\\\\\{aa\}}'.

@<Output an identifier@>=
begin out("\");
if a=identifier then
  if length(cur_name)=1 then out("|")
@.\\|@>
  else out("\")
@.\\\\@>
else out("&"); {|a=res_word|}
@.\\\&@>
if length(cur_name)=1 then out(byte_mem[cur_name mod ww,byte_start[cur_name]])
else out_name(cur_name);
end

@ @<Output a \....@>=
begin out5("\")("m")("a")("t")("h");
if a=math_bin then out3("b")("i")("n")
else if a=math_rel then out3("r")("e")("l")
else out2("o")("p");
out("{");
end

@ The current mode does not affect the behavior of \.{WEAVE}'s output routine
except when we are outputting control tokens.

@<Output a \(control...@>=
if a<break_space then
  begin if cur_mode=outer then
    begin out2("\")(a-cancel+"0");
@.\\1@>
@.\\2@>
@.\\3@>
@.\\4@>
@.\\5@>
@.\\6@>
@.\\7@>
    if a=opt then out(get_output) {|opt| is followed by a digit}
    end
  else if a=opt then b:=get_output {ignore digit following |opt|}
  end
else @<Look ahead for strongest line break, |goto reswitch|@>

@ If several of the tokens |break_space|, |force|, |big_force| occur in a
row, possibly mixed with blank spaces (which are ignored),
the largest one is used. A line break also occurs in the output file,
except at the very end of the translation. The very first line break
is suppressed (i.e., a line break that follows `\.{\\Y\\P}').

@<Look ahead for st...@>=
begin b:=a; save_mode:=cur_mode;
loop@+  begin a:=get_output;
  if (a=cancel)or(a=big_cancel) then goto reswitch;
    {|cancel| overrides everything}
  if ((a<>" ")and(a<break_space))or(a>big_force) then
    begin if save_mode=outer then
      begin if out_ptr>3 then
        if (out_buf[out_ptr]="P")and
          (out_buf[out_ptr-1]="\")and
@.\\P@>
@.\\Y@>
          (out_buf[out_ptr-2]="Y")and
          (out_buf[out_ptr-3]="\") then
          goto reswitch;
@.\\1@>
@.\\2@>
@.\\3@>
@.\\4@>
@.\\5@>
@.\\6@>
@.\\7@>
      out2("\")(b-cancel+"0");
      if a<>end_translation then finish_line;
      end
    else if (a<>end_translation)and(cur_mode=inner) then out(" ");
    goto reswitch;
    end;
  if a>b then b:=a; {if |a=" "| we have |a<b|}
  end;
end

@ The remaining part of |make_output| is somewhat more complicated. When we
output a module name, we may need to enter the parsing and translation
routines, since the name may contain \PASCAL\ code embedded in
\pb\ constructions. This \PASCAL\ code is placed at the end of the active
input buffer and the translation process uses the end of the active
|tok_mem| area.

@<Output a module name@>=
begin out2("\")("X");
@.\\X@>
cur_xref:=xref[cur_name];
if num(cur_xref)>=def_flag then
  begin out_mod(num(cur_xref)-def_flag);
  if phase_three then
    begin cur_xref:=xlink(cur_xref);
    while num(cur_xref)>=def_flag do
      begin out2(",")(" ");
      out_mod(num(cur_xref)-def_flag);
      cur_xref:=xlink(cur_xref);
      end;
    end;
  end
else out("0"); {output the module number, or zero if it was undefined}
out(":"); @<Output the text of the module name@>;
out2("\")("X");
end

@ @<Output the text...@>=
k:=byte_start[cur_name]; w:=cur_name mod ww; k_limit:=byte_start[cur_name+ww];
cur_mod_name:=cur_name;
while k<k_limit do
  begin b:=byte_mem[w,k]; incr(k);
  if b="@@" then @<Skip next character, give error if not `\.{@@}'@>;
  if b<>"|" then out(b)
  else  begin @<Copy the \PASCAL\ text into |buffer[(limit+1)..j]|@>;
    save_loc:=loc; save_limit:=limit; loc:=limit+2; limit:=j+1;
    buffer[limit]:="|"; output_Pascal;
    loc:=save_loc; limit:=save_limit;
    end;
  end

@ @<Skip next char...@>=
begin if byte_mem[w,k]<>"@@" then
  begin print_nl('! Illegal control code in section name:');
@.Illegal control code...@>
  print_nl('<'); print_id(cur_mod_name); print('> '); mark_error;
  end;
incr(k);
end

@ The \PASCAL\ text enclosed in \pb\ should not contain `\v' characters,
except within strings. We put a `\v' at the front of the buffer, so that an
error message that displays the whole buffer will look a little bit sensible.
The variable |string_delimiter| is zero outside of strings, otherwise it
equals the delimiter that began the string being copied.

@<Copy the \PASCAL\ text into...@>=
j:=limit+1; buffer[j]:="|"; string_delimiter:=0;
loop@+  begin if k>=k_limit then
    begin print_nl('! Pascal text in section name didn''t end:');
@.Pascal text...didn't end@>
    print_nl('<'); print_id(cur_mod_name); print('> '); mark_error;
    goto found;
    end;
  b:=byte_mem[w,k]; incr(k);
  if b="@@" then @<Copy a control code into the buffer@>
  else  begin if (b="""")or(b="'") then
      if string_delimiter=0 then string_delimiter:=b
      else if string_delimiter=b then string_delimiter:=0;
    if (b<>"|")or(string_delimiter<>0) then
      begin if j>long_buf_size-3 then overflow('buffer');
      incr(j); buffer[j]:=b;
      end
    else goto found;
    end;
  end;
found:

@ @<Copy a control code into the buffer@>=
begin if j>long_buf_size-4 then overflow('buffer');
buffer[j+1]:="@@"; buffer[j+2]:=byte_mem[w,k]; j:=j+2; incr(k);
end

@* Phase two processing.
We have assembled enough pieces of the puzzle in order to be ready to specify
the processing in \.{WEAVE}'s main pass over the source file. Phase two
is analogous to phase one, except that more work is involved because we must
actually output the \TeX\ material instead of merely looking at the
\.{WEB} specifications.

@<Phase II: Read all the text again and translate it to \TeX\ form@>=
reset_input; print_nl('Writing the output file...');
module_count:=0;
copy_limbo;
finish_line; flush_buffer(0,false,false); {insert a blank line, it looks nice}
while not input_has_ended do @<Translate the \(current module@>

@ The output file will contain the control sequence \.{\\Y} between non-null
sections of a module, e.g., between the \TeX\ and definition parts if both
are nonempty. This puts a little white space between the parts when they are
printed. However, we don't want \.{\\Y} to occur between two definitions
within a single module. The variables |out_line| or |out_ptr| will
change if a section is non-null, so the following macros `|save_position|'
and `|emit_space_if_needed|' are able to handle the situation:

@d save_position==save_line:=out_line; save_place:=out_ptr
@d emit_space_if_needed==if (save_line<>out_line)or(save_place<>out_ptr) then
  out2("\")("Y")
@.\\Y@>

@<Glo...@>=
@!save_line:integer; {former value of |out_line|}
@!save_place:sixteen_bits; {former value of |out_ptr|}

@ @<Translate the \(current module@>=
begin incr(module_count);@/
@<Output the code for the beginning of a new module@>;
save_position;@/
@<Translate the \TeX\ part of the current module@>;
@<Translate the \(definition part of the current module@>;
@<Translate the \PASCAL\ part of the current module@>;
@<Show cross references to this module@>;
@<Output the code for the end of a module@>;
end

@ Modules beginning with the \.{WEB} control sequence `\.{@@\ }' start in the
output with the \TeX\ control sequence `\.{\\M}', followed by the module
number. Similarly, `\.{@@*}' modules lead to the control sequence `\.{\\N}'.
If this is a changed module, we put \.{*} just before the module number.

@<Output the code for the beginning...@>=
out("\");
if buffer[loc-1]<>"*" then out("M")
@.\\M@>
else  begin out("N"); print('*',module_count:1);
@.\\N@>
  update_terminal; {print a progress report}
  end;
out_mod(module_count); out2(".")(" ")

@ In the \TeX\ part of a module, we simply copy the source text, except that
index entries are not copied and \PASCAL\ text within \pb\ is translated.

@<Translate the \T...@>=
repeat next_control:=copy_TeX;
case next_control of
"|": begin init_stack; output_Pascal;
  end;
"@@": out("@@");
octal: @<Translate an octal constant appearing in \TeX\ text@>;
hex: @<Translate a hexadecimal constant appearing in \TeX\ text@>;
TeX_string,xref_roman,xref_wildcard,xref_typewriter,module_name:
  begin loc:=loc-2; next_control:=get_next; {skip to \.{@@>}}
  if next_control=TeX_string then
    err_print('! TeX string should be in Pascal text only');
@.TeX string should be...@>
  end;
begin_comment,end_comment,check_sum,thin_space,math_break,line_break,
  big_line_break,no_line_break,join,pseudo_semi:
    err_print('! You can''t do that in TeX text');
@.You can't do that...@>
othercases do_nothing
endcases;
until next_control>=format

@ @<Translate an octal constant appearing in \TeX\ text@>=
begin out3("\")("O")("{");
@.\\O@>
while (buffer[loc]>="0")and(buffer[loc]<="7") do
  begin out(buffer[loc]); incr(loc);
  end; {since |buffer[limit]=" "|, this loop will end}
out("}");
end

@ @<Translate a hexadecimal constant appearing in \TeX\ text@>=
begin out3("\")("H")("{");
@.\\H@>
while ((buffer[loc]>="0")and(buffer[loc]<="9"))or@|
    ((buffer[loc]>="A")and(buffer[loc]<="F")) do
  begin out(buffer[loc]); incr(loc);
  end;
out("}");
end
@ When we get to the following code we have |next_control>=format|, and
the token memory is in its initial empty state.

@<Translate the \(d...@>=
if next_control<=definition then {definition part non-empty}
  begin emit_space_if_needed; save_position;
  end;
while next_control<=definition do {|format| or |definition|}
  begin init_stack;
  if next_control=definition then @<Start a macro definition@>
  else @<Start a format definition@>;
  outer_parse; finish_Pascal;
  end

@ The |finish_Pascal| procedure outputs the translation of the current
scraps, preceded by the control sequence `\.{\\P}' and followed by the
control sequence `\.{\\par}'. It also restores the token and scrap
memories to their initial empty state.

A |force| token is appended to the current scraps before translation
takes place, so that the translation will normally end with \.{\\6} or
\.{\\7} (the \TeX\ macros for |force| and |big_force|). This \.{\\6} or
\.{\\7} is replaced by the concluding \.{\\par} or by \.{\\Y\\par}.

@p procedure finish_Pascal; {finishes a definition or a \PASCAL\ part}
var p:text_pointer; {translation of the scraps}
begin out2("\")("P"); app_tok(force); app_comment; p:=translate;
@.\\P@>
app(p+tok_flag); make_output; {output the list}
if out_ptr>1 then
  if out_buf[out_ptr-1]="\" then
@.\\6@>
@.\\7@>
@.\\Y@>
    if out_buf[out_ptr]="6" then out_ptr:=out_ptr-2
    else if out_buf[out_ptr]="7" then out_buf[out_ptr]:="Y";
out4("\")("p")("a")("r"); finish_line;
stat if text_ptr>max_txt_ptr then max_txt_ptr:=text_ptr;
if tok_ptr>max_tok_ptr then max_tok_ptr:=tok_ptr;
if scrap_ptr>max_scr_ptr then max_scr_ptr:=scrap_ptr;
tats@;@/
tok_ptr:=1; text_ptr:=1; scrap_ptr:=0; {forget the tokens and the scraps}
end;

@ @<Start a macro...@>=
begin sc2("\")("D")(intro); {this will produce `\&{define }'}
@.\\D@>
next_control:=get_next;
if next_control<>identifier then err_print('! Improper macro definition')
@.Improper macro definition@>
else sc1(id_flag+id_lookup(normal))(math);
next_control:=get_next;
end

@ @<Start a format...@>=
begin sc2("\")("F")(intro); {this will produce `\&{format }'}
@.\\F@>
next_control:=get_next;
if next_control=identifier then
  begin sc1(id_flag+id_lookup(normal))(math);
  next_control:=get_next;
  if next_control=equivalence_sign then
    begin sc2("\")("S")(math); {output an equivalence sign}
@.\\S@>
    next_control:=get_next;
    if next_control=identifier then
      begin sc1(id_flag+id_lookup(normal))(math);
      sc0(semi); {insert an invisible semicolon}
      next_control:=get_next;
      end;
    end;
  end;
if scrap_ptr<>5 then err_print('! Improper format definition');
@.Improper format definition@>
end

@ Finally, when the \TeX\ and definition parts have been treated, we have
|next_control>=begin_Pascal|. We will make the global variable |this_module|
point to the current module name, if it has a name.

@<Glob...@>=@!this_module:name_pointer; {the current module name, or zero}

@ @<Translate the \P...@>=
this_module:=0;
if next_control<=module_name then
  begin emit_space_if_needed; init_stack;
  if next_control=begin_Pascal then next_control:=get_next
  else  begin this_module:=cur_module;
    @<Check that |=| or |==| follows this module name, and
      emit the scraps to start the module definition@>;
    end;
  while next_control<=module_name do
    begin outer_parse;
    @<Emit the scrap for a module name if present@>;
    end;
  finish_Pascal;
  end

@ @<Check that |=|...@>=
repeat next_control:=get_next;
until next_control<>"+"; {allow optional `\.{+=}'}
if (next_control<>"=")and(next_control<>equivalence_sign) then
  err_print('! You need an = sign after the section name')
@.You need an = sign...@>
else next_control:=get_next;
if out_ptr>1 then
  if (out_buf[out_ptr]="Y")and(out_buf[out_ptr-1]="\") then
@.\\Y@>
    begin app(backup); {the module name will be flush left}
    end;
sc1(mod_flag+this_module)(mod_scrap);
cur_xref:=xref[this_module];
if num(cur_xref)<>module_count+def_flag then
  begin sc3(math_rel)("+")("}")(math);
    {module name is multiply defined}
  this_module:=0; {so we won't give cross-reference info here}
  end;
sc2("\")("S")(math); {output an equivalence sign}
@.\\S@>
sc1(force)(semi); {this forces a line break unless `\.{@@+}' follows}

@ @<Emit the scrap...@>=
if next_control<module_name then
  begin err_print('! You can''t do that in Pascal text');
@.You can't do that...@>
  next_control:=get_next;
  end
else if next_control=module_name then
  begin sc1(mod_flag+cur_module)(mod_scrap); next_control:=get_next;
  end

@ Cross references relating to a named module are given after the module ends.

@<Show cross...@>=
if this_module>0 then
  begin @<Rearrange the list pointed to by |cur_xref|@>;
  footnote(def_flag); footnote(0);
  end

@ To rearrange the order of the linked list of cross references, we need
four more variables that point to cross reference entries.  We'll end up
with a list pointed to by |cur_xref|.

@<Glob...@>=
@!next_xref,@!this_xref,@!first_xref,@!mid_xref:xref_number;
  {pointer variables for rearranging a list}

@ We want to rearrange the cross reference list so that all the entries with
|def_flag| come first, in ascending order; then come all the other
entries, in ascending order.  There may be no entries in either one or both
of these categories.

@<Rearrange the list...@>=
first_xref:=xref[this_module];
this_xref:=xlink(first_xref); {bypass current module number}
if num(this_xref)>def_flag then
  begin mid_xref:=this_xref; cur_xref:=0; {this value doesn't matter}
  repeat  next_xref:=xlink(this_xref); xlink(this_xref):=cur_xref;
    cur_xref:=this_xref; this_xref:=next_xref;
  until num(this_xref)<=def_flag;
  xlink(first_xref):=cur_xref;
  end
else mid_xref:=0; {first list null}
cur_xref:=0;
while this_xref<>0 do
  begin next_xref:=xlink(this_xref); xlink(this_xref):=cur_xref;
  cur_xref:=this_xref; this_xref:=next_xref;
  end;
if mid_xref>0 then xlink(mid_xref):=cur_xref
else xlink(first_xref):=cur_xref;
cur_xref:=xlink(first_xref)

@ The |footnote| procedure gives cross reference information about
multiply defined module names (if the |flag| parameter is |def_flag|), or about
the uses of a module name (if the |flag| parameter is zero). It assumes that
|cur_xref| points to the first cross-reference entry of interest, and it
leaves |cur_xref| pointing to the first element not printed.  Typical outputs:
`\.{\\A101.}'; `\.{\\Us370\\ET1009.}'; `\.{\\As8, 27\\*, 51\\ETs64.}'.

@p procedure footnote(@!flag:sixteen_bits); {outputs module cross-references}
label done,exit;
var q:xref_number; {cross-reference pointer variable}
begin if num(cur_xref)<=flag then return;
finish_line; out("\");
@.\\A@>
@.\\U@>
if flag=0 then out("U")@+else out("A");
@<Output all the module numbers on the reference list |cur_xref|@>;
out(".");
exit:end;

@ The following code distinguishes three cases, according as the number
of cross references is one, two, or more than two. Variable |q| points
to the first cross reference, and the last link is a zero.

@<Output all the module numbers...@>=
q:=cur_xref; if num(xlink(q))>flag then out("s"); {plural}
@.\\As@>
@.\\Us@>
loop@+  begin out_mod(num(cur_xref)-flag);
  cur_xref:=xlink(cur_xref); {point to the next cross reference to output}
  if num(cur_xref)<=flag then goto done;
  if num(xlink(cur_xref))>flag then out2(",")(" ") {not the last}
  else begin out3("\")("E")("T"); {the last}
@.\\ET@>
    if cur_xref<>xlink(q) then out("s"); {the last of more than two}
@.\\ETs@>
    end;
  end;
done:

@ @<Output the code for the end of a module@>=
out3("\")("f")("i"); finish_line;
flush_buffer(0,false,false); {insert a blank line, it looks nice}
@.\\fi@>

@* Phase three processing.
We are nearly finished! \.{WEAVE}'s only remaining task is to write out the
index, after sorting the identifiers and index entries.

@<Phase III: Output the cross-reference index@>=
phase_three:=true; print_nl('Writing the index...');
if change_exists then
  begin finish_line; @<Tell about changed modules@>;
  end;
finish_line; out4("\")("i")("n")("x"); finish_line;
@.\\inx@>
@<Do the first pass of sorting@>;
@<Sort and output the index@>;
out4("\")("f")("i")("n"); finish_line;
@.\\fin@>
@<Output all the module names@>;
out4("\")("c")("o")("n"); finish_line;
@.\\con@>
print('Done.');

@ Just before the index comes a list of all the changed modules, including
the index module itself.

@<Glob...@>=
@!k_module:0..max_modules; {runs through the modules}

@ @<Tell about changed modules@>=
begin {remember that the index is already marked as changed}
k_module:=1;
out4("\")("c")("h")(" ");
while k_module<module_count do
  begin if changed_module[k_module] then
    begin out_mod(k_module); out2(",")(" ");
    end;
  incr(k_module);
  end;
out_mod(k_module);
out(".");
end

@ A left-to-right radix sorting method is used, since this makes it easy to
adjust the collating sequence and since the running time will be at worst
proportional to the total length of all entries in the index. We put the
identifiers into 230 different lists based on their first characters.
(Uppercase letters are put into the same list as the corresponding lowercase
letters, since we want to have `$t<\\{TeX}<\&{to}$'.) The
list for character |c| begins at location |bucket[c]| and continues through
the |blink| array.

@<Glob...@>=
@!bucket:array[ASCII_code] of name_pointer;
@!next_name: name_pointer; {successor of |cur_name| when sorting}
@!c:ASCII_code; {index into |bucket|}
@!h:0..hash_size; {index into |hash|}
@!blink:array[0..max_names] of sixteen_bits; {links in the buckets}

@ To begin the sorting, we go through all the hash lists and put each entry
having a nonempty cross-reference list into the proper bucket.

@<Do the first pass...@>=
for c:=0 to 255 do bucket[c]:=0;
for h:=0 to hash_size-1 do
  begin next_name:=hash[h];
  while next_name<>0 do
    begin cur_name:=next_name; next_name:=link[cur_name];
    if xref[cur_name]<>0 then
      begin c:=byte_mem[cur_name mod ww,byte_start[cur_name]];
      if (c<="Z")and(c>="A") then c:=c+@'40;
      blink[cur_name]:=bucket[c]; bucket[c]:=cur_name;
      end;
    end;
  end

@ During the sorting phase we shall use the |cat| and |trans| arrays from
\.{WEAVE}'s parsing algorithm and rename them |depth| and |head|. They now
represent a stack of identifier lists for all the index entries that have
not yet been output. The variable |sort_ptr| tells how many such lists are
present; the lists are output in reverse order (first |sort_ptr|, then
|sort_ptr-1|, etc.). The |j|th list starts at |head[j]|, and if the first
|k| characters of all entries on this list are known to be equal we have
|depth[j]=k|.

@d depth==cat {reclaims memory that is no longer needed for parsing}
@d head==trans {ditto}
@d sort_ptr==scrap_ptr {ditto}
@d max_sorts==max_scraps {ditto}

@<Globals...@>=
@!cur_depth:eight_bits; {depth of current buckets}
@!cur_byte:0..max_bytes; {index into |byte_mem|}
@!cur_bank:0..ww-1; {row of |byte_mem|}
@!cur_val:sixteen_bits; {current cross reference number}
stat@!max_sort_ptr:0..max_sorts;@+tats {largest value of |sort_ptr|}

@ @<Set init...@>=stat max_sort_ptr:=0;@+tats

@ The desired alphabetic order is specified by the |collate| array; namely,
|collate[0]<collate[1]<@t$\cdots$@><collate[229]|.

@<Glob...@>=@!collate:array[0..229] of ASCII_code; {collation order}

@ @<Local variables for init...@>=
@!c:ASCII_code; {used to initialize |collate|}

@ We use the order $\hbox{null}<\.\ <\hbox{other characters}<\.\_<
\.A=\.a<\cdots<\.Z=\.z<\.0<\cdots<\.9.$

@<Set init...@>=
collate[0]:=0; collate[1]:=" ";
for c:=1 to " "-1 do collate[c+1]:=c;
for c:=" "+1 to "0"-1 do collate[c]:=c;
for c:="9"+1 to "A"-1 do collate[c-10]:=c;
for c:="Z"+1 to "_"-1 do collate[c-36]:=c;
collate["_"-36]:="_"+1;
for c:="z"+1 to 255 do collate[c-63]:=c;
collate[193]:="_";
for c:="a" to "z" do collate[c-"a"+194]:=c;
for c:="0" to "9" do collate[c-"0"+220]:=c;

@ Procedure |unbucket| goes through the buckets and adds nonempty lists
to the stack, using the collating sequence specified in the |collate| array.
The parameter to |unbucket| tells the current depth in the buckets.
Any two sequences that agree in their first 255 character positions are
regarded as identical.

@d infinity=255 {$\infty$ (approximately)}

@p procedure unbucket(@!d:eight_bits); {empties buckets having depth |d|}
var c:ASCII_code; {index into |bucket|}
begin for c:=229 downto 0 do if bucket[collate[c]]>0 then
  begin if sort_ptr>max_sorts then overflow('sorting');
  incr(sort_ptr);
  stat if sort_ptr>max_sort_ptr then max_sort_ptr:=sort_ptr;@;@+tats@;@/
  if c=0 then depth[sort_ptr]:=infinity else depth[sort_ptr]:=d;
  head[sort_ptr]:=bucket[collate[c]]; bucket[collate[c]]:=0;
  end;
end;

@ @<Sort and output...@>=
sort_ptr:=0; unbucket(1);
while sort_ptr>0 do
  begin cur_depth:=cat[sort_ptr];
  if (blink[head[sort_ptr]]=0)or(cur_depth=infinity) then
    @<Output index entries for the list at |sort_ptr|@>
  else @<Split the list at |sort_ptr| into further lists@>;
  end

@ @<Split the list...@>=
begin next_name:=head[sort_ptr];
repeat cur_name:=next_name; next_name:=blink[cur_name];
  cur_byte:=byte_start[cur_name]+cur_depth; cur_bank:=cur_name mod ww;
  if cur_byte=byte_start[cur_name+ww] then c:=0 {we hit the end of the name}
  else  begin c:=byte_mem[cur_bank,cur_byte];
    if (c<="Z")and(c>="A") then c:=c+@'40;
    end;
  blink[cur_name]:=bucket[c]; bucket[c]:=cur_name;
until next_name=0;
decr(sort_ptr); unbucket(cur_depth+1);
end

@ @<Output index...@>=
begin cur_name:=head[sort_ptr];
@!debug if trouble_shooting then debug_help;@;@+gubed@/
repeat out2("\")(":");
@.\\:@>
  @<Output the name at |cur_name|@>;
  @<Output the cross-references at |cur_name|@>;
  cur_name:=blink[cur_name];
until cur_name=0;
decr(sort_ptr);
end

@ @<Output the name...@>=
case ilk[cur_name] of
normal: if length(cur_name)=1 then out2("\")("|")@+else out2("\")("\");
@.\\|@>
@.\\\\@>
roman: do_nothing;
wildcard: out2("\")("9");
@.\\9@>
typewriter: out2("\")(".");
@.\\.@>
othercases out2("\")("&")
@.\\\&@>
endcases;@/
out_name(cur_name)

@ Section numbers that are to be underlined are enclosed in
`\.{\\[}$\,\ldots\,$\.]'.

@<Output the cross-references...@>=
@<Invert the cross-reference list at |cur_name|, making |cur_xref| the head@>;
repeat out2(",")(" "); cur_val:=num(cur_xref);
if cur_val<def_flag then out_mod(cur_val)
else  begin out2("\")("["); out_mod(cur_val-def_flag); out("]");
@.\\[@>
  end;
cur_xref:=xlink(cur_xref);
until cur_xref=0;
out("."); finish_line

@ List inversion is best thought of as popping elements off one stack and
pushing them onto another. In this case |cur_xref| will be the head of
the stack that we push things onto.

@<Invert the cross-reference list at |cur_name|, making |cur_xref| the head@>=
this_xref:=xref[cur_name]; cur_xref:=0;
repeat next_xref:=xlink(this_xref); xlink(this_xref):=cur_xref;
cur_xref:=this_xref; this_xref:=next_xref;
until this_xref=0

@ The following recursive procedure walks through the tree of module names and
prints them.
@^recursion@>

@p procedure mod_print(p:name_pointer); {print all module names in subtree |p|}
begin if p>0 then
  begin mod_print(llink[p]);@/
  out2("\")(":");@/
@.\\:@>
  tok_ptr:=1; text_ptr:=1; scrap_ptr:=0; init_stack;
  app(p+mod_flag); make_output;
  footnote(0); {|cur_xref| was set by |make_output|}
  finish_line;@/
  mod_print(rlink[p]);
  end;
end;

@ @<Output all the module names@>=@+mod_print(root)

@* Debugging.
The \PASCAL\ debugger with which \.{WEAVE} was developed allows breakpoints
to be set, and variables can be read and changed, but procedures cannot be
executed. Therefore a `|debug_help|' procedure has been inserted in the main
loops of each phase of the program; when |ddt| and |dd| are set to appropriate
values, symbolic printouts of various tables will appear.

The idea is to set a breakpoint inside the |debug_help| routine, at the
place of `\ignorespaces|breakpoint:|\unskip' below.  Then when
|debug_help| is to be activated, set |trouble_shooting| equal to |true|.
The |debug_help| routine will prompt you for values of |ddt| and |dd|,
discontinuing this when |ddt<=0|; thus you type $2n+1$ integers, ending
with zero or a negative number. Then control either passes to the
breakpoint, allowing you to look at and/or change variables (if you typed
zero), or to exit the routine (if you typed a negative value).

Another global variable, |debug_cycle|, can be used to skip silently
past calls on |debug_help|. If you set |debug_cycle>1|, the program stops
only every |debug_cycle| times |debug_help| is called; however,
any error stop will set |debug_cycle| to zero.

@<Globals...@>=
@!debug@!trouble_shooting:boolean; {is |debug_help| wanted?}
@!ddt:integer; {operation code for the |debug_help| routine}
@!dd:integer; {operand in procedures performed by |debug_help|}
@!debug_cycle:integer; {threshold for |debug_help| stopping}
@!debug_skipped:integer; {we have skipped this many |debug_help| calls}
@!term_in:text_file; {the user's terminal as an input file}
gubed

@ The debugging routine needs to read from the user's terminal.
@^system dependencies@>
@<Set init...@>=
@!debug trouble_shooting:=true; debug_cycle:=1; debug_skipped:=0; tracing:=0;@/
trouble_shooting:=false; debug_cycle:=99999; {use these when it almost works}
reset(term_in,'TTY:','/I'); {open |term_in| as the terminal, don't do a |get|}
gubed

@ @d breakpoint=888 {place where a breakpoint is desirable}
@^system dependencies@>

@p @!debug procedure debug_help; {routine to display various things}
label breakpoint,exit;
var k:integer; {index into various arrays}
begin incr(debug_skipped);
if debug_skipped<debug_cycle then return;
debug_skipped:=0;
loop@+  begin print_nl('#'); update_terminal; {prompt}
  read(term_in,ddt); {read a debug-command code}
  if ddt<0 then return
  else if ddt=0 then
    begin goto breakpoint;@\ {go to every label at least once}
    breakpoint: ddt:=0;@\
    end
  else  begin read(term_in,dd);
    case ddt of
    1: print_id(dd);
    2: print_text(dd);
    3: for k:=1 to dd do print(xchr[buffer[k]]);
    4: for k:=1 to dd do print(xchr[mod_text[k]]);
    5: for k:=1 to out_ptr do print(xchr[out_buf[k]]);
    6: for k:=1 to dd do
      begin print_cat(cat[k]); print(' ');
      end;
    othercases print('?')
    endcases;
    end;
  end;
exit:end;
gubed

@* The main program.
Let's put it all together now: \.{WEAVE} starts and ends here.
@^system dependencies@>

The main procedure has been split into three sub-procedures in order to
keep certain \PASCAL\ compilers from overflowing their capacity.
@^split procedures@>

@p procedure Phase_I;
begin @<Phase I:...@>;
end;
@#
procedure Phase_II;
begin @<Phase II:...@>;
end;
@#
begin initialize; {beginning of the main program}
print_ln(banner); {print a ``banner line''}
@<Store all the reserved words@>;
Phase_I; Phase_II;@/
@<Phase III:...@>;
@<Check that all changes have been read@>;
end_of_WEAVE:
stat @<Print statistics about memory usage@>;@+tats@;@/
@t\4\4@>{here files should be closed if the operating system requires it}
@<Print the job |history|@>;
end.

@ @<Print statistics about memory usage@>=
print_nl('Memory usage statistics: ',
  name_ptr:1,' names, ', xref_ptr:1,' cross references, ',
  byte_ptr[0]:1);
for cur_bank:=1 to ww-1 do print('+',byte_ptr[cur_bank]:1);
  print(' bytes;');
print_nl('parsing required ',max_scr_ptr:1,' scraps, ',max_txt_ptr:1,
  ' texts, ',max_tok_ptr:1,' tokens, ', max_stack_ptr:1,' levels;');
print_nl('sorting required ',max_sort_ptr:1, ' levels.')

@ Some implementations may wish to pass the |history| value to the
operating system so that it can be used to govern whether or not other
programs are started. Here we simply report the history to the user.
@^system dependencies@>

@<Print the job |history|@>=
case history of
spotless: print_nl('(No errors were found.)');
harmless_message: print_nl('(Did you see the warning message above?)');
error_message: print_nl('(Pardon me, but I think I spotted something wrong.)');
fatal_message: print_nl('(That was a fatal error, my friend.)');
end {there are no other cases}

@* System-dependent changes.
This module should be replaced, if necessary, by changes to the program
that are necessary to make \.{WEAVE} work at a particular installation.
It is usually best to design your change file so that all changes to
previous modules preserve the module numbering; then everybody's version
will be consistent with the printed program. More extensive changes,
which introduce new modules, can be inserted here; then only the index
itself will get a new module number.
@^system dependencies@>

@* Index.
If you have read and understood the code for Phase III above, you know what
is in this index and how it got here. All modules in which an identifier is
used are listed with that identifier, except that reserved words are
indexed only when they appear in format definitions, and the appearances
of identifiers in module names are not indexed. Underlined entries
correspond to where the identifier was declared. Error messages, control
sequences put into the output, and a few
other things like ``recursion'' are indexed here too.