summaryrefslogtreecommitdiff
path: root/support/ltx2x/ltx2x.tex
blob: beb6807367634c766c90e27ada94f217d179bcd0 (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
4904
4905
4906
4907
4908
4909
4910
4911
4912
4913
4914
4915
4916
4917
4918
4919
4920
4921
4922
4923
4924
4925
4926
4927
4928
4929
4930
4931
4932
4933
4934
4935
4936
4937
4938
4939
4940
4941
4942
4943
4944
4945
4946
4947
4948
4949
4950
4951
4952
4953
4954
4955
4956
4957
4958
4959
4960
4961
4962
4963
4964
4965
4966
4967
4968
4969
4970
4971
4972
4973
4974
4975
4976
4977
4978
4979
4980
4981
4982
4983
4984
4985
4986
4987
4988
4989
4990
4991
4992
4993
4994
4995
4996
4997
4998
4999
5000
5001
5002
5003
5004
5005
5006
5007
5008
5009
5010
5011
5012
5013
5014
5015
5016
5017
5018
5019
5020
5021
5022
5023
5024
5025
5026
5027
5028
5029
5030
5031
5032
5033
5034
5035
5036
5037
5038
5039
5040
5041
5042
5043
5044
5045
5046
5047
5048
5049
5050
5051
5052
5053
5054
5055
5056
5057
5058
5059
5060
5061
5062
5063
5064
5065
5066
5067
5068
5069
5070
5071
5072
5073
5074
5075
5076
5077
5078
5079
5080
5081
5082
5083
5084
5085
5086
5087
5088
5089
5090
5091
5092
5093
5094
5095
5096
5097
5098
5099
5100
5101
5102
5103
5104
5105
5106
5107
5108
5109
5110
5111
5112
5113
5114
5115
5116
5117
5118
5119
5120
5121
5122
5123
5124
5125
5126
5127
5128
5129
5130
5131
5132
5133
5134
5135
5136
5137
5138
5139
5140
5141
5142
5143
5144
5145
5146
5147
5148
5149
5150
5151
5152
5153
5154
5155
5156
5157
5158
5159
5160
5161
5162
5163
5164
5165
5166
5167
5168
5169
5170
5171
5172
5173
5174
5175
5176
5177
5178
5179
5180
5181
5182
5183
5184
5185
5186
5187
5188
5189
5190
5191
5192
5193
5194
5195
5196
5197
5198
5199
5200
5201
5202
5203
5204
5205
5206
5207
5208
5209
5210
5211
5212
5213
5214
5215
5216
5217
5218
5219
5220
5221
5222
5223
5224
5225
5226
5227
5228
5229
5230
5231
5232
5233
5234
5235
5236
5237
5238
5239
5240
5241
5242
5243
5244
5245
5246
5247
5248
5249
5250
5251
5252
5253
5254
5255
5256
5257
5258
5259
5260
5261
5262
5263
5264
5265
5266
5267
5268
5269
5270
5271
5272
5273
5274
5275
5276
5277
5278
5279
5280
5281
5282
5283
5284
5285
5286
5287
5288
5289
5290
5291
5292
5293
5294
5295
5296
5297
5298
5299
5300
5301
5302
5303
5304
5305
5306
5307
5308
5309
5310
5311
5312
5313
5314
5315
5316
5317
5318
5319
5320
5321
5322
5323
5324
5325
5326
5327
5328
5329
5330
5331
5332
5333
5334
5335
5336
5337
5338
5339
5340
5341
5342
5343
5344
5345
5346
5347
5348
5349
5350
5351
5352
5353
5354
5355
5356
5357
5358
5359
5360
5361
5362
5363
5364
5365
5366
5367
5368
5369
5370
5371
5372
5373
5374
5375
5376
5377
5378
5379
5380
5381
5382
5383
5384
5385
5386
5387
5388
5389
5390
5391
5392
5393
5394
5395
5396
5397
5398
5399
5400
5401
5402
5403
5404
5405
5406
5407
5408
5409
5410
5411
5412
5413
5414
5415
5416
5417
5418
5419
5420
5421
5422
5423
5424
5425
5426
5427
5428
5429
5430
5431
5432
5433
5434
5435
5436
5437
5438
5439
5440
5441
5442
5443
5444
5445
5446
5447
5448
5449
5450
5451
5452
5453
5454
5455
5456
5457
5458
5459
5460
5461
5462
5463
5464
5465
5466
5467
5468
5469
5470
5471
5472
5473
5474
5475
5476
5477
5478
5479
5480
5481
5482
5483
5484
5485
5486
5487
5488
5489
5490
5491
5492
5493
5494
5495
5496
5497
5498
5499
5500
5501
5502
5503
5504
5505
5506
5507
5508
5509
5510
5511
5512
5513
5514
5515
5516
5517
5518
5519
5520
5521
5522
5523
5524
5525
5526
5527
5528
5529
5530
5531
5532
5533
5534
5535
5536
5537
5538
5539
5540
5541
5542
5543
5544
5545
5546
5547
5548
5549
5550
5551
5552
5553
5554
5555
5556
5557
5558
5559
5560
5561
5562
5563
5564
5565
5566
5567
5568
5569
5570
5571
5572
5573
5574
5575
5576
5577
5578
5579
5580
5581
5582
5583
5584
5585
5586
5587
5588
5589
5590
5591
5592
5593
5594
5595
5596
5597
5598
5599
5600
5601
5602
5603
5604
5605
5606
5607
5608
5609
5610
5611
5612
5613
5614
5615
5616
5617
5618
5619
5620
5621
5622
5623
5624
5625
5626
5627
5628
5629
5630
5631
5632
5633
5634
5635
5636
5637
5638
5639
5640
5641
5642
5643
5644
5645
5646
5647
5648
5649
5650
5651
5652
5653
5654
5655
5656
5657
5658
5659
5660
5661
5662
5663
5664
5665
5666
5667
5668
5669
5670
5671
5672
5673
5674
5675
5676
5677
5678
5679
5680
5681
5682
5683
5684
5685
5686
5687
5688
5689
5690
5691
5692
5693
5694
5695
5696
5697
5698
5699
5700
5701
5702
5703
5704
5705
5706
5707
5708
5709
5710
5711
5712
5713
5714
5715
5716
5717
5718
5719
5720
5721
5722
5723
5724
5725
5726
5727
5728
5729
5730
5731
5732
5733
5734
5735
5736
5737
5738
5739
5740
5741
5742
5743
5744
5745
5746
5747
5748
5749
5750
5751
5752
5753
5754
5755
5756
5757
5758
5759
5760
5761
5762
5763
5764
5765
5766
5767
5768
5769
5770
5771
5772
5773
5774
5775
5776
5777
5778
5779
5780
5781
5782
5783
5784
5785
5786
5787
5788
5789
5790
5791
5792
5793
5794
5795
5796
5797
5798
5799
5800
5801
5802
5803
5804
5805
5806
5807
5808
5809
5810
5811
5812
5813
5814
5815
5816
5817
5818
5819
5820
5821
5822
5823
5824
5825
5826
5827
5828
5829
5830
5831
5832
5833
5834
5835
5836
5837
5838
5839
5840
5841
5842
5843
5844
5845
5846
5847
5848
5849
5850
5851
5852
5853
5854
5855
5856
5857
5858
5859
5860
5861
5862
5863
5864
5865
5866
5867
5868
5869
5870
5871
5872
5873
5874
5875
5876
5877
5878
5879
5880
5881
5882
5883
5884
5885
5886
5887
5888
5889
5890
5891
5892
5893
5894
5895
5896
5897
5898
5899
5900
5901
5902
5903
5904
5905
5906
5907
5908
5909
5910
5911
5912
5913
5914
5915
5916
5917
5918
5919
5920
5921
5922
5923
5924
5925
5926
5927
5928
5929
5930
5931
5932
5933
5934
5935
5936
5937
5938
5939
5940
5941
5942
5943
5944
5945
5946
5947
5948
5949
5950
5951
5952
5953
5954
5955
5956
5957
5958
5959
5960
5961
5962
5963
5964
5965
5966
5967
5968
5969
5970
5971
5972
5973
5974
5975
5976
5977
5978
5979
5980
5981
5982
5983
5984
5985
5986
5987
5988
5989
5990
5991
5992
5993
5994
5995
5996
5997
5998
5999
6000
6001
6002
6003
6004
6005
6006
6007
6008
6009
6010
6011
6012
6013
6014
6015
6016
6017
6018
6019
6020
6021
6022
6023
6024
6025
6026
6027
6028
6029
6030
6031
6032
6033
6034
6035
6036
6037
6038
6039
6040
6041
6042
6043
6044
6045
6046
6047
6048
6049
6050
6051
6052
6053
6054
6055
6056
6057
6058
6059
6060
6061
6062
6063
6064
6065
6066
6067
6068
6069
6070
6071
6072
6073
6074
6075
6076
6077
6078
6079
6080
6081
6082
6083
6084
6085
6086
6087
6088
6089
6090
6091
6092
6093
6094
6095
6096
6097
6098
6099
6100
6101
6102
6103
6104
6105
6106
6107
6108
6109
6110
6111
6112
6113
6114
6115
6116
6117
6118
6119
6120
6121
6122
6123
6124
6125
6126
6127
6128
6129
6130
6131
6132
6133
6134
6135
6136
6137
6138
6139
6140
6141
6142
6143
6144
6145
6146
6147
6148
6149
6150
6151
6152
6153
6154
6155
6156
6157
6158
6159
6160
6161
6162
6163
6164
6165
6166
6167
6168
6169
6170
6171
6172
6173
6174
6175
6176
6177
6178
6179
6180
6181
6182
6183
6184
6185
6186
6187
6188
6189
6190
6191
6192
6193
6194
6195
6196
6197
6198
6199
6200
6201
6202
6203
6204
6205
6206
6207
6208
6209
6210
6211
6212
6213
6214
6215
6216
6217
6218
6219
6220
6221
6222
6223
6224
6225
6226
6227
6228
6229
6230
6231
6232
6233
6234
6235
6236
6237
6238
6239
6240
6241
6242
6243
6244
6245
6246
6247
6248
6249
6250
6251
6252
6253
6254
6255
6256
6257
6258
6259
6260
6261
6262
6263
6264
6265
6266
6267
6268
6269
6270
6271
6272
6273
6274
6275
6276
6277
6278
6279
6280
6281
6282
6283
6284
6285
6286
6287
6288
6289
6290
6291
6292
6293
6294
6295
6296
6297
6298
6299
6300
6301
6302
6303
6304
6305
6306
6307
6308
6309
6310
6311
6312
6313
6314
6315
6316
6317
6318
6319
6320
6321
6322
6323
6324
6325
6326
6327
6328
6329
6330
6331
6332
6333
6334
6335
6336
6337
6338
6339
6340
6341
6342
6343
6344
6345
6346
6347
6348
6349
6350
6351
6352
6353
6354
6355
6356
6357
6358
6359
6360
6361
6362
6363
6364
6365
6366
6367
6368
6369
6370
6371
6372
6373
6374
6375
6376
6377
6378
6379
6380
6381
6382
6383
6384
6385
6386
6387
6388
6389
6390
6391
6392
6393
6394
6395
6396
6397
6398
6399
6400
6401
6402
6403
6404
6405
6406
6407
6408
6409
6410
6411
6412
6413
6414
6415
6416
6417
6418
6419
6420
6421
6422
6423
6424
6425
6426
6427
6428
6429
6430
6431
6432
6433
6434
6435
6436
6437
6438
6439
6440
6441
6442
6443
6444
6445
6446
6447
6448
6449
6450
6451
6452
6453
6454
6455
6456
6457
6458
6459
6460
6461
6462
6463
6464
6465
6466
6467
6468
6469
6470
6471
6472
6473
6474
6475
6476
6477
6478
6479
6480
6481
6482
6483
6484
6485
6486
6487
6488
6489
6490
6491
6492
6493
6494
6495
6496
6497
6498
6499
6500
6501
6502
6503
6504
6505
6506
6507
6508
6509
6510
6511
6512
6513
6514
6515
6516
6517
6518
6519
6520
6521
6522
6523
6524
6525
6526
6527
6528
6529
6530
6531
6532
6533
6534
6535
6536
6537
6538
6539
6540
6541
6542
6543
6544
6545
6546
6547
6548
6549
6550
6551
6552
6553
6554
6555
6556
6557
6558
6559
6560
6561
6562
6563
6564
6565
6566
6567
6568
6569
6570
6571
6572
6573
6574
6575
6576
6577
6578
6579
6580
6581
6582
6583
6584
6585
6586
6587
6588
6589
6590
6591
6592
6593
6594
6595
6596
6597
6598
6599
6600
6601
6602
6603
6604
6605
6606
6607
6608
6609
6610
6611
6612
6613
6614
6615
6616
6617
6618
6619
6620
6621
6622
6623
6624
6625
6626
6627
6628
6629
6630
6631
6632
6633
6634
6635
6636
6637
6638
6639
6640
6641
6642
6643
6644
6645
6646
6647
6648
6649
6650
6651
6652
6653
6654
6655
6656
6657
6658
6659
6660
6661
6662
6663
6664
6665
6666
6667
6668
6669
6670
6671
6672
6673
6674
6675
6676
6677
6678
6679
6680
6681
6682
6683
6684
6685
6686
6687
6688
6689
6690
6691
6692
6693
6694
6695
6696
6697
6698
6699
6700
6701
6702
6703
6704
6705
6706
6707
6708
6709
6710
6711
6712
6713
6714
6715
6716
6717
6718
6719
6720
6721
6722
6723
6724
6725
6726
6727
6728
6729
6730
6731
6732
6733
6734
6735
6736
6737
6738
6739
6740
6741
6742
6743
6744
6745
6746
6747
6748
6749
6750
6751
6752
6753
6754
6755
6756
6757
6758
6759
6760
6761
6762
6763
6764
6765
6766
6767
6768
6769
6770
6771
6772
6773
6774
6775
6776
6777
6778
6779
6780
6781
6782
6783
6784
6785
6786
6787
6788
6789
6790
6791
6792
6793
6794
6795
6796
6797
6798
6799
6800
6801
6802
6803
6804
6805
6806
6807
6808
6809
6810
6811
6812
6813
6814
6815
6816
6817
6818
6819
6820
6821
6822
6823
6824
6825
6826
6827
6828
6829
6830
6831
6832
6833
6834
6835
6836
6837
6838
6839
6840
6841
6842
6843
6844
6845
6846
6847
6848
6849
6850
6851
6852
6853
6854
6855
6856
6857
6858
6859
6860
6861
6862
6863
6864
6865
6866
6867
6868
6869
6870
6871
6872
6873
6874
6875
6876
6877
6878
6879
6880
6881
6882
6883
6884
6885
6886
6887
6888
6889
6890
6891
6892
6893
6894
6895
6896
6897
6898
6899
6900
6901
6902
6903
6904
6905
6906
6907
6908
6909
6910
6911
6912
6913
6914
6915
6916
6917
6918
6919
6920
6921
6922
6923
6924
6925
6926
6927
6928
6929
6930
6931
6932
6933
6934
6935
6936
6937
6938
6939
6940
6941
6942
6943
6944
6945
6946
6947
6948
6949
6950
6951
6952
6953
6954
6955
6956
6957
6958
6959
6960
6961
6962
6963
6964
6965
6966
6967
6968
6969
6970
6971
6972
6973
6974
6975
6976
6977
6978
6979
6980
6981
6982
6983
6984
6985
6986
6987
6988
6989
6990
6991
6992
6993
6994
6995
6996
6997
6998
6999
7000
7001
7002
7003
7004
7005
7006
7007
7008
7009
7010
7011
7012
7013
7014
7015
7016
7017
7018
7019
7020
7021
7022
7023
7024
7025
7026
7027
7028
7029
7030
7031
7032
7033
7034
7035
7036
7037
7038
7039
7040
7041
7042
7043
7044
7045
7046
7047
7048
7049
7050
7051
7052
7053
7054
7055
7056
7057
7058
7059
7060
7061
7062
7063
7064
7065
7066
7067
7068
7069
7070
7071
7072
7073
7074
7075
7076
7077
7078
7079
7080
7081
7082
7083
7084
7085
7086
7087
7088
7089
7090
7091
7092
7093
7094
7095
7096
7097
7098
7099
7100
7101
7102
7103
7104
7105
7106
7107
7108
7109
7110
7111
7112
7113
7114
7115
7116
7117
7118
7119
7120
7121
7122
7123
7124
7125
7126
7127
7128
7129
7130
7131
7132
7133
7134
7135
7136
7137
7138
7139
7140
7141
7142
7143
7144
7145
7146
7147
7148
7149
7150
7151
7152
7153
7154
7155
7156
7157
7158
7159
7160
7161
7162
7163
7164
7165
7166
7167
7168
7169
7170
7171
7172
7173
7174
7175
7176
7177
7178
7179
7180
7181
7182
7183
7184
7185
7186
7187
7188
7189
7190
7191
7192
7193
7194
7195
7196
7197
7198
7199
7200
7201
7202
7203
7204
7205
7206
7207
7208
7209
7210
7211
7212
7213
7214
7215
7216
7217
7218
7219
7220
7221
7222
7223
7224
7225
7226
7227
7228
7229
7230
7231
7232
7233
7234
7235
7236
7237
7238
7239
7240
7241
7242
7243
7244
7245
7246
7247
7248
7249
7250
7251
7252
7253
7254
7255
7256
7257
7258
7259
7260
7261
7262
7263
7264
7265
7266
7267
7268
7269
7270
7271
7272
7273
7274
7275
7276
7277
7278
7279
7280
7281
7282
7283
7284
7285
7286
7287
7288
7289
7290
7291
7292
7293
7294
7295
7296
7297
7298
7299
7300
7301
7302
7303
7304
7305
7306
7307
7308
7309
7310
7311
7312
7313
7314
7315
7316
7317
7318
7319
7320
7321
7322
7323
7324
7325
7326
7327
7328
7329
7330
7331
7332
7333
7334
7335
7336
7337
7338
7339
7340
7341
7342
7343
7344
7345
7346
7347
7348
7349
7350
7351
7352
7353
7354
7355
7356
7357
7358
7359
7360
7361
7362
7363
7364
7365
7366
7367
7368
7369
7370
7371
7372
7373
7374
7375
7376
7377
7378
7379
7380
7381
7382
7383
7384
7385
7386
7387
7388
7389
7390
7391
7392
7393
7394
7395
7396
7397
7398
7399
7400
7401
7402
7403
7404
7405
7406
7407
7408
7409
7410
7411
7412
7413
7414
7415
7416
7417
7418
7419
7420
7421
7422
7423
7424
7425
7426
7427
7428
7429
7430
7431
7432
7433
7434
7435
7436
7437
7438
7439
7440
7441
7442
7443
7444
7445
7446
7447
7448
7449
7450
7451
7452
7453
% ltx2x.tex             Description of ltx2x program
\documentclass[11pt]{article}
\usepackage{url}
\usepackage{ltx2html}
\setlength{\textheight}{8.0in}
\setlength{\textwidth}{6.0in}
\setlength{\oddsidemargin}{0.25in}
\setlength{\evensidemargin}{0.25in}
\setlength{\marginparwidth}{0.6in}
\setcounter{secnumdepth}{4}
\setcounter{tocdepth}{4}
% define these to save some typing
\newcommand{\lx}{{\small\sl LTX2X}}
\newcommand{\ctab}{command table}
\newcommand{\Express}{{\sc Express}}
\newcommand{\ExpressA}{{\sc Express-A}}
\newcommand{\ExpressG}{{\sc Express-G}}
\newcommand{\ExpressI}{{\sc Express-I}}
\newenvironment{code}{\begin{small}}{\end{small}}
\newcommand{\keyword}[1]{\begin{small}\texttt{#1}\end{small}}
\newcommand{\keytext}[1]{\begin{small}\texttt{#1}\end{small}}
\newcommand{\file}[1]{\texttt{#1}}
\mltitle{LaTeX to X translator}
\begin{document}
\title{ \textsl{LTX2X:} A \protect\LaTeX\ to X Auto-tagger}
\author{Peter R. Wilson \\
        Catholic University of America\thanks{This work was performed
while a Guest Researcher at the National Institute of Standards and
Technology} \\
        Email: \texttt{pwilson@cme.nist.gov} }
\date{January 1997}

\bibliographystyle{unsrt}
\pagenumbering{roman}
\maketitle

\begin{abstract}
    \lx{} is a table-driven program that will replace \LaTeX\ commands
by user defined text. This report describes the beta version of the system.
\lx{} supports both a declaritive command style and an interpreted
procedural language tentatively called \ExpressA.
Details are given of the program functionality including examples.
System installation instructions are provided.
\end{abstract}

\tableofcontents
\listoftables

\clearpage
\pagenumbering{arabic}

\section{Introduction}  \label{sec:introduction}

    \LaTeX~\cite{LAMPORT94}, which is built on top of \TeX~\cite{KNUTH84a},
is a document tagging system
that is very popular in the academic and scientific publishing communities
because of the high quality typeset material that the system outputs
for normal text and especially for mathematics.

    In particular, many of the documents forming the 
International Standard ISO~ 10303, commonly referred to as STEP~\cite{STEPIS},
have been written using \LaTeX\ as
the document tagging language. Lately there have been moves towards converting
the STEP documents to embody SGML~\cite{GOLDFARB90}
rather than \LaTeX\ markup. This has led
to an interest in the automatic conversion from \LaTeX\ to SGML
documents.
The \lx\ system is an initial attempt to provide a generic capability for 
converting \LaTeX\ tags into other kinds of tags.

    The \lx\ system described below is in a beta release state. That is, there
is probably some more work to be done on it but experience from use is
needed to determine desirable additional functionality. However, the code
has been stable for some time.
Bug reports or suggested 
enhancements (especially if the suggestions are accompanied by working code)
are encouraged, as are constructive comments about this document.

    Essentially, \lx{} reads a file containing \LaTeX{} markup, 
replaces the \LaTeX{} commands by user-defined text, and writes the result 
out to another file. The program operates from a command table that specifies
the replacement text. In general, no programming knowledge or skills are
required to write a command table, which \lx{} will then interpret.
Some knowledge of \LaTeX{} is required, but no more than is necessary
for authoring a \LaTeX{} document.

    \lx{} has proved capable of performing such functions as:
\begin{itemize}
\item Conversion of documents marked up according to a specific \LaTeX{} 
      documentclass to documents tagged according to a specific SGML DTD.
\item Removal of \LaTeX{} commands to produce deTeXed source.
\item Conversion of simple \LaTeX{} documents to
  HTML~\cite{MUSCIANO96} tagged documents for publication on the 
  World Wide Web.
\end{itemize}

    The remainder of this introduction gives an overview of the \lx{} program.
The command table is described in more detail in section~\ref{sec:command-table}
and information on running the \lx{} program is provided in 
section~\ref{sec:program}. Section~\ref{sec:expressa} gives an
overview
of the \ExpressA{} language.\footnote{The overview is necessarily
rather brief as I am shortly moving to a new place of employment and
\ExpressA{} is the latest addition to the system.} 
Although the functionality available through the command table facility is 
suitable for many tasks, especially since an interpreter for the \ExpressA{} 
general programming language is included within \lx, 
section~\ref{sec:special} gives details on how the system can
be extended for cases where this proves to be inadequate.

    The report ends with several appendices. An example command table for
deTeXing a document is reproduced in~\ref{sec:detexing} and some of
the issues in converting from \LaTeX{} to HTML are discussed 
in~\ref{sec:htmling}. The known limitations
of \lx{} are listed in~\ref{sec:limitations} and a summary of the command
table facilities are given in~\ref{sec:summary}. Appendix~\ref{sec:install}
provides instructions on installing the \lx{} program, together with copyright
and warranty information. Finally, \ref{sec:ctabgrammar} and \ref{sec:expgrammar}provide grammars for the \ctab and \ExpressA, respectively.

\subsection{Overview}

    The intent of Leslie Lamport, the author of \LaTeX, was to provide a document
tagging system that enabled the capture of the logical structure of a document.
This system uses Donald Knuth's \TeX\ system as its typesetting engine~\cite{KNUTH84a},
and thus has an inherent capability for high quality typesetting.

    All \LaTeX\ commands are distinguished by starting with a backslash (\verb|\|).
Generally speaking, the name of a command is a string of alphabetic characters 
(e.g. \verb|\acommand|). Commands may take arguments. Required arguments are
enclosed in curly braces (i.e. \verb|{| and \verb|}|). Optional arguments
are enclosed in square brackets (i.e. \verb|[| and \verb|]|). The general syntax
for a command is the command name (preceded by a backslash) followed by the
argument list with a maximum\footnote{Under very unusual
circumstances this limit may be exceeded.} of nine arguments.

    The \lx\ program reads a \LaTeX\ document file and outputs a
transformation of this file. By default it outputs the normal text
while for each \LaTeX{} command and argument performs some
user-specified actions; typically these actions involve the output
of specific text corresponding to the particular command.
The actions are specified in a \emph{\ctab} file, written by the user, 
which is read into the \lx\ system before document processing is
begun. A \ctab\ consists of a listing of the \LaTeX\ commands of interest
together with the desired actiond for each of these commands and their
arguments.
Different effects may be easily obtained by changing the \ctab\
file. For example, a simple \ctab{} file may be written that will delete
all the \LaTeX\ commands from a document, resulting in a plain ASCII file
with no embedded markup.\footnote{To afficionados, 
this process is known as de-\TeX ing.} 
A more complex command table may be written that will replace \LaTeX\ tags 
with appropriate SGML tags.

    In some circles it is traditional to introduce a programming
language by providing an example program that prints `Hello world'.
In contrast, the following \ctab{} file called \file{bye.ct}, 
when used in conjunction
with a typical vanilla \LaTeX{} file, will transform the \LaTeX{} file
to a file that consists only of the words `Goodbye document'.

\begin{code}
\begin{verbatim}
C=        bye.ct   "Goodbye document" for ltx2x

TYPE= COMMAND
NAME= \documentclass
  START_TAG= "Goodbye document"
  PC_AT_END= NO_PRINT
END_TYPE
  
C= just in case a LaTeX v2.09 document
TYPE= COMMAND
NAME= \documentstyle
  START_TAG= "Goodbye document"
  PC_AT_END= NO_PRINT
END_TYPE
  
C= just in case there is no \documentclass/style command
TYPE= BEGIN_DOCUMENT
  START_TAG= "Goodbye document"
  PC_AT_END= NO_PRINT
END_TYPE

TYPE= OTHER_COMMAND
  PRINT_CONTROL= NO_PRINT
END_TYPE

TYPE= OTHER_BEGIN
  PRINT_CONTROL= NO_PRINT
END_TYPE

TYPE= OTHER_END
  PRINT_CONTROL= NO_PRINT
END_TYPE

END_CTFILE=  end of bye.ct
\end{verbatim}
\end{code}

    Essentially the \ctab{} instructs \lx{} what to print for each \LaTeX{}
command. A \ctab{} file consists of a series of commands, one per line
and introduced by a keyword such as \keyword{TYPE=}. Keywords are case
insensitive but by convention are written in upper case. Comments in
a \ctab{} are introduced by the keyword \keyword{C=}.

    The main body of a \ctab{} consists of the specification of
\LaTeX{} commands of interest and the actions to be taken for these.
Each specification commences with the keyword \keyword{TYPE=} and is
completed by the keyword \keyword{END\_TYPE}, the relevant actions
being listed between these two keywords.

    \lx{} treats some \LaTeX{} commands specially; among these are
\verb|\begin{document}| and \verb|\end{document}|. In a \ctab{}
these are specified by the types \keyword{TYPE= BEGIN\_DOCUMENT} and
\keyword{TYPE= END\_DOCUMENT}. The actions at
\verb|\begin{document}| are firstly to print the string `Goodbye document'
(specified in the line \keyword{START\_TAG= "Goodbye document"}) and
secondly to stop printing any output (specified in the line 
\keyword{PC\_AT\_END= NO\_PRINT}).

    By not specifying the \keyword{END\_DOCUMENT} entry, the default
action is used for the \verb|\end{document}| command.

    The \ctab{} entries for the commands \verb|\documentclass| and
\verb|\documentstyle| specify that, if either of these is in the
source document, then it is to be replaced by the text string
\keytext{"Goodbye document"}, and then all further printing is to
be switched off.

    The other three entries in the \ctab{} specify the actions for any
other kind of \LaTeX{} command. The keyword \keyword{OTHER\_BEGIN}
signifies a \LaTeX{} command of the form \verb|\begin{name}| and
\keyword{OTHER\_END} signifies a command of the form \verb|\end{name}|.
The keyword \keyword{OTHER\_COMMAND} signifies any other kind of
\LaTeX{} command (e.g., \verb|\acommand ... |). The actions declared
for these are all \keyword{PRINT\_CONTROL= NO\_PRINT} which shuts off
any printing of the command or its arguments. In the \ctab{} \file{bye.ct}
these are only included to prevent printing before the
\verb|\begin{document}|.

    To run \lx{} with the above \ctab, type the following (where \verb|>| 
is assumed to be the system prompt):
\begin{verbatim}
> ltx2x -f bye.ct input.tex output.tex
\end{verbatim}
where \file{bye.ct} is the name of the \ctab, and 
\file{input.tex} and \file{output.tex} are the names of the input \LaTeX{}
file and the resulting processed file respectively.


    As an example of a more useful \ctab\ file, the following one called
\file{decomm.ct} will remove all \LaTeX\ comments from a typical
\LaTeX{} source file.

\begin{code}
\begin{verbatim}
C=  decomm.ct  Command table file for ltx2x to de-comment LaTeX source

C= ------------------------------------ set newline characters
ESCAPE_CHAR= ?
NEWLINE_CHAR= N

C=   ----------------------------------- built in commands
TYPE= BEGIN_DOCUMENT
  START_TAG= "\begin{document}"
END_TYPE

TYPE= END_DOCUMENT
  START_TAG= "\end{document}"
END_TYPE

TYPE= BEGIN_VERB
  START_TAG= "\verb|"
END_TYPE

TYPE= END_VERB
  START_TAG= "|"
END_TYPE

TYPE= BEGIN_VERBATIM
  START_TAG= "\begin{verbatim}"
END_TYPE
\end{verbatim}
\verb|TYPE= END_VERBATIM| \\
\verb|  START_TAG= "\end{verbatim}"| \\
\verb|END_TYPE|
\begin{verbatim}
TYPE= LBRACE
  START_TAG= "{"
END_TYPE

TYPE= RBRACE
  START_TAG= "}"
END_TYPE

TYPE= PARAGRAPH
  START_TAG= "?N?N    "
END_TYPE

C= ------------------- define '\item' tags within lists

TYPE= BEGIN_LIST_ENV
NAME= itemize
  START_TAG= "\begin{itemize}"
  START_ITEM= "\item "
END_TYPE

TYPE= BEGIN_LIST_ENV
NAME= enumerate
  START_TAG= "\begin{enumerate}"
  START_ITEM= "\item "
END_TYPE

TYPE= BEGIN_LIST_ENV
NAME= description
  START_TAG= "\begin{description}"
  START_ITEM= "\item"
  START_ITEM_PARAM= "["
  END_ITEM_PARAM= "] "
END_TYPE

TYPE= END_LIST_ENV
  NAME= itemize
END_TYPE

TYPE= END_LIST_ENV
  NAME= enumerate
END_TYPE

TYPE= END_LIST_ENV
  NAME= description
END_TYPE

C=    --------------------- pass through all other LaTeX commands

TYPE= OTHER_COMMAND
END_TYPE

TYPE= OTHER_BEGIN
END_TYPE

TYPE= OTHER_END
END_TYPE

END_CTFILE= end of file decomm.ct
\end{verbatim}
\end{code} % end small

    In the above \ctab\ file, the first pair of commands (\keyword{ESCAPE\_CHAR=}
and \keyword{NEWLINE\_CHAR=}) define the character pair that are to be used to
signify a `newline' within a tag. An example of their use is later in the
file in the \keyword{PARAGRAPH} command type.

    As indicated above, \lx\ treats some \LaTeX\ commands specially. 
These are listed next in the
\ctab. The special \LaTeX{} commands are the begin and end of the 
\verb|document| and \verb|verbatim|
environments, together with the \verb|\verb| command, left and right braces,
the \verb*|\ | command, and the \lx{} \keyword{PARAGRAPH} specification.
There are default actions for these, but apart from the \verb*|\ | command
the defaults are not appropriate in this case. 
Above, the actions are to replace the
\LaTeX{} command by the string forming the \LaTeX{} command. The exception
is that paragraphs (the \keyword{PARAGRAPH} specification) should start 
with at least one blank line and be indented some spaces.

    The \LaTeX\ \verb|\item| command is used within lists. \lx\ has to be
told how to treat the \verb|\item| command within each kind of list. This
has been done above for the \verb|itemize|, \verb|enumerate| and 
\verb|description| environments.

    The final instructions in the \ctab\ file tell \lx\ to pass through the
text of all other commands and their arguments. The end of the \ctab\ file
is either the physical end of the file or the command \keyword{END\_CTFILE=},
whichever comes first. The \keyword{END\_CTFILE=} command acts like the
\keyword{C=} command in that arbitrary text can be put after the command.

    To use the \file{decomm.ct} \ctab{} to de-comment a \LaTeX\ file, type 
the following (where \verb|>| is assumed to be the system prompt):
\begin{verbatim}
> ltx2x -f decomm.ct input.tex output.tex
\end{verbatim}
where \file{input.tex} and \file{output.tex} are the names of the input \LaTeX\
file for de-commenting and the resulting de-commented version respectively.

\section{The \ctab\ file} \label{sec:command-table}

    By default, \lx\ does not output any \LaTeX\ comments. 
Otherwise, whenever it comes
across a \LaTeX\ command it looks at the data in the \ctab\ file to determine
what actions it should take. The two most typical actions are either
to print out the command as read in, or to replace the command by some (possibly
empty) text.

    Each line in a \ctab\ file is either blank or starts with a keyword followed
by one or more blanks. For
example, a comment in the file is a line that starts with \keyword{C= };
the remainder of the line is any comment text. Comments may be placed anywhere
in the file.


\subsection{Special print characters in tags}

    \lx\ is written in C~\cite{KERNIGHAN88}. 
The C language enables certain non-printing characters
to be defined. These are typically written in the form \verb|\c| where \verb|\|
is the C escape character and \verb|c|
is a particular character. \lx\ understands some of these special printing
characters and the \ctab\ enables these to be given non-default values.

    The default escape character (\verb|\|) may be redefined via the 
\keyword{ESCAPE\_CHAR=} command. For example,
\begin{code}
\begin{verbatim}
ESCAPE_CHAR= ?
\end{verbatim}
\end{code}
will make the question mark character the escape character. Typically, the escape 
character is changed in most \ctab s to avoid clashing with the \LaTeX{} \verb|\|
character.
The following commands
can be used to redefine the C special characters. Each of these commands takes
a single character as its value. If a relevant command is not given, then the
default value is used. 
\begin{description}
\item[\keyword{NEWLINE\_CHAR=}] a new line (default is \verb|n|) \\
\item[\keyword{HORIZONTAL\_TAB\_CHAR=}] horizontal tab  (default is \verb|t|) \\
\item[\keyword{VERTICAL\_TAB\_CHAR=}] vertical tab (default is \verb|v|) \\
\item[\keyword{BACKSPACE\_CHAR=}] backspace (default is \verb|b|) \\
\item[\keyword{CARRIAGE\_RETURN\_CHAR=}] carriage return (default is \verb|r|) \\
\item[\keyword{FORMFEED\_CHAR=}] formfeed (default is \verb|f|) \\
\item[\keyword{AUDIBLE\_ALLERT\_CHAR=}] beep the terminal (default is \verb|a|) \\
\item[\keyword{HEX\_CHAR=}] following characters form the hexadecimal number of 
      the character
                  to be printed (default is \verb|x|) (e.g. \verb|?xA3|) \\
\end{description}
    These command lines are all optional within a \ctab\ and their ordering is
immaterial. However, if any are present then they must be at the beginning of 
the \ctab.

    The above special characters are useful when specifying the replacement text
for \LaTeX\ commands.


\subsection{\protect\LaTeX\ command types}

    The commands for controlling the actions performed on \LaTeX\ commands
are enclosed between the command lines \keyword{TYPE= } and \keyword{END\_TYPE}, 
as below.
\begin{code}
\begin{verbatim}
TYPE= CommandType
  C= a possibly empty set of commands
END_TYPE
\end{verbatim}
\end{code}
where \keyword{CommandType} is an \lx\ keyword signifying the kind of \LaTeX\ 
command being specified.

\subsubsection{Built in command types}

    Some \LaTeX\ commands are pre-defined within \lx. Default actions
are provided for these but it is recommended that type specifications
for each of these commands be put in the \ctab{} anyway. The keywords for
these commands are:
\begin{description}
\item[\keyword{BEGIN\_DOCUMENT}] Corresponds to the \LaTeX\ command 
      \verb|\begin{document}|.
\item[\keyword{END\_DOCUMENT}] Corresponds to the \LaTeX\ command
      \verb|\end{document}|.
\item[\keyword{BEGIN\_VERBATIM}] Corresponds to the \LaTeX\ commands
      \verb|\begin{verbatim}| and \\
      \verb|\begin{verbatim*}|.
\item[\keyword{END\_VERBATIM}] Corresponds to the \LaTeX\ commands
      \verb|\end{verbatim}| and \verb|\end{verbatim*}|.
\item[\keyword{BEGIN\_VERB}] Corresponds to the \LaTeX\ commands
      \verb|\verb| and \verb|\verb*|, together with the succeeding character.
\item[\keyword{END\_VERB}] Corresponds to the appearance of the character
      that completes the \LaTeX\ commands
      \verb|\verb| and \verb|\verb*|.
\item[\keyword{LBRACE}] Corresponds to the \LaTeX\ left brace character
      \verb|{|.
\item[\keyword{RBRACE}] Corresponds to the \LaTeX\ right brace character
      \verb|}|.
\item[\keyword{BEGIN\_DOLLAR}] Corresponds to the \LaTeX\ \verb|$| symbol signalling the
   start of an in-text math formula.
\item[\keyword{END\_DOLLAR}] Corresponds to the \LaTeX\ \verb|$| symbol signalling the
   end of an in-text math formula.
\item[\keyword{PARAGRAPH}] Corresponds to the \LaTeX\ protocol of a blank
     line signalling the start/end of a paragraph.
\item[\keyword{SLASH\_SPACE}] Corresponds to the \LaTeX\ \verb*|\ | command.
\item[\keyword{OTHER\_COMMAND}] Corresponds to any \LaTeX\ command of the form
      \verb|\command| not specified elsewhere within the \ctab.
\item[\keyword{OTHER\_BEGIN}] Corresponds to any \LaTeX\ command of the form
      \verb|\begin{environment}| not specified elsewhere within the \ctab.
\item[\keyword{OTHER\_END}] Corresponds to any \LaTeX\ command of the form
      \verb|\end{environment}| not specified elsewhere within the \ctab.
\end{description}


    The ordering of these built in type specifications is immaterial. If
any of the above are not specified within the \ctab{} then \lx{} will use
their default action.
    With the exception of the \keyword{SLASH\_SPACE} command type, the
default action is to do nothing (i.e., produce no output). 
The default action for the \keyword{SLASH\_SPACE}
command type is to output a space.

\subsubsection{Optional command types}

    For the purposes of \lx, \LaTeX\ commands are divided into various classes.
The keywords for these clases, and the class descriptions, are listed below.

\begin{description}
\item[\keyword{TEX\_CHAR}] Corresponding to \LaTeX's special characters (with the exception
     of the \$, \{\ and \}\ characters).
\item[\keyword{CHAR\_COMMAND}] Corresponding to \LaTeX\ commands of the type
     \verb|\c| where \verb|c| is a single non-alphabetic character.
\item[\keyword{COMMAND}] Corresponding to \LaTeX\ commands of the type
     \verb|\command|, where \verb|command| is the name of the command (except for
      \verb|\begin|, \verb|\end| and \verb|\item|).
\item[\keyword{BEGIN\_ENV}] Corresponding to \LaTeX\ commands of the type
     \verb|\begin{environment}| where \verb|environment| is the name of the
      environment, except for those list environments whose bodies
      consist of \verb|\item| commands.
\item[\keyword{END\_ENV}] Corresponding to \LaTeX\ commands of the type
     \verb|\end{environment}|, with the same restrictions as for \verb|BEGIN_ENV|.
\item[\keyword{BEGIN\_LIST\_ENV}] Corresponding to \LaTeX\ commands of the type
     \verb|\begin{environment}| where \verb|environment| is the name of an
     environment whose body consists of \verb|\item| commands.
\item[\keyword{END\_LIST\_ENV}] Corresponding to \LaTeX\ commands of the type
     \verb|\end{environment}| to match \verb|BEGIN_LIST_ENV|.
\item[\keyword{VCOMMAND}] Corresponding to a \LaTeX{} \verb|\verb|-like command.
\item[\keyword{BEGIN\_VENV}] Corresponding to the start of a verbatim-like
     environment.
\item[\keyword{END\_VENV}] Corresponding to the end of a verbatim-like
     environment.
\item[\keyword{SECTIONING}] Corresponding to \LaTeX\ commands of the type
     \verb|\command|, where \verb|command| is a document sectioning command
      such as \verb|chapter| or \verb|subsection|.
\item[\keyword{SPECIAL}] Reserved for possible future use.
\item[\keyword{SPECIAL\_COMMAND}] Corresponding to the \verb|COMMAND| keyword,
     except that some special output processing is to be defined.
\item[\keyword{SPECIAL\_BEGIN\_ENV}] Corresponding to the \verb|BEGIN_ENV| keyword,
     except that some special output processing is to be defined.
\item[\keyword{SPECIAL\_END\_ENV}] Corresponding to the \verb|END_ENV| keyword, 
     except that some special output processing is to be defined.
\item[\keyword{SPECIAL\_BEGIN\_LIST}] Corresponding to the \verb|BEGIN_LIST_ENV| 
     keyword, 
     except that some special output processing is to be defined.
\item[\keyword{SPECIAL\_END\_LIST}] Corresponding to the \verb|END_LIST_ENV| keyword,
     except that some special output processing is to be defined.
\item[\keyword{SPECIAL\_SECTIONING}] Corresponding to the \verb|SECTIONING| keyword,
     except that some special output processing is to be defined.
\item[\keyword{\_PICTURE\_}] Corresponding to some of the \LaTeX\ picture
     drawing commands.
\item[\keyword{COMMAND\_...}] Corresponding to some of the \LaTeX{} commands
     whose arrangements of required and optional arguments are untypical.
\end{description}

    The ordering of these types within a \ctab\ is immaterial.

    Each of the above type specifications requires a \keyword{NAME=} command, 
whose value is the
name of the relevant command or environment being specified. For example, the
following is a (partial) specification of the figure environment and the caption
command.

\begin{code}
\begin{verbatim}
TYPE= BEGIN_ENV
NAME= figure
END_TYPE

TYPE= END_ENV
NAME= figure
END_TYPE

TYPE= COMMAND
NAME= \caption
END_TYPE
\end{verbatim}
\end{code}

\subsection{Command action tags}

    When \lx\ reads a \LaTeX\ command it performs the following actions:
\begin{enumerate}
\item Looks up the name of the command or environment in the \ctab. If
      it is not found, then the appropriate default type is used.
\item Sets the printing mode according to the \keyword{PC\_AT\_START=}
      command.
\item Performs the actions specified in the \ctab\ by the 
      \keyword{START\_TAG=} command.
\item Processes any specified arguments to the command.
\item Performs the actions specified in the \ctab\ by the \keyword{END\_TAG=}
      command.
\item Sets the printing mode according to the \keyword{PC\_AT\_END=} command.
\end{enumerate}

\begin{description}
\item[NOTES]:
\begin{enumerate}
\item Except for the default processing of \keyword{OTHER\_} types, it does not
      output the command itself.
\item If a tag action is not specified, then the default action is null (e.g.,
      nothing will appear in the output).
\end{enumerate}
\end{description}

    Within a \ctab\ all text strings for output are enclosed within double 
quotes. For example:
\begin{code}
\begin{verbatim}
START_TAG=     "Some "text" string\n another line of text."
\end{verbatim}
\end{code}

    Assuming that \verb|\n| means a newline, when this string action is performed
by \lx\ it will appear in the output file as:
\begin{code}
\begin{verbatim}
Some "text" string
another line of text.
\end{verbatim}
\end{code}

    A text string starts with the first double quote and ends with the last double
quote on the command line. A text string has to be written on a single line
within the \ctab. C language special print characters can be embedded within the
text string (e.g. the \verb|\n| for a newline in the above example). Remember
that the first section of the \ctab\ is used for specifying the 
particular \ctab\ version of these.

    If a text string is too long to fit comfortably on a single line in the
\ctab, it may be continued via the \keyword{STRING:} command. As many of these
can be used in succession as required (subject to internal limitations within \lx).

    For instance,
\begin{code}
\begin{verbatim}
START_TAG=     "Some "text" string\n"
  STRING: "another line of text."
\end{verbatim}
\end{code}
has the same effect as the previous example.

    The following specification is designed to write out the contents of the
\verb|\caption| command\footnote{Strictly speaking, the specification does not
do this exactly, but this simplified illustration will be corrected in 
the next sections.}, 
preceded by the word `CAPTION' and followed by at least one
blank line (assuming that the escape character has been set to \verb|?|). 

\begin{code}
\begin{verbatim}
TYPE= COMMAND
NAME= \caption
  START_TAG= "?n      CAPTION "
  END_TAG= "?n?n"
END_TYPE
\end{verbatim}
\end{code}
Assuming that somewhere in a \LaTeX\ file there is the command
\begin{code}
\begin{verbatim}
stuff
\caption{This is a caption.}
more stuff
\end{verbatim}
\end{code}
then the expected effect (see footnote) is
\begin{code}
\begin{verbatim}
stuff

    CAPTION This is a caption.

more stuff
\end{verbatim}
\end{code}

\subsection{Argument actions}

    \LaTeX\ commands can take arguments. The text for a required argument is
enclosed in curly braces, while the text for an optional argument is enclosed
in square brackets. \lx\ can be directed to perform actions at the start and end
of each argument. 

    The number of required arguments is specified by the command line 
\keyword{REQPARAMS=}
where the value of the command is a digit between 1 and 9 inclusive.

    \lx\ assumes that a command can have only one optional argument, and that this
is either first or last in the argument list. The potential presence of an
optional argument is indicated by the command line \keyword{OPT\_PARAM=}, 
where the
value is either the keyword \keyword{FIRST} (for first in the list) or 
\keyword{LAST} (for last in the list).

    The actions to be performed at the start and end of each required argument
are specified via the commands \keyword{START\_TAG\_1=} and \keyword{END\_TAG\_1=} 
for the first required argument, through \keyword{START\_TAG\_9=} and 
\keyword{END\_TAG\_9=} for the ninth argument.
The actions to be performed at the start and end of the optional argument
are specified by the command lines \keyword{START\_OPT=} and \keyword{END\_OPT=}.

    The argument delimiters (the braces or brackets) are not printed.

    In the simplest case, the action is to print a specified text string 
(enclosed in double quotes, and continued with \keyword{STRING:} commands 
if necessary). Other kinds of actions are also possible.
An unspecified tag defaults to doing no action.

\subsubsection{Print options}

\paragraph{Argument processing}

    By default, \lx\ processes (i.e. outputs as appropriate) 
the text of a argument.
Printing of the argument text may be disabled, if required. The command line
that controls argument printing is of the form \keyword{PRINT\_P1=} through
\keyword{PRINT\_P9=} for required arguments and 
\keyword{PRINT\_OPT=} for the optional
argument. The value of these commands is one from several keywords,
the most common being \keyword{NO\_PRINT}; this
switches off printing of the text of the indicated argument.
Default printing is resumed after the indicated argument.

    Continuing the caption example from earlier, we can now complete it. The full
syntax of the \LaTeX\ command is:
\begin{code}
\begin{verbatim}
\caption[optional table of contents entry]{Caption in the text}
\end{verbatim}
\end{code}
That is, it has one required argument, which prints the caption text both in
the body of the document and in the table of contents, unless the first optional
argument is present, in which case its value gets printed in the table of 
contents instead.

    Assume that an instance of the caption command in a document is:
\begin{code}
\begin{verbatim}
Some stuff
\caption[Short caption]{Long caption for the body of the text.}
More stuff
\end{verbatim}
\end{code}
Recall the previous \ctab\ caption specification. The actual output from 
processing this would be
\begin{code}
\begin{verbatim}
Some stuff

    CAPTION [Short caption]{Long caption for the body of the text.}

More stuff
\end{verbatim}
\end{code}
because, unless \lx\ is told that there are command arguments and how they should
be treated, it will just print them out together with their surrounding 
delimiters.

    The following \ctab\ entry will give more acceptable results.
\begin{code}
\begin{verbatim}
TYPE= COMMAND
NAME= \caption
  START_TAG= "?n      CAPTION "
  END_TAG= "?n?n"
  OPT_PARAM= FIRST
  PRINT_OPT= NO_PRINT
  REQPARAMS= 1
END_TYPE
\end{verbatim}
\end{code}

    For the above captioning instance, the output will now be:
\begin{code}
\begin{verbatim}
Some stuff

    CAPTION Long caption for the body of the text.

More stuff
\end{verbatim}
\end{code}

    The default print mode is to print text to the output file.

    The keywords that can be used to control argument printing are:
\begin{description}
\item[\keyword{NO\_PRINT}] Do not print anything.
\item[\keyword{TO\_SYSBUF}] Print to the \lx{} system buffer.
\item[\keyword{TO\_BUFFER num}] Print to the \lx{} buffer 
      number \keyword{num}.
\item[\keyword{TO\_FILE name}] Print to the file called \keyword{name}.
\item[\keyword{NO\_OP}] Skip all processing of the argument.
\end{description}
Note that even if the print mode is set to \keyword{NO\_PRINT}, the
argument text will still be processed. Only the \keyword{NO\_OP}
specification temporarly turns off the processing.


\paragraph{General printing}

    Just as the printing mode can be set for each argument, it can also be
set at the start and end of processing a \LaTeX{} command or environment.

    The specifications \keyword{PC\_AT\_START=} and \keyword{PC\_AT\_END=}
can be used to set the printing mode at the start of processing a command
and at the end, respectively. The keywords that can be used in these
specifications are:
\begin{description}
\item[\keyword{NO\_PRINT}] Do not print anything.
\item[\keyword{TO\_SYSBUF}] Print to the \lx{} system buffer.
\item[\keyword{TO\_BUFFER num}] Print to the \lx{} buffer 
      number \keyword{num}.
\item[\keyword{TO\_FILE name}] Print to the file called \keyword{name}.
\item[\keyword{RESET}] Reset the print mode back to what it was.
\end{description}

    Unlike the argument printing controls, the print mode is not
automatically reset. This has to be explicitly specified.

    As an example, assume that it is required to remove all \keytext{figure}
environments from a \LaTeX{} source and put them into a file on their own.
The following \ctab{} code could be used to accomplish this.
\begin{code}
\begin{verbatim}
TYPE= BEGIN_ENV
NAME= figure
  PC_AT_START= TO_FILE allfigs.tex
  START_TAG= "?n\begin{figure}"
END_TYPE

TYPE= END_ENV
NAME= figure
  START_TAG= "\end{figure}"
  PC_AT_END= RESET
END_TYPE
\end{verbatim}
\end{code}
When a \LaTeX{} \keytext{figure} environment is started, printing is switched
to go to the file called \file{allfigs.tex}. At the end of the \keytext{figure}
environment, the print mode is reset back to what it was before the environment
began. If at the first \keytext{figure} environment the \file{allfigs.tex} 
file did not exist, then \lx{} would create it automatically.

\paragraph{Read actions}

    As noted above, one of the actions that can be specified for a
\LaTeX{} comand's argument is to set the print mode for printing to a buffer
or a file. Similarly there are actions which will read from a buffer or
a file and print the contents. Within an argument tag these kinds of actions are
specified via the keyword \keyword{SOURCE:}. This can take one of several
values:
\begin{description}
\item[\keyword{SYSBUF}] Print the contents of the \lx{} system buffer.
\item[\keyword{BUFFER num}] Print the contents of the \lx{} buffer 
      number \keyword{num}.
\item[\keyword{FILE name}] Print the contents of the file called 
   \keyword{name}.
\end{description}

    In a previous example, the \LaTeX{} \keytext{figure} environments
were all written to the file \file{allfig.tex}. This file could be read
in again just before the end of the document so that all figures will be
typeset after everything else.
\begin{code}
\begin{verbatim}
TYPE= END_DOCUMENT
  END_TAG= "?n %  figures collected here by LTX2X ?n"
    SOURCE: FILE allfigs.tex
    STRING: "?n\end{document}?n"
END_TYPE
\end{verbatim}
\end{code}

    As another example of the use of the print actions consider the \LaTeX{}
\verb|\maketitle| command. This typesets the arguments of the \verb|\title|,
\verb|\author| and \verb|\date| commands, which must have been previously
specified but not necessarily in this ordering. Here is one way this can
be simulated using \lx.
\begin{code}
\begin{verbatim}
TYPE= COMMAND
NAME= \title
  START_TAG=
    RESET_BUFFER: 1
  REQPARAMS= 1
  PRINT_P1= TO_BUFFER 1
END_TYPE

TYPE= COMMAND
NAME= \author
  START_TAG=
    RESET_BUFFER: 2
  REQPARAMS= 1
  PRINT_P1= TO_BUFFER 2
END_TYPE

TYPE= COMMAND
NAME= \date
  START_TAG=
    RESET_BUFFER: 3
  REQPARAMS= 1
  PRINT_P1= TO_BUFFER 3
END_TYPE

TYPE= COMMAND
NAME= \maketitle
  START_TAG= "?n"
    SOURCE: BUFFER 1
    STRING: "?n?n"
    SOURCE: BUFFER 2
    STRING: "?n?n"
    SOURCE: BUFFER 3
    STRING: "?n?n"
  END_TAG=
    RESET_BUFFER: 1
    RESET_BUFFER: 2
    RESET_BUFFER: 3
END_TYPE
\end{verbatim}
\end{code}
For the \verb|\title| command, the print mode for its argument is set 
for printing to the buffer number~1. The single action at the start of
the command is to make sure that buffer~1 is empty (the line
\keyword{RESET\_BUFFER: 1}). The actions for the \verb|\author| and
\verb|\date| commands are similar, except that they print their argument
texts to buffers~2 and~3 respectively.

    The \verb|\maketitle| command takes no arguments, so all actions
must be placed under \keyword{START\_TAG=} and/or \keyword{END\_TAG=}.
There are a set of actions specified for \keyword{START\_TAG=}. Firstly
a newline is printed and this is followed by the contents of buffer~1
(i.e., the text of the argument of the \verb|\title| command).
Then two new lines are printed, followed by the contents of buffer~2
(the author). Finally another two newlines are printed, the contents
of buffer~3 (the date), and another two newlines. The actions
for \keyword{END\_TAG=} are to clear the contents of the three buffers.

    Just to extend the example, here is a specification for the
\LaTeX{} \verb|\thanks| command. \lx{} is not designed to do footnoting 
(as it does not do page breaking)
so instead the thanks text will be placed inside parentheses on a new line.
\begin{code}
\begin{verbatim}
TYPE= COMMAND
NAME= \thanks
  START_TAG= "?n ("
  REQPARAMS= 1
  END_TAG= ") "
END_TYPE
\end{verbatim}
\end{code}


    Given these \ctab{} specification and the following portion of a
\LaTeX{} document
\begin{code}
\begin{verbatim}
\date{29 February 2000}
\title{The Calculation of Leap Days\thanks{Originally published in JIR}}
\author{A. N. Other}
...
\maketitle
\end{verbatim}
\end{code}
then output from \lx{} will be:
\begin{code}
\begin{verbatim}
The Calculation of Leap Days
 (Originally published in JIR)

A. N. Other 

29 February 2000
\end{verbatim}
\end{code}
Note that as the \verb|\thanks| command appears within the argument of the
\verb|\title| command, it is written to the same place as the text of
the argument of \verb|\title|. Thus, it also gets written to the output file
when \verb|\maketitle| is processed.

\subsubsection{Print switching}

    There are individual actions that enable the printing destination
to be changed at will within the action set for any particular tag.
\begin{description}
\item[\keyword{SWITCH\_TO\_BUFFER: num}] Direct any following printing
  to the \lx{} buffer number \keyword{num}.
\item[\keyword{SWITCH\_TO\_FILE: name}] Direct any following printing
  to the file called \keyword{name}.
\item[\keyword{SWITCH\_TO\_SYSBUF}] Direct any following printing
  to the \lx{} system buffer.
\item[\keyword{SWITCH\_BACK:}] Undo the effect of the last 
  \keytext{SWITCH\_TO...} action.
\end{description}

    As an example of the utility of this type of action, consider
again the \LaTeX{} \verb|\maketitle| command. When \LaTeX{} processes
this command, it typesets the date as specified by the \verb|\date|
command, or if this has not been specified then it prints the current 
date instead. We can arrange for \lx{} to do something similar by
adding the following to the \ctab{} shown earlier for the \verb|\date|
and \verb|\maketitle| commands.
\begin{code}
\begin{verbatim}
TYPE= COMMAND
NAME= \documentclass
  OPT_PARAM= FIRST
  REQPARAMS= 1
  PRINT_OPT= NO_PRINT
  PRINT_P1= NO_PRINT
  START_TAG=
      c= Initialise buffer 3 to `Today'
    RESET_BUFFER: 3
    SWITCH_TO_BUFFER: 3
    STRING: "Today"
    SWITCH_BACK:
END_TYPE
\end{verbatim}
\end{code}
    At the start of the document, the above actions put the string 
\keytext{Today} into \keytext{BUFFER 3}, having first ensured that it is
empty. If the \LaTeX{} source includes a \verb|\date| command, then
the contents of the buffer will be overwritten, otherwise it will be
as initialised. In any event, when the \verb|\maketitle| command is
processed, the value output for the date will be either \keytext{Today}
or whatever the argument was of the \verb|\date| command.

\subsubsection{Notes on the use of buffers and files}

    Resetting a buffer or a file always has the effect of emptying it
of an prior contents.

    When printing from a buffer or a file, the entire contents are
printed. There is no limit to the number of times that a buffer
or a file can be used as a printing source.

    When printing to a buffer, the new strings are appended at
the end of the current contents of the buffer, at least until it
overflows. Unlike the behaviour of files,
this is independant of any intervening prints from the buffer.

    When printing to a file, the new strings are appended at the
end of the current contents of the file. However, if a file is printed
to after it has been printed from, the prior contents of the file
are lost, and the new string is added at the start of the file.
In general, it is safest to treat files as either read-only or write-only.



\subsubsection{User specified modes}

    Consider the \LaTeX{} command \verb|\\|. In normal text this signifies
that a line break must occur. In a \verb|tabular| environment, though,
it signifies the end of a row in a table. Suppose that in the \lx{}
procesing of a tabular environment it is required to start and end each
row with a vertical bar and to seperate each column also with a vertical
bar. However, in normal text a \verb|\\| command should just translate
into a newline. Just to complicate matters further, assume that in
an \verb|eqnarray| environment, the \verb|&| column seperator is to
be translated to some spaces, and that the string `(X)' is to be
put at the end of every row.

   In other words, we need to process some commands differently
according to where they appear in the LaTeX{} source. An \lx{} \ctab{}
provides this capability through mode setting and mode-dependent actions.
Here is an example of using this facility to solve the requirements 
outlined above.
\begin{code}
\begin{verbatim}
TYPE= BEGIN_ENV
NAME= tabular
  C= starting actions, etc., here
  END_TAG=
    SET_MODE: tabular
END_TYPE

TYPE= END_ENV
NAME= tabular
  START_TAG=
    RESET_MODE:
END_TYPE

TYPE= BEGIN_ENV
NAME= eqnarry
  C= starting actions, etc., here
  END_TAG=
    SET_MODE: eqn
END_TYPE

TYPE= END_ENV
NAME= eqnarray
  START_TAG= "    (X)?n"
    RESET_MODE:
END_TYPE

TYPE= TEX_CHAR
NAME= &
  START_TAG= "  |  "
IN_MODE= eqn
  START_TAG= "  "
END_MODE
END_TYPE

TYPE= CHAR_COMMAND
NAME= \\
  START_TAG= "?n"
IN_MODE= tabular
  START_TAG= " |?n"
    STRING: "     |  "    
END_MODE
IN_MODE= eqn
  START_TAG= "    (X)?n"
END_MODE
END_TYPE
\end{verbatim}
\end{code}

    Let us look at the specification for the \verb|\tabular| environment first.
The \keyword{END\_TAG=} action is specified by the single command line
\keyword{SET\_MODE:}~\keytext{tabular}, where \keytext{tabular} is any convenient
name for identifying a mode. Thus, this will set the mode to be \keytext{tabular}.
The action at the end of the environment is to reset the mode 
(\keyword{RESET\_MODE:})
to whatever its previous value was. It is assumed that the last row in any
\verb|tabular| environment is finished by \verb|\\|. Similar actions are
performed for the \verb|eqnarray| environment, except that the mode is called
\keytext{eqn} instead of \keytext{tabular}. The other difference is that it
is assumed that the last row is not ended by \verb|\\|, so the end of
the \verb|eqnarray| environment has to also act like the \verb|\\|.

    Turning now to the specification for the \verb|&| command, the first part
of the specification identifies the type and name of the \LaTeX{} command.
This is then followed by the mode-independent set of actions, 
which in this case
consists of printing a vertical bar with some spaces on either side of it.
Following these are any mode-dependent actions, bracketed between 
\keyword{IN\_MODE=} and \keyword{END\_MODE}. The value for \keyword{IN\_MODE=}
is the name of the relevent mode. In this case the only mode-dependent
action occurs when \keytext{MODE eqn} is in effect and it is to print
some spaces instead of the default spaces and vertical bar.

    The specification for the \verb|\\| command has its set of 
mode-independent default actions,
namely just to print a newline, and two sets of mode-dependent actions.
When the \keytext{tabular} mode is in effect, it prints some spaces, a vertical
bar, a newline, more spaces, a vertical bar, and finally some more spaces.
On the other hand, when the \keytext{eqn} mode is in effect, it prints some
spaces, the string `(X)' and a newline. If a mode is in effect
that is not defined within the specification (e.g., mode \keytext{anon})
it performs the default mode-independent actions.

    As a perhaps more practical example, the following \ctab{} code will 
convert simple \LaTeX{} \verb|tabular|
 environments to appropriate mark-up for HTML tables. It is assumed that
the \verb|tabular| environment is always within a \verb|table| environment.

    To set the perspective a little, here is the code for a simple table
in \LaTeX:
\begin{code}
\begin{verbatim}
\begin{table}[tbp]
\centering
\caption{A simple table typeset by \LaTeX.} \label{tab:lxtab}
\begin{tabular}{|l||r|r||r|r|} \hline
Stock & \multicolumn{2}{c||}{1994} & \multicolumn{2}{c|}{1995} \\ \cline{2-5}
      &  low    &  high  &   low  & high  \\ \hline
ABC   &  27     &  36    &   23   & 45     \\
DEF   &  53     &  72    &   19   & 54     \\
GHI   &  28     &  49    &   17   & 79     \\ \hline
\end{tabular}
\end{table}
\end{verbatim}
\end{code}
This will be typeset as shown in table~\ref{tab:lxtab}.
\begin{table}[tbp]
\centering
\caption{A simple table typeset by \LaTeX.} \label{tab:lxtab}
\begin{tabular}{|l||r|r||r|r|} \hline
Stock & \multicolumn{2}{c||}{1994} & \multicolumn{2}{c|}{1995} \\ \cline{2-5}
      &  low    &  high  &   low  & high  \\ \hline
ABC   &  27     &  36    &   23   & 45     \\
DEF   &  53     &  72    &   19   & 54     \\
GHI   &  28     &  49    &   17   & 79     \\ \hline
\end{tabular}
\end{table}

    The corresponding HTML code for the table after translation is:
\begin{latexonly}
\begin{code}
\begin{verbatim}
<p><center><table border>
<caption>A simple table typeset by LaTeX.</caption> <a name="tab:lxtab"></a>

<tr><td> Stock </td><td colspan=2> 1994 </td><td colspan=2> 1995 </tr>
<tr><td > 
       </td><td > low </td><td > high </td><td > low </td><td > high </tr>
<tr><td > ABC </td><td > 27 </td><td > 36 </td><td > 23 </td><td > 45 </tr>
<tr><td > 
DEF </td><td > 53 </td><td > 72 </td><td > 19 </td><td > 54 </tr>
<tr><td > 
GHI </td><td > 28 </td><td > 49 </td><td > 17 </td><td > 79 </tr>
<tr><td >
</table></center>
\end{verbatim}
\end{code}
\end{latexonly}

\begin{code}
\begin{htmlverbatim}
\ST{p}\ST{center}\ST{table border}
\ST{caption}A simple table typeset by LaTeX.\ET{caption} \ST{a name="tab:lxtab"}\ET{a}

\ST{tr}\ST{td} Stock \ET{td}\ST{td colspan=2} 1994 \ET{td}\ST{td colspan=2} 1995 \ET{tr}
\ST{tr}\ST{td} 
       \ET{td}\ST{td} low \ET{td}\ST{td} high \ET{td}\ST{td} low \ET{td}\ST{td} high \ET{tr}
\ST{tr}\ST{td} ABC \ET{td}\ST{td} 27 \ET{td}\ST{td} 36 \ET{td}\ST{td} 23 \ET{td}\ST{td} 45 \ET{tr}
\ST{tr}\ST{td} 
DEF \ET{td}\ST{td} 53 \ET{td}\ST{td} 72 \ET{td}\ST{td} 19 \ET{td}\ST{td} 54 \ET{tr}
\ST{tr}\ST{td} 
GHI \ET{td}\ST{td} 28 \ET{td}\ST{td} 49 \ET{td}\ST{td} 17 \ET{td}\ST{td} 79 \ET{tr}
\ST{tr}\ST{td}
\ET{table}\ET{center}
\end{htmlverbatim}
\end{code}

    In the HTML browser that I use this is displayed
approximately as shown for table~\ref{tab:httab}.

\begin{table}[tbp]
\centering
\caption{A simple table typeset after translation to HTML.} \label{tab:httab}
\begin{tabular}{||l|l|l|l|l||} \hline\hline
Stock & \multicolumn{2}{l||}{1994} & \multicolumn{2}{l|}{1995} \\ \hline
      &  low    &  high  &   low  & high  \\ \hline
ABC   &  27     &  36    &   23   & 45     \\
DEF   &  53     &  72    &   19   & 54     \\
GHI   &  28     &  49    &   17   & 79     \\ \hline \hline
\end{tabular}
\end{table}

    In HTML a table is enclosed between 
\keytext{\ST{table}} and \keytext{\ET{table}} tags.
Each row of the table is enclosed between 
\keytext{\ST{tr}} and \keytext{\ET{tr}} tags,
and each element in a row is enclosed between 
\keytext{\ST{td}} and \keytext{\ET{td}} tags.
Under certain circumstances the closing tags (i.e.,
those like \keytext{\ET{...}})
can be inferred by the HTML procesors and need
not be explicitly put into the source text. The equivalent HTML tags to a
\LaTeX{} \verb|\multicolumn{num}{col}{text}| command are\\
\keytext{\ST{td colspan=num} text \ET{td}}.
 
    The general actions that \lx{} has to perform in doing the \LaTeX{} to
HTML translation are:
\begin{itemize}
\item The start and end of a \verb|table| environment has to translate to
      the HTML start and end table tags \keytext{\ST{table}} and 
      \keytext{\ET{table}}.
      (Actually this also needs to handle the
      centering of the HTML table and drawing a border round it as well.)

\item The start and end of the \verb|tabular| environment has to translate
      into a row start 
      \keytext{\ST{tr}\ST{td}} and end \keytext{\ET{tr}}
      in the HTML table (and set the mode for the
      \LaTeX{} \verb|\\| command).

\item The \verb|\\| command must end one row of the HTML table and start the
      next row 
      (\keytext{\ET{tr}?n\ST{tr}\ST{td}}).
      It need not end a data element as
      this is automatically closed by the end of the row.

\item The \verb|&| column delimeter must end one HTML data element and start
      another one (i.e., \keytext{\ET{td}\ST{td}}).

\item The difficulty is in handling the \verb|\multicolumn| command. In the easy
      case the \LaTeX{} to HTML translation is: \\
      \keytext{... \Amp{}  text \Amp{} ...} maps to \\
      \keytext{... \ET{td}\ST{td} text \ET{td}\ST{td} ...}. \\
     However, when a multicolumn is involved the translation is \\
\verb|... & \multicolumn{N}{P}{text} & ...| maps to \\
\keytext{... \ET{td}\ST{td colspan=N} text \ET{td}\ST{td} ...}. \\
As there is no look-ahead in \lx{} we have to be careful about starting a
data element after a \verb|&| because at that point \lx{} cannot know
whether or not a \verb|\multicolumn| command comes next, or just an ordinary
data element.

\end{itemize}

    We solve this last problem partly by using buffers 
(numbers \keytext{8} and \keytext{9} in the specification below) 
as temporary storage, and partly by a subtle specification for the
\verb|\multicolumn| command.

\begin{latexonly}
\begin{code}
\begin{verbatim}
C=   start of a table
TYPE= BEGIN_ENV
NAME= table
  START_TAG= "<center><table border>"
  OPT_PARAM= FIRST
  C=  ignore the optional positioning argument
  PRINT_OPT= NO_PRINT
END_TYPE

C=  end a table
TYPE= END_ENV
NAME= table
  START_TAG= "</table></center>"
END_TYPE

C=  start a tabular
TYPE= BEGIN_ENV
NAME= tabular
  START_TAG= "?n<tr><td"
    RESET_BUFFER: 8
    RESET_BUFFER: 9
  OPT_PARAM= FIRST
  C=  ignore the optional positioning argument
  PRINT_OPT= NO_PRINT
  REQPARAMS= 1
  C=  ignore the column specification
  PRINT_P1= NO_OP
  END_TAG=
    SET_MODE: tabular
  PC_AT_END= TO_BUFFER 9
END_TYPE

C=  end a tabular
TYPE= END_ENV
NAME= tabular
  PC_AT_START= RESET
  START_TAG= ">"
    RESET_BUFFER: 8
    RESET_BUFFER: 9
    RESET_MODE:
END_TYPE

C=  we can do some processing of the \mutlicolumn command
TYPE= COMMAND
NAME= \multicolumn
  PC_AT_START= TO_BUFFER 8
  REQPARAMS= 2
  START_TAG_1= " colspan="
  PRINT_P2= NO_PRINT
  PC_AT_END= RESET
END_TYPE

C=  now for the end/start of a row
TYPE= CHAR_COMMAND
NAME= \\
  START_TAG= "<br>"
IN_MODE= tabular
  PC_AT_START= RESET
  START_TAG=
    SOURCE: BUFFER 8
    STRING: "> "
    RESET_BUFFER: 8
    SOURCE: BUFFER 9
  END_TAG= "</tr>?n<tr><td "
    RESET_BUFFER: 9
  PC_AT_END= TO_BUFFER 9
END_MODE
END_TYPE

C= and the column seperator
TYPE= TEX_CHAR
NAME= &
  PC_AT_START= RESET
  START_TAG= 
    SOURCE: BUFFER 8
    STRING: "> "
    RESET_BUFFER: 8
    SOURCE: BUFFER 9
  END_TAG= " </td><td "
    RESET_BUFFER: 9
  PC_AT_END= TO_BUFFER 9
END_TYPE
\end{verbatim}
\end{code}
\end{latexonly}

\begin{htmlverbatim}
C=   start of a table
TYPE= BEGIN\_ENV
NAME= table
  START\_TAG= "\ST{center}\ST{table border}"
  OPT\_PARAM= FIRST
  C=  ignore the optional positioning argument
  PRINT\_OPT= NO\_PRINT
END\_TYPE

C=  end a table
TYPE= END\_ENV
NAME= table
  START\_TAG= "\ET{table}\ET{center}"
END\_TYPE

C=  start a tabular
TYPE= BEGIN\_ENV
NAME= tabular
  START\_TAG= "?n\ST{tr}\LT{}td"
    RESET\_BUFFER: 8
    RESET\_BUFFER: 9
  OPT\_PARAM= FIRST
  C=  ignore the optional positioning argument
  PRINT\_OPT= NO\_PRINT
  REQPARAMS= 1
  C=  ignore the column specification
  PRINT\_P1= NO\_OP
  END\_TAG=
    SET\_MODE: tabular
  PC\_AT\_END= TO\_BUFFER 9
END\_TYPE

C=  end a tabular
TYPE= END\_ENV
NAME= tabular
  PC\_AT\_START= RESET
  START\_TAG= "\GT"
    RESET\_BUFFER: 8
    RESET\_BUFFER: 9
    RESET\_MODE:
END\_TYPE

C=  we can do some processing of the \verb|\multicolumn| command
TYPE= COMMAND
NAME= \verb|\multicolumn|
  PC\_AT\_START= TO\_BUFFER 8
  REQPARAMS= 2
  START\_TAG\_1= " colspan="
  PRINT\_P2= NO\_PRINT
  PC\_AT\_END= RESET
END\_TYPE

C=  now for the end/start of a row
TYPE= CHAR\_COMMAND
NAME= \verb|\\|
  START\_TAG= "\ST{br}"
IN\_MODE= tabular
  PC\_AT\_START= RESET
  START\_TAG=
    SOURCE: BUFFER 8
    STRING: "\GT{} "
    RESET\_BUFFER: 8
    SOURCE: BUFFER 9
  END\_TAG= "\ET{tr}?n\ST{tr}\LT{}td "
    RESET\_BUFFER: 9
  PC\_AT\_END= TO\_BUFFER 9
END\_MODE
END\_TYPE

C= and the column seperator
TYPE= TEX\_CHAR
NAME= \Amp
  PC\_AT\_START= RESET
  START\_TAG= 
    SOURCE: BUFFER 8
    STRING: "\GT "
    RESET\_BUFFER: 8
    SOURCE: BUFFER 9
  END\_TAG= " \ET{td}\LT{}td "
    RESET\_BUFFER: 9
  PC\_AT\_END= TO\_BUFFER 9
END\_TYPE
\end{htmlverbatim}

    Regarding the \verb|\multicolumn| specification, we state that as far as
\lx{} is concerned, it only has two required parameters, and that the action
for the second one is \keyword{NO\_PRINT}. The first argument is written to
buffer \keytext{8} after `colspan=' has first been put into it. \lx{} will treat
the actual third argument to the \verb|\multicolumn| as ordinary text, just
as if there was no \verb|\multicolumn| in the \LaTeX{} source. We use buffer
\keytext{9} for storing the text of a data element. When \lx{} processes
a \keytext{\Amp} column delimeter it first outputs the contents of
buffer \keytext{8} (the number of columns specification) and then appropriate
HTML characters. It then outputs the contents of buffer \keytext{9} (the
element text), finishes off the element and partially starts the next element.
Similar actions are performed at the start of the \keytext{tabular} environment
and at the end of each row in the table.

\subsection{Sectioning command types}

    \lx\ does some particular processing for sectioning command types. Although
\LaTeX\ can determine where any section of a document ends, other tagging systems
cannot always do this. They require both a `begin section' and an `end section'
tag. \lx\ can take account of the nesting depth of document sections and,
given appropriate specifications, can supply both `begin section' and `end section'
tags appropriately. This requires a little bit more in the way of specifications
than we have met so far.

    For a \keyword{SECTIONING} command type, the command line 
\keyword{SECTIONING\_LEVEL=}
must be included within the specification. The value of this command is a keyword
from the following list.
\begin{description}
\item[\keyword{PART}] For a sectioning command equivalent to the 
              \LaTeX\ \verb|\part| command.
\item[\keyword{CHAPTER}] For a sectioning command equivalent to the 
              \LaTeX\ \verb|\chapter| command.
\item[\keyword{SECT}] For a sectioning command equivalent to the 
              \LaTeX\ \verb|\section| command.
\item[\keyword{SUBSECT}] For a sectioning command equivalent to the 
              \LaTeX\ \verb|\subsection| command.
\item[\keyword{SUBSUBSECT}] For a sectioning command equivalent to the 
              \LaTeX\ \verb|\subsubsection| command.
\item[\keyword{PARA}] For a sectioning command equivalent to the 
              \LaTeX\ \verb|\paragraph| command.
\item[\keyword{SUBPARA}] For a sectioning command equivalent to the 
              \LaTeX\ \verb|\subparagraph| command.
\end{description}

    When a sectioning command is read from the \LaTeX\ source, \lx\ firstly
performs the \keyword{END\_TAG=} actions for any `lower level' sections
that this one is closing off. It then performs the \keyword{START\_TAG=} 
actions for the current command, and stores its own \keyword{END\_TAG=} actions for
later use. It then goes on and process any arguments as usual.
 The \keyword{END\_DOCUMENT} command automatically closes off any opened
sections.

    As an example, assume that some kind soul has supplied a \LaTeX\ style
file that makes the commands \verb|\clause| synonymous with \verb|\subsection|,
and \verb|\sclause| synonymous with \verb|\subsubsection|, etc. Also assume
that it is required to output start and end tags of the form 
\keytext{\ST{div.1}} and  \keytext{\ET{div.1}} 
for sections, \keytext{\ST{div.2}} for clauses, etc., and surround the
headings with tags \keytext{\ST{heading}} and \keytext{\ET{heading}}. 
Further, the first
optional argument is of no interest as the output is going to be
used by a processing system unable to automatically handle tables of contents.
Part of an appropriate \ctab\ for doing this is:

\begin{latexonly}
\begin{code}
\begin{verbatim}
TYPE= SECTIONING
NAME= \section
  SECTIONING_LEVEL= SECT
  START_TAG= "?n?n<div.1>?n"
  END_TAG= "?n</div.1>"
  OPT_PARAM= FIRST
  PRINT_OPT= NO_PRINT
  REQPARAMS= 1
  START_TAG_1= "<heading>"
  END_TAG_1= "</heading>?n"
END_TYPE

TYPE= SECTIONING
NAME= \clause
  SECTIONING_LEVEL= SUBSECT
  START_TAG= "?n?n<div.2>?n"
  END_TAG= "?n</div.2>"
  OPT_PARAM= FIRST
  PRINT_OPT= NO_PRINT
  REQPARAMS= 1
  START_TAG_1= "<heading>"
  END_TAG_1= "</heading>?n"
END_TYPE
\end{verbatim}
\end{code}
\end{latexonly}
\begin{htmlverbatim}
TYPE= SECTIONING
NAME= \verb|\section|
  SECTIONING\_LEVEL= SECT
  START\_TAG= "?n?n\ST{div.1}?n"
  END\_TAG= "?n\ET{div.1}"
  OPT\_PARAM= FIRST
  PRINT\_OPT= NO\_PRINT
  REQPARAMS= 1
  START\_TAG\_1= "\ST{heading}"
  END\_TAG\_1= "\ET{heading}?n"
END\_TYPE

TYPE= SECTIONING
NAME= \verb|\clause|
  SECTIONING\_LEVEL= SUBSECT
  START\_TAG= "?n?n\ST{div.2}?n"
  END\_TAG= "?n\ET{div.2}"
  OPT\_PARAM= FIRST
  PRINT\_OPT= NO\_PRINT
  REQPARAMS= 1
  START\_TAG\_1= "\ST{heading}"
  END\_TAG\_1= "\ET{heading}?n"
END\_TYPE
\end{htmlverbatim}

    An example output resulting from this \ctab\ (if it had been applied to this
document) is:
\begin{latexonly}
\begin{code}
\begin{verbatim}
...
</div.2>
</div.1>

<div.1>
<heading>The command table file</heading>

    By default, ...
\end{verbatim}
\end{code}
\end{latexonly}
\begin{htmlverbatim}
...
\ET{div.2}
\ET{div.1}

\ST{div.1}
\ST{heading}The command table file\ET{heading}

    By default, ...
\end{htmlverbatim}

\subsection{List environment types}

    In \LaTeX\ the use of the \verb|\item| command is restricted to within a
list environment. The typeset appearance of an \verb|\item| typically depends
on the particular environment in which it is used. \lx\ has a limited capability
of modifying its \verb|\item| tagging output. It can also provide an `end item'
tag for those tagging systems that require such a thing.

    For such list environments, identified by the command type keyword 
\keyword{BEGIN\_LIST\_ENV},
the following command lines should be included within the type specification.
\begin{description}
\item[\keyword{START\_ITEM=}] Actions to be performed at the start 
   of each \verb|\item| command in the list.
\item[\keyword{END\_ITEM=}] Actions to be performed after processing all 
    the \verb|\item|'s text.
\item[\keyword{START\_ITEM\_PARAM=}] Actions to be performed at the start of an 
   \verb|\item|'s optional argument text.
\item[\keyword{END\_ITEM\_PARAM=}] Actions to be performed at the end of an
   \verb|\item|'s optional argument text.
\end{description}
As usual, an unspecified tag defaults to no actions.

    For example, assume that we are not interested in tagging the end of an item,
but we do want to mark each item in an \verb|itemize| environment with the lowercase
letter `o', each \verb|enumerate| item with `(N)' and put a colon after the
optional argument in a description environment. Also, each item should have some 
indentation from the left hand margin.
    
\begin{code}
\begin{verbatim}
TYPE= BEGIN_LIST_ENV
NAME= itemize
  START_ITEM= "?n    o "
END_TYPE

TYPE= END_LIST_ENV
NAME= itemize
END_TYPE

TYPE= BEGIN_LIST_ENV
NAME= enumerate
  START_ITEM= "?n    (N) "
END_TYPE

TYPE= END_LIST_ENV
NAME= enumerate
END_TYPE

TYPE= BEGIN_LIST_ENV
NAME= description
  START_ITEM= "?n  "
  END_ITEM_PARAM= " : "
END_TYPE

TYPE= END_LIST_ENV
NAME= description
END_TYPE
\end{verbatim}
\end{code}

    With the above commands, this \LaTeX{} text:
\begin{verbatim}
\begin{description}
\item[An example]
  \begin{itemize}
  \item the first item;
  \item the second item.
  \end{itemize}
\end{description}
\end{verbatim}
will be transformed into:
\begin{verbatim}
  An example :
    o the first item;
    o the second item.
\end{verbatim}

\subsection{Character types}

    \LaTeX\ treats some characters specially. These special characters are: 
\verb|#|, 
\verb|$|,  
\verb|%|, 
\verb|&|, 
\verb|~|, 
\verb|_|, 
\verb|^|,
\verb|\|,
\verb|{|,
\verb|}|,
and, under some circumstances, also the 
character \verb|@|. 
 \lx\ recognizes these special characters and, if directed, will
perform specified actions; otherwise it treats them as it treats any alphanumeric
character, which is just to print it.

    It has already been stated that commands for the left and right braces
(i.e. \verb|{| and \verb|}|) must be given 
within the \ctab\ as command types
\keyword{LBRACE}, \keyword{RBRACE} respectively.
The dollar symbol (\$) must also be specified via the two command types
\keyword{BEGIN\_DOLLAR} and \keyword{END\_DOLLAR}. Here is an
example of replacing the dollar signs by tags intended to indicate
the start and end of a mathematical phrase.
\begin{latexonly}
\begin{code}
\begin{verbatim}
TYPE= BEGIN_DOLLAR
  START_TAG= "<math>"
END_TYPE

TYPE= END_DOLLAR
  START_TAG= "</math>"
END_TYPE
\end{verbatim}
\end{code}
\end{latexonly}
\begin{htmlverbatim}
TYPE= BEGIN\_DOLLAR
  START\_TAG= "\ST{math}"
END\_TYPE

TYPE= END\_DOLLAR
  START\_TAG= "\ET{math}"
END\_TYPE
\end{htmlverbatim}

    Commands for the other special \LaTeX\ characters are specified with the
\keyword{TEX\_CHAR} command type keyword. 

The characters \verb|_| (underscore) and \verb|^| (caret) are used in
\LaTeX{} math mode to indicate subscripting and superscripting respectively. The
following will replace \verb|^| by \keytext{\ST{sup}}, print the superscript
text (which must be enclosed in braces\footnote{It is good practice to
always enclose superscript and subscript text in braces, even though
\TeX\ does not always require this.}) and at the end close with
\keytext{\ET{sup}}.
\begin{latexonly}
\begin{code}
\begin{verbatim}
TYPE= TEX_CHAR
NAME= ^
  START_TAG= "<sup>"
  REQPARAMS= 1
  END_TAG= "</sup>"
END_TYPE
\end{verbatim}
\end{code}
\end{latexonly}

\begin{htmlverbatim}
TYPE= TEX\_CHAR
NAME= \verb|^|
  START\_TAG= "\ST{sup}"
  REQPARAMS= 1
  END\_TAG= "\ET{sup}"
END\_TYPE
\end{htmlverbatim}

Given the above specifications, then \verb|$(2^{15} - 1)$| will be transformed
into \\
\keytext{\ST{math}(2\ST{sup}15\ET{sup} - 1)\ET{math}}.

\subsection{Verbatim like types}

    The command type \keyword{VCOMMAND} is for the procesing of \LaTeX{}
\verb|\verb|-like commands where the argument of the command is to be
typeset as-is. For example, there might be a command called \verb|\url|
which takes one argument which is meant to be an Internet URL. If the
application was the conversion of a \LaTeX{} document to HTML, then the
following specification could be useful.
\begin{latexonly}
\begin{code}
\begin{verbatim}
TYPE= VCOMMAND
NAME= \url
  REQPARAMS= 1
  PRINT_P1= TO_BUFFER 7
  START_TAG=
    RESET_BUFFER: 7
  END_TAG= "<a href=""
    SOURCE: BUFFER 7
    STRING: "">"
    SOURCE: BUFFER 7
    STRING: "</a>"
    RESET_BUFFER: 7
END_TYPE
\end{verbatim}
\end{code}
\end{latexonly}
\begin{htmlverbatim}
TYPE= VCOMMAND
NAME= \verb|\url|
  REQPARAMS= 1
  PRINT\_P1= TO\_BUFFER 7
  START\_TAG=
    RESET\_BUFFER: 7
  END\_TAG= "\LT{}a href=""
    SOURCE: BUFFER 7
    STRING: ""\GT"
    SOURCE: BUFFER 7
    STRING: "\ET{a}"
    RESET\_BUFFER: 7
END\_TYPE
\end{htmlverbatim}

If the \LaTeX{} source included:
\begin{code}
\begin{verbatim}
... obtainable from 
\url{http://www.cdrom.com/pub/tex}
\end{verbatim}
\end{code}
then the resulting \lx{} output would be:
\begin{latexonly}
\begin{code}
\begin{verbatim}
... obtainable from 
<a href="http://www.cdrom.com/pub/tex">http://www.cdrom.com/pub/tex</a>
\end{verbatim}
\end{code}
\end{latexonly}
\begin{htmlverbatim}
... obtainable from 
\ST{a href="http://www.cdrom.com/pub/tex"}http://www.cdrom.com/pub/tex\ET{a}
\end{htmlverbatim} 
which, if this was then read via an appropriate browser, a link to the URL 
\begin{htmlonly}
<a href="http://www.cdrom.com/pub/tex">http://www.cdrom.com/pub/tex</a>
\end{htmlonly}
would be automatically established.

    Similarly \verb|verbatim|-like environments can also be specified with
the types \keyword{BEGIN\_VENV} and \keyword{END\_VENV}. 
For example, the \file{html.sty} package defines three \LaTeX{}
environments for documents that might be converted from \LaTeX{} tagging
to HTML tagging. One of these, \verb|latexonly| is for \LaTeX{} code
that is not to occur in the HTMLed document and another is \verb|htmlonly|
which contains HTML code that is required for an HTML version
of the document but which is not to appear in the \LaTeX ed document.
The third one is \verb|rawhtml| which is for HTML code to be output
verbatim to the HTML document source.
These could be simulated by:
\begin{code}
\begin{verbatim}
TYPE= BEGIN_VENV
NAME= latexonly
  PC_AT_START= NO_PRINT
END_TYPE

TYPE= END_VENV
NAME= latexonly
  PC_AT_END= RESET
END_TYPE

TYPE= BEGIN_ENV
NAME= htmlonly
END_TYPE

TYPE= END_ENV
NAME= htmlonly
END_TYPE

TYPE= BEGIN_VENV
NAME= rawhtml
END_TYPE

TYPE= END_VENV
NAME= rawhtml
END_TYPE
\end{verbatim}
\end{code}


\subsection{Odd command types}

    The majority of commands in \LaTeX{} that take optional arguments
have only a single optional argument that is either immediately after
the command or after all the required arguments. There are, however, some
commands that do not fit this pattern. This set of command types enables
at least some of these `odd' commands to be handled.

    The command type keyword is of the form \keytext{COMMAND\_code}, where
\keytext{code} indicates the type and ordering of the arguments. The
\keytext{code} is composed from combinations of the letters \keytext{O}
(for an optional argument) and \keytext{P} (for a required parameter (i.e.,
argument)). The ordering of these letters in the \keytext{code} specifies
the type and ordering of the command's arguments.

    The `odd' command types are:
\begin{description}
\item[\keyword{COMMAND\_OOP}] Corresponding to a \LaTeX{} command of the form \\
\verb|\com[OptParam][OptParam]{ReqParam}|.
For example, the \verb|\makebox|
command falls into this category.

\item[\keyword{COMMAND\_OOOPP}] Corresponding to a \LaTeX{} command of the form \\
\verb|\com[OptParam][OptParam][OptParam]{ReqParam}{ReqParam}|.
For example, the \verb|\parbox|
command falls into this category.

\item[\keyword{COMMAND\_OPO}] Corresponding to a \LaTeX{} command of the form \\
\verb|\com[OptParam]{ReqParam}[OptParam]|.
For example, the \verb|\RequirePackage| and \verb|\LoadClass|
commands fall into this category.

\item[\keyword{COMMAND\_POOOP}] Corresponding to a \LaTeX{} command of the form \\
\verb|\com{ReqParam}[OptParam][OptParam][OptParam]{ReqParam}|.

\item[\keyword{COMMAND\_POOP}] Corresponding to a \LaTeX{} command of the form \\
\verb|\com{ReqParam}[OptParam][OptParam]{ReqParam}|.
For example, the \verb|\newcommand| and its companion commands
fall into this category.

\item[\keyword{COMMAND\_POOPP}] Corresponding to a \LaTeX{} command of the form \\
\verb|\com{ReqParam}[OptParam][OptParam]{ReqParam}{ReqParam}|.
For example, the \verb|\newenvironment| and its companion command
fall into this category.
\end{description}

    As usual, the command name is required, as are any actions. However,
it is not necessary to specify the number of required arguments (i.e.
\keyword{REQPARAMS=}) nor the position of the optional argument (i.e. 
\keyword{OPT\_PARAM=}), as \lx\ already has this information. The tag actions
are according to the argument ordering given in the \keytext{code} and are
specified by the required argument tags (e.g. \keytext{START\_TAG\_n=} and
\keytext{END\_TAG\_n=}). 
Do not use any of the command lines for optional arguments. Argument
actions are controlled in the usual manner.

    A typical example of the use of these commands is to supress any processing
of the \LaTeX{} \verb|\newcommand| and its ilk. For example:
\begin{code}
\begin{verbatim}
TYPE= COMMAND_POOP
NAME= \providecommand
  PRINT_P1= NO_OP
  PRINT_P2= NO_OP
  PRINT_P3= NO_OP
  PRINT_P4= NO_OP
END_TYPE

TYPE= COMMAND_POOPP
NAME= \renewenvironment
  PRINT_P1= NO_OP
  PRINT_P2= NO_OP
  PRINT_P3= NO_OP
  PRINT_P4= NO_OP
  PRINT_P5= NO_OP
END_TYPE
\end{verbatim}
\end{code}    


\subsection{Other command types}

    The \keytext{OTHER\_} command types (\keyword{OTHER\_COMMAND}, 
\keyword{OTHER\_BEGIN} 
and \keyword{OTHER\_END})
are very limited in what can be affected. Basically, these provide for
default printing actions if the corresponding \LaTeX\ command has not been
identified elsewhere in the \ctab.

    If there are no commands within the specification, the name of the command and
all its arguments will be printed verbatim.

    The command lines \keyword{START\_TAG=} and \keyword{END\_TAG=} 
cause the corresponding
actions to be performed before and after the name of the command is printed. Any
arguments are printed verbatim. 

    The command line \keyword{PRINT\_CONTROL=} with a value of \keyword{NO\_PRINT}
causes the command name not to be printed, nor any arguments that \lx\ may 
find associated with the command.

\subsection{Picture types}

    The \keytext{\_PICTURE\_} command types differ from all the other types in
\lx, just as they do in \LaTeX. In \LaTeX\ some of the picture drawing commands 
take arguments of the form \verb|(number, number)|, representing a coordinate
pair,  as well as the usual
required arguments enclosed in curly braces and possibly an optional 
argument enclosed in square brackets. Within \lx, commands that take coordinate
arguments are treated specially in the \ctab.

    Generally speaking, the \lx\ command types are of the form 
\keytext{PICTURE\_code},
where \keytext{code} indicates the type and ordering of the arguments. The
\keytext{code} is composed from combinations of the letters \keytext{C} (for a
coordinate argument), \keytext{O} (for an optional argument) and \keytext{P} (for
a required argument). For example, \keyword{PICTURE\_PCOP} indicates a picture
command that has a required argument, followed by a coordinate argument,
followed by an optional argument and finally another required argument.

    The provided picture types are:
\begin{description}
\item[\keyword{BEGIN\_PICTURE\_CC}] Corresponding to a \LaTeX\ command of the form \\
     \verb|\begin{PictureEnv}(coords)(coords)|, where the final coordinate argument
      is optional.
\item[\keyword{PICTURE\_CCPP}] Corresponding to a \LaTeX\ command of the form \\
     \verb|\com(coords)(coords){ReqParam}{ReqParam}|. 
     For example, the \verb|\multiput| command falls into this category.
\item[\keyword{PICTURE\_CO}]  Corresponding to a \LaTeX\ command of the form \\
     \verb|\com(coords)[OptParam]|.
     For example, the standard \LaTeX\ \verb|\oval| command falls into 
     this category.
\item[\keyword{PICTURE\_COP}]  Corresponding to a \LaTeX\ command of the form \\
     \verb|\com(coords)[OptParam]{ReqParam}|.
     For example, the \verb|\makebox| and \verb|\framebox| commands fall 
     into this category.
\item[\keyword{PICTURE\_CP}]  Corresponding to a \LaTeX\ command of the form \\
     \verb|\com(coords){ReqParam}|.
     For example, the \verb|\put|, \verb|\line| and \verb|\vector| commands 
     fall into this category.
\item[\keyword{PICTURE\_OCC}]  Corresponding to a \LaTeX\ command of the form \\
     \verb|\com[OptParam](coords)(coords)|.
     For example, the \verb|\graphpaper| command from the \verb|graphpap|
     package falls into this category.
\item[\keyword{PICTURE\_OCCC}]  Corresponding to a \LaTeX\ command of the form \\
     \verb|\com[OptParam](coords)(coords)(coords)|.
     For example, the \verb|\qbezier| command falls into this category.
\item[\keyword{PICTURE\_OCO}]  Corresponding to a \LaTeX\ command of the form \\
     \verb|\com[OptParam](coords)[OptParam]|.
     For example, the \verb|\oval| command from the \verb|pict2e| package
     falls into this category.
\item[\keyword{PICTURE\_PCOP}]  Corresponding to a \LaTeX\ command of the form \\
     \verb|\com{ReqParam}(coords)[OptParam]{ReqParam}|.
     For example, the \verb|\dashbox| and \verb|\savebox| commands fall
     into this category.
\item[\keyword{END\_PICTURE}]  Corresponding to a \LaTeX\ command of the form \\
    \verb|\end{PictureEnv}|.
\end{description}

    As usual, the command name is required, as are any actions. However,
it is not necessary to specify the number of required arguments (i.e.
\keyword{REQPARAMS=}) nor the position of the optional argument (i.e. 
\keyword{OPT\_PARAM=}), as \lx\ already has this information. The tag actions
are according to the argument ordering given in the \keytext{code} and are
specified by the required argument tags (e.g. \keytext{START\_TAG\_n=} and
\keytext{END\_TAG\_n=}). 
Do not use any of the command lines for optional arguments. Argument
actions controlled in the usual manner.

    As an example, the following specifications within a \ctab\ should be
sufficient to ensure that any picture commands in a source file are 
not passed through to the output file.

\begin{code}
\begin{verbatim}
TYPE= BEGIN_PICTURE_CC
NAME= picture
PRINT_P1= NO_PRINT
PRINT_P2 = NO_PRINT
END_TYPE

TYPE= PICTURE_CP
NAME= \put
PRINT_P1= NO_PRINT
PRINT_P2= NO_OP
END_TYPE

TYPE= PICTURE_CCPP
NAME= \multiput
PRINT_P1= NO_PRINT
PRINT_P2= NO_PRINT
PRINT_P3= NO_OP
PRINT_P4= NO_OP
END_TYPE

TYPE= PICTURE_PCOP
NAME= \savebox
PRINT_P1= NO_OP
PRINT_P2= NO_PRINT
PRINT_P3= NO_OP
PRINT_P4= NO_OP
END_TYPE

TYPE= PICTURE_OCC
NAME= \graphpaper
PRINT_P1= NO_OP
PRINT_P2= NO_PRINT
PRINT_P3= NO_PRINT
END_TYPE

TYPE= PICTURE_OCCC
NAME= \qbezier
PRINT_P1= NO_OP
PRINT_P2= NO_PRINT
PRINT_P3= NO_PRINT
PRINT_P4= NO_PRINT
END_TYPE

TYPE= END_PICTURE
NAME= picture
END_TYPE
\end{verbatim}
\end{code}

\begin{description}
\item[NOTE 1:] The action \keyword{NO\_OP} cannot be applied to an
 argument that is a coordinate pair.

\item[NOTE 2:] As \lx\ is essentially limited to printing actions, 
and cannot actually process any
\LaTeX\ picture drawing commands, the suppression of picture printing is 
probably the most usual use of the picture commands.
\end{description}

\subsection{Special command types}

    The \keytext{SPECIAL\_} commands, namely \keyword{SPECIAL\-\_COMMAND}, 
\keyword{SPECIAL\-\_BEGIN\-\_ENV},
 \keyword{SPECIAL\-\_BEGIN\-\_LIST}, 
\keyword{SPECIAL\-\_END\-\_ENV},
\keyword{SPECIAL\-\_END\-\_LIST} and
\keyword{SPECIAL\-\_SECTIONING}, are provided for cases where some special kind of
output processing is required that is not built into \lx. In order to implement
any commands of these types, it is necessary to modify the internals of \lx\
and recompile the source code. This is not recommended.

\subsection{File inclusion}

    A \ctab\ file can include other \ctab\ files. In turn an included
file can recursively include other \ctab\ files. The file inclusion command
line is
\begin{code}
\begin{verbatim}
INCLUDE= FileName
\end{verbatim}
\end{code}
where \keyword{FileName} is the name of the \ctab\ file to be included. The effect
is that the above line is replaced by the contents of \keyword{FileName}.

    For example, assume that there are three \ctab\ files called respectively
\file{detex.ct}, \file{detex.l2x} and \file{detex.fl}. The contents of these 
files are:
\begin{code}
\begin{verbatim}
C=  ----------file detex.ct
...
INCLUDE= detex.l2x
...
C= ----------end of detex.ct
END_CTFILE=        end of detex.ct
\end{verbatim}
\end{code}
and for \file{detex.l2x} as:
\begin{code}
\begin{verbatim}
C= ---------- file detex.l2x

TYPE= COMMAND
NAME= \lx
  START_TAG= "LTX2X"
END_TYPE

INCLUDE= detex.fl

TYPE= COMMAND
NAME= \ctab
  START_TAG= "command table"
END_TYPE

C= ---------- end of file detex.l2x
END_CTFILE=         end of file detex.l2x
\end{verbatim}
\end{code}
and lastly \file{detex.fl} is:
\begin{code}
\begin{verbatim}
C= ---------- file detex.fl

TYPE= COMMAND
NAME= \fl
  START_TAG= "FLaTTeN"
END_TYPE

C= ---------- end file detex.fl
END_CTFILE=         end file detex.fl
\end{verbatim}
\end{code}
    Then, as far as \lx\ is concerned, the original \file{detex.ct} file is 
treated as though it had been written as:
\begin{code}
\begin{verbatim}
C=  ----------file detex.ct
...
C= ---------- file detex.l2x

TYPE= COMMAND
NAME= \lx
  START_TAG= "LTX2X"
END_TYPE

C= ---------- file detex.fl

TYPE= COMMAND
NAME= \fl
  START_TAG= "FLaTTeN"
END_TYPE

C= ---------- end file detex.fl

TYPE= COMMAND
NAME= \ctab
  START_TAG= "command table"
END_TYPE

C= ---------- end of file detex.l2x
...
C= ----------end of detex.ct
END_CTFILE=        end of detex.ct
\end{verbatim}
\end{code}

    Note that nasty things will happen if you have a cycle of inclusions. That is,
you must not have anything similar to file \file{A} including file \file{B} which
includes file \file{C} which in turn includes either file \file{A} or \file{B}.

\subsection{Interpreter commands} \label{sec:intcom}

    \lx\ includes an interpreter for a procedural programming language
that is based on the ISO international standard \Express{} information
modeling language~\cite{EBOOK, EXPRESSIS}. At the moment the
programming language within \lx{} is anonymous, but for ease
of reference I will call it \ExpressA 
(\Express{} -Almost? -Approximate? -Anonymous?). 
The \ExpressA{} language is described later in section~\ref{sec:expressa}, 
but for now it is sufficient to know the commands that signify
the start and end of this code.

    The command \keyword{CODE\_SETUP=} indicates the commencement of
code to be run before any document processing occurs. The
\keyword{END\_CODE} command signifies the end of this code block.
This block should be placed in the \ctab{} before any other commands
except for the \keytext{ESCAPE...} commands, if any. This block
can contain variable declarations, function and procedure declarations,
and statements.

    Code consisting purely of statements can be placed anywhere that
a tagging action may be specified. These statements are enclosed
between a \keyword{CODE:} and \keyword{END\_CODE} pair of commands.

    The \ExpressA{} language is described in detail in \ref{sec:expressa}, 
but to give a flavour of it here 
is a simple possible application. It has been noted that \lx{} will find
difficulty in processing the contents of the \LaTeX{} \keytext{picture}
environment. The following portions of a \ctab{} write the contents
of a \keytext{figure} environment to an external file and uses the programming
language to keep a count of the number of figures so processed.

\begin{code}
\begin{verbatim}
c=  declare and initialise a variable
CODE_SETUP=
  LOCAL
    fignum : INTEGER;
  END_LOCAL;
  fignum := 0;
END_CODE

c= write figure contents to an external file
TYPE= BEGIN_ENV
NAME= figure
  OPT_PARAM= FIRST
  PRINT_OPT= NO_PRINT
  PC_AT_START= TO_FILE figs.tmp
  START_TAG=
    CODE:
      fignum := fignum + 1;           -- increment figure counter
      println;                        -- print a blank line
      println('%%% FIGURE ', fignum); -- write counter as a LaTeX comment
    END_CODE
    STRING: "\begin{figure}"
END_TYPE

c= close figure environment, back to normal output, and output
c= text indicating that a figure should be here
TYPE= END_ENV
NAME= figure
  PC_AT_START= RESET
  START_TAG=
    SWITCH_TO_FILE: figs.tmp
    STRING: "\end{figure}?n?n"
    SWITCH_BACK:
    CODE:
      println;
      println('PLACE FOR FIGURE ', fignum);
      println;
   END_CODE
END_TYPE
\end{verbatim}
\end{code}

\section{The LTX2X program} \label{sec:program}

    \lx\ is written using flex and bison. The resulting C code should
compile on any system. More details are given later, but for the end-user
the next section describes how to run the program, assuming that is available
on your system.

\subsection{Running LTX2X}

    The syntax for running the compiled version of \lx\ is:
\begin{verbatim}
ltx2x [-c] [-f table-file] [-p number] [-w] [-D dir_cat_char]
      [-P path_seperators] [-S]
      [-i number] [-l number] [-t] [-y number] [-C] [-E] 
      input-file output-file
\end{verbatim}
where elements in square brackets are options. The options fall into
two groups, one for the casual user and the other for those who may be
interested in the internals of \lx. The first group of options includes:
\begin{description}
\item[{\tt -c}] By default, \lx\ ignores all \LaTeX\ comments in the input
     file. This option causes \lx\ to write the comments to the output file.

\item[{\tt -f}] By default, \lx\ reads the \ctab\ from a file called
     \verb|ltx2x.ct|. If the required \ctab\ is in a file with another name this
     option is used to change from the default file. For example,
\begin{verbatim}
> ltx2x in.tex out.l2x
\end{verbatim}
reads a \ctab\ from \verb|ltx2x.ct|, while
\begin{verbatim}
> ltx2x -f detex.ct in.tex out.l2x
\end{verbatim}
reads a \ctab\ from file \verb|detex.ct|.

\item[{\tt -p}] This option causes \lx\ to  `pretty print' the output file
     (as far as it is able to). The \verb|number| is required and it indicates 
     the desired maximum number
     of characters per output line. If this is considered to be too small,
     then \lx\ chooses a value. Note that pretty printing is only applied
     to the source file --- not to any replacement tags. That is, it
     only tries to format the running text from the source file.

\item[{\tt -w}] By default, \lx\ outputs source white space just at it reads it.
     This option causes \lx\ to collapse any amount of contiguous white space
     to a single space. The \verb|-p| option includes the \verb|-w| option.

\item[{\tt -D}] The value of this option is the character that the operating system
    uses to catenate directory names to form a path (see~\ref{sec:search}). 
    The default value is a
    slash (i.e. \verb|/|). The default could be changed to a backslash, for example,
    by \verb|-D \|.

\item[{\tt -P}] The environment variable (see~\ref{sec:search})
   contains a list of directories (also known
   as path names). In the operating system that I use, these are separated by
   the colon (\verb|:|) character which, together with the semi-colon
   and space characters, form
   the \lx\ default separators. The path separator characters can be changed 
   with this option.
   For example, \verb|-P :| will make the separators be a colon
   or a space (space is automatically included in the separator list).

\item[{\tt -S}] This option enables the source level debugger 
   (see~\ref{sec:sld}) for any embedded \ExpressA{} code.
\end{description}

The second group of options are principally for those who might be
extending the \lx{} system.

\begin{description}
\item[{\tt -i}] This produces information that may be useful for debugging
     the \ExpressA{} interpreter. \verb|number| is an integer 
     between 1 and 9 inclusive.
     The greater the number, the more diagnostics are generated.

\item[{\tt -l}] This produces information that may be useful for debugging
     the \lx{} program. \verb|number| is an integer between 1 and 9 inclusive.
     The greater the number, the more diagnostics are generated.

\item[{\tt -t}] This generates diagnostics related to the processing of
    the \ctab\ file.

\item[{\tt -y}] Like the \verb|l| option, but produces diagnostic information
     from the parser (this is actually a null option, but may be useful
     in the future).

\item[{\tt -C}] Disable any interpreter debugging information during
     the code generation pass. This is not necessary unless the {\tt -i}
     option is used.

\item[{\tt -E}] Disable any interpreter debugging information during
     the code execution processing.This is not necessary unless the {\tt -i}
     option is used.

\end{description}




    \lx\ first reads the specified \ctab\ file, together with any included files,
looking first in the current directory, then in the directories specified by
the environment variable (if it exists).
 It then reads the \verb|input-file| from the current directory,
performs the actions specified in the \ctab\ and outputs the results to
the \verb|output-file|.

    Three other files are also generated.
\begin{itemize}
\item \verb|ltx2xct.lis| --- This contains a human-readable form of the internal
     representation of the \ctab. It may be useful if there are any errors
     in the original \ctab.
\item \verb|ltx2x.err| --- This contains any error or warning messages generated
     by \lx. It also contains any diagnostic information that may have been
     requested via a command line option.
\item \verb|interp.csg| --- This contains a human readable listing of the
     internal byte code generated by the \ExpressA{} interpreter.
\end{itemize}

    When \lx\ is running normally it prints out a counter to the terminal
indicating how many hundreds of input source file lines it has processed.
Lack of such output is an indication that the program may be in a loop and
chewing up CPU cycles to no avail. In this case, stop the program and examine
the output for indications of where the trouble is occurring.

    A limited number of errors are allowed when processing the \ctab\
and the input \LaTeX\ file before \lx\ gives up and quits. In
particular, if it is reading a \ctab\ file that includes another file, say one
called \file{zilch},
that it cannot read, it prints the following message to the user's terminal.
\begin{verbatim}
Can't open file zilch
Enter new file name, or I to ignore, or Q to quit
: 
\end{verbatim}
A {\tt Q} (or {\tt q}) response stops \lx\ from any further processing. An
{\tt I} (or {\tt i}) response causes \lx\ to stop looking for the included file 
and continue processing the current file. Any other response is taken to be
the name of an included file, which \lx\ then tries to read. If it fails, then
the above message is repeated. The user is given a limited number of opportunities
to identify a readable file before \lx\ quits altogether with this message:
\begin{verbatim}
Last attempt. Can't open file zilch. I'm giving up.
\end{verbatim}


    Regarding performance, the time taken by \lx\ to process a document does
not appear to be significantly different from the time to \LaTeX\ the 
same document.

\subsubsection{Directory searching} \label{sec:search}

    The program employs a search algorithm to find files that are not
in the current directory. It first looks in the current directory and
if a file of the given name is found, then that is used. If the file
is not found, then it searches for it among directories that are
specified in a system environment variable. This variable specifies
a list of pathnames, where the directories forming the path are
combined using a catenation character. For example, \verb|dir1/dir2/dir3|
could be a pathname, where the slash (\verb|/|) is the catenation character.
If it is looking for file \verb|afile.txt| it will catenate the file name
to the path name (e.g. \verb|dir1/dir2/dir3/afile.txt|) and look for
that. The pathnames in the list are separated by another character
(in fact it can be one from a list of characters). For example here
is a list of two pathnames; \verb|dir1/dir2;dir1/dir4|, where the semi-colon
(\verb|;|) is the pathname separator.

    By default, the program uses a slash (\verb|/|) as the directory
catenation character and the pathname separators can be a space, or
a colon or a semi-colon (i.e., any of \verb*| :;|). All these characters
can be altered via the program command line options, and should be set to
match the conventions of your operating system.

    The environment variable used by the program is LTX2XTABLES. 
On the operating system that I use, I set this in my login file like:
\begin{verbatim}
setenv LTX2XTABLES .:/dir1/dir2:/dir3/dir4
\end{verbatim}
Your system may have different conventions. Note that if the environment
variable is not set, only files in the current directory are considered.


\subsection{System components}

    The system consists of five main components --- a lexer, a parser, a
library of support functions and \ctab\ parsing code, a 
user-defined library of functions, and an interpreter for the \ExpressA{}
language.

\subsubsection{The lexer}

    The lexer is generated by flex~\cite{LEVINE92} 
(a more functional version of lex~\cite{LESK75}). 
The source for the lexer is in file \file{l2x.l}.
Its principal function is to read a \LaTeX\
source file and recognize \LaTeX\ commands. In general, it passes off the
relevant command tokens to the parser for performing appropriate actions.

    However, the lexer does do some processing of the source itself.
\begin{itemize}
\item It recognizes \LaTeX\ comments (i.e. any text starting with a percent
      sign and ending with a newline). It silently ignores these comments, unless
      run with the \verb|-c| option.
\item It recognizes the `standard' \LaTeX\ verbatims. It will write out the
      appropriate tags at the start and end of the verbatim text, while writing
      the verbatim text directly to the output file, bypassing the parser.
      It does not distinguish between the unstarred and starred
      versions of the verbatims.
\item Newlines and whitespace are directly written to the output file, again
      bypassing the parser. The \verb|-p| and \verb|-w| options control the
      final appearance of whitespace, newlines and paragraphing.
\item It recognizes the command \verb*|\ | i.e. a backslash followed by a
      space, and writes the tags defined in the \verb|SLASH_SPACE| specification
      directly to the output file.
\end{itemize}

    The lexer is designed to recognize four kinds of \LaTeX\ commands.
\begin{itemize}
\item Commands of the form \verb|\begin{environment}|
\item Commands of the form \verb|\end{environment}|
\item Any other command of the form \verb|\command|
\item As special cases, commands that are 'verbatim-like' or `verb-like'.
\end{itemize}
When it finds a command, it looks up the command or environment name in the
\ctab\ and sends the appropriate token and its \ctab\ location to the
parser. As a special case the contents of verbatim-like environments and
the argument of verb-like coommands are processesd within
the lexer and not sent to the parser.


\subsubsection{The parser}

    The parser is generated by bison~\cite{LEVINE92} 
(a more powerful version of YACC~\cite{JOHNSON75}). 
The source for the parser is in file \file{l2x.y}.
Essentially it defines a very simple
grammar for a \LaTeX\ document. That is, the grammar is limited to
generic kinds of commands and command arguments. It does not understand
the `meaning' of any of the commands or arguments.

    When the parser receives a token from the lexer it tries to match it with
one of the grammar rules, performing the actions specified by the \ctab.
Here is an extract from the parser grammar file, \file{l2x.y},
for a \LaTeX\ command that has
two required arguments followed by an optional argument.

\begin{code}
\begin{verbatim}
l2xComm2Opt: COMMAND_2_OPT
        {
          start_with_req($1);
        }
        ReqParam
        {
          action_p_p1($1,1);
        }
        ReqParam
        {
          action_p_opt($1,2);
        }
        OptParam
        {
          action_last_opt($1);
        }
        ;
\end{verbatim}
\end{code}

    The actions are enclosed in braces, and are interspersed with the elements
of the grammar.

    The token \verb|COMMAND_2_OPT| indicates that the lexer has found a command
that takes two required arguments followed by an optional argument. 
The parser then performs some
actions. The \verb|start_with_req| function is the standard \lx\ function
for the first action in a command production where the final argument
is optional. The \verb|$1| refers to the
location of the particular command in the \ctab, and its value is passed to the
parser by the lexer.

    The parser then expects a required argument (i.e. \verb|{|, token \verb|LBRACE|)
as the start of the required argument, followed by the text of the argument and
finished off by a right brace (i.e. \verb|}|, token \verb|RBRACE|); the grammar
for all of this is specified in the production called \verb|ReqParam|). If it
finds these it performs some further actions, otherwise it reports an
error.
In this case the action is defined by the function \verb|action_p_p1|,
which is the standard action performed between two required arguments
(the second argument in the function call specifies the Pth argument that
has been recognized). Another required argument is then expected.
In this case the action is defined by the function \verb|action_p_opt|,
which is the standard action performed between the end of the Pth required argument
and the start of an optional argument. It then looks for an optional
argument, the grammar for which is specified in the production called
\verb|OptParam|. The final action is specified by the standard function
\verb|action_last_opt| for finishing off a command that ends with an
optional argument.

    The grammar for a command that that has two required arguments, 
and possibly an
initial optional argument is similar:

\begin{code}
\begin{verbatim}
l2xComm2: COMMAND_2
        {
          start_with_opt($1);
        }
        OptParam
        {
          action_opt_first($1);
        }
        ReqParam
        {
          action_p_p1($1,1);
        }
        ReqParam
        {
          action_last_p($1,2);
        }
        ;
\end{verbatim}
\end{code}

\subsubsection{The support libraries}

    Source code for the C main program and support functions is in file
\file{l2xlib.c}. 
    The main program is responsible for reading in the \ctab\ and calling the
lexer and parser to do the appropriate processing.
    The file also contains a variety of support functions that are, or could 
be, used in the lexer, parser, action library, or user-defined library.

    The standard actions for the grammar are contained in file \file{l2xacts.c}.

\subsubsection{The user-defined library}

    The intent of this library is that masochistic users can define their
own functions for use within \lx\ when processing their \verb|SPECIAL_|
commands, without having to modify the \lx\ support or action libraries.

    Source code for the user-defined library should be maintained in a file
called \file{l2xusrlb.c} and a corresponding header file called \file{l2xusrlb.h}.

\subsubsection{The \ExpressA{} interpreter}

    The \ExpressA{} interpreter is based on algorithms originally developed
by Ronald Mak~\cite{MAKR91} for interpreting Pascal. His original
algorithms have been modified and extended to cater for \ExpressA.
The interpreter module has a minimal interface with the rest of the
\lx{} system, and could easily be modified to be a stand-alone program
(in fact it started that way in the first place). The interface
between \lx{} and the interpreter is confined to the small
\file{l2xistup.c} file.


\section{The \ExpressA{} programming language} \label{sec:expressa}

    \Express{} is a language for information modeling and includes both
declarative and procedural aspects~\cite{EBOOK}. There are also two other
companion languages called respectively \ExpressG{} and \ExpressI. The former
of these is a graphical form of the declaritive aspects of \Express, and the
later is an instiation and test case specification language. These languages
are either ISO international standards~\cite{EXPRESSIS} or on the way
to becoming so~\cite{EXPRESSITR}.

    Certain of the procedural aspects of \Express{} and \ExpressI{} are relevent
to the \lx{} concepts and so, together with some other reasons,
it seemed appropriate to provide an interpreter for a similar language for
use within \lx. \ExpressA{} provides a major subset of the \Express{} procedural
language, together with some Pascal-like additions for input and output.
Of particular note, strings are a built-in type in \ExpressA. The language
also supports three-valued logic and the concept of an `indeterminate'
value of any type.

    Earlier I gave an example \ctab{} to replace the text of a
\LaTeX{} document with the words `Goodbye document'. Here is
an \ExpressA{} program that outputs `Goodbye document'.
\begin{code}
\begin{verbatim}
println('Goodbye document');
END_CODE
\end{verbatim}
\end{code}

    The following gives a brief overview of \ExpressA. For more details
consult Schenck \& Wilson~\cite{EBOOK}.

\subsection{Basic elements}

    \ExpressA{} is a case-insensitive language and uses the ASCII character
set. Two kinds of comments are supported --- an end of line comment,
which starts with a \verb|--| pair and continues until the end of the current
line --- and an extended comment. An extended comment starts with a
\verb|(*| pair and is ended by a matching \verb|*)| pair; extended comments
may be nested.

    The language contains many reserved words, some of which are only
applicable to the \Express{} and \ExpressI{} languages.

    Identifiers are composed of an initial letter, possibly followed by
any number of letters, digits, and the underscore character.

    Literals are self defining constant values. An integer literal consists
of one or more digits, the first of which shall not be zero. Real numbers
start with one or more digits, followed by a decimal point. Further
digits may occur after the point, and finaly there may be an exponent
in the `e' notation format (e.g., \verb|123.456e-78|).

    A string literal is any sequence of characters enclosed by single
quote marks. If a single quote mark is meant to form part of the string,
two quote marks must be used at that point.

    Logical literals consists of one of these keywords: \keyword{FALSE},
\keyword{UNKNOWN} or \keyword{TRUE}.

    \ExpressA{} also includes some other constants. \keyword{PI} stands
for the value of the mathematical constant $\pi$ (3.1415\ldots), 
and \keyword{CONST\_E}
stands for the value of the mathematical constant $e$ (2.7182\ldots), 
the base of natural logarithms. The special token \verb|?| stands for
an indeterminate value of any type. The three constants
\keyword{THE\_DAY}, \keyword{THE\_MONTH} and \keyword{THE\_YEAR} are integer
values for the current date holding the day of the month (1--31), the
month of the year (1--12) and the year (four digits), respectively.


\subsection{Data types}

    \ExpressA{} is a typed language. The simple data types are: \keyword{INTEGER},
\keyword{REAL}, \keyword{STRING} and \keyword{LOGICAL}.

    The aggregation data types are \keyword{ARRAY}, \keyword{BAG}, \keyword{LIST},
and \keyword{SET}. The array data type is of a fixed size and must have
declared lower and upper bounds (index range), such as \verb|ARRAY [-7:10] OF|.
The other aggregate data types are dynamic in size, but may have lower and
upper bounds specified for the number of elements, such as \verb|SET [2:5] OF|,
meaning a set that should have between two and five members. For the
dynamic aggregates the upper bound may be given as \verb|?|, which means
an unlimited upper bound, such as \verb|LIST [2:?] OF|. If a bound
specification is absent, then the dynamic aggregate can hold from zero
to any number of elements.\footnote{The dynamic aggregates may not
be fully implemented due to lack of time.}

    Aggregates are one dimensional, but can be chained together for 
multi-dimensional aggregates, like 
\begin{code}
\begin{verbatim}
ARRAY [1:4] OF LIST OF INTEGER;
\end{verbatim}
\end{code}

    The enumeration data type is a parenthesised comma seperated list of
identifiers. These identifiers represent the values of the enumerated type;
for instance
\begin{code}
\begin{verbatim}
ENUMERATION OF (red, green, blue)
\end{verbatim}
\end{code}

    A defined data type is one declared and named by the user using the
\keyword{TYPE} and \keyword{END\_TYPE} construct. For example
\begin{code}
\begin{verbatim}
TYPE length = REAL; END_TYPE;
TYPE crowd_size = INTEGER; END_TYPE;
TYPE signal_colour = ENUMERATION OF (red, amber, green); END_TYPE;
\end{verbatim}
\end{code}

  An entity data type consists of a list of attributes and their types, enclosed
in a \keyword{ENTITY} and \keyword{END\_ENTITY} pair. An entity type
is named.
\begin{code}
\begin{verbatim}
ENTITY an_ent;
  auditorium_width : length;
  audience         : crowd_size;
  title            : STRING;
  profit           : REAL;
END_ENTITY;
\end{verbatim}
\end{code}

   \ExpressA{} provides for algorithms in the form of functions and procedures.

A \keyword{FUNCTION} is an algorithm that operates on parameters and returns
a single resultant value of a specified data type. An invocation of a function
in an expression evaluates to the resultant value at the point of invocation.
For example:
\begin{code}
\begin{verbatim}
FUNCTION func (par1 : INTEGER; par2 : STRING) : STRING;
  LOCAL
    str : STRING;
    -- other variable declarations
  END_LOCAL;
  -- the algorithm statements are here
  RETURN(str);
END_FUNCTION;
\end{verbatim}
\end{code}
Note that the parameters are typed.

    A \keyword{PROCEDURE} is an algorithm that receives parameters from the 
point of invocation and operates on them in some manner. Changes to the parameters
within the procedure are only reflected to the point of invocation
when the formal parameter is preceded by the keyword \keyword{VAR}.
For example:
\begin{code}
\begin{verbatim}
PROCEDURE proc (par1 : INTEGER; VAR par2 : STRING);
  -- local declarations and the algorithm statements
END_PROCEDURE;
\end{verbatim}
\end{code}
Note that the parameters are typed. In this case the value of \keytext{par2}
may be changed.

    Variables are declared in a local block, enclosed by the keywords
\keyword{LOCAL} and \keyword{END\_LOCAL}. A variable declaration consists
of an identifer and its type, such as:
\begin{code}
\begin{verbatim}
LOCAL
  str    : STRING;
  e1, e2 : an_ent;     -- e1 and e2 are both of type an_ent
  e3     : an_ent;     -- so is e3
  num    : INTEGER;
  col    : signal_colour;
  matrix : ARRAY [1:15] OF ARRAY [1:15] OF REAL;
END_LOCAL;
\end{verbatim}
\end{code}

   The above declarations must be in the following order:
\begin{enumerate}
\item \keyword{ENTITY} and/or \keyword{TYPE} declarations
\item \keyword{FUNCTION} and/or \keyword{PROCEDURE} declarations
\item a \keyword{LOCAL} declaration block
\end{enumerate}

    After the above can come any number of statements.

\subsection{Statements}

    \ExpressA{} supports the following statements:
\begin{itemize}
\item Null statement
\item Assignment statement
\item Call statement
\item \keyword{BEGIN} \ldots \keyword{END} compound statement
\item \keyword{CASE} \ldots \keyword{END\_CASE} statement
\item \keyword{IF} \ldots \keyword{THEN} \ldots \keyword{ELSE} 
      \ldots \keyword{END\_IF} statement
\item \keyword{REPEAT} \ldots \keyword{WHILE} \ldots \keyword{UNTIL} \ldots
      \keyword{END\_REPEAT} statement. This also includes the
      \keyword{ESCAPE} and \keyword{SKIP} statements
\item \keyword{RETURN} statement
\end{itemize}

    All the above statements are completed by a \keytext{;} (semicolon).
The \emph{null} statement just consists of a semicolon.

    The \emph{assignment} statement is used to assign an instance to a local
variable or parameter. The data types must be compatible.
\begin{code}
\begin{verbatim}
LOCAL
  a, b, c : REAL;
END_LOCAL;
...
  a := 2.3E-6;
  b := a;
  a := -27.0;
  c := 33.3*b;
\end{verbatim}
\end{code}

    The \emph{call} statement invokes a procedure or a function. The actual
parameters provided with the call must agree in number, order and type
with the formal parameters specified in the procedure or function
declaration. The supplied parameter values must be assignment compatible
with the formal parameters. This is an example of calling the \ExpressA{}
defined \keyword{INSERT} procedure which takes three parameters:
\begin{code}
\begin{verbatim}
INSERT(my_list, list_element, 0);
\end{verbatim}
\end{code}

    The \emph{compound} statement consists of one or more statements enclosed
between a \keyword{BEGIN} and \keyword{END} pair. The enclosed statements
are treated as a single statement.
\begin{code}
\begin{verbatim}
...
  BEGIN
    a := 2.3e-7;
    b := a;
    c := b*33.3;
  END;
\end{verbatim}
\end{code}

    The \emph{case} statement is a means of selectively executing statements
based on the value of an expresion.
\begin{code}
\begin{verbatim}
LOCAL
  a : INTEGER;
  x, y : REAL;
END_LOCAL;
...
  a := 2;
  x := 21.9;
  CASE 2*a OF
    1         : x := SIN{x};
    2         : x := SQRT(x);
    3         : x := LOG(x);
    4         : x := COS(x);  -- this is executed
    5, 6      : y := y**x;
    OTHERWISE : x := 0.0;
  END_CASE;
\end{verbatim}
\end{code}
The integer expression following the \keyword{CASE} keyword is evaluated. 
The result is compared to the values of the case labels and the 
statement following the first matching label is executed. Execution then
continues at the statement following the \keytext{END\_CASE;}. If no
label matches, then no statements within the case block are executed,
except if an \keyword{OTHERWISE} label is included, which will match
anything. All other labels are examined before looking for the
\keyword{OTHERWISE}.

    The \emph{if \ldots then \ldots else} statement allows the conditional
execution of statements depending on the value of a \keyword{LOGICAL}
expression. When the expression evaluates to \keyword{TRUE} the statement(s)
following the \keyword{THEN} are executed, after which control passes
to the statement following the closing \keyword{END\_IF}. When the logical
expression evaluates to \keyword{FALSE} or \keyword{UNKNOWN} the \keyword{THEN}
statements are jumped over and execution starts at the statement(s) following
the \keyword{ELSE} keyword if present, or at the statement following
the \keyword{END\_IF} keyword.
\begin{code}
\begin{verbatim}
IF a > 20 THEN
  b := a + 2;
  c := c - 1;
ELSE
  IF a > 10 THEN
    b := a + 1;
  ELSE
    c := c + 1;
  END_IF;
END_IF;
\end{verbatim}
\end{code}

    The \emph{repeat} statement is used to control the conditional repetition
of a series of statements. The control conditions are:
\begin{itemize}
\item finite iteration until an integer expression reaches a specified
      value;
\item \keyword{WHILE} a logical condition is \keyword{TRUE};
\item \keyword{UNTIL} a logical condition is \keyword{TRUE}.
\end{itemize}
\begin{code}
\begin{verbatim}
REPEAT i := 100 TO 0 BY -7 WHILE r >= 0.0 UNTIL err < 1.0e-8;
  ...
  r := ...;
  err := ...;
END_REPEAT;
\end{verbatim}
\end{code}
At entry to the \keyword{REPEAT} statement the iteration variable is 
initialized to the first bound. If the variable less than or equal to the
\keyword{TO} bound and the increment is positive, or the variable is less
than the \keyword{TO} bound and the increment is negative, processing
jumps to after the \keyword{END\_REPEAT}, otherwise processing continues.
The \keyword{WHILE} condition is checked and if 
\keyword{TRUE} then the statements in the body are executed. After
these have been executed the \keyword{UNTIL} condition is checked. If this
is not \keyword{TRUE} then processing continues by incrementing the iteration
variable by either unity or by the \keyword{BY} value if present. The whole
process then starts again with the checking of the iteration variable
against the \keyword{TO} bound.

   All three types of controls are optional. If none are given then the
\keyword{REPEAT} statement will loop for ever. The \emph{escape} statement
causes an immediate transfer out of the \keyword{REPEAT} statement
in which it occurs. The \emph{skip} statement causes a jump to the
end of the \keyword{REPEAT} statement in which it occurs (i.e., to the point
where the \keyword{UNTIL} expression is tested).
\begin{code}
\begin{verbatim}
REPEAT UNTIL (a = 1);
  ...
  IF a = 0 THEN 
    ESCAPE;
  END_IF;
  ...
  IF a > 10 THEN
    SKIP;
  END_IF;
  ...
  ...
-- SKIP transfers control to here
END_REPEAT;
 -- ESCAPE transfers control to here
\end{verbatim}
\end{code}

    The \emph{return} statement terminates the execution of a \keyword{FUNCTION}
or \keyword{PROCEDURE}. The \keyword{RETURN} statement within a function
must specify an expression, the value of which is the value returned
by the function. A \keyword{RETURN} in a procedure must not specify an
expression.
\begin{code}
\begin{verbatim}
RETURN(a <> b);  -- example for within a function
RETURN;          -- example for within a procedure
\end{verbatim}
\end{code}

\subsection{Expressions}

    Expressions are combinations of operators, operands and function calls
which are evaluated to produce a value. The simplest expression is
either a literal value or the name of a variable.

\subsubsection{Arithmetic operators}

    The arithmetic operators act on number values and produce a number
result. If any operand
is indeterminate (i.e., \verb|?|) then the result is also
indeterminate. The operators are:
\begin{description}
\item[Unary] The operators \verb|+| and \verb|-|, the latter of which
negates its following operand.
\item[Binary] Addition (\verb|+|), 
   subtraction (\verb|-|), 
   multiplication (\verb|*|), 
   real division (\verb|/|), 
   exponentiation (\verb|**|),
   integer division (\keyword{DIV}),
    and modulo (\keyword{MOD}).
\end{description}

\subsubsection{Relational operators}

    The result of a relational expression is a \keyword{LOGICAL} value.
If either operand is indeterminate, the expression evaluates to
\keyword{UNKNOWN}.

\begin{description}
\item[Value comparison] Equal (\verb|=|), 
     not equal (\verb|<>|),
     greater than (\verb|>|),
     less than (\verb|<|),
     greater than or equal (\verb|>=|), and
     less than or equal (\verb|<=|).

\item[Membership] The \keyword{IN} operator tests an item for membership
in a dynamic aggregate (e.g., \keytext{IF fred IN mylist THEN ...}).

\item[Matching] The \keyword{LIKE} operator compares a string against a pattern,
evaluating to \keyword{TRUE} if they match. The pattern characters are:
  \begin{itemize}
  \item \verb|@| Matches any letter.
  \item \verb|^| Matches any upper-case letter.
  \item \verb|?| Matches any character.
  \item \verb|&| Matches remainder of string.
  \item \verb|#| Matches any digit.
  \item \verb|$| Matches a substring terminated by a space character 
                 or end-of-string.
  \item \verb|*| Matches any number of characters.
  \item \verb|\| Begins a pattern escape sequence.
  \item \verb|!| Negation character (used with the other characters).
  \item Any other character matches itself.
  \end{itemize}
  
  Some examples:
  \begin{itemize}
  \item \verb|'The quick red fox' LIKE '$$$$'| is \keyword{TRUE}.
  \item \verb|'Page 231' LIKE '$ ###'| is \keyword{TRUE}.
  \item \verb|'Page 27' LIKE 'Page ###'|  is \keyword{FALSE}.
  \item \verb|'\aaaa' LIKE '\\aaaa'| is \keyword{TRUE}.
  \item \verb|'\aaaa' LIKE '\aaaa'| is \keyword{FALSE}.
  \item \verb|'aaaa' LIKE 'a@@a'| is \keyword{TRUE}.
  \end{itemize}

\end{description}

\subsubsection{Logical operators}

    The logical operators produce a logical result. Except for the
\keyword{NOT} operator which takes one logical operand (e.g., \keytext{NOT op}), 
they take two logical operands (e.g., \keytext{op1 XOR op2}).

    The evaluation of the \keyword{NOT} operator is given in table~\ref{tab:not}.

\begin{table}
\centering
\caption{The NOT logical operator} \label{tab:not}
\begin{tabular}{|c|c|} \hline
Operand value & Result value \\ \hline
\keyword{TRUE} & \keyword{FALSE} \\
\keyword{UNKNOWN} & \keyword{UNKNOWN} \\
\keyword{FALSE} & \keyword{TRUE} \\ \hline
\end{tabular}
\end{table}

    The evaluation of the \keyword{AND}, \keyword{OR} and \keyword{XOR} operators 
is given in table~\ref{tab:andorxor}.

\begin{table}
\centering
\caption{The AND, OR and XOR logical operators} 
\label{tab:andorxor}
\begin{tabular}{|c|c||c|c|c|} \hline
Op1            & Op2           & Op1 \keyword{AND} Op2 & Op1 \keyword{OR} Op2 & Op1 \keyword{XOR} Op2 \\ \hline
\keyword{TRUE} & \keyword{TRUE}       & \keyword{TRUE}    & \keyword{TRUE}    & \keyword{FALSE} \\
\keyword{TRUE} & \keyword{UNKNOWN}    & \keyword{UNKNOWN} & \keyword{TRUE}    & \keyword{UNKNOWN} \\
\keyword{TRUE} & \keyword{FALSE}      & \keyword{FALSE}   & \keyword{TRUE}    & \keyword{TRUE} \\
\keyword{UNKNOWN} & \keyword{TRUE}    & \keyword{UNKNOWN} & \keyword{TRUE}    & \keyword{UNKNOWN} \\
\keyword{UNKNOWN} & \keyword{UNKNOWN} & \keyword{UNKNOWN} & \keyword{UNKNOWN} & \keyword{UNKNOWN} \\
\keyword{UNKNOWN} & \keyword{FALSE}   & \keyword{FALSE}   & \keyword{UNKNOWN} & \keyword{UNKNOWN} \\
\keyword{FALSE} & \keyword{TRUE}      & \keyword{FALSE}   & \keyword{TRUE}    & \keyword{TRUE} \\
\keyword{FALSE} & \keyword{UNKNOWN}   & \keyword{FALSE}   & \keyword{UNKNOWN} & \keyword{UNKNOWN} \\
\keyword{FALSE} & \keyword{FALSE}     & \keyword{FALSE}   & \keyword{FALSE}   & \keyword{FALSE} \\ \hline
\end{tabular}
\end{table}

\subsubsection{Miscellaneous}

\begin{description}

\item[Function call] A function may be called without the result necessarily
being assigned to a variable. If \keytext{fun} is a function with two
arguments (for simplicitly integer arguments) and returning a logical
value, then
\begin{code}
\begin{verbatim}
log := fun(i1, i2);
fun(i3, 24*i4);
\end{verbatim}
\end{code}
are both legitimate calls.


\item[Dot operator] The dot operator is used to access an attribute from an 
entity. If \keytext{ent} is an \keyword{ENTITY} type with an attribute
\keytext{att}, then \keytext{ent.attr} evaluates to the value of the
\keytext{attr} attribute within the \keytext{ent}.

\item[String operators] \mbox{} \\
 The \verb|+| operator takes two strings as
its operands and evaluates to the string that is the concatenation of its
operands. For example:
\begin{code}
\begin{verbatim}
str1 := 'string1';
str2 := 'string2';
str1 := str1 + str2;
-- str1 = 'string1string2'   is TRUE
\end{verbatim}
\end{code}

    The substring operator \verb|[i1:i2]| is a postfix operator that when
applied to a string, evalutes to the string whose characters are composed
of the \verb|i1|'th through the \verb|i2|'th characters, inclusively,
of its operand. Note that \verb|i2| must be greater than or equal to
\verb|i1|, and both must be within the limits of the number of characters
in the string. For example:
\begin{code}
\begin{verbatim}
str1 := 'string';
str2 := str1[2:4];
str1 := str1 + str2;
-- str1 = 'tristring'   is TRUE
\end{verbatim}
\end{code}

\item[Aggregate operators] \mbox{} \\
    The index operator \verb|[i]| is a postfix operator that can be applied
to an aggregate operand; the expression evaluates to the value of the
aggregate at the index position. For example, if \keytext{lagg} is a
list of integers:
\begin{code}
\begin{verbatim}
insert(lagg, 20, 0);
insert(lagg, 40, 0);
insert(lagg, 60, 0);
insert(lagg, 80, 0);
-- lagg[2] = 60    is TRUE
\end{verbatim}
\end{code}

\item[Interval expression] \mbox{} \\
    An \emph{interval expression} is a \keyword{LOGICAL} expression 
consisting of three operands and two operators. It has the form:
\begin{code}
\begin{verbatim}
{ low op1 test op2 high }
\end{verbatim}
\end{code}
where \keytext{op1} and \keytext{op2} are either of the two relational
operators \verb|<| or \verb|<=|, and \keytext{low}, \keytext{test} and
\keytext{high} are expressions of the same type. The interval expression
is equivalent to:
\begin{code}
\begin{verbatim}
((low op1 test) AND (test op2 high))
\end{verbatim}
\end{code}
The value of the interval expression is given by
\begin{enumerate}
\item If any operand is indeterminate, then it evauates to \keyword{UNKNOWN}.
\item If either of the logical relationships evaluates to \keyword{FALSE},
      then it evauates to \keyword{FALSE}.
\item If both logical relationships evalute to \keyword{TRUE},
      then it evauates to \keyword{TRUE}.
\item Otherwise it evaluates to \keyword{UNKNOWN}.
\end{enumerate}
For example:
\begin{code}
\begin{verbatim}
i := 10;
{1 <= i < 20}  -- is TRUE
{1 <= i < 10}  -- is FALSE
i := ?;
{1 <= i < 10}  -- is UNKNOWN
\end{verbatim}
\end{code}


\end{description}


\subsection{Built in procedures and functions}

\subsubsection{Procedures}

    The following procedures are an integral part of \ExpressA. They are
shown as signatures to inidicate the data types of the formal parameters.
For convenience, \keytext{GENERIC} is used to indicate any type.

\begin{itemize}
\item \keytext{INSERT (VAR L:LIST OF GENERIC; E:GENERIC; P:INTEGER)} \\
      \keyword{INSERT} inserts the element \keytext{E} into a list
\keytext{L} at position \keytext{P}. The insertion follows the existing
element at \keytext{P}, so that if \keytext{P=0}, \keytext{E} will
become the first element.

\item \keytext{REMOVE (VAR L:LIST OF GENERIC; P:INTEGER)} \\
     \keyword{REMOVE} modifies the list \keytext{L} by deleting the
element at position \keytext{P}.

\item \keytext{SYSTEM (V:STRING)} \\
     \keyword{SYSTEM} passes the string \keytext{V} to the operating system.
This is typically used to get the operating system to perform some action.

\item \keytext{ READ(VAR V1, V2,...:GENERIC)}, \keytext{READLN(VAR V1, V2,...:GENERIC)} \\
     These two procedures are similar to the Pascal procedures of the same
     name and put data from standard input into the variable(s)
     \keytext{V1}, etc.

     The argument is a comma-seperated list of variables. The variables may be
     of different types, but the types are limited to 
     \keyword{INTEGER},
     \keyword{REAL},
     \keyword{LOGICAL}, and
     \keyword{STRING}.
     The procedure gets the next value of the variable's type from standard input
     and assigns it to the variable. An integer is recognised as a set of digits,
     optinally preceeded by a sign. A real is in either decimal or scientific
     notation (e.g., \verb|12.34| or \verb|1.234e1|). A logical is \verb|TRUE|, 
     \verb|FALSE| or \verb|UNKNOWN| (case independent, so \verb|TRUE| could also 
     be \verb|tRuE|). A string is
     any non-empty set of characters ended by white space (e.g., \verb*|string |
     is one string but \verb*|ball of str8 string | is four strings). The difference
     between \keyword{READ} and \keyword{READLN} is that the former performs the
     actions described above, while the latter will discard any remaining characters
     in the input line after processing its arguments.
     

\item \keytext{ WRITE(format)}, \keytext{WRITELN(format)} \\
     These two procedures are similar to the Pascal procedures of the same name.
     They write data to standard output.

     The \keytext{format} consists of a comma-seperated list of variables with
     optional spacing specifications. The variable types may be 
     \keyword{INTEGER},
     \keyword{REAL},
     \keyword{LOGICAL}, or
     \keyword{STRING}.
     The \keyword{LOGICAL} and \keyword{STRING} types take no spacing declarations.
     An \keyword{INTEGER} variable can take one optional space specification which
     is an integer number specifying the minimum field width for printing the value
     (e.g., \keytext{int:6} to specify a minimum field width of 6 characters).
     A \keyword{REAL} variable can take two optional space specifications. The
     first is the field width and the second is the number of digits to be printed
     (e.g., \keytext{r:10:5} for printing with a field width of 10 characters
      and to a pecision of 5 digits). For example:
\begin{code}
\begin{verbatim}
BEGIN_LOCAL
  int : INTEGER;
  r   : REAL;
  log : LOGICAL;
  str : STRING;
END_LOCAL;
  int := 23;
  r := 23.0;
  log := true;
  str := 'This is a string.';
WRITE('Example', int, r:10:5, ' ', log, ' ', str);
\end{verbatim}
\end{code}
will produce:
\begin{code}
\begin{verbatim}
Example      23     23.000 TRUE This is a string.
\end{verbatim}
\end{code}

    The difference between \keyword{WRITE} and \keyword{WRITELN} is that the latter
    will end the output line after it has output the values of its arguments.
    (\keyword{WRITELN} need take no arguments, in which case it justs ends the current
     output line).
     
\item \keytext{ PRINT(format)}, \keytext{PRINTLN(format)} \\
     These \keyword{PRINT} procedures are the same as the
     \keyword{WRITE} procedures, except that they send the data
      to the current \lx{} output destination.

\end{itemize}

\subsubsection{Functions}

    The following functions are supplied as part of \ExpressA. They are
exhibited as signatures to show the formal parameters. For convenience, 
\keytext{NUMBER} is being used to denote either an \keyword{INTEGER} or a
\keyword{REAL} number.

\begin{itemize}
\item \keytext{ABS (V:NUMBER) : NUMBER;} \\
      \keyword{ABS} returns the absolute value of its argument.
\item \keytext{COS (V:NUMBER) : REAL;} \\
       Returns the cosine of an an angle specified in radians.
\item \keytext{EOF () : LOGICAL;} \\
       Returns \keyword{TRUE} if the next character from standard input
       is `end-of-file', otherwise it returns \keyword{FALSE}.
\item \keytext{EOLN () : LOGICAL;} \\
       Returns \keyword{TRUE} if the next character from standard input
       is `end-of-line', otherwise it returns \keyword{FALSE}.
\item \keytext{EXISTS (V:GENERIC) : LOGICAL;} \\
       The function \keyword{EXISTS} returns \keyword{FALSE} if its
     argument is indeterminate or does not exist, otherwise it returns
     \keyword{TRUE}.
\item \keytext{EXP (V:NUMBER) : REAL;} \\
      Returns $e$ (the base of natural logarithms (\keyword{CONST\_E})) 
      raised to the power of \keytext{V}.
\item \keytext{HIBOUND (V:AGGREGATE OF GENERIC) : INTEGER;} \\
      \keyword{HIBOUND} returns the declared upper index of an \keyword{ARRAY}
       or the declared upper bound of a 
       \keyword{BAG}, \keyword{LIST} or \keyword{SET}.
\item \keytext{HIINDEX (V:AGGREGATE OF GENERIC) : INTEGER;} \\
      \keyword{HIINDEX} returns the declared upper index of an \keyword{ARRAY}
       or the number of elements in a 
       \keyword{BAG}, \keyword{LIST} or \keyword{SET}.
\item \keytext{LENGTH (V:STRING) : INTEGER;} \\
       Returns the number of characters in its argument.
\item \keytext{LOBOUND (V:AGGREGATE OF GENERIC) : INTEGER;} \\
      \keyword{LOBOUND} returns the declared lower index of an \keyword{ARRAY}
       or the declared lower bound of a 
       \keyword{BAG}, \keyword{LIST} or \keyword{SET}.
\item \keytext{LOG (V:NUMBER) : REAL;} \\
       Returns the natural logarithm of its argument.
\item \keytext{LOG2 (V:NUMBER) : REAL;} \\
       Returns the base 2 logarithm of its argument.
\item \keytext{LOG10 (V:NUMBER) : REAL;} \\
       Returns the base 10 logarithm of its argument.
\item \keytext{LOINDEX (V:AGGREGATE OF GENERIC) : INTEGER;} \\
      \keyword{LOINDEX} returns the declared lower index of an \keyword{ARRAY}
       or the value 1 for a 
       \keyword{BAG}, \keyword{LIST} or \keyword{SET}.

       The \keytext{..INDEX} functions are useful for iterating over
       aggregates. For example, if \keytext{lagg} is a list of integer,
       then all the elements can be printed out as a comma-seperated
       list enclosed in parentheses by:
\begin{code}
\begin{verbatim}
writeln;
write('lagg = (');
REPEAT i := LOINDEX(lagg) TO HIINDEX(lagg);
  IF (i = HIINDEX(lagg)) THEN write(lagg[i]:1);
  ELSE write(lagg[i]:1, ', ');
  END_IF;
END_REPEAT;
writeln(')');
\end{verbatim}
\end{code}
\item \keytext{NVL (V:GENERIC; SUBS:GENERIC) : GENERIC;} \\
       If the argument \keytext{V} exists then it is returned, otherwise
       the argument \keytext{SUBS} is returned. Both arguments must be
       of the same type.
\item \keytext{ODD (V:INTEGER) : LOGICAL;} \\
       Returns \keyword{TRUE} or \keyword{FALSE} depending on whether or not
       its argument is odd or even.
\item \keytext{REXPR (V:STRING; E:STRING) : LOGICAL;} \\
       This function tests whether the \keytext{V} string parameter
       matches a regular expression \keytext{E}. \keyword{REXPR}
       returns \keyword{TRUE} if there is a match, \keyword{FALSE}
       if there is not a match, or \keyword{UNKNOWN} if the regular
       expression is ill-formed.

       In the regular expression, most characters stand for themselves,
       but \verb|\| can be used to escape any of the meta-characters.
       \begin{itemize}
       \item The meta-characters \keytext{(} and \keytext{)} are used for
       grouping sub-expressions. 
       \item \verb?|? between expressions means one or the other.
       \item \keytext{+} following an expression means match one or more times.
       \item \keytext{*} following an expression means match zero or more times.
       \item \keytext{?} following an expression means match zero or one times.
       \item \verb|[...]| is an expression indicating that any of the enclosed
       characters are acceptable. 
       \item \verb|[^...]| is an expression indicating that any characters
       except those enclosed are acceptable.
       \item Within a bracket expression a range of characters can be
       specified by providing the first and last with a seperating hyphen.
       For instance, \keytext{[a-zA-Z]} will match any alphabetic character.
       \end{itemize}

       Some examples:
       \begin{itemize}
       \item \verb|[a-zA-Z]+| match one or more letters.
       \item \verb|[0-9]+.[0-9]+([eE][\-\+]?[0-9]+)?| match a floating
             point number \\
             (e.g., \verb|1.23e-27| or \verb|0.987|)
       \item \verb|[a-zA-Z][0-9a-zA-Z_]*| match an \ExpressA{} variable.
       \item \verb|[^0-9a-zA-Z]| match anything except letters or digits.
       \item \verb?(I|i)(F|f)? case insensitive match for the word \verb|IF|.
       \end{itemize}

\item \keytext{ROUND (V:NUMBER) : INTEGER;} \\
       Returns the nearest integer to its argument value.
\item \keytext{SIN (V:NUMBER) : REAL;} \\
       Returns the sine of an an angle specified in radians.
\item \keytext{SIZEOF (V:AGGREGATE OF GENERIC) : INTEGER;} \\
       \keyword{SIZEOF} returns the number of elements in its argument.
       When \keytext{V} is an \keyword{ARRAY} this is the declared number
       of elements. When \keytext{V} is a 
       \keyword{BAG}, \keyword{LIST} or \keyword{SET} this is the actual
       number of elements.
\item \keytext{SQRT (V:NUMBER) : REAL;} \\
       Returns the square root of its argument.
\item \keytext{TAN (V:NUMBER) : REAL;} \\
       Returns the tangent of an an angle specified in radians.
\item \keytext{TRUNC (V:NUMBER) : INTEGER;} \\
       Chops off any decimal part of its argument, returning the corresponding
       integer value.

\end{itemize}


\subsection{Source level debugger} \label{sec:sld}

    The \ExpressA{} interpreter includes a source level debugger for
use when your code appears to be misbehaving. When in operation the
debugger will prompt for a command to be entered. It understands
the following commands.

\begin{itemize}
\item \keytext{<return>} Continue processing.
\item \keyword{break} \keytext{<number>} Place a breakpoint at the statement
  on line \keytext{<number>}.
\item \keyword{break} Print the line numbers of all the breakpoints.
\item \keyword{unbreak} \keytext{<number>} Remove the breakpoint from line
  \keytext{<number>}.
\item \keyword{unbreak} Remove all breakpoints.
\item \keyword{trace} Turn on statement tracing.
\item \keyword{untrace} Turn off statement tracing.
\item \keyword{entry} Turn on tracing of entry to procedures and functions.
\item \keyword{unentry} Turn off entry tracing.
\item \keyword{exit} Turn on tracing of exits from procedures and functions.
\item \keyword{unexit} Turn off exit tracing.
\item \keyword{traceall} Turn on all tracing.
\item \keyword{untraceall} Turn off all tracing.
\item \keyword{stack} Turn on display of the runtime stack accesses.
\item \keyword{unstack} Turn off stack display.
\item \keyword{step} Turn on single-stepping.
\item \keyword{unstep} Turn off single stepping.
\item \keyword{fetch} \keytext{<variable>}  Print data fetches for 
    \keytext{<variable>}.
\item \keyword{store} \keytext{<variable>}   Print data stores for 
    \keytext{<variable>}.
\item \keyword{watch} \keytext{<variable>}   Print both data fetches and
    stores for  \keytext{<variable>}.
\item \keyword{watch} Print the names of all variables being watched.
\item \keyword{unwatch} \keytext{<variable>}  Remove the watch from
      \keytext{<variable>}.
\item \keyword{unwatch} Remove all watches.
\item \keyword{show} \keytext{<expression>} Print the value of 
       the \ExpressA{} expresion \keytext{<expression>}. The variables
       in the expression must have been declared in the \ExpressA{} code.
        For example:
\begin{code}
\begin{verbatim}
show (23.0 + LOG(num))/(PI*r**2)
\end{verbatim}
\end{code}
\item \keyword{assign} \keytext{<variable := expression>} Assign the value
    of \keytext{<expression>} to the \ExpressA{} variable \keytext{<variable>}.
    For example:
\begin{code}
\begin{verbatim}
assign num := SIN(theta/300.0) 
\end{verbatim}
\end{code}
\item \keyword{where} Print the current line number and the text of the
       next statement to be executed.
\item \keyword{kill} Terminate the execution of the \lx{} program.
\end{itemize}

\subsection{Example \ExpressA{} code}

    The following demonstrates most of the functionality of \ExpressA.
Most of this is not particularly interesting, except possibly for the
algorithms for calculating the date of Easter and for generating
magic squares.

\begin{code}
\begin{verbatim}
      c=        fun.ct  Test of CODE ltx2x

CODE_SETUP=
  ENTITY ent;
    attr1, attr3 : INTEGER;
    attr2 : STRING;
  END_ENTITY;

  TYPE joe = INTEGER;
  END_TYPE;

  TYPE colour = ENUMERATION OF (red, blue, green);
  END_TYPE;


PROCEDURE easter;
(* calculates the date of Easter for the present year 
   The algorithm can be applied to any year between 
   1900 and 2099 inclusive, but if so, then the year
   should be checked to ensure that it is within this range. *)
  LOCAL
    n, a, b, m, q, w : INTEGER;
    day : INTEGER;
    month : STRING;
  END_LOCAL;

  n := THE_YEAR - 1900;
  a := n MOD 19;
  b := (7*a + 1) DIV 19;
  m := (11*a + 4 - b) MOD 29;
  q := n DIV 4;
  w := (n + q + 31 - m) MOD 7;
  day := 25 - m - w;
  month := 'April';
  IF (day < 1) THEN
    month := 'March';
    day := day + 31;
  END_IF;
  writeln('In ', THE_YEAR:1, ' Easter is on ', month,  day:3);
END_PROCEDURE;


FUNCTION magic_square(order:INTEGER): LOGICAL;
(* calculates magic squares from order 1 through 15.
   The order must be an odd number. *)
  LOCAL
  row, col, num : INTEGER;
  sqr_order : INTEGER;
  magic : ARRAY[1:15] OF ARRAY[1:15] OF INTEGER;
  END_LOCAL;

  IF (order > 15) THEN  -- only squares up to order 15
    RETURN(FALSE);
  ELSE
    IF (order < 1) THEN -- squares have at least one entry
      RETURN(FALSE);
    ELSE
      IF (NOT ODD(order)) THEN -- squares are odd
        RETURN(FALSE);
      END_IF;
    END_IF;
  END_IF;

  sqr_order := order**2;
  row := 1;
  col := (order + 1) DIV 2;
  REPEAT num := 1 TO sqr_order;
    magic[row][col] := num;
    IF ((num MOD order) <> 0) THEN
      IF (row = 1) THEN row := order; ELSE row := row - 1; END_IF;
      IF (col = order) THEN col := 1; ELSE col := col + 1; END_IF;
    ELSE
      IF (num <> sqr_order) THEN row := row + 1; END_IF;
    END_IF;
  END_REPEAT;

  writeln(Magic square of order ',order:2);
  REPEAT row := 1 TO order;
    REPEAT col := 1 TO order;
      write(magic[row][col]:4);
    END_REPEAT;
    writeln;
  END_REPEAT;
  writeln;

  RETURN(TRUE);
END_FUNCTION;

FUNCTION month(mnum:INTEGER) : STRING;
(* Given an integer representing the month in a year,
   returns the name of the month. *)
LOCAL
  str : STRING;
END_LOCAL;

  CASE mnum OF
    1 : str := 'January';
    2 : str := 'February';
    3 : str := 'March';
    4 : str := 'April';
    5 : str := 'May';
    6 : str := 'June';
    7 : str := 'July';
    8 : str := 'August';
    9 : str := 'September';
    10 : str := 'October';
    11 : str := 'November';
    12 : str := 'December';
    OTHERWISE : str := '';
  END_CASE;
RETURN(str);
END_FUNCTION;

 LOCAL
  a : array[1:3] of integer;
  lagg : list [0:5] of integer;
  a23 : array[1:2] of array[1:3] of integer;
  i, n : integer; 
  s1, s2 : string;
  b : logical;
  r1, r2 : real;
  nega : array[-3:-1] of integer;
  posa : array[3:5] of integer;
  j : joe;
  ex : ent;
 END_LOCAL;

    -- start with a massive compound statement
 BEGIN 

  writeln; 
  println;

  (* write today's date *)
  writeln('Today is ', THE_DAY:1, ' ', month(THE_MONTH), ' ', THE_YEAR:1);
  writeln;

  (* The user might be interested in Easter *)
  easter;
  writeln;

  (* Call some math functions *)
  r1 := PI/4;
  writeln('r1 = PI/4 (0.78539...)', r1);
  writeln('cos(r1) (0.70710...)', cos(r1));
  writeln('sin(r1) (0.70710...)', sin(r1));
  writeln('tan(r1) (1.0)', tan(r1));
  
  r1 := CONST_E;
  writeln('r1 = CONST_E (2.7182...)', r1);
  writeln('log(4.5) (1.50407...)', log(4.5));
  writeln('log2(8) (3.0)', log2(8));
  writeln('log10(10) (1.0)', log10(10));

  r2 := exp(10);
  writeln('exp(10) (2.203...e4)', r2);

  r2 := sqrt(121);
  writeln('sqrt(121) (11.0)', r2);

  (* populate and print some arrays *)
  writeln;
  posa[3] := 10;
  posa[4] := 20;
  posa[5] := 30;
  REPEAT i := LOINDEX(posa) TO HIINDEX(posa);
    writeln('posa[', i:1, '] = ', posa[i]);
  END_REPEAT;

  writeln;
  nega[-3] := 1;
  nega[-2] := 2;
  nega[-1] := 3;
  REPEAT i := LOINDEX(nega) TO HIINDEX(nega);
    writeln('nega[', i:1, '] = ', nega[i]);
  END_REPEAT;

  (* Do some things with a list *)

      -- check the initial size (should be empty)
  i := SIZEOF(lagg);
  writeln('no. of els in lagg = ', i);

      -- insert elements at the front
  INSERT(lagg, 10, 0);
  i := SIZEOF(lagg);
  writeln('no. of els in lagg = ', i);
  INSERT(lagg, 20, 0);
  writeln('no. of els in lagg = ', SIZEOF(lagg));

     -- print some of the elements
  i := lagg[1];
  writeln('first in lagg = ', i);
  writeln('lagg[2] = ', lagg[2]);

      -- check if a value in in the list
  b := 10 IN lagg;
  writeln(b);           -- should be TRUE
  b := 30 IN lagg;
  writeln(b);           -- should be FALSE

      -- write all the elements
  REPEAT i := LOINDEX(lagg) TO HIINDEX(lagg);
    writeln('lagg[', i:1, '] = ', lagg[i]);
    println('lagg[', i:1, '] = ', lagg[i]);
  END_REPEAT;

  (* see what happens with an indeterminate value *)
  b := FALSE;
  b := ?;
  writeln(b);
  println(b);
  (* Some more attempts with indeterminate *)
  i := 2;
  n := 3*i;
  writeln(i, n);    -- should be 2 6
  n := 3*?;
  writeln(i, n);    -- should be 2 ?
  i := ?;
  n := 3*i;
  writeln(i, n);    -- should be ? ?

END;   -- end of compound statement
       -- but we can have individual statements

 
  (* Try to provide some excitement by making a magic square *)
  writeln;
  write('Enter an odd number between 1 and 15: ');
  readln(n);
  IF NOT magic_square(n) THEN
    writeln('I did not like your number which was ', n:1);
    writeln('If you get it right next time, something magic will happen.');
    write('Enter an odd number between 1 and 15: ');
    readln(n);
    magic_square(n);  
  END_IF;


  (* Try a couple of REPEAT statements *)
  writeln('Test REPEAT (should print -2)');
  i := -2;
  REPEAT UNTIL i = 0;
    writeln(i);
    println(i);
    ESCAPE;
    i := i + 1;
  END_REPEAT;

  writeln('Test REPEAT (should print 3, 2, 1)');
  REPEAT i := 3 TO 1 BY -1;
    writeln(i);
  END_REPEAT;


  (* Try the LIKE operator *)
  writeln('Test LIKE');
  writeln(('A' LIKE 'A'));             -- should be TRUE
  writeln(('A' LIKE 'b'));             -- should be FALSE
  writeln(('Page 407' LIKE '$###'));   -- should be TRUE
  writeln(('Page 23' LIKE '$###'));    -- should be FALSE


  (* Try the REXPR function *)
  writeln('Test rexpr');
  writeln(rexpr('A', 'A'));            -- should be TRUE
  writeln(rexpr('A', 'b'));            -- should be FALSE
  writeln(rexpr('Page 407', '[a-zA-Z]+\ [0-9]+')); -- should be TRUE
  writeln(rexpr('Page 23', '[a-zA-Z]+\ [0-9]'));   -- should be FALSE


  (* Try an ARRAY OF ARRAY *)
  a23[1][1] := 11;
  a23[1][2] := 12;
  a23[1][3] := 13;
  a23[2][1] := 21;
  a23[2][2] := 22;
  a23[2][3] := 23;

  writeln('Test REPEAT (should be 1 1 11, 1 2 12, 1 3 13, 2 1 21, 2 2 22 etc)');
  REPEAT n := 1 TO 2;
    REPEAT i := 1 TO 3;
        writeln(n, i, a23[n][i]);
    END_REPEAT;
  END_REPEAT;

  
  (* do some simple string operations *)
  s1 := 'string';
  writeln(s1);        -- should be string
  s2 := s1[2:4];
  writeln(s2);        -- should be tri
  b := s1 <> s2;
  writeln(b);         -- should be TRUE
  writeln(s2 + s1);   -- should be tristring


  (* Assign and print to a user-defined type *)
  j := 33;
  writeln(j*3);     -- should be 99

  (* Do something with a variable of type ENTITY */
  ex.attr1 := 33;
  ex.attr2 := 'The attribute named attr2';
  ex.attr3 := ex.attr1/3;
  writeln('ex.attr1 should be 33 and is: ', ex.attr1);
  writeln('ex.attr2 is: ', ex.attr2);
  writeln('ex.attr3 should be 11 and is: ', ex.attr3);

END_CODE
\end{verbatim}
\end{code}

\section{Specifying a {\tt SPECIAL\_} command} \label{sec:special}

    This section gives some hints on how to specify a \LaTeX\ command that
requires some special processing. The faint-hearted should skip this. It is
assumed that the implementor will have knowledge of \LaTeX, C programming, 
and lex and
YACC style lexer and parser generator systems.

    There are two ways of defining \verb|SPECIAL_| kinds of commands though 
neither is particularly simple. The easiest is by what is termed the
{\em coding} method. This involves modifying the standard actions. The
more complicated means is by the {\em grammar} method, which involves extending
the production grammar and, typically, also coding new kinds of actions.

    The process of specifying one of the \verb|SPECIAL_| kinds of command
actions is:
\begin{itemize}
\item Seriously question the need for the special command. One is only required if
      the standard actions cannot be coerced into serving the needs of the command
      processing and/or the command grammar is not supported by the \lx\ system.
\item Design the required entry for the \ctab.
\item Decide whether the coding or the grammar method is to be used for
      extending \lx.
  \begin{description}
  \item[Coding method] Modify the actions in \file{l2xusrlb.c}, 
       and possibly
       add new functions in \file{l2xusrlb.c} and \file{l2xusrlb.h}.

  \item[Grammar method] Extend the grammar in \file{l2x.y}. Typically it
       be necessary to add new functions to the user-defined
       library \file{l2xusrlb} as well.
  \end{description}
\item Compile the modified \lx\ system. A \verb|make| file for this is given
      in Appendix~\ref{sec:install}.
\item Test the extensions and debug the program.
\end{itemize}

    The \verb|l2xlib| has many functions that may be of use in this process.
 Some of these are indicated below.

\begin{itemize}
\item \verb|char *strsave(char s[])| saves a string somewhere
\item \verb|void myprint(char s[])| writes a string to the output medium. Its
       particular action is controlled by the \verb|set_print| and
       \verb|reset_print| functions, as well as the \verb|-p| option.
\item \verb|void verbatim_print(char s[])| like \verb|myprint|, 
      writes a string to the output medium. Its actions are controlled
      by the current print mode, and newlines are obeyed (i.e., it ignores
      any pretty-printing option).
\item \verb|void yyerror(char s[])| used by the lexer and parser to print
      an error message string.
\item \verb|void warning(char s[])| writes a warning message string.
\item \verb|void do_newline()| used within the lexer to set internal variables
      whenever a newline is encountered in the input.
\item \verb|void initialise_sysbuf()| initialises the system supplied string 
      buffer.
\item \verb|void print_sysbuf()| writes the content of the system string buffer
      to the output file.
\item \verb|void copy_sysbuf(char s[])| copies the contents of the system
      string buffer to the user-supplied string. It is the user's responsibility
      to ensure that the string is big enough.
\item \verb|void set_print(PSTRWC pswitch)| controls the action of \verb|myprint|,
      \verb|print_newline| and \verb|verbatim_print|. If the input argument is 
      \verb|p_default_print|
      then the print functions should write to the output file; this is the
      default behavior. If the
      argument is \verb|p_no_print|, then no writing occurs. If the argument
      is \verb|p_print_to_sysbuf|, then the print functions write to the system
      string buffer.
\item \verb|void reset_print()| resets the behavior of the print functions. This
      function should always be used after a call to \verb|set_print|.
\item \verb|int lookup_entry(char s[], int kind)| returns the location
      within the \ctab\ of the
      command name given in \verb|s| of the command type given in \verb|kind|.
      If \verb|kind| is \verb|DONT_CARE| then the position of the first occurrence
      of \verb|s| is returned.
\item \verb|void get_env_name(char s[])| extracts the name of a \LaTeX\ 
      environment from \verb|s|, which is assumed to have the form
      \verb|\something { environment }|. The name of the environment is put
      into the global string \verb|env_name|.
\item \verb|PSENTRY get_mode_sym(int loc)| returns a pointer to the
      symbol table entry at position \verb|loc| in the \ctab{}
      for the current mode.
\item \verb|int command_type(int loc)| returns the system defined 
      kind of command at location
      \verb|loc| in the \ctab.
\item \verb|int get_user_type(int loc)| returns the user input (\verb|TYPE=|)
      kind of command at location
      \verb|loc| in the \ctab.
\item \verb|PSTRWC get_t(PSENTRY loc)| returns a pointer to the 
      \verb|START_TAG=| specification for symbol entry \verb|loc|.
      There are similar functions for other tagging specifications.
\item \verb|PSTRWC get_tag_t(PSENTRY loc, int n)| returns a pointer
      to the \verb|START_TAG_n| specification for the \verb|n|'th
      argument for symbol entry \verb|loc|. There are similar
      functions for other argument tagging specifications.
\item \verb|PSTRWC get_param_print(PSENTRY loc, int n)| returns a
      pointer to the print control specification for the
      \verb|n|'th required argument for symbol entry \verb|loc|.
      There are similar functions for other print controls.
\item \verb|int get_level(PSENTRY loc)| returns the \verb|SECTIONING_LEVEL=| 
      value for symbol entry \verb|loc|.
\end{itemize}

    The process of specifying a \verb|SPECIAL_| is best described via
an example.

\subsection{Example}

    Assume that there is a `non-standard' \LaTeX\ command 
which has one required argument. When this command is processed by \LaTeX\ its
effect is to start a new section in a document entitled 
{\em Normative References}. Some boilerplate text is then typeset (specified
within the definition of the command). This boilerplate includes two
instances of the text from the argument of the command. Finally, a 
{\tt description}
list environment is started.

    In \LaTeX\ terms, this command could have been defined as:
\begin{code}
\begin{verbatim}
\newcommand{\XXspecial}[1]{\section{Normative References}
          Some boilerplate text with #1
          in the middle. Now there is
          some more boilerplate with #1
          in the middle of it.
          \begin{description} }
\end{verbatim}
\end{code}

    For the purposes of the example, it is desired to replace the occurrence
of the \verb|\XXspecial| command by the `normal' section heading for the
output tagged style, and also print out the boilerplate text including
the argument text in the right places. The start of the list environment has
also to be taken into account. The \verb|\item| optional argument text is
to be enclosed in parentheses, with a dash before the main text.
These requirements are not something that can
be currently accomplished with the standard \lx\ system.

    To make the requirements more concrete, if the input \LaTeX\ source 
includes:
\begin{code}
\begin{verbatim}
....
\XXspecial{REQ PARAM TEXT}

\item[Ref 1] Text 1.
\item[Ref 2] Text 2.
\end{description}
....
\end{verbatim}
\end{code}
then the desired output is to look like:
\begin{code}
\begin{verbatim}
....

</div.1>

<div.1>
<heading>Normative References</heading>

Some boilerplate text with REQ PARAM TEXT
in the middle. Now there is
some more boilerplate with REQ PARAM TEXT
in the middle of it.

    (Ref 1) -- Text 1.
    (Ref 2) -- Text 2.
....
\end{verbatim}
\end{code}


   Now, let's write a specification for the \ctab, which we will do in pieces,
starting with the sectioning tags. In this tagging style, end tags for sections
take the form \keytext{\ET{div.1}}, and start tags the form \keytext{\ST{div.1}}. 
The titles of sections are enclosed between \keytext{\ST{heading}} and 
\keytext{\ET{heading}} tags. We also
want some newlines in the output to set things off. If \verb|?| is used as the
escape character, then we can specify for the sectioning tagging:
\begin{latexonly}
\begin{code}
\begin{verbatim}
SECTIONING_LEVEL= SECT
START_TAG= "?n?n<div.1>?n"
  STRING: "<heading>Normative References</heading>?n"
END_TAG= "?n</div.1>"
\end{verbatim}
\end{code}
\end{latexonly}
\begin{htmlverbatim}
SECTIONING\_LEVEL= SECT
START\_TAG= "?n?n\ST{div.1}?n"
  STRING: "\ST{heading}Normative References\ET{heading}?n"
END\_TAG= "?n\ET{div.1}"
\end{htmlverbatim}

    There is one required argument and no optional arguments, so we need:
\begin{code}
\begin{verbatim}
REQPARAMS= 1
\end{verbatim}
\end{code}

    The \LaTeX\ command also starts off a \verb|description| environment, so we have
to set the tags for the \verb|\item| commands that will follow. This is done by:
\begin{code}
\begin{verbatim}
START_ITEM= "?n"
START_ITEM_PARAM= "    ("
END_ITEM_PARAM= ") -- "
\end{verbatim}
\end{code}

    Most of the work is now completed though we still have to give the command name,
decide what sort of \verb|SPECIAL_| it will be and set the \verb|SPECIAL_TOKEN|
value. None of the provided \verb|SPECIAL_| types exactly fit this entry as it is
a mixture of sectioning and list environment, so we will just call it a
\verb|SPECIAL_COMMAND| type.
To summarize, the effective state of the \ctab\ entry is:
\begin{latexonly}
\begin{code}
\begin{verbatim}
TYPE= SPECIAL_COMMAND
C=       NAME= to be specified
C=       SPECIAL_TOKEN= to be specified
  SECTIONING_LEVEL= SECT
  START_TAG= "?n?n<div.1>?n"
    STRING: "<heading>Normative References</heading>?n"
  END_TAG= "?n</div.1>"
  REQPARAMS= 1
  START_ITEM= "?n"
  START_ITEM_PARAM= "    ("
  END_ITEM_PARAM= ") -- "
END_TYPE
\end{verbatim}
\end{code}
\end{latexonly}
\begin{htmlverbatim}
TYPE= SPECIAL\_COMMAND
C=       NAME= to be specified
C=       SPECIAL\_TOKEN= to be specified
  SECTIONING\_LEVEL= SECT
  START\_TAG= "?n?n\ST{div.1}?n"
    STRING: "\ST{heading}Normative References\ET{heading}?n"
  END\_TAG= "?n\ET{div.1}"
  REQPARAMS= 1
  START\_ITEM= "?n"
  START\_ITEM\_PARAM= "    ("
  END\_ITEM\_PARAM= ") -- "
END\_TYPE
\end{htmlverbatim}

    For pedagogical purposes, this special will be implemented using both the
grammar and code methods, and the command names used will be \verb|\GRAMMspecial|
and \verb|\CODEspecial| respectively.

\subsubsection{Grammar method implementation}

    The command name for this implementation will be \verb|\GRAMMspecial|.

    The grammar method requires changes to the grammar specified in \file{l2x.y}.

\begin{enumerate}
\item A new token has to be defined, call it \verb|GRAMMSPECIAL|, in the first
part of the file. There is a slot for this under the comment \verb|/* specials */|.
An integer number, greater than or equal to 10,000 (ten thousand) and less than
32,768 ($2^{15}$), has to be
associated with this token.\footnote{The upper limit of $(2^{15}-1)$ is
set by the bison processor.}
 Further, this number must not be the same as any other
number associated with any other token. Let us use
the maximum number 32,767. The relevant portion of \file{l2x.y} will look like
\begin{latexonly}
\begin{code}
\begin{verbatim}
                                      /* specials */
%token <pos> /* other specials here */
%token <pos> GRAMMSPECIAL 32767
                                      /* precedences */
\end{verbatim}
\end{code}
\end{latexonly}
\begin{htmlverbatim}
                                      /* specials */
\%token \ST{pos} /* other specials here */
\%token \ST{pos} GRAMMSPECIAL 32767
                                      /* precedences */
\end{htmlverbatim}
This number is used for communication within the \lx\ system, and is the number
set as the value of the \verb|SPECIAL_TOKEN| in the \ctab. We can now finalize
the \ctab\ entry as:
\begin{latexonly}
\begin{code}
\begin{verbatim}
TYPE= SPECIAL_COMMAND
NAME= \GRAMMspecial
SPECIAL_TOKEN= 32767
  SECTIONING_LEVEL= SECT
  START_TAG= "?n?n<div.1>?n"
    STRING: "<heading>Normative References</heading>?n"
  END_TAG= "?n</div.1>"
  REQPARAMS= 1
  START_ITEM= "?n"
  START_ITEM_PARAM= "    ("
  END_ITEM_PARAM= ") -- "
END_TYPE
\end{verbatim}
\end{code}
\end{latexonly}
\begin{htmlverbatim}
TYPE= SPECIAL\_COMMAND
NAME= \verb|\GRAMMspecial|
SPECIAL\_TOKEN= 32767
  SECTIONING\_LEVEL= SECT
  START\_TAG= "?n?n\ST{div.1}?n"
    STRING: "\ST{heading}Normative References\ET{heading}?n"
  END\_TAG= "?n\ET{div.1}"
  REQPARAMS= 1
  START\_ITEM= "?n"
  START\_ITEM\_PARAM= "    ("
  END\_ITEM\_PARAM= ") -- "
END\_TYPE
\end{htmlverbatim}

\item A new production, or productions, has to be added to the grammar. There is
a place for this at the end of the rules section in the file, under the predefined
production \verb|l2xSpecials|. Let us call our new production \verb|GrammSpecial|,
and add it as:
\begin{code}
\begin{verbatim}
l2xSpecials: ASpecial
     | AnotherSpecial
     | GrammSpecial
     ;
\end{verbatim}
\end{code}
where the \verb|ASpecial| and \verb|AnotherSpecial| are pre-existing specials.

\item The production now has to be defined, specifying the expected syntax
and required actions. This looks like:
\begin{code}
\begin{verbatim}
GrammSpecial: GRAMMSPECIAL
    {  
       start_section($1);
       myprint(get_t($1));
       myprint(get_tag_t($1,1));
       initialise_sysbuf();
       set_print(p_print_to_sysbuf);
    }
    ReqParam
    {
      initialise_string(grammbuf);
      copy_sysbuf(grammbuf);
      reset_print();
      prwboiler1();
      print_sysbuf();
      prwboiler2();
      myprint(grammbuf);
      prwboiler3();
      start_list($1);
    }
    ;
\end{verbatim}
\end{code}
    The actions are enclosed in braces and are defined in terms of
C code. 

    Once the parser has been given the \verb|GRAMMSPECIAL| token from the lexer,
it will attempt to
perform the actions within the first set of braces. The first of these,
\verb|start_section($1)|, is the \lx\ action for starting a sectioning command.
Basically, this deals with any closing of prior sections of the document and 
remembering the closing tag for this section.
The next two actions 
print the start tags for the command and its required argument,
taking the strings from the \ctab.
\verb|initialise_sysbuf()| initializes the
system string buffer ready for new input. Then the print control is set so
that any output will be directed into the system string buffer rather 
than the output
file. This finishes the first set of actions.

    The production grammar for the required argument comes next. If this
is incorrect, the parser automatically gives an (uninformative) error message.
Otherwise, the last set of actions are done. At this point, the text 
of the required argument will be contained in the system string buffer.
This is then copied to a temporary buffer \verb|grammbuf|, that we have yet
to define, by calling
\verb|copy_sysbuf(grammbuf)| having first made sure that this buffer has
been cleared of any previous contents (the \verb|initialise_string(grammbuf)|
action). The printing control must now be reset (\verb|reset_print()|), or 
things might get corrupted later. A function \verb|prwboiler1()| is called to
print the first part of the boilerplate text, followed by printing the contents
of the system buffer by the action \verb|print_sysbuf()| (remember that this should
contain the text of the required argument). The second part of the boilerplate
is written by the function \verb|prwboiler2()|. Just for pedagogical purposes,
the required argument text is written out using the text stored in the temporary
buffer (\verb|myprint(grammbuf)|) rather than from the system buffer. The penultimate
action is the printing of the last piece of boilerplate.

    The final action --- \verb|start_list($1)| --- is the standard \lx\ action
at the start of a list environment. This remembers the various tags for the list
items to follow.

    A character buffer, \verb|grammbuf|, is now defined in the initial
section of the \file{l2x.y} file, as:
\begin{code}
\begin{verbatim}
char grammbuf[80];
\end{verbatim}
\end{code}
which is intended to be large enough to hold the text of the required
argument of the command.

    This completes the changes to the grammar file.

\item The three functions called out in the above actions for printing
the boilerplate are coded and placed in the user library file
\file{l2xusrlb.c} and are also added to \file{l2xusrlb.h}. Here is
the relevant code as it would appear in \file{l2xusrlb.c}.
\begin{code}
\begin{verbatim}
             /* demonstration string definition */

STRING boiler_string_3 = "\nin the middle of it.\n\n";

                   /* demonstration functions */

/* PRWBOILER1 print some demonstration boilerplate */
void prwboiler1()
{
  myprint("\nSome boilerplate text with ");
}                                 /* end PRWBOILER1 */

/* PRWBOILER2 print some demonstration boilerplate */
void prwboiler2()                 
{
  myprint("\nin the middle. Now there is\n");
  myprint("some more boilerplate with ");
}                                 /* end PRWBOILER2 */

/* PRWBOILER3 yet more demonstration boilerplate */
void prwboiler3()                 
{
  myprint(boiler_string_3);
}                                 /* end PRWBOILER1 */
\end{verbatim}
\end{code}

\item The system is recompiled, using \verb|make|, and tested on some example
\LaTeX\ files.

\end{enumerate}



\subsubsection{Code method implementation}

    This method `merely' requires extending the standard actions to
account for the new requirements. First, however, we must complete
the definition of the \ctab\ entry. We will call the new 
command \verb|\CODEspecial|. Also a unique value has to be assigned
to the \verb|SPECIAL_TOKEN|. This must have a value greater than or
equal to 50,000 (fifty thousand). We will use a value 59,999. Later this
value is used within the action code to identify the special.
The \ctab\ entry is thus:
\begin{latexonly}
\begin{code}
\begin{verbatim}
TYPE= SPECIAL_COMMAND
NAME= \CODEspecial
SPECIAL_TOKEN= 59999
  SECTIONING_LEVEL= SECT
  START_TAG= "?n?n<div.1>?n"
    STRING: "<heading>Normative References</heading>?n"
  END_TAG= "?n</div.1>"
  REQPARAMS= 1
  START_ITEM= "?n"
  START_ITEM_PARAM= "    ("
  END_ITEM_PARAM= ") -- "
END_TYPE
\end{verbatim}
\end{code}
\end{latexonly}
\begin{htmlverbatim}
TYPE= SPECIAL\_COMMAND
NAME= \verb|\CODEspecial|
SPECIAL\_TOKEN= 59999
  SECTIONING\_LEVEL= SECT
  START\_TAG= "?n?n\ST{div.1}?n"
    STRING: "\ST{heading}Normative References\ET{heading}?n"
  END\_TAG= "?n\ET{div.1}"
  REQPARAMS= 1
  START\_ITEM= "?n"
  START\_ITEM\_PARAM= "    ("
  END\_ITEM\_PARAM= ") -- "
END\_TYPE
\end{htmlverbatim}
which only differs from that for the grammar implemented special in the
\verb|SPECIAL_TOKEN=| and the \verb|NAME=| values.

    Before proceeding further, some explanation of the internals of
the \lx\ system is in order.

\begin{description}
\item[Command table entry] Internally, an array of  C {\tt struct}s 
is used for storing the data corresponding to the \ctab. The {\tt struct}
is fully
defined in file \file{l2xcom.h}, and type {\tt PSENTRY} is a
pointer to an instance of the {\tt struct}. There is an entry in
the internal \ctab{} for each command. Where a command specification
is mode-dependent, then the entries for this are stored as a list (the
\ctab{} array is actually an array of lists of command specifications,
one list per command). 

For the purposes at hand, only a few
of the elements are of concern; these are \verb|kind|, \verb|parse_kind|
and \verb|special_token|. The element \verb|kind| contains an identifier
of the \verb|TYPE=| value; that is, the type of the command as specified
by the user. The element \verb|special_token| contains the 
\verb|SPECIAL_TOKEN=| value. The \verb|parse_kind| element contains
an identifier of the type of command as assigned internally by \lx.
This last identifier is generated by the table processing code
in \verb|l2xlib.c| and corresponds to one of the token values
acceptable to the parser.

\item[The lexer] The lexer reads the source \LaTeX\ file, looking for
\LaTeX\ commands (essentially anything starting with a backslash). Each
time it finds a command it looks it up in the command table array, and
sends its parser token value (the \verb|parse_kind| value) and the command
table array position to the parser. 

\item[The parser] Given a token from the lexer, the parser finds the 
appropriate grammar production and performs the specified actions. It
is able to access command information through having the command table
position.

\item[The grammar] The grammar used for the \LaTeX\ general commands (and 
environments) is actually very simple --- the complexity is reserved for the
lexer and the actions. At the grammar level, no distinction is made
between a command and an environment. There are a total of 19 different
command types (tokens), which fall into a smaller number of groups.
\begin{enumerate}
\item A command with no arguments.
\item A command with just a single optional argument.
\item Commands with a final optional argument and between 1 and 8 required
      arguments.
\item Commands with between 1 and 8 required arguments. In this case
      it is always assumed that there might be an initial optional
      argument.
\item A command with 9 required arguments.
\end{enumerate}
Note that this partitioning is based solely on the number of required
arguments and the position (if any is declared) of an optional
argument.

    For example, if a command/environment is specified in the \ctab\ as
having one required argument and no optional arguments, then this will
be treated as a command with possibly an initial optional argument and
one required argument. The grammar for this is:
\begin{code}
\begin{verbatim}
l2xComm1: COMMAND_1
        {
          start_with_opt($1);
        }
        OptParam
        {
          action_opt_first($1);
        }
        ReqParam
        {
          action_last_p($1,1);
        }
        ;
\end{verbatim}
\end{code}
where the words in all upper case are grammar tokens, and words in mixed
case are other grammar productions. The actions are enclosed between braces.
The \verb|$1| is the position of the command in the command table array.

\item[Actions] The standard actions are contained in file \file{l2xacts.c}.
Within the code for each standard action, provision is made for
calling 
action code for specials. All the functions have the same
general structure. Here, for instance, is the code for the standard
action that is called between the start of a command and a first optional
argument.
\begin{code}
\begin{verbatim}
/* START_WITH_OPT start action for command with optional param */
void start_with_opt(pos)  
int pos;                       /* position of command in table */
{
  int user_kind;               /* user-specified command type */

  user_kind = get_user_type(pos);

  switch(user_kind) {
  case TEX_CHAR:               /* the general, non-specials */
  case CHAR_COMMAND:
  case COMMAND:
  case BEGIN_ENV:
  case END_ENV:
  case BEGIN_LIST_ENV:
  case END_LIST_ENV:
  case SECTIONING:
    start_it(pos);                 /* command start action */
    default_start_with_opt(pos);   /* start optional param */
    break;
  case SPECIAL:                    /* the specials */
  case SPECIAL_BEGIN_ENV:
  case SPECIAL_END_ENV:
  case SPECIAL_BEGIN_LIST:
  case SPECIAL_END_LIST:
  case SPECIAL_COMMAND:
  case SPECIAL_SECTIONING:
    special_start_with_opt(pos);
    break;
  default:                         /* should not be here! */
    warning("(start_with_opt) Unrecognized command type");
    break;
  } /* end switch on user_kind */
}                                  /* end START_WITH_OPT */
\end{verbatim}
\end{code}

    The special actions code is in file \verb|l2xusrlib.c|. The code
for these all follow the same general pattern. For example, here is
the code implementing the special action between the start of a
command and a first optional argument.
\begin{code}
\begin{verbatim}
/* SPECIAL_START_WITH_OPT special start for command with opt param */
void special_start_with_opt(pos)
int pos;                           /* command position in table */
{
  int special_kind;                /* user-specified special token */

  special_kind = get_special_token(pos);

  switch(special_kind) {
    /* additional cases for specials added here */

    /* end of cases for specials */
  default:                        /* should not be here! */
    warning("(special_start_with_opt) Unrecognized SPECIAL");
    tdebug_str_int("SPECIAL_TOKEN =",special_kind);
    break;
  }  /* end of switch on user_kind */
}                            /* end SPECIAL_START_WITH_OPT */
\end{verbatim}
\end{code}
Note that the code as provided just issues a warning message.


\end{description}


    With this background, we will now go on with the example.

\begin{enumerate}
\item Decide on how the \lx\ system will translate your command/environment
description into its internal grammar command type. In this case it
will translate into a command with possibly an initial optional argument
and one required argument.

\item Examine the grammar for the command and hence determine which standard
actions will be called. In this case there are three of these, namely
\verb|start_with_opt|, \verb|action_opt_first| and \verb|action_last_p|.
These are the actions that might require modification.

\item Determine what actions are required for your special. Conceptually
replace the standard actions in the grammar by your actions. Then determine
how these should be incorporated into the special action code in
\verb|l2xusrlb|. In plain
language, the grammar and conceptual actions for the example are:
\begin{code}
\begin{verbatim}
l2xComm1: COMMAND_1
        {
          start of as a sectioning command
          ignore the optional argument as there isn't one
        }
        OptParam
        {
          finish processing the non-existent optional
          get ready to store the argument text in a buffer
        }
        ReqParam
        {
          print the boilerplate and argument text
          start the description list
        }
        ;
\end{verbatim}
\end{code}
Note that this is essentially the same as we did for the grammar 
implementation for \verb|\GRAMMspecial|, except that there is the additional
optional argument to be dealt with.

\item Modify the requisite special action code.

    In the example, three standard actions have to be modified. Here is
the modification to \verb|special_start_with_opt|:
\begin{code}
\begin{verbatim}
/* SPECIAL_START_WITH_OPT special start for command with opt param */
void special_start_with_opt(pos)
int pos;                           /* command position in table */
{
  int special_kind;                /* user-specified special token */

  special_kind = get_special_token(pos);

  switch(special_kind) {
    /* additional cases for specials added here */
  case 59999:                    /* example coded special */
    codespecial_start(pos);
    default_start_with_opt(pos);
    break;

    /* end of cases for specials */
  default:                        /* should not be here! */
    warning("(special_start_with_opt) Unrecognized SPECIAL");
    tdebug_str_int("SPECIAL_TOKEN =",special_kind);
    break;
  }  /* end of switch on user_kind */
}                            /* end SPECIAL_START_WITH_OPT */
\end{verbatim}
\end{code}
The addition is done by adding a new \verb|case 59999:| together with
appropriate code. The number 59999 is that corresponding to the
value for \verb|SPECIAL_TOKEN=| in the command table specification
of \verb|\CODEspecial|. The function \verb|codespecial_start| is to
be written, while \verb|default_start_with_opt| is an \lx\ defined
function which initiates processing of an initial optional argument.

    Similarly, here is the modification to \verb|special_action_opt_first|:
\begin{code}
\begin{verbatim}
     /* additional cases for specials added here */
      case 59999:              /* example coded special */
        default_end_start_opt(pos);
        codespecial_p1(pos);
        break;

     /* end of cases for specials */
\end{verbatim}
\end{code}
where \verb|codespecial_p1| is to be written and \verb|default_end_start_opt|
is the standard \lx\ action at the end of an initial optional argument.

Finally, here is the modification to \verb|special_action_last_p|:
\begin{code}
\begin{verbatim}
/* SPECIAL_ACTION_LAST_P action after last req argument */
void special_action_last_p(pos,p)    
int pos;                       /* position of command in table */
int p;                         /* number of last argument */
{
  int special_kind;                /* user-specified special token */

  special_kind = get_special_token(pos);

  switch(special_kind) {
     /* additional cases for specials added here */
      case 59999:              /* example coded special */
        if (p == 1) {          /* has only one req param */
          codespecial_end(pos);
        }
        break;

     /* end of cases for specials */
   /* stuff deleted to save space */
\end{verbatim}
\end{code}

\item Code the functions for the new actions.

    Code for these functions should be put into file \verb|l2xusrlb.c|
and file \verb|l2xusrlb.h| modified accordingly.

    Here is the code for the three \verb|codespecial_| functions.
\begin{code}
\begin{verbatim}
char codebuf[80];                  /* a string buffer */

/* CODESPECIAL_START actions for start of CODEspecial command */
void codespecial_start(pos)
int pos;                       /* command table position */
{
  start_section(pos);          /* do start of sectioning */
  myprint(get_t(pos));         /* print start tag */
}                              /* end CODESPECIAL_START */

/* CODESPECIAL_P1 actions at start of CODEspecial param 1 */
void codespecial_p1(pos)
int pos;                       /* command table position */
{
  myprint(get_tag_t(pos,1));   /* print 1st param start tag */
  initialise_sysbuf();         /* clear system string buffer */
  set_print(p_print_to_sysbuf); /* put arg text into sys buffer */
}                              /* end CODESPECIAL_P1 */

/* CODESPECIAL_END actions at end of CODEspecial command */
void codespecial_end(pos)
int pos;                       /* command table position */
{
  initialise_string(codebuf);  /* clear this string buffer */
  copy_sysbuf(codebuf);        /* copy sys buffer into codebuf */
  reset_print();               /* normal printing */
  prwboiler1();                /* print some boilerplate */
  print_sysbuf();              /* print system buffer */
  prwboiler2();                /* print more boilerplate */
  myprint(codebuf);            /* print codebuff */
  prwboiler3();                /* print yet more boilerplate */
  start_list(pos);             /* start a list environment */
}                              /* end CODESPECIAL_END */
\end{verbatim}
\end{code}
Note that these actions are almost identical to those that were used
within the grammar when implementing the \verb|\GRAMMspecial| command.

\item Compile the modified system and test it on example \LaTeX\ files.

\end{enumerate}

\subsection{Notes}

\begin{enumerate}
\item Installation of a \keyword{SPECIAL\_} can be limited to making changes 
      to the parser (file \verb|l2x.y|) and/or the user library
      (files \verb|l2xusrlb.c| and \verb|l2xusrlb.h|).
      It should not be necessary to touch any other part of the system.

\item Changes to \file{l2x.y} will necessitate executing the parser generator
      on this file and
      system compilation. Changes to the other files will only necessitate
      compilation.
      
\item Always use the \keytext{myprint}, \keytext{verbatim\_print} 
      or \keytext{print\_sysbuf} functions for
      printing because they incorporate the print control
      capability.

\item The printing in the above example is trivial. However, it is good practice
      to define printed output separately from the parser. It makes for easier
      maintenance. If, for example the boilerplate above was several thousand
      characters, it might have been an idea to store the text in a file, or
      files, and then have the boilerplate printing functions read from 
      the file(s).
      If the text is in a state of flux this could be a good design decision
      in any case, as changing the text would only involve modifying the
      text file(s) and avoid recompilation of \lx.
\end{enumerate}

\subsubsection{An updated method}

    The above descriptions of installing a \verb|SPECIAL_| command were
written for the original release of the \lx{} system, which did not
have the input and output specification facilities currently available
within a \ctab. Below is given a possible \ctab{} entry using these
facilities.
\begin{latexonly}
\begin{code}
\begin{verbatim}
TYPE= SPECIAL_COMMAND
NAME= \THIRDspecial
  C= SPECIAL_TOKEN=  set the appropriate number
  SECTIONING_LEVEL= SECT
  START_TAG= "?n?n<div.1>?n"
    STRING: "<heading>Normative References</heading>?n"
    RESET_SYSBUF:
  END_TAG= "?n</div.1>"
  REQPARAMS= 1
  PRINT_P1= TO_SYSBUF
  END_TAG_1=
    STRING: "?nSome boilerplate text with "
    SOURCE: SYSBUF
    STRING: "?nin the middle. Now there is?n"
    STRING: "some more boilerplate with "
    SOURCE: SYSBUF
    STRING: "?nin the middle of it.?n"
  START_ITEM= "?n"
  START_ITEM_PARAM= "    ("
  END_ITEM_PARAM= ") -- "
END_TYPE
\end{verbatim}
\end{code}
\end{latexonly}
\begin{htmlverbatim}
TYPE= SPECIAL\_COMMAND
NAME= \THIRDspecial
  C= SPECIAL\_TOKEN=  set the appropriate number
  SECTIONING\_LEVEL= SECT
  START\_TAG= "?n?n\ST{div.1}?n"
    STRING: "\ST{heading}Normative References\ET{heading}?n"
    RESET\_SYSBUF:
  END\_TAG= "?n\ET{div.1}"
  REQPARAMS= 1
  PRINT\_P1= TO\_SYSBUF
  END\_TAG\_1=
    STRING: "?nSome boilerplate text with "
    SOURCE: SYSBUF
    STRING: "?nin the middle. Now there is?n"
    STRING: "some more boilerplate with "
    SOURCE: SYSBUF
    STRING: "?nin the middle of it.?n"
  START\_ITEM= "?n"
  START\_ITEM\_PARAM= "    ("
  END\_ITEM\_PARAM= ") -- "
END\_TYPE
\end{htmlverbatim}
The actual implementation of this as either a grammar special or a code
special is left as an exercise for the reader. Basically it involves
the deletion of the specific print action and buffer code because this is now
handled automatically via the \ctab{} specification.


\clearpage
\appendix
\section{Example \protect\ctab\ file for de-\TeX ing}  \label{sec:detexing}

    This appendix provides the skeleton of a \ctab\ file that could be used for
de-\TeX ing a \LaTeX\ document.

\begin{code}
\begin{verbatim}
C=  detex.ct command table file for ltx2x to deTeX source

C=   -----------------------------------escape sequences

C= don't use default here as it may clash with command name output
ESCAPE_CHAR= ?
C=       keep tye default vaues for the rest

C=   ----------------------------------- the built in commands
TYPE= BEGIN_DOCUMENT
END_TYPE

TYPE= END_DOCUMENT
END_TYPE

TYPE= BEGIN_VERB
END_TYPE

TYPE= END_VERB
END_TYPE

TYPE= BEGIN_VERBATIM
  START_TAG= "?n"
END_TYPE

TYPE= END_VERBATIM
  START_TAG= "?n"
END_TYPE

TYPE= BEGIN_DOLLAR
END_TYPE

TYPE= END_DOLLAR
END_TYPE

TYPE= SLASH_SPACE
  START_TAG= " "
END_TYPE

TYPE= OTHER_COMMAND
  PRINT_CONTROL= NO_PRINT
END_TYPE

TYPE= OTHER_BEGIN
  PRINT_CONTROL= NO_PRINT
END_TYPE

TYPE= OTHER_END
  PRINT_CONTROL= NO_PRINT
END_TYPE

C=       throw away naked braces
TYPE= LBRACE
END_TYPE

TYPE= RBRACE
END_TYPE

C=  Pretty printing will probably be applied. Indent start of paragraphs
TYPE= PARAGRAPH
  START_TAG= "?n?n    "
END_TYPE

C= -------------------------------------(La)TeX special characters

C= hash (for use in \def s )
TYPE= TEX_CHAR
NAME= #
END_TYPE

C= ampersand (tabular column delimiter, replace by some spaces)
TYPE= TEX_CHAR
NAME= &
  START_TAG= "   "
END_TYPE

C= twiddle (unbreakable space)
TYPE= TEX_CHAR
NAME= ~
  START_TAG= " "
END_TYPE

C= underscore (math subscript)
TYPE= TEX_CHAR
NAME= _
  START_TAG= "_"
END_TYPE

C= caret (math superscript)
TYPE= TEX_CHAR
NAME= ^
  START_TAG= "^"
END_TYPE

C= at 
TYPE= TEX_CHAR
NAME= @
  START_TAG= "@"
END_TYPE

C= ------------------------- default single character commands 
C=        (replace by appropriate character)

C= LaTeX start a new line
TYPE= CHAR_COMMAND
NAME= \\
  START_TAG= "?n"
END_TYPE

C= small space
TYPE= CHAR_COMMAND
  NAME= \,
START_TAG= " "
END_TYPE

C= end of sentence space
TYPE= CHAR_COMMAND
NAME= \@
  START_TAG= " "
END_TYPE

C= hash
TYPE= CHAR_COMMAND
NAME= \#
  START_TAG= "#"
END_TYPE

C= dollar
TYPE= CHAR_COMMAND
NAME= \$
  START_TAG= "$"
END_TYPE

C= ampersand
TYPE= CHAR_COMMAND
NAME= \&
  START_TAG= "&"
END_TYPE

C= underscore
TYPE= CHAR_COMMAND
NAME= \_
  START_TAG= "_"
END_TYPE

C= percent
TYPE= CHAR_COMMAND
NAME= \%
  START_TAG= "%"
END_TYPE

C= left brace
TYPE= CHAR_COMMAND
NAME= \{
  START_TAG= "{"
END_TYPE

C= right brace
TYPE= CHAR_COMMAND
NAME= \}
  START_TAG= "}"
END_TYPE

C= optional hyphenation
TYPE= CHAR_COMMAND
NAME= \-
  START_TAG= ""
END_TYPE

C= ----------------------------- General LaTeX

TYPE= COMMAND
NAME= \caption
  START_TAG= "?n    CAPTION: "
  OPT_PARAM= FIRST
  PRINT_OPT= NO_PRINT
  REQPARAMS= 1
END_TYPE

TYPE= BEGIN_LIST_ENV
NAME= itemize
  START_TAG= "?n"
  START_ITEM= "?n   o "
END_TYPE

TYPE= END_LIST_ENV
NAME= itemize
  START_TAG= "?n"
END_TYPE

TYPE= BEGIN_LIST_ENV
NAME= enumerate
  START_TAG= "?n"
  START_ITEM= "?n   -- "
END_TYPE

TYPE= END_LIST_ENV
NAME= enumerate
  START_TAG= "?n"
END_TYPE

TYPE= BEGIN_LIST_ENV
NAME= description
  START_TAG= "?n"
  START_ITEM= "?n    "
  END_ITEM_PARAM= " : "
END_TYPE

TYPE= END_LIST_ENV
  NAME= description
START_TAG= "?n"
END_TYPE

C=       replace \footnote with parenthesized text
TYPE= COMMAND
NAME= \footnote
  START_TAG= " ("
  END_TAG= ") "
  OPT_PARAM= FIRST
  PRINT_OPT= NO_PRINT
  REQPARAMS= 1
END_TYPE

C=          ----------------------- sectioning (keep headers only)

C=           repeat for all the other sectioning commands
TYPE= SECTIONING
NAME= \section
  SECTIONING_LEVEL= SECT
  START_TAG= "?n?n"
  OPT_PARAM= FIRST
  PRINT_OPT= NO_PRINT
  REQPARAMS= 1
  END_TAG_1= "?n?n"
END_TYPE

C=         repeat for all the other starred sectioning commands
TYPE= SECTIONING
NAME= \section*
  SECTIONING_LEVEL= SECT
  START_TAG= "?n?n"
  REQPARAMS= 1
  END_TAG_1= "?n?n"
END_TYPE

C=        and whatever else is interesting
END_CTFILE= 
\end{verbatim}
\end{code}

\section{LaTeX to HTML translation} \label{sec:htmling}

    The \ctab{} file \file{l2h.ct} contains a set of commands that
enable simple \LaTeX{} documents to be translated into HTML tagged
documents for display using a World Wide Web browser. At a minumum
this \ctab{} can be used for conversion of the \LaTeX{} source of
this manual. It can also handle some very simple mathematics but not
pictures.\footnote{HTML itself cannot handle pictures directly (i.e.,
there is no equivalent to the \LaTeX{} \keytext{picture} environment),
and can only handle simple mathematics.} The specification
for the HTML tags was taken from Musciano and Kennedy~\cite{MUSCIANO96}.

    Generally speaking and subject to the above limitations, 
a \LaTeX{} document can be translated 
to HTML without the document having been planned for this purpose, 
with one exception.
The exception is that a new \LaTeX{} command should be used in the
document preamble.
I have called this \verb|\mltitle| and its purpose to to define
the contents of the header for the HTML text. The definition of this command
is:
\begin{verbatim}
\newcommand{\mltitle}[1]{}
\end{verbatim}
That is, as far as \LaTeX{} is concerned, the argument to the command is
thrown away and is a non-event. As far as the \file{l2h.ct} \ctab{} is concerned
the argument is the header title. As an example, this manual starts with:
\begin{verbatim}
...
\mltitle{LaTeX to X translator}
\begin{document}
\title{\lx: A \LaTeX{} to X Auto-tagger}
...
\end{verbatim}
which gets converted into:
\begin{latexonly}
\begin{verbatim}
<html>
<head>
<title>LaTeX to X translator</title>
</head>
<body>

<h1 align=center>
 LTX2X: A LaTeX to X Auto-tagger
</h1>
...
\end{verbatim}
\end{latexonly}
\begin{htmlverbatim}
<html>
<head>
<title>LaTeX to X translator\ET{title}
\ET{head}
<body>

<h1 align=center>
 LTX2X: A LaTeX to X Auto-tagger
\ET{h1}
...
\end{htmlverbatim} 
If the \verb|\mltitle| command is not used, then the effect is to have
an empty \ST{title} in the \ST{head} of the HTML document.


    Several aspects of the design of \file{l2h.ct} in the context of
the conversion of typical \LaTeX{} documents have been discussed 
as examples in the body of the manual. However, there are some aspects 
specific to the translation of this document should be mentioned.
These stem from the fact that HTML has no tags corresponding to
to the \LaTeX{} \verb|\verb| command or \verb|verbatim| environment which
switch off the meanings of special characters.

    HTML treats the characters \LT, \GT, \Amp{} and \HASH{} specially.
Within a \ST{pre}...\ET{pre} the browser honours the line breaks
but does not switch off the meanings of the special characters. In \LaTeX{},
the \verb|\verb| command switches off all special characters but prohibits
any line breaking. The \verb|verbatim| environment both honours line breaks
and switches off all special characters. The difficulty with this particular
document is that I want to show author-formatted HTML source, and that is not
easly possible, unlike using the \LaTeX{} \verb|verbatim| environment for
showing user-formatted \LaTeX{} source.

    The problem was solved through the use of two \LaTeX{} environments.
The first of these is \keytext{latexonly} which is used for input that is
to be processed normally by \LaTeX{} but which is to be totally ignored 
by \lx. The other environment is \keytext{htmlverbatim} which is used
for input that is to be totally ignored by \LaTeX{} but which is to be
processed by \lx{} into an HTML \ST{pre} environment.

    A package file has been written which provides some addtional
commands and environments.
\begin{latexonly}
\begin{code}
\begin{verbatim}
% ltx2html.sty  --- Some useful commands and environments when using
%                   ltx2x to convert from LaTeX to HTML tagging.
%
% Author: Peter Wilson    August 1996
%
\ProvidesPackage{ltx2html}[1996/08/29 ltx2x HTMLing]
\RequirePackage{html}  % the package file for the Perl program
                        % latex2html

% The document title for the WWW browser. 
% If used, must be placed in the preamble.
\newcommand{\mltitle}[1]{}

% argument is for processing by LaTeX only
\providecommand{\latex}[1]{#1}

% argument is for HTML processing only
\providecommand{\html}[1]{}

% print argument as an SGML/HTML start tag
\newcommand{\ST}[1]{\texttt{<#1>}}

% print argument as an SGML/HTML end tag
\newcommand{\ET}[1]{\texttt{</#1>}}

% print HTML special characters
\newcommand{\Amp}{\&}
\newcommand{\GT}{\texttt{>}}
\newcommand{\LT}{\texttt{<}}
\newcommand{\HASH}{\#}

% treat contents as a LaTeX comment but
% translate contents into an HTML "verbatim" environment
% Use as: \begin{htmlverbatim} ... \end{htmlverbatim}
\excludecomment{htmlverbatim}

\endinput
\end{verbatim}
\end{code}
\end{latexonly}

\begin{htmlverbatim}
% ltx2html.sty  --- Some useful commands and environments when using
%                   ltx2x to convert from LaTeX to HTML tagging.
%
% Author: Peter Wilson    August 1996
%
\verb|\ProvidesPackage{ltx2html}[1996/08/29 ltx2x HTMLing]|
\verb|\RequirePackage{html}  % the package file for the Perl program|
                        \% latex2html

\% The document title for the WWW browser. 
\% If used, must be placed in the preamble.
\verb|\newcommand{\mltitle}[1]{}|

\% argument is for processing by LaTeX only
\verb|\providecommand{\latex}[1]|\{\HASH{}1\}

\% argument is for HTML processing only
\verb|\providecommand{\html}[1]{}|

\% print argument as an SGML/HTML start tag
\verb|\newcommand{\ST}|[1]\{\ST{\HASH{}1}\} 

\% print argument as an SGML/HTML end tag
\verb|\newcommand{\ET}|[1]\{\ET{\HASH{}1}\}

\% print HTML special characters
\verb|\newcommand{\Amp}|\{\Amp\}
\verb|\newcommand{\GT}|\{\GT\}
\verb|\newcommand{\LT}|\{\LT\}
\verb|\newcommand{\HASH}|\{\HASH\}

\% treat contents as a LaTeX comment but
\% translate contents into an HTML "verbatim" environment
\verb|% Use as: \begin{htmlverbatim} ... \end{htmlverbatim}|
\verb|\excludecomment{htmlverbatim}|

\verb|\endinput|
\end{htmlverbatim}

    The \ctab{} entries for some of these are:
\begin{latexonly}
\begin{code}
\begin{verbatim}
TYPE= COMMAND
NAME= \Amp
  START_TAG= "&amp;"
END_TYPE

TYPE= COMMAND
NAME= \GT
  START_TAG= "&gt;"
END_TYPE

TYPE= COMMAND
NAME= \LT
  START_TAG= "&lt;"
END_TYPE

TYPE= COMMAND
NAME= \HASH
  START_TAG= "&#035;"
END_TYPE

TYPE= COMMAND
NAME= \ST
  START_TAG= "&lt;"
  END_TAG= "&gt;"
  REQPARAMS= 1
END_TYPE

TYPE= COMMAND
NAME= \ET
  START_TAG= "&lt;/"
  END_TAG= "&gt;"
  REQPARAMS= 1
END_TYPE
\end{verbatim}
\end{code}
\end{latexonly}
\begin{htmlverbatim}
TYPE= COMMAND
NAME= \Amp
  START\_TAG= "\Amp{}amp;"
END\_TYPE

TYPE= COMMAND
NAME= \GT
  START\_TAG= "\Amp{}gt;"
END\_TYPE

TYPE= COMMAND
NAME= \LT
  START\_TAG= "\Amp{}lt;"
END\_TYPE

TYPE= COMMAND
NAME= \HASH
  START\_TAG= "\Amp\HASH035;"
END\_TYPE

TYPE= COMMAND
NAME= \verb|\ST|
  START\_TAG= "\Amp{}lt;"
  END\_TAG= "\Amp{}gt;"
  REQPARAMS= 1
END\_TYPE

TYPE= COMMAND
NAME= \verb|\ET|
  START\_TAG= "\Amp{}lt;/"
  END\_TAG= "\Amp{}gt;"
  REQPARAMS= 1
END\_TYPE
\end{htmlverbatim}

    Finally, as an example, this is how some of the prior example text
could be
written in the source of this document.
\begin{latexonly}
\begin{verbatim}
\begin{latexonly}
\begin{verbatim}
<html>
<head>
<title>LaTeX to X translator</title>
</head>
<body>

<h1 align=center>
 LTX2X: A LaTeX to X Auto-tagger
</h1>
...
\end{verbatim}
\verb|\end{verbatim}| \\
\verb.\end{latexonly}.
\end{latexonly}
\begin{latexonly}
\begin{verbatim}

\begin{htmlverbatim}
<html>
<head>
<title>LaTeX to X translator\ET{title}
\ET{head}
<body>

<h1 align=center>
 LTX2X: A LaTeX to X Auto-tagger
\ET{h1}
...
\end{htmlverbatim}
\end{verbatim}
\end{latexonly}

\begin{htmlverbatim}
\verb|\begin{latexonly}|
\verb|\begin{verbatim}|
<html>
<head>
<title>LaTeX to X translator</title>
</head>
<body>

<h1 align=center>
 LTX2X: A LaTeX to X Auto-tagger
</h1>
...
\verb|\end{verbatim}|
\verb|\end{latexonly}|

\verb|\begin{htmlverbatim}|
<html>
<head>
<title>LaTeX to X translator\verb|\ET{title}|
\verb|\ET{head}|
<body>

<h1 align=center>
<title>LaTeX to X translator\verb|\ET{title}|
\verb|\ET{head}|
\verb|...|
\verb|\end{htmlverbatim}|
\end{htmlverbatim}

    Reading the \LaTeX{} source of this document will reveal some
other details. Admittedly the problem was compounded by the fact
that this document contains demonstrations of both \LaTeX{} and
HTML commands which will be processed through both \LaTeX{} and HTML
browsers, thus a modicum of care is required to appropriately
process both sets of special characters.


\section{Known limitations}  \label{sec:limitations}

    \lx\ does not do everything that it might (and probably never will). 
The following are some of the things that it does not do.

\begin{itemize}
\item It does not understand the \LaTeX\ \verb|\input| or \verb|\include| 
      commands ---
      it just reads the source file as given. It may be useful to pre-process the
      source file through a program that will automatically incorporate included
      files into a \LaTeX\ root file~\cite{PRW94b}.

\item The \verb|\newcommand| and friends do not readily
      fit into the command patterns that
      \lx\ can deal with. In particular, if it comes across a \verb|\newcommand|
      specification for a command that is specified in the \ctab, interesting
      results might occur (for example, all the following output could be thrown 
      away if the command takes any arguments). 
      
      For instance, if the document and the \ctab\ contain:
\begin{code}
\begin{verbatim}
\newcommand{\lx}{LTX2X}
....
The \lx\ program ...

TYPE= COMMAND
NAME= \lx
  START_TAG= "LTX2X"
END_TYPE
\end{verbatim}
\end{code}
      then there is usually no problem. On the other hand, if the document and
      the \ctab\ contain:
\begin{code}
\begin{verbatim}
\newcommand{\fd}[1]{\texttt{#1}}
....
where \fd{InputFile} is the name ...

TYPE= COMMAND
NAME= \fd
  REQPARAMS= 1
END_TYPE
\end{verbatim}
\end{code}
      then there may be a problem, which might be as `minor' as \lx\ reporting
      a parse error when it has reached \verb|\newcommand{\fd}| in the input
      file and then carrying on, or it may be more serious.

\item There is a slight problem with optional arguments. \lx\ always takes the
      first close bracket (\verb|]|) after the opening bracket as signalling
      the end of the argument text. This occurs even if the close bracket
      is enclosed in braces (i.e. \verb|{]}|). Opening brackets within optional
      argument text are handled correctly.

\item It cannot sensibly handle \LaTeX{}
      constructs of the form \verb|{\em emph text}|.
      That is, except for command arguments, it does not recognize
      \verb|{...}| as a grouping construct, so cannot successfully
      tag the end of the \verb|emph text| in the example. On the other
      hand, if constructs like \verb|\emph{emph text}| or
      \verb|\begin{em}emph text\end{em}| are used instead, start and end
      tags can be generated, given appropriate specifications in the
      \ctab.

\item It assumes that all commands that take arguments are written so
      that each argument is enclosed in braces. For example, the 
      superscripting command should be written as \verb|^{2}| and not
      as \verb|^2|. Similarly, accent commands should be written as
      \verb|\={o}| rather than \verb|\=o|, and so on.

\item There has not been time to test all aspects of the \ExpressA{}
      interpreter. It is possible that this may not perform quite
      as advertised. In particular dynamic aggregates have not been fully
      implemented. For example:
\begin{code}
\begin{verbatim}
LIST OF INTEGER;
\end{verbatim}
\end{code}
      appears to be handled correctly. More complicated constructs involving
      dynamic aggregates, such as
\begin{code}
\begin{verbatim}
ARRAY [1:7] OF LIST OF ARRAY [-21:21] OF INTEGER;
\end{verbatim}
\end{code}
      have not been tested. It is improbable that \keyword{BAG} will
      work; the status of \keyword{SET} is similar and additionally 
      the uniqueness test for set membership has not been implemented.
\item No doubt other limitations will come to light as \lx\ gets more use. 
      On the other
      hand, \lx{} has been able to handle a broader range of cases than
      it was designed to address.


\end{itemize}


\section{Command table summary} \label{sec:summary}

    This section summarizes the commands and specifications available
for defining a \ctab.

\subsection{Special print characters}

    The combination of an escape character and another character can be used to
specify certain non-visible characters within a tag string. The commands are
given in Table~\ref{tab:spc}.

\begin{table}[htbp]
\centering
\caption{Special print character commands.} \label{tab:spc}
\begin{tabular}{|l|c|} \hline
Command & Default \\ \hline
\keyword{AUDIBLE\_ALERT\_CHAR=} & \verb|a| \\
\keyword{BACKSPACE\_CHAR=} & \verb|b| \\
\keyword{CARRIAGE\_RETURN\_CHAR=} & \verb|r| \\
\keyword{ESCAPE\_CHAR=} & \verb|\| \\
\keyword{FORMFEED\_CHAR=} & \verb|f| \\
\keyword{HEX\_CHAR=} & \verb|x| \\
\keyword{HORIZONTAL\_TAB\_CHAR=} & \verb|t| \\
\keyword{NEWLINE\_CHAR=} & \verb|n| \\
\keyword{VERTICAL\_TAB\_CHAR=} & \verb|v| \\ \hline
\end{tabular}
\end{table}

    These commands take one character as their value. If any commands are not
specified, then the default value is used. These commands, if used,  must be
at the beginning of the \ctab\ before any \keyword{TYPE=} commands, 
although their ordering is not significant among themselves.

\subsection{\ExpressA{} code initialization}

    The keyword \keyword{CODE\_SETUP=} indicates that the following part
of the \ctab, up until the \keyword{END\_CODE} keyword, contains
\ExpressA{} code declarations and/or statements. If used, this block
must come before any of the \keyword{TYPE=} commands.

\subsection{Comments and file inclusion}

    A comment within a \ctab\ file is any line starting with \keyword{C= }.

    A file can be included within another \ctab\ file with the command line
\begin{verbatim}
INCLUDE= FileName
\end{verbatim}
where \keytext{FileName} is the name of the file to be included. The 
\keyword{INCLUDE=}
command cannot appear between the command pair \keyword{TYPE=} and its following
\keyword{END\_TYPE}.

    The end of a \ctab\ file is either the physical end of the file or
the command \keyword{END\_CTFILE=}, whichever occurs first.

\subsection{Command types}

    All command type specifications have the general form:
\begin{verbatim}
TYPE= CommandType
NAME= CommandName
   C= a possibly empty list of mode-independent commands
   C= possibly sets of mode-dependent commands
END_TYPE
\end{verbatim}
where \keytext{CommandType} is a keyword identifying the kind of command being 
specified and \keytext{CommandName} is the identifier of a \LaTeX{} command
or environment. The potential set of commands that can be used between the 
\keyword{TYPE=}
and \keyword{END\_TYPE} commands depends on the kind of command being specified,
but the special print character commands, Table~\ref{tab:spc}, 
and the \keyword{INCLUDE=} command cannot
appear within a type specification. All command specifications, except
for the built in command types (see Table~\ref{tab:rct}), 
must include at least a \keyword{NAME=} command.
The ordering of commands within a type
specification is not significant. The ordering of type specifications within
a \ctab\ file is not significant.

    The \keyword{NAME=} command takes as its value the name of a \LaTeX\ command or
environment. The name must be written exactly as it would appear in a \LaTeX\
source file. That is, \verb|\command| for any command except \verb|\begin{}|
or \verb|\end{}|, and as \verb|env| for an
environment begun as \verb|\begin{env}| or ended by \verb|\end{env}|.

\subsubsection{Built in command types}

    Table~\ref{tab:rct} lists the keywords for the built in command types.

\begin{table}[htbp]
\centering
\caption{Built in command type keywords.} \label{tab:rct}
\begin{tabular}{|l|c|} \hline
Keyword & \LaTeX\ command \\ \hline
\keyword{BEGIN\_DOCUMENT} & \verb|\begin{document}| \\
\keyword{BEGIN\_DOLLAR} & \verb|$| at start of in-text math \\
\keyword{BEGIN\_VERB} & \verb|\verb| or \verb|\verb*| and its following character \\
\keyword{BEGIN\_VERBATIM} & \verb|\begin{verbatim}| or \verb|\begin{verbatim*}| \\
\keyword{END\_DOCUMENT} & \verb|\end{document}| \\
\keyword{END\_DOLLAR} & \verb|$| at end of in-text math \\
\keyword{END\_VERB} & the ending character for \verb|\verb| or \verb|\verb*| \\
\keyword{END\_VERBATIM} & \verb|\end{verbatim}| or \verb|\end{verbatim*}| \\
\keyword{LBRACE} & \verb|{| \\
\keyword{OTHER\_BEGIN} & of the form \verb|\begin{env}| not specified elsewhere \\
\keyword{OTHER\_COMMAND} & of the form \verb|\comm| not specified elsewhere \\
\keyword{OTHER\_END} & of the form \verb|\end{env}| not specified elsewhere \\
\keyword{PARAGRAPH} & blank source line \\
\keyword{RBRACE} & \verb|}| \\
\keyword{SLASH\_SPACE} & \verb*|\ | \\ \hline
\end{tabular}
\end{table}

    The built in command type specifications can only sensibly use two kinds
of actions ---
those specified at the start of the command (e.g., \keyword{PC\_AT\_START=}
and \keyword{START\_TAG=}) and/or actions at the end of the command
(e.g., \keyword{PC\_AT\_END} and \keyword{END\_TAG=}).
The \keyword{NAME=} command must not be used. 

    The \keyword{OTHER\_} types are an exception to the above, in that they can include
the command line \keyword{PRINT\_CONTROL= NO\_PRINT}.

    \lx\ checks the command table for the presence of these required types. If one
or more have not been specified, then they are automatically added to the command table 
with default values (e.g. empty strings) for the tags, and a warning message is 
printed giving the default value(s).

\subsubsection{Optional command types}

    For discussion purposes, the optional command types have been tabulated
in different categories. The basic distinction between these categories is
the sets of commands that are permissible within the command specification.

    At a minimum, all the specifications must include a \keyword{NAME=} command
and must not contain any \keyword{PRINT\_CONTROL=} or \keyword{INCLUDE=} commands
or the special
print character commands listed in Table~\ref{tab:spc}.


    The keywords for the general command types are given Table~\ref{tab:gct}.

\begin{table}[htbp]
\centering
\caption{General command type keywords.} \label{tab:gct}
\begin{tabular}{|l|c|} \hline
Keyword & \LaTeX\ command form \\ \hline
\keyword{TEX\_CHAR} & \LaTeX\ special characters (except \verb|{ } $|) \\
\keyword{CHAR\_COMMAND} & \verb|\c|, where \verb|c| is non-alphabetic \\
\keyword{COMMAND} & \verb|\command| except for sectioning or picture commands \\
\keyword{BEGIN\_ENV} & \verb|\begin{env}| except for \verb|\item| lists \\
\keyword{END\_ENV} & \verb|\end{env}| except for \verb|\item| lists \\
\keyword{VCOMMAND} & a \verb|\verb|-like command \\
\keyword{BEGIN\_VENV} & start of a \verb|verbatim|-like environment \\
\keyword{END\_VENV} & end of a \verb|verbatim|-like environment \\ \hline
\end{tabular}
\end{table}

    A general command type specification can include any of the tagging and print
option commands. They cannot contain a \keyword{SECTION\_LEVEL=} command, nor can
they contain any of the \keyword{\_ITEM\_} commands.

    The keywords for the specific command types are given in Table~\ref{tab:sct}.

\begin{table}[htbp]
\centering
\caption{Specific command type keywords.} \label{tab:sct}
\begin{tabular}{|l|c|} \hline
Keyword & \LaTeX\ command form \\ \hline
\keyword{BEGIN\_LIST\_ENV} & \verb|\begin{env}| for \verb|\item| lists \\
\keyword{BEGIN\_PICTURE\_CC} & \verb|\begin{pic}()()| \\
\keyword{END\_LIST\_ENV} & \verb|\end{env}| for \verb|\item| lists \\
\keyword{END\_PICTURE} & \verb|\end{pic}| \\
\keyword{PICTURE\_CCPP} & \verb|\pic()(){}{}| \\
\keyword{PICTURE\_CO} & \verb|\pic()[]| \\
\keyword{PICTURE\_COP} & \verb|\pic()[]{}| \\
\keyword{PICTURE\_CP} & \verb|\pic(){}| \\
\keyword{PICTURE\_OCC} & \verb|\pic[]()()| \\
\keyword{PICTURE\_OCCC} & \verb|\pic[]()()()| \\
\keyword{PICTURE\_OCO} & \verb|\pic[]()[]| \\
\keyword{PICTURE\_PCOP} & \verb|\pic{}()[]{}| \\
\keyword{SECTIONING} & \verb|\command| for a document section \\
\keyword{COMMAND\_OOP} & \verb|\com[][]{}| \\
\keyword{COMMAND\_OOOPP} & \verb|\com[][][]{}{}| \\
\keyword{COMMAND\_OPO} & \verb|\com[]{}[]| \\
\keyword{COMMAND\_POOOP} & \verb|\com{}[][][]{}| \\
\keyword{COMMAND\_POOP} & \verb|\com{}[][]{}| \\
\keyword{COMMAND\_POOPP} & \verb|\com{}[][]{}{}| \\ \hline
\end{tabular}
\end{table}

    A \keyword{BEGIN\_LIST\_ENV} specification should include at least a 
\keyword{START\_ITEM=} command. The other \keyword{\_ITEM\_} commands 
are optional.
Other commands follow the rules for the general command types.

    The potential commands for the \keyword{\_PICTURE\_} commands are the same as
for the general commands, with the exception that commands related to optional
argument processing are not available for use.

    A \keyword{SECTIONING} command specification must include a 
\keyword{SECTIONING\_LEVEL=}
command. Other commands follow the rules for the general command types.

    The keywords for the special command types are given in 
Table~\ref{tab:specct}.

\begin{table}[htbp]
\centering
\caption{Special command type keywords.} \label{tab:specct}
\begin{tabular}{|l|c|} \hline
Keyword & \LaTeX\ command form \\ \hline
\keyword{SPECIAL} & reserved for possible future use \\
\keyword{SPECIAL\_BEGIN\_ENV} & \verb|\begin{env}| except for \verb|\item| lists \\
\keyword{SPECIAL\_BEGIN\_LIST} & \verb|\begin{env}| for \verb|\item| lists \\
\keyword{SPECIAL\_COMMAND} & \verb|\command| \\
\keyword{SPECIAL\_END\_ENV} & \verb|\end{env}| except for \verb|\item| lists \\
\keyword{SPECIAL\_END\_LIST} & \verb|\end{env}| for \verb|\item| lists \\
\keyword{SPECIAL\_SECTIONING} & \verb|\command| for a document section \\ \hline
\end{tabular}
\end{table}

    Apart from the general restrictions on the allowed commands within
a specification, there are no restrictions on the commands that can be
included within the specification of a \keyword{SPECIAL\_} command. It is up
to the creator of the special to decide what is appropriate. However,
each \keyword{SPECIAL\_} specification must include the command
\begin{verbatim}
SPECIAL_TOKEN= N
\end{verbatim}
where \keytext{N} is an integer number (with $10000 \leq N \leq 32767$ for a
grammar special, or $N > 50000$ for a code special) that has been specified
within \lx\ as being identified with the grammar and actions corresponding to the
value of the \keyword{NAME=} command for the \keyword{SPECIAL\_}.

\subsection{Tag specification commands}

\subsubsection{Arguments}

    The commands relating to the specification of \LaTeX\ command arguments
are given in Table~\ref{tab:param}.

\begin{table}[htbp]
\centering
\caption{Argument commands.} \label{tab:param}
\begin{tabular}{|l|c|} \hline
Command & Value \\ \hline
\keyword{OPT\_PARAM=} & \keyword{FIRST} or \keyword{LAST} \\
\keyword{REQPARAMS=} & Integer. The number of required arguments \\ \hline
\end{tabular}
\end{table}

    The \keyword{OPT\_PARAM=} command specifies that the \LaTeX\ command takes one
optional argument and it is the \keyword{FIRST} or \keyword{LAST} in the argument
list.

    The \keyword{REQPARAMS=} command specifies that the \LaTeX\ command has 
\verb|Integer| number of required arguments. \verb|Integer| must be between
one and nine\footnote{Or eight if \keyword{OPT\_PARAM=} is specified.} inclusive.

    Absence of these commands implies that the relevant \LaTeX\ command has
no arguments of the unspecified kind.

\subsubsection{Tag actions}

    The commands for specifying the tag actions are summarized in 
Table~\ref{tab:tag}.
The \keyword{\_ITEM\_} commands can only be used within a 
\keyword{BEGIN\_LIST\_ENV} or a \keyword{SPECIAL\_} command specification.

\begin{table}[htbp]
\centering
\caption{Tag commands.} \label{tab:tag}
\begin{tabular}{|l|c|} \hline
Command & Application \\ \hline
\keyword{END\_ITEM=} & actions after \verb|\item| text \\
\keyword{END\_ITEM\_PARAM=} & actions after \verb|\item| optional argument \\
\keyword{END\_OPT=} & actions after optional argument \\
\keyword{END\_TAG=}   & actions after all arguments processed \\
\keyword{END\_TAG\_n=} & actions after n'th required argument \\
\keyword{START\_ITEM=} & actions before \verb|\item| \\
\keyword{START\_ITEM\_PARAM=} & actions before \verb|\item| optional argument \\
\keyword{START\_OPT=} & actions before optional argument \\
\keyword{START\_TAG=} & actions at start of command \\
\keyword{START\_TAG\_n=} & actions before n'th required argument \\ \hline
\end{tabular}
\end{table}



    Each of these commands can specify a list of actions to be performed; 
typically this is just to print a text string. A string is any set of
characters enclosed in double
quote marks. The string can include any special printing characters. The
text string starts immediately after the first double quote and ends immediately
before the last double quote. The string cannot include a physical linebreak
within the \ctab\ file. If the first action is to print a string then the
string may be placed on the same line as the keyword.

    The actions are listed one per line and are performed in the order they
are listed. Table~\ref{tab:tagaction} lists the action commands.

\begin{table}[htbp]
\centering
\caption{Tag actions.} \label{tab:tagaction}
\begin{tabular}{|l|l|l|} \hline
Keyword &  Value & Application \\ \hline
\keyword{STRING:} & text string & Print the string \\
\keyword{SOURCE:} & \keyword{BUFFER} \keytext{num} & Print the contents of 
         buffer number \keytext{num} \\
\keyword{SOURCE:} & \keyword{FILE} \keytext{name} & Print the contents of file
\keytext{name} \\
\keyword{SOURCE:} & \keyword{SYSBUF} & Print the contents of the system buffer \\
\keyword{RESET\_BUFFER:} & \keytext{num} & Reset the buffer \keytext{num} \\
\keyword{RESET\_FILE:} & \keytext{name} & Reset the file \keytext{name} \\
\keyword{RESET\_SYSBUF:} &  & Reset the system buffer \\
\keyword{SWITCH\_TO\_BUFFER:} & \keytext{num} & Print to buffer number \keytext{num} \\
\keyword{SWITCH\_TO\_FILE:} & \keytext{name} & Print to file called \keytext{name} \\
\keyword{SWITCH\_TO\_SYSBUF:} &  & Print to the system buffer \\
\keyword{SWITCH\_BACK:} &  & Reset the print mode \\
\keyword{SET\_MODE:} & \keytext{name} & Set the mode to \keytext{name} \\
\keyword{RESET\_MODE:} &  & Reset the mode to its prior value \\
\keyword{CODE:} &  & Start of a set of \ExpressA{} statements \\ \hline
\end{tabular}
\end{table}

\subsubsection{Print control}

    The print control commands are summarized in Table~\ref{tab:print}.
These are used to set the print mode at the start and end of a command, and for
each argument. The exception is the \keyword{PRINT\_CONTROL=} command
which can only be used within an \keyword{OTHER\_} command type
specification, and which is the only print control that can be
specified for the \keyword{OTHER\_} commands.

\begin{table}[htbp]
\centering
\caption{Print control commands.} \label{tab:print}
\begin{tabular}{|l|l|} \hline
Command & Application \\ \hline
\keyword{PRINT\_CONTROL=} & printing of \keyword{OTHER\_} commands \\
\keyword{PC\_AT\_START=} & set printing at start of command \\
\keyword{PC\_AT\_END=} & set printing at end of command \\
\keyword{PRINT\_OPT=} & printing of optional argument  \\
\keyword{PRINT\_Pn=} & printing of n'th required argument  \\ \hline
\end{tabular}
\end{table}

The values that these commands may take are given in Table~\ref{tab:pcvalues}.
These direct where any print output is to be directed. The default is to
send all output the the file named as the output on the command line when
starting \lx.

\begin{table}[htbp]
\centering
\caption{Print control values.} \label{tab:pcvalues}
\begin{tabular}{|l|l|} \hline
Value & Application \\ \hline
\keyword{NO\_PRINT} & Do not print at all \\
\keyword{TO\_SYSBUF} & Print to the system buffer \\
\keyword{TO\_BUFFER} \keytext{num} & Print to buffer number \keytext{num} \\
\keyword{TO\_FILE} \keytext{name} & Print to file called \keytext{name}  \\
\keyword{NO\_OP} & Do not do any processing   \\
\keyword{RESET} & Reset the print mode \\ \hline
\end{tabular}
\end{table}

    \keyword{NO\_PRINT} and \keyword{NO\_OP} both produce no printed output.
However, in the \keyword{NO\_OP} case the lexer handles all the processing,
and effectively just ignores the source document text. In the \keyword{NO\_PRINT}
case, the source text is processed as normal, but the printing is directed
to a black hole.

    

\subsubsection{Sectioning}


    \keyword{SECTIONING} command specifications require a 
\keyword{SECTIONING\_LEVEL=}
command. The values that this can take are listed in Table~\ref{tab:level}.

\begin{table}[htbp]
\centering
\caption{Sectioning level values.} \label{tab:level}
\begin{tabular}{|l|l|} \hline
Value & Application \\ \hline
\keyword{PART} & sectioning equivalent to \verb|\part| \\
\keyword{CHAPTER} & sectioning equivalent to \verb|\chapter| \\
\keyword{SECT} & sectioning equivalent to \verb|\section| \\
\keyword{SUBSECT} & sectioning equivalent to \verb|\subsection| \\
\keyword{SUBSUBSECT} & sectioning equivalent to \verb|\subsubsection| \\
\keyword{PARA} & sectioning equivalent to \verb|\paragraph| \\
\keyword{SUBPARA} & sectioning equivalent to \verb|\subprargraph| \\ \hline
\end{tabular}
\end{table}

    A sectioning command specification uses the \keyword{END\_TAG=} text tag differently
from its use by any other specification. In this case, the tag is printed at
the closure of the text forming the body of the section of the document. A
document section is considered to be closed when it is followed by a higher
level sectioning command. The values in Table~\ref{tab:level} are listed
in decreasing level. That is, a section at level \keyword{CHAPTER} is at a higher
level than a section at level \keyword{PARA}.

\begin{description}
\item[NOTE] For the use of writers of \keyword{SPECIAL\_} command specifications, 
\keyword{SECTIONING\_LEVEL=} can be given some additional values. These are
\keyword{PARTm2} and \keyword{PARTm1} for levels respectively two and one higher
than \keyword{PART}, and \keyword{SUBPARAp1} and \keyword{SUBPARAp2} for levels respectively
one and two lower than \keyword{SUBPARA}.
\end{description}

\section{System installation}  \label{sec:install}

    This section describes how to install the \lx\ program and some of the
internal size limits within \lx.


    The basic \lx\ system requires the following source files:
\begin{description}
\item[\file{l2x.l}] the lexer source.
\item[\file{l2x.y}] the parser source.
\item[\file{l2xlib.c}, \file{l2xlib.h}] main program and support functions.
\item[\file{l2xlibtc.h}] header file containing keywords and their
                         representations as strings.
\item[\file{l2xcom.h}] header file for all system components 
      (except for getopt, srchenv and the interpreter).
\item[\file{l2xacts.c}, \file{l2xacts.h}] standard action functions.
\item[\file{l2xusrlb.c}, \file{l2xusrlb.h}] special actions and user-defined functions.
\item[\file{strtypes.h}] header file with some type definitions.
\item[\file{getopt.c}, \file{getopt.h}] functions for handling command line 
       options~\cite[Chapter 6]{LIBES93}.
\item[\file{srchenv.c}, \file{srchenv.h}] functions for searching directories 
      for files~\cite[page 747]{HOLUB90}.
\end{description}

    The \ExpressA{} interpreter also requires the following files:
\begin{description}
\item[\file{l2xistup.c}] the interface between the main part of \lx{}
   and the interpreter.
\item[\file{l2xicmon.h}] header file for the interface.
\item[\file{l2xirtne.c}, \file{l2xistd.c}, \file{l2xidecl.c}, 
      \file{l2xistmt.c}, \file{l2xiexpr.c}] the files that contain the code for
     parsing \ExpressA. Respectively they deal with functions and procedures,
     the built-in functions, declarations, statements, and expressions.
\item[\file{l2xiprse.h}] header file for parsing.
\item[\file{l2xixutl.c}, \file{l2xiexec.h}] utility routines 
     supporting the execution module and
     for managing the interpreter's stack.
\item[\file{l2xixstd.c}, \file{l2xixstm.c}, \file{l2xixxpr.c}] functions for
     executing the \ExpressA{} built in functions, statements and expressions.
\item[\file{l2xirexp.c}, \file{l2xirexpr.h}] general functions for processing
     and executing regular expressions.
\item[\file{listsetc.c}, \file{listsetc.h}] general functions for processing
     lists.
\item[\file{l2xiscan.c}, \file{l2xiscan.h}] lexing routines for the interpreter.
\item[\file{l2xisymt.c}, \file{l2xisymt.h}] routines for managing the 
     interpreter's symbol tables.
\item[\file{l2xidbug.c}] the source level debugger.
\item[\file{l2xierr.c}, \file{l2xierr.h}]  \ExpressA{} language error handling
     and diagnostic output for the user.
\item[\file{l2xiidbg.c}, \file{l2xiidbg.h}, \file{l2xisdcl.c}] diagnostics 
     for a developer of the interpreter.
\item[\file{licomsym.h}] general header file for the interpreter modules.
\item[\file{l2xidftc.h}, \file{l2xiertc.h}, \file{l2xisctc.h}, \file{l2xisftc.h}]
header files containing keywords and their representations as strings.
\end{description}

The following files may be useful:
\begin{description}
\item[\file{man}] the manpage
\item[\file{printct.c}] a program to print and update \ctab{} files;
\item[\file{ltx2html.sty}] a \LaTeX{} package file to assist in retagging
a \LaTeX{} document to an HTML document.
\end{description}

    Essentially, installing \lx\ consists of processing the file \file{l2x.l}
through a lexer generator, processing the file \file{l2x.y} through a 
parser generator, and then compiling the results together with the other
supplied source files.

    The lexer source file \file{l2x.l} and the parser source file 
\file{l2x.y} have to be processed by flex (or equivalent) and bison
(or equivalent) respectively to generate C code. This code, together 
with the code in the other source files must then be compiled 
and linked to form the executable.

    The executable must then, after suitable testing,  be moved to
its final place in your system and the manpage (file \file{man})
also copied to its final position in your directory structure.

    Included in the \lx{} distribution are several \ctab{} files. One is 
\file{detex.ct} which provides an example of commands for de-\TeX ing
a document.\footnote{You may wish to try using \file{detex.ct} on the
\LaTeX\ source of this document to see what the effect is. This can
also serve as a check on the system installation.}
Another is \file{remcom.ct}
which provides an example of commands to remove comments from a
\LaTeX\ document. The \ctab{} file \file{bye.ct} replaces a \LaTeX{}
document by "Goodbye document".
Another is \file{ltx2x.ct} which does nothing except try and include
another file named \file{ZiLcH}, which presumably is not on anyone's
system. Running \lx\ with this file will prompt for another name of a
file if it cannot find \file{ZiLcH}; enter an existing file (like \file{detex.ct})
at the prompt.\footnote{This is one way of setting up \lx\ for interactive
specification of the desired \ctab\ file(s).}

    The \ctab{} file \file{l2h.ct} has proven to be adequate for converting
the \LaTeX{} source of this manual, and other \LaTeX{} documents without
pictures and only limited mathematics, into an ASCII file with HTML 
tags instead.

    The file \file{fun.ct} contains some test code for the \ExpressA{}
interpreter. The contents are similar to the example shown at the end of
section~\ref{sec:expressa}.

The \file{l2xusrlb} files are skeletons. The system does include
the functions and parser constructs for the \verb|\GRAMMspecial| and
\verb|\CODEspecial| commands used as examples previously. The last two
entries in \file{remcom.ct} are the specification of these, and the
implementation is as described previously.

\subsection{Command table printing}

    The grammar of the \ctab{} has been changed slightly since the
initial release of \lx. The utility C program in \file{printct.c} may be used to:
\begin{itemize}
\item Pretty-print a \ctab;
\item Convert an original \ctab{} to one that conforms to the new grammar.
\end{itemize}

    The syntax for running \file{printct} is:
\begin{verbatim}
printct [-D dir_cat_char] [-P path_seperators] [-f table_file] [-t]
\end{verbatim}
where elements in square brackets are options. These options are identical
to the corresponding ones for \lx{} and are as follows:
\begin{description}
\item[{\tt -f}] By default, \file{printct} reads the \ctab\ from a file called
     \file{ltx2x.ct}. If the required \ctab\ is in a file with another name this
     option is used to change from the default file. For example,
\begin{verbatim}
> printct
\end{verbatim}
reads a \ctab\ from \verb|ltx2x.ct|, while
\begin{verbatim}
> printct -f detex.ct 
\end{verbatim}
reads a \ctab\ from file \verb|detex.ct|.

\item[{\tt -t}] This generates some diagnostics related to the processing of
    the \ctab\ file.

\item[{\tt -D}] The value of this option is the character that the operating system
    uses to catenate directory names to form a path (see~\ref{sec:search}). 
    The default value is a
    slash (i.e. \verb|/|). The default could be changed to a backslash, for example,
    by \verb|-D \|.

\item[{\tt -P}] The environment variable (see~\ref{sec:search})
   contains a list of directories (also known
   as path names). In the operating system that I use, these are separated by
   the colon (\verb|:|) character which, together with the semi-colon
   and space characters, form
   the \lx\ default separators. The path separator characters can be changed 
   with this option.
   For example, \verb|-P :| will make the separators be a colon
   or a space (space is automatically included in the separator list).
\end{description}

    \file{printct} only reads a single \ctab{} file and outputs the
pretty-printed and updated version to file \file{printct.lis}. It performs
a very limited amount of error checking and writes error messages and
statistics to the file \file{printct.err}.


\subsection{A {\tt make} file}


 Here is a UNIX \file{make} file~\cite{ORAM91} for the \lx\ system.

\begin{code}
\begin{verbatim}
# makefile for program ltx2x --- LaTeX to X autotagger
#
##################### Change the following for your setup
# The compiler
CC = cc

# We use flex (or equivalent, but not lex) to generate the lexer
LEX = flex
# and the options
LEXFLAGS = -v

# We use bison (or equivalent) to generate the parser
YACC = bison
# and the options
YACCFLAGS = -y -d -v

# Libraries to be used
LIBS = -ly -ll -lm

# The root directory for the installation (e.g., /usr/local )
ROOTDIR = /proj/ltx/teTeX033

# Where to place the running code (e.g. /usr/local/bin )
BINDIR = ${ROOTDIR}/bin

# Where to place the manpage (e.g., /usr/local/man/man1 )
MANEXT = 1
MANDIR = ${ROOTDIR}/man/man${MANEXT}

# Just in case you want to change the name of the binary
# (and then you should also change the man page and documentation).
# So, do not change this.
PROG = ltx2x

# Where to place the user documentation (e.g., /usr/local/doc/ltx2x )
DOCDIR = ${ROOTDIR}/doc/${PROG}

# Where to place the example command tables (e.g., /usr/local/lib/config/ltx2x )
CTDIR = ${ROOTDIR}/lib/config/${PROG}

# The file copy command (copy but do not delete original)
COPY = cp

# The file move command (move and delete original)
MOVE = mv

# The file delete command
DELETE = rm

# The make directory (hierarchy) command
MAKEDIR = mkdirhier

# The stream editor command
SED = sed

# Command to write to the terminal (stdout)
ECHO = echo

################### You should not have to change anything after this

# The source modules
L2XSRCS = l2xytab.c l2xlexyy.c l2xlib.c l2xacts.c l2xusrlb.c 
getopt.c srchenv.c

INTSRCS = l2xirtne.c l2xistd.c l2xidecl.c l2xistmt.c l2xiexpr.c
l2xiscan.c l2xisymt.c l2xierr.c l2xiidbg.c l2xistup.c l2xistm.c
l2xixxpr.c l2xixstd.c l2xidbug.c l2xisdcl.c l2xirexp.c listsetc.c

# The object modules
L2XOBJS = l2xytab.o l2xlexyy.o l2xlib.o l2xacts.o l2xusrlb.o 
          getopt.o srchenv.o

INTSRCS = l2xirtne.o l2xistd.o l2xidecl.o l2xistmt.o l2xiexpr.o
l2xiscan.o l2xisymt.o l2xierr.o l2xiidbg.o l2xistup.o l2xistm.o
l2xixxpr.o l2xixstd.o l2xidbug.o l2xisdcl.o l2xirexp.o listsetc.o

OBJS = ${L2XOBJS} ${INTOBJS}

# Link object code together into PROG
ltx2x : ${OBJS}
        ${CC} -o ${PROG} ${OBJS} ${LIBS}

# Compile C source code into object code
getopt.o : getopt.c getopt.h
        ${CC} -c getopt.c
l2xytab.o : l2xytab.c l2xlib.h l2xusrlb.h  l2xacts.h strtypes.h l2xcom.h
        ${CC} -c l2xytab.c
l2xlexyy.o : l2xlexyy.c l2xytab.h l2xlib.h  l2xusrlb.h l2xcom.h
        ${CC} -c l2xlexyy.c
l2xlib.o : l2xlib.c getopt.h l2xytab.h strtypes.h l2xcom.h
        ${CC} -c l2xlib.c
l2xusrlb.o : l2xusrlb.c l2xlib.h l2xytab.h strtypes.h l2xcom.h
        ${CC} -c l2xusrlb.c
l2xacts.o : l2xacts.c l2xusrlb.h l2xlib.h l2xytab.h strtypes.h l2xcom.h
        ${CC} -c l2xacts.c
srchenv.o : srchenv.c srchenv.h
        ${CC} -c srchenv.c

# Generate C code for parsing
l2xytab.c l2xytab.h: l2x.y
        @ ${ECHO} "Expect 10 shift/reduce conflicts to be reported"
        ${YACC} ${YACCFLAGS} l2x.y
        ${MOVE} y.tab.c l2xytab.c
        ${MOVE} y.tab.h l2xytab.h

# Generate C code for lexing
l2xlexyy.c : l2x.l
        ${LEX} ${LEXFLAGS} l2x.l
        ${MOVE} lex.yy.c l2xlexyy.c

# the interpreter modules

# compiler flags for analyze and execute modules
ANLFLAG = -Danalyze
RUNFLAG = -Dtrace

# interpreter header files
SOMEH = l2xicmon.h l2xierr.h l2xiscan.h l2xisymt.h licomsym.h l2xiidbg.h
MOSTH = ${SOMEH} l2xiprse.h
ALLH = ${MOSTH} l2xicpr.h l2xiexec.h

# interpreter interface

l2xistup.o : l2xistup.c ${ALLH}
        ${CC} -c ${ANLFLAG} ${RUNFLAG} l2xistup.c

# the parser module

l2xirtne.o : l2xirtne.c ${ALLH}
        ${CC} -c ${ANLFLAG} l2xirtne.c

l2xistd.o : l2xistd.c ${MOSTH}
        ${CC} -c ${ANLFLAG} ${RUNFLAG} l2xistup.c

l2xistup.o : l2xistup.c ${ALLH}
        ${CC} -c l2xistd.c

l2xidecl.o : l2xidecl.c ${MOSTH} l2xicpr.h
        ${CC} -c ${ANLFLAG} l2xisdecl.c

l2xistmt.o : l2xistmt.c ${ALLH}
        ${CC} -c ${ANLFLAG} l2xistmt.c

l2xiexpr.o : l2xiexpr.c ${MOSTH} l2xicpr.h
        ${CC} -c ${ANLFLAG} l2xiexpr.c

# the scanner module

l2xiscan.o : l2xiscan.c ${SOMEH} l2xicpr.h
        ${CC} -c ${ANLFLAG} l2xiscan.c

# symbol table module

l2xisymt.o : l2xisymt.c l2xicmon.h l2xierr.h l2xisymt.h licomsym.h l2xiidbg.h
        ${CC} -c l2xisymt.c

# executor module

l2xixutl.o : l2xixutl.c ${MOSTH} l2xiexec.h listsetc.h
        ${CC} -c ${RUNFLAG} l2xixutl.c

l2xixstm.o : l2xixstm.c ${MOSTH} l2xiexec.h listsetc.h
        ${CC} -c ${RUNFLAG} l2xixstm.c

l2xixxpr.o : l2xixxpr.c ${MOSTH} l2xiexec.h listsetc.h
        ${CC} -c ${RUNFLAG} l2xixxpr.c

l2xixstd.o : l2xixstd.c ${MOSTH} l2xiexec.h listsetc.h
        ${CC} -c ${RUNFLAG} l2xixstd.c

l2xidbug.o : l2xidbug.c ${SOMEH} l2xiexec.h listsetc.h
        ${CC} -c ${RUNFLAG} l2xidbug.c

# error and miscellaneous

l2xisdcl.o : l2xisdcl.c ${SOMEH}
        ${CC} -c ${ANLFLAG} ${RUNFLAG} l2xisdcl.c

l2xiidbg.o : l2xiidbg.c ${SOMEH} l2xiexec.h
        ${CC} -c l2xiidbg.c

l2xirexp.o : l2xirexp.c l2xirexp.h
        ${CC} -c l2xirexp.c

listsetc.o : listsetc.c listsetc.h
        ${CC} -c listsetc.c

# only call make install if BINDIR has been set
install : ltx2x
        ${MAKEDIR} ${BINDIR}
        ${MOVE} ${PROG} ${BINDIR}

# Edit the file man to replace DOCUMENTDIR by the actual directory
# where the user manual is to be placed, and CTDIR by the location
# of the example command table files.
# Then copy the manpage to the proper place
manpage :
        ${SED} 's!DOCUMENTDIR!${DOCDIR}!; s!CTDIR!${CTDIR}!' man > tman
        ${MAKEDIR} ${MANDIR}
        ${COPY} tman ${MANDIR}/${PROG}.${MANEXT}

# Copy the user manuals to the proper place
doc :
        ${MAKEDIR} ${DOCDIR}
        ${COPY} ltx2x.tex ${DOCDIR}/${PROG}.tex
        ${COPY} ltx2x.ps ${DOCDIR}/${PROG}.ps
        ${COPY} ltx2x.txt ${DOCDIR}/${PROG}.txt
        ${COPY} ltx2x.html ${DOCDIR}/${PROG}.html

# Copy the example command tables to their final location
ctables :
        ${MAKEDIR} ${CTDIR}
        ${COPY} ltx2x.ct ${CTDIR}/ltx2x.ct
        ${COPY} detex.ct ${CTDIR}/detex.ct
        ${COPY} remcom.ct ${CTDIR}/remcom.ct
        ${COPY} l2h.ct ${CTDIR}/l2h.ct
        ${COPY} bye.ct ${CTDIR}/bye.ct
        ${COPY} fun.ct ${CTDIR}/fun.ct

# Do almost everything except clean up
all : ltx2x install manpage doc ctables

# call make clean to remove the object files, info from YACC,
# and the edited version of the manpage
clean :
        ${DELETE}  *.o
        ${DELETE} y.output
        ${DELETE} tman

# Compile the command table printer
printct : printct.o getopt.o srchenv.o
        ${CC} -o printct printct.o getopt.o srchenv.o

printct.o : printct.c getopt.h strtypes.h l2xcom.h
        ${CC} -c printct.c
\end{verbatim}
\end{code}

    If you use the above makefile then the first part should be edited
to reflect your system's configuration. You could do \verb|make all|
which should do everything for you, except the cleaning up. 
A more conservative approach is recommended. First
just do \verb|make| which will generate the executable. This can then be
tested. When all is well do \verb|make install| and \verb|make manpage|
which will put the executable and the manpage into their final positions.
Finally, \verb|make clean| will remove the intermediate files generated
during the build process.

    The above \file{make} file uses flex as the lexer generator. You can use your
favorite one instead but it must, unlike lex, support exclusive start states.
Also, bison is used above as the parser generator. Again, you can use your
favorite one. As far as I am aware, there is nothing remarkable about the
grammar, except that during early development I exceeded the size limits
of yacc. The grammar has been simplified since then, so this may no longer
be a problem. \\
NOTE: If bison is used it reports that there are 10 shift/reduce
conflicts. It appears that these can be safely ignored.

    One compilation problem has been noted by Uwe 
Sassenberg\footnote{\texttt{<sassen@hal1.physik.uni-dortmund.de>}} 
on AIX~3.2 and 
IRIX~5.3 systems, but I could not reproduce it on a SunOS 4.1.3 system. This
is when the main procedure of \lx{} is processing the optional command
line arguments. For some reason it had difficulties with the C
\verb|EOF|. The symptom was that the program compiled but when it was
run
it sat there absorbing CPU cycles and doing nothing as it had got into
an infinite \verb|while| loop. The cure was to insert
the following line of code in file \file{l2xlib.c}:
\begin{verbatim}
main(argc,argv)
...
  /* get command line optional parameters */
  opterr = 1;       /* getopt prints errors if opterr is 1 */
  while (EOF != (optchar =
        getopt(argc,argv, "l:ty:f:cp:wE:P:D:"))) {
/* insert this line of code:  if (optchar == 255) break;  end insert */
        switch(optchar) {
...
\end{verbatim}
This code line which you may need to insert is supplied as a comment in 
the distributed source.

\subsection{Limits and errors}

    The \lx\ system has some built-in limits which are defined in \file{l2xlib.c}. 
The following is a listing of the relevant sizes.

\begin{description}
\item[\keyword{CLAUSE\_STACK\_SIZE}] The maximum nesting depth of
document sectioning. This is set somewhat larger than the number of 
standard \LaTeX\ sectioning command types.
(Default~10)

\item[\keyword{EVERY\_N\_LINES}] Controls the frequency of printing 
processed line numbers to the terminal. 
(Default~100)

\item[\keyword{LIST\_STACK\_SIZE}] The maximum nesting depth of list 
environments. This is set somewhat larger than the standard \LaTeX\ nesting depth. 
(Default~10)

\item[\keyword{MAX\_BUFFER}] The maximum number of characters that can be held 
in the system buffer, and also the maximum number of characters in a 
pretty-printed output line.
(Default~2000)

\item[\keyword{MAX\_CT\_STACK}] The maximum nesting depth for included 
\ctab\ files.
(Default~20)

\item[\keyword{MAX\_ERRORS}] The maximum number of non-fatal errors
discovered in \ctab\ processing or in source file processing before
\lx\ quits.
(Default~10)

\item[\keyword{MAX\_LINE}] The maximum number of characters in a line of 
a \LaTeX\ source file.
(Default~2000)

\item[\keyword{MAX\_PRINT\_STACK}] The maximum nesting depth for print 
control commands.
(Default~100)

\item[\keyword{MAX\_TABLE\_ENTRIES}] The maximum number of 
\keyword{TYPE} specifications in a \ctab\ (including the built in
type specifications).
(Default~1000)

\item[\keyword{MAX\_TABLE\_LINE}] The maximum number of characters in a line in 
a \ctab\  file.
(Default~254)

\item[\keyword{MAX\_USER\_BUFFS}] The maximum number of user buffers.
(Default 20)

\item[\keyword{MAX\_UBUFF\_LEN}] The maximum number of characters that can be
stored in a user buffer.
(Default 510)

\item[\keyword{MAX\_USER\_FILES}] The maximum number of user files.
(Default 16)
\end{description}

    \lx{} prints out a summary of the program statistices at the end of
the \file{ltx2x.err} file.
    If the limits are not suitable for your purposes, then they may be changed and 
the system rebuilt.

    \lx\ can produce a variety of error and warning messages, for example
when any of the above limits are exceeded. Some of the messages are related
to command table processing, while others are related to \LaTeX\ document
processing. Both these kinds of messages are targeted to the normal
end user. There is another set of messages that are aimed at the implementor
of new \keyword{SPECIAL\_} commands. An implementor may also find some of the
debugging options useful if things really fall apart.


\subsection{Availability}

    Source code and documentation for \lx\ is available from the
NIST SOLIS (SC4 On-Line Information Service) system~\cite{RINAUDOT94}
in directory \\
\file{/subject/sc4/editing/latex/programs/ltx2x}. \\
 SOLIS can be accessed by:
\begin{itemize}
\item Anonymous ftp to \file{ftp.cme.nist.gov} (\texttt{cd} to \file{/pub/subject/sc4...})
\item URL \url{http://www.nist.gov/sc4} 
\end{itemize}

    Any comments should be directed to \texttt{apde@cme.nist.gov}.

\subsubsection{Copyright}

    Development of this software was funded by the United States Government
and is not subject to copyright. It was developed by the
Manufacturing Systems Integration Division (MSID) of the
Manufacturing Engineering Laboratory (MEL) of the
National Institute of Standards and Technology (NIST). 

\subsubsection{Disclaimer}

    There is no warranty for the \lx\ software. If the \lx\ software
is modified by someone else and passed on, NIST requests that the software's
recipients be notified that what they have is not what NIST distributed.

\begin{description}
\item[Policies] \mbox{}
\begin{enumerate}
\item Anyone may copy and distribute verbatim copies of the
      source code as received in any medium.
\item Anyone may modify your copy or copies of the \lx\ source
      code or any portion of it, and copy and distribute such
      modifications provided that all modifications are clearly 
      associated with the entity that performs the modifications.
\end{enumerate}

\item[NO WARRANTY] \mbox{}

    NIST PROVIDES ABSOLUTELY NO WARRANTY. THE \lx\ SOFTWARE IS
PROVIDED `AS IS' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE
RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.
SHOULD ANY PORTION OF THE \lx\ SOFTWARE PROVE DEFECTIVE, YOU ASSUME
THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.

    IN NO EVENT WILL NIST BE LIABLE FOR DAMAGES, INCLUDING ANY
LOST PROFITS, LOST MONIES, OR OTHER SPECIAL, INCIDENTAL OR
CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE
(INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED
INACCURATE OR LOSSES SUSTAINED BY THIRD PARTIES OR A FAILURE OF
THE PROGRAM TO OPERATE WITH PROGRAMS NOT DISTRIBUTED BY NIST)
THE PROGRAMS, EVEN IF YOU HAVE BEEN ADVISED OF THE POSSIBILITY 
OF SUCH DAMAGES, OR FOR ANY CLAIM BY ANY OTHER PARTY.
\end{description}


\section{A grammar for the \ctab} \label{sec:ctabgrammar}

\subsection{Notation}

    The syntactical constructs used correspond to a derivative of 
the Wirth Syntax Notation (WSN)~\cite{WIRTH77}. The semantics of the
enclosing braces are:
\begin{itemize}
\item curly braces `\texttt{\{ \}}' indicate xero or more repetitions;
\item square brackets `\texttt{[ ]}' indicate an optional element;
\item parenthesis `\texttt{( )}' indicates a group;
\item vertical bar `\texttt{|}' indicates that exactly one of the
    terms in the expression shall be chosen.
\end{itemize}

    Here is the grammar for WSN defined in itself.
\begin{code}
\begin{verbatim}
syntax     = { production } .
production = identifier '=' expression '.' .
expression = term { '|' term } .
term       = factor { factor } .
factor     = identifier | literal | group | option | repetition .
identifier = character { character } .
literal    = '''' character { character } '''' .
group      = '(' expression ')' .
option     = '[' expression ']' .
repetition = '{' expression '}' .
\end{verbatim}
\end{code}

    We also use the following shorthand notation for particular characters:
\begin{itemize}
\item \verb|\c| --- any printable character
\item \verb|\n| --- the end of line character(s)
\item \verb|eof| --- the end of file character(s)
\end{itemize}

\subsection{Grammar}

    First, the keywords. Note that these are case insensitive.
\begin{code}
\begin{verbatim}
AudibleAlertChar = 'AUDIBLE_ALERT_CHAR=' .
BackspaceChar = 'BACKSPACE_CHAR=' .
BeginDocument = 'BEGIN_DOCUMENT' .
BeginDollar = 'BEGIN_DOLAR' .
BeginEnv = 'BEGIN_ENV' .
BeginListEnv = 'BEGIN_LIST_ENV' .
BeginPictureCc = 'BEGIN_PICTURE_CC' .
BeginVenv = 'BEGIN_VENV' .
BeginVerb = 'BEGIN_VERB' .
BeginVerbatim = 'BEGIN_VERBATIM' .
Buffer = 'BUFFER' .
CarriageReturnChar = 'CARRIAGE_RETURN_CHAR=' .
Chapter = 'CHAPTER' .
CharCommand = 'CHAR_COMMAND' .
Command = 'COMMAND' .
CommandOop = 'COMMAND_OOP' .
CommandOoopp = 'COMMAND_OOOPP' .
CommandOpo = 'COMMAND_OPO' .
CommandPooop = 'COMMAND_POOOP' .
CommandPoop = 'COMMAND_POOP' .
CommandPoopp = 'COMMAND_POOPP' .
Comment = 'C=' .
EndCtfile = 'END_CTFILE=' .
EndDocument = 'END_DOCUMENT' .
EndDollar = 'END_DOLAR' .
EndEnv = 'END_ENV' .
EndItem = 'END_ITEM=' .
EndItemParam = 'END_ITEM_PARAM=' .
EndListEnv = 'END_LIST_ENV' .
EndMode = 'END_MODE' .
EndOpt = 'END_OPT=' .
EndPicture = 'END_PICTURE' .
EndTag = 'END_TAG=' .
EndTag1 = 'END_TAG_1=' .
EndTag2 = 'END_TAG_2=' .
EndTag3 = 'END_TAG_3=' .
EndTag4 = 'END_TAG_4=' .
EndTag5 = 'END_TAG_5=' .
EndTag6 = 'END_TAG_6=' .
EndTag7 = 'END_TAG_7=' .
EndTag8 = 'END_TAG_8=' .
EndTag9 = 'END_TAG_9=' .
EndType = 'END_TYPE' .
EndVenv = 'END_VENV' .
EndVerb = 'END_VERB' .
EndVerbatim = 'END_VERBATIM' .
EscapeChar = 'ESCAPE_CHAR=' .
File = 'FILE' .
First = 'FIRST' .
FormfeedChar = 'FORMFEED_CHAR=' .
HexChar = 'HEX_CHAR=' .
HorizontalTabChar = 'HORIZONTAL_TAB_CHAR=' .
Include = 'INCLUDE=' .
InMode = 'IN_MODE=' .
Last = 'LAST' .
Lbrace = 'LBRACE' .
Name = 'NAME=' .
NewlineChar = 'NEWLINE_CHAR=' .
NoOp = 'NO_OP' .
NoPrint = 'NO_PRINT' .
OptParam = 'OPT_PARAM=' .
OtherBegin = 'OTHER_BEGIN' .
OtherCommand = 'OTHER_COMMAND' .
OtherEnd = 'OTHER_END' .
Para = 'PARA' .
Paragraph = 'PARAGRAPH' .
Part = 'PART' .
Partm1 = 'PARTm1' .
Partm2 = 'PARTm2' .
PcAtEnd = 'PC_AT_END=' .
PcAtStart = 'PC_AT_START=' .
PictureCcpp = 'PICTURE_CCPP' .
PictureCo = 'PICTURE_CO' .
PictureCop = 'PICTURE_COP' .
PictureCp = 'PICTURE_CP' .
PictureOcc = 'PICTURE_OCC' .
PictureOccc = 'PICTURE_OCCC' .
PictureOco = 'PICTURE_OCO' .
PicturePcop = 'PICTURE_PCOP' .
PrintControl = 'PRINT_CONTROL=' .
PrintP1 = 'PRINT_P1=' .
PrintP2 = 'PRINT_P2=' .
PrintP3 = 'PRINT_P3=' .
PrintP4 = 'PRINT_P4=' .
PrintP5 = 'PRINT_P5=' .
PrintP6 = 'PRINT_P6=' .
PrintP7 = 'PRINT_P7=' .
PrintP8 = 'PRINT_P8=' .
PrintP9 = 'PRINT_P9=' .
PrintOpt = 'PRINT_OPT=' .
Rbrace = 'RBRACE' .
Reqparams = 'REQPARAMS=' .
Reset = 'RESET' .
ResetBuffer = 'RESET_BUFFER:' .
ResetMode = 'RESET_MODE:' .
Sect = 'SECT' .
Sectioning = 'SECTIONING' .
SectioningLevel = 'SECTIONING_LEVEL=' .
SetMode = 'SET_MODE:' .
SlashSpace = 'SLASH_SPACE' .
Source = 'SOURCE:' .
Special = 'SPECIAL' .
SpecialBeginEnv = 'SPECIAL_BEGIN_ENV' .
SpecialBeginList = 'SPECIAL_BEGIN_LIST' .
SpecialCommand = 'SPECIAL_COMMAND' .
SpecialEndEnv = 'SPECIAL_END_ENV' .
SpecialEndList = 'SPECIAL_END_LIST' .
SpecialSectioning = 'SPECIAL_SECTIONING' .
StartItem = 'START_ITEM=' .
StartItemParam = 'START_ITEM_PARAM=' .
StartOpt = 'START_OPT=' .
StartTag = 'START_TAG=' .
StartTag1 = 'START_TAG_1=' .
StartTag2 = 'START_TAG_2=' .
StartTag3 = 'START_TAG_3=' .
StartTag4 = 'START_TAG_4=' .
StartTag5 = 'START_TAG_5=' .
StartTag6 = 'START_TAG_6=' .
StartTag7 = 'START_TAG_7=' .
StartTag8 = 'START_TAG_8=' .
StartTag9 = 'START_TAG_9=' .
String = 'STRING:' .
SubPara = 'SUBPARA' .
SubParap1 = 'SUBPARAp1' .
SubParap2 = 'SUBPARAp2' .
SubSect = 'SUBSECT' .
SubSubSect = 'SUBSUBSECT' .
SwitchBack = 'SWITCH_BACL: ' .
SwitchToBuffer = 'SWITCH_TO_BUFFER: ' .
SwitchToFile = 'SWITCH_TO_FILE: ' .
SwitchToSysbuf = 'SWITCH_TO_SYSBUF: ' .
Sysbuf = 'SYSBUF' .
TexChar = 'TEX_CHAR' .
ToBuffer = 'TO_BUFFER' .
ToFile = 'TO_FILE' .
ToSysbuf = 'TO_SYSBUF' .
Type = 'TYPE=' .
Vcommand = 'VCOMMAND' .
VerticalTabChar = 'VERTICAL_TAB_CHAR=' .
\end{verbatim}
\end{code}

Some utility productions.
\begin{code}
\begin{verbatim}
latex_id = \c { \c } .
name = \c { \c } .
text = '"' { \c } '"' .
Eol = \n .
digit = '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' .
integer = digit { digit } .
ct_file_name = name .
file_id = name .
buffer_id = integer .
mode_id = name .
\end{verbatim}
\end{code}

The starting production.
\begin{code}
\begin{verbatim}
table = [ special_chars ] { specification | inclusion | comment } eof .
\end{verbatim}
\end{code}

Productions for \keytext{inclusion} and \keytext{comment} and \keytext{eof}.
\begin{code}
\begin{verbatim}
inclusion = Include ct_file_name Eol .
comment = Comment { \c } Eol .
eof = EndCtfile { \c } Eol .
\end{verbatim}
\end{code}

Productions for \keytext{special\_chars}.
\begin{code}
\begin{verbatim}
special_chars = [ escape ] [ alert ] [ backspace ] [ return ] [ feed ]
                [ hex ] [ htab ] [ newline ] [ vtab ] { comment } .
escape = EscapeChar \c Eol Eol .
alert = AudibleAlertChar \c Eol .
backspace = BackspaceChar \c Eol .
return = CarriageReturnChar \c Eol .
feed = FormfeedChar \c Eol .
hex = HexChar \c Eol .
htab = HorizontalTabChar \c Eol .
newline = NewlineChar \c Eol .
vtab = VerticalTabChar \c Eol .
\end{verbatim}
\end{code}



Productions for \keytext{specification}.
\begin{code}
\begin{verbatim}
specification = built_in | normal | list | section | special | picture | odd .
built_in = (Type built_in_type Eol) [ built_in_body ] end_type .
end_type = EndType Eol .
built_in_type = BeginDocument | BeginDollar | BeginVerb | BeginVerbatim |
                EndDocument | EndDollar | EndVerb | EndVerbatim |
                Lbrace | OtherBegin | OtherCommand | OtherEnd |
                Paragraph | Rbrace | SlashSpace .
normal = (Type normal_type Eol) type_name [ normal_body ] end_type .
type_name = Name latex_id Eol .
normal_type = BeginEnv | BeginVenv | CharCommand | Command | 
              EndEnv | EndVenv | TexChar | Vcommand .
list = (Type list_type Eol) type_name [ list_body ] end_type .
list_type = BeginListEnv | EndListEnv .
section = (Type Sectioning Eol) type_name [ section_body ] end_type .
special = (Type special_type Eol) type_name [ special_body ] end_type .
special_type = Special | SpecialBeginEnv | SpecialBeginList |
               SpecialCommand | SpecialEndEnv | SpecialEndList |
               SpecialSectioning .
picture = (Type picture_type Eol) type_name [ picture_body ] end_type  .
picture_type = BeginPictureCc | EndPicture | PictureCcpp | PictureCo |
               PictureCop | PictureCp | PictureOcc | 
               PictureOccc | PictureOco | PicturePcop .
odd = (Type odd_type Eol) type_name [ odd_body ] end_type .
odd_type = CommandOop | CommandOoopp | CommandOpo | 
           CommandPooop | CommandPoop | CommandPoopp .
\end{verbatim}
\end{code}

The \keytext{X\_body} productions.
\begin{code}
\begin{verbatim}
built_in_body = [ basic_body ] 
                { start_mode [ basic_body ] end_mode } .
start_mode = InMode mode_id Eol .
end_mode = EndMode Eol .
normal_body = [ basic_norm_body ] 
              { start_mode [ basic_norm_body ] end_mode } .
sect_body = [ basic_sect_body ] 
            { start_mode [ basic_sect_body ] end_mode } .
list_body = [ basic_list_body ] 
            { start_mode [ basic_list_body ] end_mode } .
picture_body = [ basic_defarg_body ] 
               { start_mode [ basic_defarg_body ] end_mode } .
odd_body =  [ basic_defarg_body ] 
            { start_mode [ basic_defarg_body ] end_mode } .
special_body = [ basic_special_body ] 
               { start_mode [ basic_special_body ] end_mode } .
\end{verbatim}
\end{code}


Note: the ordering of the components of the following 
\keytext{basic\_X\_body} productions is immaterial.
\begin{code}
\begin{verbatim}
basic_body = [ start_it ] [ end_it ] .
basic_norm_body = [ basic_body ] [ no_req_arg ] [ opt_arg_pos ] 
             { arg_print } { arg_action } .
basic_sect_body = sect_level [ basic_norm_body ] .
sect_level = SectioningLevel div_level Eol .
div_level = Chapter | Para | Part | Partm1 | Partm2 | Sect | Subpara |
            Subparap1 | Subparap2 | Subsect | Subsubsect .
basic_defarg_body = [ basic_body ] { arg_print } { arg_action } .
basic_list_body = [ basic_norm_body ] { item_action } .
basic_special_body = [ sect_level ] [ basic_list_body ] .
no_req_arg = Reqparams integer Eol .
opt_arg_pos = OptParam ( First | Last ) Eol .
\end{verbatim}
\end{code}

The \keytext{start\_it} and \keytext{end\_it} productions.
\begin{code}
\begin{verbatim}
start_it = [ start_print ] [start_action ] .
start_print = PcAtStart ( basic_pc_kind | Reset ) Eol .
basic_pc_kind = NoPrint | ToSysbuf | print_to_buffer | print_to_file .
print_to_buffer = ToBuffer buffer_id .
print_to_file = ToFile file_id .
start_action = StartTag [ text ] Eol { tag_action } .
tag_action = ( String text |
               Source ( Sysbuf | user_buffer | user_file ) |
               ResetBuffer buffer_id |
               ResetFile file_id |
               ResetSysbuf |
               SwitchToBuffer buffer_id |
               SwitchToFile file_id |
               SwitchToSysbuf |
               SwitchBack |
               SetMode mode_id |
               ResetMode )
               Eol .
user_buffer = Buffer buffer_id .
user_file = File file_id .
end_it = [ end_print ] [ end_action ] .
end_print = PcAtEnd (basic_pc_kind | Reset) Eol .
end_action = EndTag [ text ] Eol { tag_action } .
\end{verbatim}
\end{code}

The \keytext{arg\_print} productions.
\begin{code}
\begin{verbatim}
arg_print = print_arg_kind (basic_pc_kind | NoOp ) Eol .
print_arg_kind = PrintOpt | PrintP1 | PrintP2 | PrintP3 | PrintP4 | 
                  PrintP5 | PrintP6 | PrintP7 | PrintP8 | PrintP9 .
\end{verbatim}
\end{code}

The \keytext{arg\_action} productions.
\begin{code}
\begin{verbatim}
arg_action = arg_tag_kind [ text ] Eol { tag_action } .
arg_tag_kind = EndOpt | EndTag1 | EndTag2 | EndTag3 | EndTag4 | 
              EndTag5 | EndTag6 | EndTag7 | EndTag8 | EndTag9 |
             StartOpt | StartTag1 | StartTag2 | StartTag3 | StartTag4 | 
            StartTag5 | StartTag6 | StartTag7 | StartTag8 | StartTag9 .
\end{verbatim}
\end{code}

The \keytext{item\_action} productions.
\begin{code}
\begin{verbatim}
item_action = item_tag_kind [ text ] Eol { tag_action } .
item_tag_kind = EndItem | EndItemParam | StartItem | StartItemParam .
\end{verbatim}
\end{code}

    The parser in \lx{} for the \ctab{} is very simple. For each \keyword{TYPE=}
in the \ctab{} it creates a \keytext{struct} to hold the specification
data. If any type is multiply defined, then which one will be finally used
is somewhat random because of the sorting and searching algorithms employed
internally. No checks are made for multiply defined entries.

    Each command in the \ctab{} starts on a seperate line.
    The parser reads only as much of a table line as is necessary to parse that
line according to the first token that it finds on the line. The data in
each line after parsing is added to the current \keytext{struct} for the
\LaTeX{} command.
If any of the command lines within an entry are multiply defined,
then the latest one will overwrite any earlier ones.

    This line-based parsing means that effectively anything between the
end of the required data on the line is ignored by the parser, and so could
be treated as a comment. There is no guarantee that this behaviour will
be maintained in future releases of \lx.

\section{A grammar for \ExpressA} \label{sec:expgrammar}

    The same WSN notation is used for the grammar for \ExpressA{} as
for the \ctab{} grammar.

    First the keywords. Note that these are case insensitive. Also
not all of the keywords have been used in this implementation
of \ExpressA; those that have not been used are reserved for the
future.

\begin{code}
\begin{verbatim}
 ABS = 'abs' .
 ABSTRACT = 'abstract' .
 ACOS = 'acos' .
 AGGREGATE = 'aggregate' .
 ALIAS = 'alias' .
 AND = 'and' .
 ANDOR = 'andor' .
 ARRAY = 'array' .
 AS = 'as' .
 ASIN = 'asin' .
\end{verbatim}

\begin{verbatim}
 ATAN = 'atan' .
 BAG = 'bag' .
 BEGIN = 'begin' .
 BINARY = 'binary' .
 BLENGTH = 'blength' .
 BOOLEAN = 'boolean' .
 BY = 'by' .
 CALL = 'call' .
 CASE = 'case' .
 CONSTANT = 'constant' .
\end{verbatim}

\begin{verbatim}
 CONST_E = 'const_e' .
 CONTEXT = 'context' .
 COS = 'cos' .
 CRITERIA = 'criteria' .
 DERIVE = 'derive' .
 DIV = 'div' .
 ELSE = 'else' .
 END = 'end' .
 END_ALIAS = 'end_alias' .
 END_CALL = 'end_call' .
\end{verbatim}

\begin{verbatim}
 END_CASE = 'end_case' .
 END_CODE = 'end_code' .
 END_CONSTANT = 'end_constant' .
 END_CONTEXT = 'end_context' .
 END_CRITERIA = 'end_criteria' .
 END_ENTITY = 'end_entity' .
 END_FUNCTION = 'end_function' .
 END_IF = 'end_if' .
 END_LOCAL = 'end_local' .
 END_MODEL = 'end_model' .
\end{verbatim}

\begin{verbatim}
 END_NOTES = 'end_notes' .
 END_OBJECTIVE = 'end_objective' .
 END_PARAMETER = 'end_parameter' .
 END_PROCEDURE = 'end_procedure' .
 END_PURPOSE = 'end_purpose' .
 END_REALIZATION = 'end_realization' .
 END_REFERENCES = 'end_references' .
 END_REPEAT = 'end_repeat' .
 END_RULE = 'end_rule' .
 END_SCHEMA = 'end_schema' .
\end{verbatim}

\begin{verbatim}
 END_SCHEMA_DATA = 'end_schema_data' .
 END_TEST_CASE = 'end_test_case' .
 END_TYPE = 'end_type' .
 ENTITY = 'entity' .
 ENUMERATION = 'enumeration' .
 EOF = 'eof' .
 EOLN = 'eoln' .
 ESCAPE = 'escape' .
 EXISTS = 'exists' .
 EXP = 'exp' .
 FALSE = 'false' .
\end{verbatim}

\begin{verbatim}
 FIXED = 'fixed' .
 FOR = 'for' .
 FORMAT = 'format' .
 FROM = 'from' . 
 FUNCTION = 'function' .
 GENERIC = 'generic' .
 HIBOUND = 'hibound' .
 HIINDEX = 'hiindex' .
 IF = 'if' .
 IMPORT = 'import' .
\end{verbatim}

\begin{verbatim}
 IN = 'in' .
 INSERT = 'insert' .
 INTEGER = 'integer' .
 INVERSE = 'inverse' .
 LENGTH = 'length' .
 LIKE = 'like' .
 LIST = 'list' .
 LOBOUND = 'lobound' .
 LOINDEX = 'loindex' .
 LOCAL = 'local' .
\end{verbatim}

\begin{verbatim}
 LOG = 'log' .
 LOG10 = 'log10' .
 LOG2 = 'log2' .
 LOGICAL = 'logical' .
 MOD = 'mod' .
 MODEL = 'model' .
 NOT = 'not' .
 NOTES = 'notes' .
 NUMBER = 'number' .
 NVL = 'nvl' .
\end{verbatim}

\begin{verbatim}
 OBJECTIVE = 'objective' .
 ODD = 'odd' .
 OF = 'of' .
 ONEOF = 'oneof' .
 OPTIONAL = 'optional' .
 OR = 'or' .
 ORD = 'ord' .
 OTHERWISE = 'otherwise' .
 PARAMETERi = 'parameter' .
 PI = 'pi' .
\end{verbatim}

\begin{verbatim}
 PRED = 'pred' .
 PROCEDURE = 'procedure' .
 PURPOSE = 'purpose' .
 QUERY = 'query' .
 READ = 'read' .
 READLN = 'readln' .
 REAL = 'real' .
 REALIZATION = 'realization' .
 REFERENCE = 'reference' .
 REFERENCES = 'references' .
\end{verbatim}

\begin{verbatim}
 REMOVE = 'remove' .
 REPEAT = 'repeat' .
 RETURN = 'return' .
 REXPR = 'rexpr' .
 ROLESOF = 'rolesof' .
 ROUND = 'round' .
 RULE = 'rule . 
 SCHEMA = 'schema' .
 SCHEMA_DATA = 'schema_data' .
 SELECT = 'select' .
\end{verbatim}

\begin{verbatim}
 SELF = 'self' .
 SET = 'set' .
 SIN = 'sin' .
 SIZEOF = 'sizeof' .
 SKIP = 'skip' .
 SQRT = 'sqrt' .
 STRING = 'string' .
 SUBOF = 'subof' .
 SUBTYPE = 'subtype' .
 SUCC = 'succ' .
\end{verbatim}

\begin{verbatim}
 SUPERTYPE = 'supertype' .
 SUPOF = 'supof' .
 SYSTEM = 'system' .
 TAN = 'tan' . 
 TEST_CASE = 'test_case' .
 THE_DAY = 'the_day' .
 THE_MONTH = 'the_month' .
 THE_YEAR = 'the_year' .
 THEN = 'then' .
 TO = 'to' .
\end{verbatim}

\begin{verbatim}
 TRUE = 'true' .
 TRUNC = 'trunc' .
 TYPE = 'type' .
 TYPEOF = 'typeof' .
 UNIQUE = 'unique' .
 UNKNOWN = 'unknown' .
 UNTIL = 'until' .
 USE = 'use' . 
 USEDIN = 'usedin' .
 USING = 'using' .
\end{verbatim}

\begin{verbatim}
 VALUE = 'value' .
 VALUE_IN = 'value_in' .
 VALUE_UNIQUE = 'value_unique' .
 VAR = 'var' .
 WHERE = 'where' .
 WHILE = 'while' .
 WITH = 'with' .
 WRITE = 'write' .
 WRITELN = 'writeln' .
 XOR = 'xor' .
\end{verbatim}
\end{code}

The following rules define various classes of characters which are used in
constructing the tokens.

\begin{code}
\begin{verbatim}
 digit = '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' .
 digits = digit { digit } .
 letter = 'a' | 'b' | 'c' | 'd' | 'e' | 'f' | 'g' | 'h' | 'i' | 'j' | 'k' |
                'l' | 'm' | 'n' | 'o' | 'p' | 'q' | 'r' | 's' | 't' | 'u' | 'v' |
                'w' | 'x' | 'y' | 'z' .
 lparen_not_star = '(' not_star .
 not_lparen_star = not_paren_star | ')' .
 not_paren_star = letter | digit | not_paren_star_special .
 not_paren_star_quote_special = '!' | '"' | '#' | '$' | '%' | '&' | '+' |
                    ',' | '-' | '.' | '/' | ':' | ';' | '<' | '=' | '>' | '?' |
                    '@' | '[' | '\' | ']' | '^' | '_' | '`' | '{' | '|' | '}' |
                    '~' .
 not_paren_star_special = not_paren_star_quote_special | '''' .
 not_quote = not_paren_star_quote_special | letter | digit | '(' | ')' | '*' .
 not_rparen = not_paren_star | '*' | '(' .
\end{verbatim}

\begin{verbatim}
 not_star = not_paren_star | '(' | ')' .
 octet = hex_digit hex_digit .
 special = not_paren_star_quote_special | '(' | ')' | '*' | '''' .
 star_not_rparen = '*' not_rparen .
\end{verbatim}
\end{code}


    The following rules specify how certain combinations of characters are
interpreted as lexical elements within the language.

\begin{code}
\begin{verbatim}
 integer_literal = digits .
 real_literal = digits '.' [ digits ] [ 'e' [ sign ] digits ] .
 simple_id = letter { letter | digit | '_' } .
 simple_string_literal = \q { ( \q \q ) | not_quote | \s | \o } \q .
\end{verbatim}
\end{code}

The following rules specify the syntax of comments in \ExpressA.


\begin{code}
\begin{verbatim}
 embedded_remark = '(*' { not_lparen_star | lparen_not_star | 
                      star_not_rparen | embedded_remark } '*)' .
 remark = embedded_remark | tail_remark .
 tail_remark = '--' { \a | \s | \o } \n .
\end{verbatim}
\end{code}


The following rules represent identifiers which are known to have a particular
meaning (i.e., to be declared elsewhere as types or functions, etc.).



\begin{code}
\begin{verbatim}
 attribute_ref = attribute_id .
 constant_ref = constant_id .
 entity_ref = entity_id .
 enumeration_ref = enumeration_id .
 function_ref = function_id .
 parameter_ref = parameter_id .
 procedure_ref = procedure_id .
 type_ref = type_id .
 variable_ref = variable_id .
\end{verbatim}
\end{code}



    The following rules specify how the previous lexical elements may be
combined into constructs of \ExpressA. White space and/or remark(s) may appear 
between any two tokens in these rules. The primary syntax rule for \ExpressA{}
is \verb|express_a|.



\begin{code}
\begin{verbatim}
 actual_parameter_list = '(' parameter { ',' parameter } ')' .
 add_like_op = '+' | '-' | OR | XOR .
 aggregation_types = array_type | bag_type | list_type | set_type .
 algorithm_head = { declaration } [ local_decl ] .
 array_type = ARRAY bound_spec OF base_type .
 assignment_stmt = general_ref { qualifier } ':=' expression ';' .
 attribute_decl = attribute_id .
 attribute_id = simple_id .
 attribute_qualifier = '.' attribute_ref .
 bag_type = BAG [ bound_spec ] OF base_type .
\end{verbatim}

\begin{verbatim}
 base_type = aggregation_types | simple_types | named_types .
 boolean_type = BOOLEAN .
 bound_1 = numeric_expression .
 bound_2 = numeric_expression .
 bound_spec = '[' bound_1 ':' bound_2 ']' .
 built_in_constant = CONST_E | PI | THE_DAY | THE_MONTH | THE_YEAR | '?' .
 built_in_function = ABS | COS | EOF | EOLN | EXISTS | EXP |
                     HIBOUND | HIINDEX | LENGTH | LOBOUND | LOINDEX |
                     LOG | LOG2 | LOG10 | NVL | ODD | ORD | PRED | 
                     REXPR | ROUND | SIN | SIZEOF |
                     SQRT | SUCC | TAN | TRUNC .
 built_in_procedure = INSERT | PRINT | PRINTLN | READ | READLN | REMOVE |
                      SYSTEM | WRITE | WRITELN .
 case_action = case_label { ',' case_label } ':' stmt .
 case_label = expression .
\end{verbatim}

\begin{verbatim}
 case_stmt = CASE selector OF { case_action } [ OTHERWISE ':' stmt ]
                   END_CASE ';' .
 compound_stmt = BEGIN stmt { stmt } END ';' .
 constant_factor = built_in_constant .
 constructed_types = enumeration_type .
 declaration = entity_decl | function_decl | procedure_decl | type_decl .
 entity_body = { explicit_attr } .
 entity_decl = entity_head entity_body END_ENTITY ';' .
 entity_head = ENTITY entity_id ';' .
 entity_id = simple_id .
 enum_id = simple_id .
\end{verbatim}

\begin{verbatim}
 enumeration_reference = enum_id .
 enumeration_type = ENUMERATION OF '(' enum_id { ',' enum_id } ')' .
 escape_stmt = ESCAPE ';' .
 explicit_attr = attribute_decl { ',' attribute_decl } ':' base_type ';' .
 express_a = { declaration } [ local_decl ] { stmt } END_CODE .
 expression = simple_expression [ rel_op_extended simple_expression ] .
 factor = simple_factor [ '**' simple_factor ] .
 formal_parameter = parameter_id { ',' parameter_id } ':' parameter_type .
 function_call = ( built_in_function | function_ref ) 
                       [ actual_parameter_list ] .
 function_decl = function_head [ algorithm_head ] stmt { stmt } 
                       END_FUNCTION ';' .
\end{verbatim}

\begin{verbatim}
 function_head = FUNCTION function_id [ '(' formal_parameter
                       { ';' formal_parameter } ')' ] ':' parameter_type ';' .
 function_id = simple_id .
 generalized_types = general_aggregation_types .
 general_aggregation_types = general_array_type | general_bag_type |
                             general_list_type | general_set_type .
 general_array_type = ARRAY [ bound_spec ] OF parameter_type .
 general_bag_type = BAG [ bound_spec ] OF parameter_type .
 general_list_type = LIST [ bound_spec ] OF parameter_type .
 general_ref =  parameter_ref | variable_ref .
 general_set_type = SET [ bound_spec ] OF parameter_type .
 if_stmt = IF logical_expression THEN stmt { stmt } [ ELSE stmt { stmt } ]
                 END_IF ';' .
\end{verbatim}

\begin{verbatim}
 increment = numeric_expression .
 increment_control = variable_id ':=' bound_1 TO bound_2 [ BY increment ] .
 index = numeric_expression .
 index_1 = index .
 index_2 = index .
 index_qualifier = '[' index_1 [ ':' index_2 ] ']' .
 integer_type = INTEGER .
 interval = '{' interval_low interval_op interval_item interval_op 
                interval_high '}' .
 interval_high = simple_expression .
 interval_item = simple_expression .
\end{verbatim}

\begin{verbatim}
 interval_low = simple_expression .
 interval_op = '<' | '<=' .
 list_type = LIST [ bound_spec ] OF base_type .
 literal = integer_literal | logical_literal | real_literal |
                 string_literal .
 local_decl = LOCAL local_variable { local_variable } END_LOCAL ';' .
 local_variable = variable_id { ',' variable_id } ':' parameter_type ';' .
 logical_expression = expression .
 logical_literal = FALSE | TRUE | UNKNOWN .
 logical_type = LOGICAL .
 multiplication_like_op = '*' | '/' | DIV | MOD | AND | '||' .
\end{verbatim}

\begin{verbatim}
 named_types = entity_ref | type_ref .
 null_stmt = ';' .
 numeric_expression = simple_expression .
 parameter = expression .
 parameter_id = simple_id .
 parameter_type = generalized_types | named_types | simple_types .
 population = entity_ref .
 primary = literal | ( qualifiable_factor { qualifier } ) .
 procedure_call_stmt = ( built_in_procedure | procedure_ref )
                             [ actual_parameter_list ] ';' .
 procedure_decl = procedure_head [ algorithm_head ] { stmt } END_PROCEDURE ';' .
\end{verbatim}

\begin{verbatim}
 procedure_head = PROCEDURE procedure_id [ '(' [ VAR ] formal_parameter
                        { ';' [ VAR ] formal_parameter } ')' ] ';' .
 procedure_id = simple_id .
 qualifiable_factor = attribute_ref | constant_factor | function_call |
                            general_ref | population .
 qualifier = attribute_qualifier | index_qualifier .
 real_type = REAL .
 referenced_attribute = attribute_ref | qualified_attribute .
 rel_op = '<' | '>' | '<=' | '>=' | '<>' | '=' | ':<>:' | ':=:' .
 rel_op_extended = rel_op | IN | LIKE .
 repeat_control = [ increment_control ] [ while_control ] [ until_control ] .
 repeat_stmt = REPEAT repeat_control ';' stmt { stmt } END_REPEAT ';' .
\end{verbatim}

\begin{verbatim}
 return_stmt = RETURN [ '(' expression ')' ] ';' .
 selector = expression .
 set_type = SET [ bound_spec ] OF base_type .
 sign = '+' | '-' .
 simple_expression = term { add_like_op term } .
 simple_factor = enumeration_reference | interval |
                 ( [ unary_op ] ( '(' expression ')' | primary ) ) .
 simple_types = integer_type | logical_type | real_type | string_type .
 skip_stmt = SKIP ';' .
 stmt = assignment_stmt | case_stmt | compound_stmt | escape_stmt |
        if_stmt | null_stmt | procedure_call_stmt | repeat_stmt | return_stmt |
        skip_stmt .
 string_literal = simple_string_literal .
\end{verbatim}

\begin{verbatim}
 string_type = STRING .
 term = factor { multiplication_like_op factor } .
 type_decl = TYPE type_id '=' underlying_type ';' END_TYPE ';' .
 type_id = simple_id .
 unary_op = '+' | '-' | NOT .
 underlying_type = constructed_types | aggregation_types | simple_types |
                   type_ref .
 until_control = UNTIL logical_expression .
 variable_id = simple_id .
 while_control = WHILE logical_expression .
\end{verbatim}
\end{code}




\addcontentsline{toc}{section}{References}
%\bibliography{refs,prw}

\begin{thebibliography}{10}

\bibitem{LAMPORT94}
Leslie Lamport.
\newblock {\em LaTeX: A Document Preparation System}.
\newblock Addison-Wesley Publishing Company, second edition, 1994.

\bibitem{KNUTH84a}
Donald~E. Knuth.
\newblock {\em The TeXbook}.
\newblock Addison-Wesley Publishing Company, 1984.

\bibitem{STEPIS}
ISO 10303.
\newblock {\em Industrial automation systems and integration --- Product data
  representation and exchange}, 1994.

\bibitem{GOLDFARB90}
C.~A. Goldfarb.
\newblock {\em The SGML Handbook}.
\newblock Oxford University Press, 1990.
\newblock (Edited and with a foreword by Yuri Rubinsky).

\bibitem{MUSCIANO96}
Chuck Musciano and Bill Kennedy.
\newblock {\em {HTML --- The Definitive Guide}}.
\newblock O'Reilly \& Associates, Inc., 1996.

\bibitem{KERNIGHAN88}
Brian~W. Kernighan and Dennis~M. Ritchie.
\newblock {\em The C Programming Language}.
\newblock Prentice Hall, second edition, 1988.

\bibitem{EBOOK}
Douglas~A. Schenck and Peter~R. Wilson.
\newblock {\em Information Modeling the EXPRESS Way}.
\newblock Oxford University Press (ISBN 0-19-308714-3), 1994.

\bibitem{EXPRESSIS}
ISO 10303-11:1994.
\newblock {\em Industrial automation systems and integration --- Product data
  representation and exchange --- Part 11: Description methods: The EXPRESS
  language reference manual}, 1994.

\bibitem{LEVINE92}
John~R. Levine, Tony Mason, and Doug Brown.
\newblock {\em lex \& yacc}.
\newblock O'Reilly \& Associates, Inc., second edition, 1992.

\bibitem{LESK75}
M.~E. Lesk and E.~Schmidt.
\newblock `{LEX --- A Lexical Analyser Generator}'.
\newblock In {\em UNIX Programmer's Manual 2}. AT\&T Bell Laboratories, Murray
  Hill, NJ, 1975.

\bibitem{JOHNSON75}
S.~C. Johnson.
\newblock {\em YACC --- Yet Another Compiler Compiler}.
\newblock C S Technical Report 32, Bell Telephone Laboratories, Murray Hill,
  NJ, 1975.

\bibitem{EXPRESSITR}
ISO/TR 10303-12:1997.
\newblock {\em Industrial automation systems and integration --- Product data
  representation and exchange --- Part 12: Description method: The EXPRESS-I
  language reference manual}, 1997.

\bibitem{PRW94b}
Peter~R. Wilson.
\newblock {\em `{FLaTTeN: A Program to Flatten LaTeX Source Files}'}.
\newblock NIST, Gaithersburg, MD 20899, December 1994.
\newblock (In draft).

\bibitem{LIBES93}
Don Libes.
\newblock {\em Obfuscated C and Other Mysteries}.
\newblock John Wiley \& Sons, Inc., 1993.

\bibitem{HOLUB90}
A.~I. Holub.
\newblock {\em Compiler Design in C}.
\newblock Prentice-Hall, Inc., 1990.

\bibitem{ORAM91}
Andrew Oram and Steve Talbott.
\newblock {\em Managing Projects with make}.
\newblock O'Reilly \& Associates, Inc., second edition, 1991.

\bibitem{RINAUDOT94}
Gaylen~R. Rinaudot.
\newblock {\em {The IGES/PDES Organization STEP On-Line Information Service}}.
\newblock NISTIR 5511, NIST, Gaithersburg, MD 20899, October 1994.

\bibitem{WIRTH77}
N.~Wirth.
\newblock `{What Can We Do About the Unnecessary Diversity of Notation for
  Syntactic Definitions?}'.
\newblock {\em Communications of the ACM}, 20(11):822--823, November 1977.

\bibitem{MAKR91}
Ronald Mak.
\newblock {\em Writing Compilers \& Interpreters --- An Applied Approach}.
\newblock John Wiley \& Sons, Inc., 1991.

\end{thebibliography}



\end{document}