summaryrefslogtreecommitdiff
path: root/systems/stanford/patgen/patgen.web
blob: a78d895c4f8ab892839c409088f784ea7d216dab (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
% This program is not copyrighted and can be used freely.
% This is PATGEN.WEB in text format, as of August 23, 2004.
% Version 1.0 was finished in 1983.
% Version 2.0 major revision for `8-bit TeX' (November 8, 1991).
% Version 2.1 allows left/right_hypen_min from terminal (April, 1992).
% Version 2.2 added `close_in(dictionary)' (August, 1996).
% Version 2.3 avoided division by zero - Karl Berry (October, 1996).
% Version 2.4 avoided use of uninitialized variables (September, 2009).
% A few typos fixed, no version change (April, 2020).

% Here is TeX material that gets inserted after \input webmac
\def\hang{\hangindent 3em\indent\ignorespaces}
\def\PASCAL{Pascal}

\def\title{PATGEN}
\def\contentspagenumber{45} % should be odd
\def\topofcontents{
  \line{\tenit Appendix\hfil \mainfont\contentspagenumber}
  \vfill
  \null\vskip 40pt
  \centerline{\titlefont {\ttitlefont PAT}tern {\ttitlefont GEN}eration
    program}
  \vskip 8pt
  \centerline{\titlefont for the \TeX 82 hyphenator}
  \vskip 15pt
  \centerline{(Version 2.4, April 2020)}
  \vfill}
\pageno=\contentspagenumber \advance\pageno by 1

@* Introduction.
This program takes a list of hyphenated words and generates a set of
patterns that can be used by the \TeX 82 hyphenation algorithm.

The patterns consist of strings of letters and digits, where a digit
indicates a `hyphenation value' for some intercharacter position.  For
example, the pattern \.{3t2ion} specifies that if the string \.{tion}
occurs in a word, we should assign a hyphenation value of 3 to the
position immediately before the \.{t}, and a value of 2 to the position
between the \.{t} and the \.{i}.

To hyphenate a word, we find all patterns that match within the word and
determine the hyphenation values for each intercharacter position.  If
more than one pattern applies to a given position, we take the maximum of
the values specified (i.e., the higher value takes priority).  If the
resulting hyphenation value is odd, this position is a feasible
breakpoint; if the value is even or if no value has been specified, we are
not allowed to break at this position.

In order to find quickly the patterns that match in a given word and to
compute the associated hyphenation values, the patterns generated by this
program are compiled by \.{INITEX} into a compact version of a finite
state machine.  For further details, see the \TeX 82 source.

The |banner| string defined here should be changed whenever \.{PATGEN}
gets modified.

@d banner=='This is PATGEN, Version 2.4' {printed when the program starts}

@ The original version~1 of \.{PATGEN} was written by Frank~M. Liang
@^Liang, Franklin Mark@>
in 1982; a major revision (version~2) by Peter Breitenlohner in 1991
@^Breitenlohner, Peter@>
is mostly related to the new features of `8-bit \TeX' (version~3 of
\TeX 82). The differences between versions~1 and~2 fall into several
categories (all of Liang's algorithms have been left essentially
unchanged): (1)~enhancements related to 8-bit \TeX, e.g., the
introduction of 8-bit |ASCII_code| values and of \.{\\lefthyphenmin} and
\.{\\righthyphenmin}; (2)~a modification of the input and output
procedures which should make language specific modifications of this
program unnecessary (information about the external representation of
all `letters' used by a particular language is obtained from the
|translate| file); (3)~removal of ANSI standard \PASCAL\ and range check
violations; (4)~removal of uninitialized variables; (5)~minor
modifications in order to simplify system-dependent modifications.
@^range check violations@>

@ This program is written in standard \PASCAL, except where it is
necessary to use extensions.  All places where nonstandard constructions
are used have been listed in the index under ``system dependencies.''
@!@^system dependencies@>

The program uses \PASCAL's standard |input| and |output| files to read
from and write to the user's terminal.

@d print(#)==write(output,#)
@d print_ln(#)==write_ln(output,#)
@d get_input(#)==read(input,#)
@d get_input_ln(#)==
  begin if eoln(input) then read_ln(input);
  read(input,#);
  end
@#
@d end_of_PATGEN=9999

@p @<Compiler directives@>@/
program PATGEN(@!dictionary,@!patterns,@!translate,@!patout);
label end_of_PATGEN;
const @<Constants in the outer block@>@/
type @<Types in the outer block@>@/
var @<Globals in the outer block@>@/
procedure initialize; {this procedure gets things started properly}
  var @<Local variables for initialization@>@/
  begin print_ln(banner);@/
  @<Set initial values@>@/
  end;

@ The patterns are generated in a series of sequential passes through the
dictionary.  In each pass, we collect count statistics for a particular
type of pattern, taking into account the effect of patterns chosen in
previous passes.  At the end of a pass, the counts are examined and new
patterns are selected.

Patterns are chosen one level at a time, in order of increasing
hyphenation value.  In the sample run shown below, the parameters
|hyph_start| and |hyph_finish| specify the first and last levels,
respectively, to be generated.

Patterns at each level are chosen in order of increasing pattern length
(usually starting with length~2).  This is controlled by the parameters
|pat_start| and |pat_finish| specified at the beginning of each level.

Furthermore patterns of the same length applying to different
intercharacter positions are chosen in separate passes through the
dictionary.  Since patterns of length $n$ may apply to $n+1$ different
positions, choosing a set of patterns of lengths $2$ through $n$ for a
given level requires $(n+1)(n+2)/2-3$ passes through the word list.

At each level, the selection of patterns is controlled by the three
parameters |good_wt|, |bad_wt|, and |thresh|.  A hyphenating pattern will
be selected if |good*good_wt-bad*bad_wt>=thresh|, where |good| and
|bad| are the number of times the pattern could and could not be
hyphenated, respectively, at a particular point.  For inhibiting patterns,
|good| is the number of errors inhibited, and |bad| is the number of
previously found hyphens inhibited.

@<Globals...@>=
@!pat_start, @!pat_finish: dot_type;
@!hyph_start, @!hyph_finish: val_type;
@!good_wt, @!bad_wt, @!thresh: integer;

@ The proper choice of the parameters to achieve a desired degree of
hyphenation is discussed in Chapter~4.  Below we show part of a sample run
of \.{PATGEN}, with the user's inputs underlined.
$$\vbox{\halign{\.{#\hfil}\cr
$\underline{\smash{\.{ex patgen}}}$\cr
DICTIONARY : $\underline{\smash{\.{murray.hyf}}}$\cr
PATTERNS   : $\underline{\smash{\.{nul:}}}$\cr
TRANSLATE  : $\underline{\smash{\.{nul:}}}$\cr
PATOUT     : $\underline{\smash{\.{murray.pat}}}$\cr
This is PATGEN, Version 2.0\cr
left\_hyphen\_min = 2, right\_hyphen\_min = 3, 26 letters\cr
0 patterns read in\cr
pattern trie has 256 nodes, trie\_max = 256, 0 outputs\cr
hyph\_start, hyph\_finish: $\underline{\.{1 1}}$\cr
pat\_start, pat\_finish: $\underline{\.{2 3}}$\cr
good weight, bad weight, threshold: $\underline{\.{1 3 3}}$\cr
processing dictionary with pat\_len = 2, pat\_dot = 1\cr
\cr
0 good, 0 bad, 3265 missed\cr
 0.00 \%,  0.00 \%,  100.00 \%\cr
338 patterns, 466 nodes in count trie, triec\_max = 983\cr
46 good and 152 bad patterns added (more to come)\cr
finding 715 good and 62 bad hyphens, efficiency =  10.72\cr
pattern trie has 326 nodes, trie\_max = 509, 2 outputs\cr
processing dictionary with pat\_len = 2, pat\_dot = 0\cr
\cr
\hskip 1.5em ...\cr
\cr
1592 nodes and 39 outputs deleted\cr
total of 220 patterns at hyph\_level 1\cr
hyphenate word list? $\underline{\smash{\.{y}}}$\cr
writing pattmp.1\cr
\cr
2529 good, 243 bad, 736 missed\cr
 77.46 \%,  7.44 \%,  22.54 \%\cr}}$$

@ Note that before beginning a pattern selection run, a file of existing
patterns may be read in.  In order for pattern selection to work properly,
this file should only contain patterns with hyphenation values less than
|hyph_start|.  Each word in the dictionary is hyphenated according to the
existing set of patterns (including those chosen on previous passes of the
current run) before pattern statistics are collected.

Also, a hyphenated word list may be written out at the end of a run.  This
list can be read back in as the `dictionary' to continue pattern selection
from this point.  In addition to ordinary hyphens (|'-'|) the new list
will contain two additional kinds of ``hyphens'' between letters, namely
hyphens that have been found by previously generated patterns, as well
as erroneous hyphens that have been inserted by those patterns.  These
are represented by the symbols |'*'| and |'.'|, respectively. The three
characters |'-'|, |'*'|, and |'.'| are, in fact, just the default values
used to represent the three kinds of hyphens, the |translate| file may
specify different characters to be used instead of them.

In addition, a word list can include hyphen weights, both for entire words
and for individual hyphen positions.  (The syntax for this is explained in
the dictionary processing routines.)  Thus common words can be weighted
more heavily, or, more generally, words can be weighted according to their
frequency of occurrence, if such information is available.  The use of
hyphen weights combined with an appropriate setting of the pattern
selection threshold can be used to guarantee hyphenation of certain words
or certain hyphen positions within a word.

@ Below we show the first few lines of a typical word list,
before and after generating a level of patterns.
$$\vbox{\halign{\tabskip 1in\.{#\hfil}&\.{#\hfil}\cr
abil-i-ty&  abil*i*ty\cr
ab-sence&  ab*sence\cr
ab-stract&  ab*stract\cr
ac-a-dem-ic&  ac-a-d.em-ic\cr
ac-cept&  ac*cept\cr
ac-cept-able&  ac*cept-able\cr
ac-cept-ed&  ac*cept*ed\cr
\hskip 1.5em ...&\hskip 1.5em ...\cr
}}$$

@ We augment \PASCAL 's control structures a bit using |goto|\unskip's
and the following symbolic labels.

@d exit=10 {go here to leave a procedure}
@d continue=22 {go here to resume a loop}
@d done=30 {go here to exit a loop}
@d found=40 {go here when you've found it}
@d not_found=41 {go here when you've found something else}

@ Here are some macros for common programming idioms.

@d incr(#)==#:=#+1 {increase a variable by unity}
@d decr(#)==#:=#-1 {decrease a variable by unity}
@#
@d Incr_Decr_end(#)==#
@d Incr(#)==#:=#+Incr_Decr_end {we use |Incr(a)(b)| to increase \dots}
@d Decr(#)==#:=#-Incr_Decr_end {\dots\ and |Decr(a)(b)| to decrease
  variable |a| by |b|; this can be optimized for some compilers}
@#
@d loop == @+ while true do@+ {repeat over and over until a |goto| happens}
@d do_nothing == {empty statement}
@d return==goto exit {terminate a procedure call}
@f return==nil
@f loop == xclause

@ In case of serious problems \.{PATGEN} will give up, after issuing an
error message about what caused the error. Such errors might be
discovered inside of subroutines inside of subroutines, so a \.{WEB}
macro called |jump_out| has been introduced. This macro, which transfers
control to the label |end_of_PATGEN| at the end of the program, contains
the only non-local |@!goto| statement in \.{PATGEN}. Some \PASCAL\
compilers do not implement non-local |goto| statements. In such cases
the |goto end_of_PATGEN| in the definition of |jump_out| should simply
be replaced by a call on some system procedure that quietly terminates
the program.
@^system dependencies@>

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

@d jump_out==goto end_of_PATGEN {terminates \.{PATGEN}}
@#
@d error(#)==begin print_ln(#); jump_out; end
@d overflow(#)==error('PATGEN capacity exceeded, sorry [',#,'].')
@.PATGEN capacity exceeded ...@>

@ @<Compiler directives@>=
@{@&$C-,A+,D-@} {no range check, catch arithmetic overflow, no debug overhead}
@^system dependencies@>

@* The character set.
Since different \PASCAL\ systems may use different character sets, we use
the name |text_char| to stand for the data type of characters appearing in
external text files.  We also assume that |text_char| consists of the
elements |chr(first_text_char)| through |chr(last_text_char)|, inclusive.
The definitions below should be adjusted if necessary.
@^system dependencies@>
@^character set dependencies@>

Internally, characters will be represented using the type |ASCII_code|.
Note, however, that only some of the standard ASCII characters are
assigned a fixed |ASCII_code|; all other characters are assigned an
|ASCII_code| dynamically when they are first read from the |translate|
file specifying the external representation of the `letters' used by a
particular language. For the sake of generality the standard version of
this program allows for 256 different |ASCII_code| values, but 128 of
them would probably suffice for all practical purposes.

@d first_text_char=0 {ordinal number of the smallest element of |text_char|}
@d last_text_char=255 {ordinal number of the largest element of |text_char|}
@#
@d last_ASCII_code=255 {the highest allowed |ASCII_code| value}

@<Types...@>=
@!text_char=char; {the data type of characters in text files}
@!ASCII_code=0..last_ASCII_code; {internal representation of input characters}
@!text_file=text;

@ Some \PASCAL s can store only signed eight-bit quantities (|-128..127|)
but not unsigned ones (|0..255|) in one byte. If storage is tight we
must, for such \PASCAL s, either restrict |ASCII_code| to the range
|0..127| (with some loss of generality) or convert between |ASCII_code|
and |packed_ASCII_code| and vice versa by subtracting or adding an
offset. (Or we might define |packed_ASCII_code| as |char| and use
suitable typecasts for the conversion.) Only the type |packed_ASCII_code|
will be used for large arrays and the \.{WEB} macros |si| and |so| will
always be used to convert an |ASCII_code| into a |packed_ASCII_code| and
vice versa.
@^system dependencies@>

@d min_packed=0 {change this to `$\\{min\_packed}=-128$' when necessary;
  and don't forget to change the definitions of |si| and |so| below
  accordingly}
@#
@d si(#)==# {converts |ASCII_code| to |packed_ASCII_code|}
@d so(#)==# {converts |packed_ASCII_code| to |ASCII_code|}

@<Types...@>=
@!packed_ASCII_code=min_packed..last_ASCII_code+min_packed;

@ We want to make sure that the ``constants'' defined in this program
satisfy all the required relations. Some of them are needed to avoid
time-consuming checks while processing the dictionary and\slash or to
prevent range check and array bound violations.
@^range check violations@>

Here we check that the definitions of |ASCII_code| and
|packed_ASCII_code| are consistent with those of |si| and |so|.

@<Set init...@>=
bad:=0;@/
if last_ASCII_code<127 then bad:=1;
if (si(0)<>min_packed)or(so(min_packed)<>0) then bad:=2;@/
@<Check the ``constant'' values for consistency@>@;
if bad>0 then error('Bad constants---case ',bad:1);
@.Bad constants@>

@ @<Local variables for init...@>=
@!bad:integer;
@!i:text_char;
@!j:ASCII_code;

@ We convert between |ASCII_code| and the user's external character set by
means of arrays |xord| and |xchr| that are analogous to \PASCAL's |ord|
and |chr| functions.

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

@ The following code initializes the |xchr| array with some of the
standard ASCII characters.

@<Set init...@>=
for j:=0 to last_ASCII_code do xchr[j]:=' ';
xchr["."]:='.';@/
xchr["0"]:='0'; xchr["1"]:='1'; xchr["2"]:='2'; xchr["3"]:='3';
xchr["4"]:='4'; xchr["5"]:='5'; xchr["6"]:='6'; xchr["7"]:='7';
xchr["8"]:='8'; xchr["9"]:='9';@/
xchr["A"]:='A'; xchr["B"]:='B'; xchr["C"]:='C'; xchr["D"]:='D';
xchr["E"]:='E'; xchr["F"]:='F'; xchr["G"]:='G'; xchr["H"]:='H';
xchr["I"]:='I'; xchr["J"]:='J'; xchr["K"]:='K'; xchr["L"]:='L';
xchr["M"]:='M'; xchr["N"]:='N'; xchr["O"]:='O'; xchr["P"]:='P';
xchr["Q"]:='Q'; xchr["R"]:='R'; xchr["S"]:='S'; xchr["T"]:='T';
xchr["U"]:='U'; xchr["V"]:='V'; xchr["W"]:='W'; xchr["X"]:='X';
xchr["Y"]:='Y'; xchr["Z"]:='Z';@/
xchr["a"]:='a'; xchr["b"]:='b'; xchr["c"]:='c'; xchr["d"]:='d';
xchr["e"]:='e'; xchr["f"]:='f'; xchr["g"]:='g'; xchr["h"]:='h';
xchr["i"]:='i'; xchr["j"]:='j'; xchr["k"]:='k'; xchr["l"]:='l';
xchr["m"]:='m'; xchr["n"]:='n'; xchr["o"]:='o'; xchr["p"]:='p';
xchr["q"]:='q'; xchr["r"]:='r'; xchr["s"]:='s'; xchr["t"]:='t';
xchr["u"]:='u'; xchr["v"]:='v'; xchr["w"]:='w'; xchr["x"]:='x';
xchr["y"]:='y'; xchr["z"]:='z';

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

@d invalid_code=0 {|ASCII_code| that should not appear}
@d tab_char=@'11 {|ord| of tab character; tab characters seem to be
  unavoidable with files from UNIX systems}
@^system dependencies@>
@^character set dependencies@>

@<Set init...@>=
for i:=chr(first_text_char) to chr(last_text_char) do
  xord[i]:=invalid_code;
for j:=0 to last_ASCII_code do xord[xchr[j]]:=j;
xord[' ']:=" "; xord[chr(tab_char)]:=" ";

@ So far each invalid |ASCII_code| has been assigned the character |' '|
and all invalid characters have been assigned |ASCII_code=invalid_code|.
The |get_ASCII| function, used only while reading the |translate| file,
returns the |ASCII_code| corresponding to a character, assigning a new
|ASCII_code| first if necessary.

@d num_ASCII_codes=last_ASCII_code+1 {number of different |ASCII_code| values}

@p function get_ASCII(@!c:text_char):ASCII_code;
label found;
var i: ASCII_code;
begin i:=xord[c];
if i=invalid_code then
  begin while i<last_ASCII_code do
    begin incr(i);
    if (xchr[i]=' ')and(i<>" ") then goto found;
    end;
  overflow(num_ASCII_codes:1,' characters');
  found: xord[c]:=i; xchr[i]:=c;
  end;
get_ASCII:=i;
end;

@ The \TeX 82 hyphenation algorithm operates on `hyphenable words'
converted temporarily to lower case, i.e., they may consist of up to
255 different `letters' corresponding to \.{\\lccode}s |1..255|. These
\.{\\lccode}s could, in principle, be language dependent but this might
lead to undesirable results when hyphenating multilingual paragraphs.
No more than 245 different letters can occur in hyphenation patterns
since the characters |'0'..'9'| and |'.'| play a special r\^^Dole when
reading patterns. For the purpose of this program each letter is
represented internally by a unique |internal_code>=2| (|internal_code=1|
is the |edge_of_word| indicator); |internal_code| values |2..127| will
probably suffice for all practical purposes, but we allow the range
|2..last_ASCII_code| for the sake of generality. Syntactically
|internal_code| and |ASCII_code| are the same, we will use one or the
other name according to the semantic context.

@d edge_of_word=1 {|internal_code| for start and end of a word}

@<Types...@>=
@!internal_code=ASCII_code;
@!packed_internal_code=packed_ASCII_code;

@ Note that an |internal_code| used by this program is in general quite
different from the |ASCII_code| (or rather \.{\\lccode}) used by \TeX
82. This program allows the input of characters (from the |dictionary|
and |patterns| file) corresponding to an |internal_code| in either lower
or upper case form; the output (to the |patout| and |pattmp| file) will
always be in lower case form.

Unfortunately there does not (yet?) exist a standardized and widely
accepted 8-bit character set (or a unique one-to-one translation between
such sets). On the other hand macro expansion takes place in \TeX 82
when reading hyphenable words and when reading patterns. Thus the lower
and upper case versions of all `letters' used by a particular language
can (and for the sake of portability should) be represented entirely in
terms of the standard ASCII character set; either directly as characters
or via macros (or active characters) with or without arguments. The
macro definitions for such a representation will in general be language
dependent.

For the purpose of this program the external representation of the lower
and upper case version of a letter (i.e., |internal_code|) consists of a
unique sequence of characters (or \\{ASCII\_codes}), the only restriction
being that no such sequence must be a subsequence of an other one.
Moreover such sequences must not start with |' '|, |'.'|, |'0'..'9'| or
with one of the three characters (|'-'|, |'*'|, and |'.'|) representing
hyphens in the |dictionary| file; a sequence may, however, end with a
mandatory |' '| as, e.g., the sequence |'\ss '|.

The language dependent values of \.{\\lefthyphenmin} and
\.{\\righthyphenmin} as well as the external representation of the lower
and upper case letters and their collating sequence are specified in the
|translate| file, thus making any language dependent modifications of
this program unnecessary. If the |translate| file is empty (or does not
exist) the values \.{\\lefthyphenmin=2} and \.{\\righthyphenmin=3} and
|internal_code| values |2..27| with the one character external
representations |'a'..'z'| and |'A'..'Z'| will be used as defaults.

Incidentally this program can be used to convert a |dictionary| and
|patterns| file from one (``upper case'') to another (``lower case'')
external representation of letters.

@ When reading the |dictionary| (and |patterns|) file sequences of
characters must be recognized and converted to their corresponding
|internal_code|. This conversion is part of \.{PATGEN}s inner loop and
@^inner loop@>
must therefore be done as efficient as possible. Thus we will
mostly bypass the conversion from character to |ASCII_code| and convert
directly to the corresponding |internal_code| using the |xclass|
and |xint| arrays. Six types of characters are distinguished by their
|xclass|:

\yskip\hang |space_class| character |' '| terminates a pattern or word.

\yskip\hang |digit_class| characters |'0'..'9'| are hyphen values for a
pattern or hyphen weights for a word; their |xint| is the corresponding
numeric value |0..9|.

\yskip\hang |hyf_class| characters (|'.'|, |'-'|, and |'*'|) are `dots'
and indicate hyphens in a word; their |xint| is the corresponding
numeric value |err_hyf..found_hyf|.

\yskip\hang |letter_class| characters represent a letter; their |xint|
is the corresponding |internal_code|.

\yskip\hang |escape_class| characters indicate the start of a
multi-character sequence representing a letter.

\yskip\hang |invalid_class| characters should not occur except as part
of multi-character sequences.

@d space_class=0 {the character |' '|}
@d digit_class=1 {the characters |'0'..'9'|}
@d hyf_class=2 {the `hyphen' characters (|'.'|, |'-'|, and |'*'|)}
@d letter_class=3 {characters representing a letter}
@d escape_class=4 {characters that start a multi-character sequence
  representing a letter}
@d invalid_class=5 {characters that normally should not occur}
@#
@d no_hyf=0 {no hyphen}
@d err_hyf=1 {erroneous hyphen}
@d is_hyf=2 {hyphen}
@d found_hyf=3 {found hyphen}

@<Types...@>=
@!class_type=space_class..invalid_class; {class of a character}
@!digit=0..9; {a hyphen weight (or word weight)}
@!hyf_type=no_hyf..found_hyf; {type of a hyphen}

@ In addition we will use the |xext|, |xdig|, and |xdot| arrays to
convert from the internal representation to the corresponding
characters.

@<Globals...@>=
@!xclass: array [text_char] of class_type;
  {specifies the class of a character}
@!xint: array [text_char] of internal_code;
  {specifies the |internal_code| for a character}
@!xdig: array [0..9] of text_char;
  {specifies conversion of output characters}
@!xext: array [internal_code] of text_char;
  {specifies conversion of output characters}
@!xhyf: array [err_hyf..found_hyf] of text_char;
  {specifies conversion of output characters}

@ @<Set init...@>=
for i:=chr(first_text_char) to chr(last_text_char) do
  begin xclass[i]:=invalid_class; xint[i]:=0;
  end;
xclass[' ']:=space_class;
for j:=0 to last_ASCII_code do xext[j]:=' ';
xext[edge_of_word]:='.';
for j:=0 to 9 do
  begin xdig[j]:=xchr[j+"0"];
  xclass[xdig[j]]:=digit_class; xint[xdig[j]]:=j;
  end;
xhyf[err_hyf]:='.'; xhyf[is_hyf]:='-'; xhyf[found_hyf]:='*';
  {default representation for hyphens}

@ We assume that words use only the letters |cmin+1| through |cmax|.
This allows us to save some time on trie operations that involve
searching for packed transitions belonging to a particular state.

@d cmin=edge_of_word

@<Globals...@>=
@!cmax: internal_code; {largest |internal_code| or |ASCII_code|}

@* Data structures.
The main data structure used in this program is a dynamic packed trie.
In fact we use two of them, one for the set of patterns selected so far,
and one for the patterns being considered in the current pass.

For a pattern $p_1\ldots p_k$, the information associated with that
pattern is accessed by setting |@t$t_1$@>:=trie_root+@t$p_1$@>| and
then, for |1<i<=k|, setting |@t$t_i$@>:=trie_link(@t$t_{i-1}$@>)+
@t$p_i$@>|; the pattern information is then stored in a location addressed
by |@t$t_k$@>|.  Since all trie nodes are packed into a single array, in
order to distinguish nodes belonging to different trie families, a special
field is provided such that |trie_char@t$(t_i)=si(p_i)$@>| for all |i|.

In addition the trie must support dynamic insertions and deletions.  This
is done by maintaining a doubly linked list of unoccupied cells and
repacking trie families as necessary when insertions are made.

Each trie node consists of three fields:  the character |trie_char|, and
the two link fields |trie_link| and |trie_back|.  In addition there is a
separate boolean array |trie_base_used|.  When a node is unoccupied,
|trie_char=min_packed| and the link fields point to the next and previous
unoccupied nodes, respectively, in the doubly linked list.  When a node is
occupied, |trie_link| points to the next trie family, and |trie_back|
(renamed |trie_outp|) contains the output associated with this transition.
The |trie_base_used| bit indicates that some family has been packed at
this base location, and is used to prevent two families from being packed
at the same location.

@ The sizes of the pattern tries may have to be adjusted depending
on the particular application (i.e., the parameter settings and the
size of the dictionary).  The sizes below were sufficient to generate
the original set of english \TeX 82 hyphenation patterns (file
\.{hyphen.tex}).

@<Constants...@>=
@!trie_size=55000; {space for pattern trie}
@!triec_size=26000; {space for pattern count trie, must be less than
 |trie_size| and greater than the number of occurrences of any pattern in
 the dictionary}
@!max_ops=4080; {size of output hash table, should be a multiple of 510}
@!max_val=10; {maximum number of levels$+1$, also used to denote bad patterns}
@!max_dot=15; {maximum pattern length, also maximum length of external
  representation of a `letter'}
@!max_len=50; {maximum word length}
@!max_buf_len=80; {maximum length of input lines, must be at least |max_len|}

@ @<Check the ``constant'' values for consistency@>=
if (triec_size<4096)or(trie_size<triec_size) then bad:=3;
if max_ops>trie_size then bad:=4;
if max_val>10 then bad:=5;
if max_buf_len<max_len then bad:=6;

@ @<Types...@>=
@!q_index=1..last_ASCII_code; {number of transitions in a state}
@!val_type=0..max_val; {hyphenation values}
@!dot_type=0..max_dot; {dot positions}
@!op_type=0..max_ops; {index into output hash table}
@!word_index=0..max_len; {index into |word|}
@!trie_pointer=0..trie_size;
@!triec_pointer=0..triec_size;@/
@!op_word=packed record dot: dot_type; val: val_type; op: op_type end;

@ Trie is actually stored with its components in separate packed arrays,
in order to save space and time (although this depends on the computer's
word size and the size of the trie pointers).

@<Globals...@>=
@!trie_c: packed array[trie_pointer] of packed_internal_code;
@!trie_l, @!trie_r: packed array[trie_pointer] of trie_pointer;
@!trie_taken: packed array[trie_pointer] of boolean;
@!triec_c: packed array[triec_pointer] of packed_internal_code;
@!triec_l, @!triec_r: packed array[triec_pointer] of triec_pointer;
@!triec_taken: packed array[triec_pointer] of boolean;
@!ops: array[op_type] of op_word; {output hash table}

@ When some trie state is being worked on, an unpacked version of the
state is kept in positions |1..qmax| of the global arrays |trieq_c|,
|trieq_l|, and |trieq_r|. The character fields need not be in any
particular order.

@<Globals...@>=
@!trieq_c: array[q_index] of internal_code; {character fields of a
  single trie state}
@!trieq_l, @!trieq_r: array[q_index] of trie_pointer; {link fields}
@!qmax: q_index; {number of transitions in an unpacked state}
@!qmax_thresh: q_index; {controls density of first-fit packing}

@ Trie fields are accessed using the following macros.

@d trie_char(#)==trie_c[#]
@d trie_link(#)==trie_l[#]
@d trie_back(#)==trie_r[#]
@d trie_outp(#)==trie_r[#]
@d trie_base_used(#)==trie_taken[#]
@#
@d triec_char(#)==triec_c[#]
@d triec_link(#)==triec_l[#]
@d triec_back(#)==triec_r[#]
@d triec_good(#)==triec_l[#]
@d triec_bad(#)==triec_r[#]
@d triec_base_used(#)==triec_taken[#]
@#
@d q_char(#)==trieq_c[#]
@d q_link(#)==trieq_l[#]
@d q_back(#)==trieq_r[#]
@d q_outp(#)==trieq_r[#]
@#
@d hyf_val(#)==ops[#].val
@d hyf_dot(#)==ops[#].dot
@d hyf_nxt(#)==ops[#].op

@* Routines for pattern trie.
The pattern trie holds the set of patterns chosen prior to the current
pass, including bad or ``hopeless'' patterns at the current level that
occur too few times in the dictionary to be of use.  Each transition of
the trie includes an output field pointing to the hyphenation information
associated with this transition.

@<Globals...@>=
@!trie_max: trie_pointer; {maximum occupied trie node}
@!trie_bmax: trie_pointer; {maximum base of trie family}
@!trie_count: trie_pointer; {number of occupied trie nodes, for space usage
 statistics}
@!op_count: op_type; {number of outputs in hash table}

@ Initially, the dynamic packed trie has just one state, namely the root,
with all transitions present (but with null links).  This is convenient
because the root will never need to be repacked and also we won't have to
check that the base is nonnegative when packing other states.
Moreover in many cases we need not check for a vanishing link field:
if |trie_link(t)=0| then a subsequent test for
|trie_char(trie_link(t)+c)=si(c)| will always fail due to |trie_root=1|.

@d trie_root=1

@p procedure init_pattern_trie;
var c: internal_code; @!h: op_type;
begin  for c:=0 to last_ASCII_code do
  begin  trie_char(trie_root+c):=si(c); {indicates node occupied;
      fake for |c=0|}
    trie_link(trie_root+c):=0;
    trie_outp(trie_root+c):=0;
    trie_base_used(trie_root+c):=false;
  end;
  trie_base_used(trie_root):=true;
  trie_bmax:=trie_root;
  trie_max:=trie_root+last_ASCII_code;
  trie_count:=num_ASCII_codes;@/
  qmax_thresh:=5;@/
  trie_link(0):=trie_max+1;
  trie_back(trie_max+1):=0;@/
  {|trie_link(0)| is used as the head of the doubly linked list of
    unoccupied cells}
  for h:=1 to max_ops do hyf_val(h):=0; {clear output hash table}
  op_count:=0;
end;

@ The |first_fit| procedure finds a hole in the packed trie into which the
state in |trieq_c|, |trieq_l|, and |trieq_r| will fit.  This is normally
done by going through the linked list of unoccupied cells and testing if
the state will fit at each position.  However if a state has too many
transitions (and is therefore unlikely to fit among existing
transitions) we don't bother and instead just pack it immediately to the
right of the occupied region (starting at |trie_max+1|).

@p function first_fit: trie_pointer;
label found, not_found;
var s, @!t: trie_pointer; @!q: q_index;
begin  @<Set |s| to the trie base location at which this state should be
    packed@>;
  for q:=1 to qmax do {pack it}
  begin  t:=s+q_char(q);@/
    trie_link(trie_back(t)):=trie_link(t);
    trie_back(trie_link(t)):=trie_back(t); {link around
      filled cell}
    trie_char(t):=si(q_char(q));
    trie_link(t):=q_link(q);
    trie_outp(t):=q_outp(q);
    if t>trie_max then trie_max:=t;
  end;
  trie_base_used(s):=true;
  first_fit:=s
end;

@ The threshold for large states is initially 5 transitions.  If more than
one level of patterns is being generated, the threshold is set to 7 on
subsequent levels because the pattern trie will be sparser after bad
patterns are deleted (see |delete_bad_patterns|).

@<Set |s| to the trie base location at which this state should be packed@>=
if qmax>qmax_thresh then t:=trie_back(trie_max+1) @+else t:=0;
loop  begin t:=trie_link(t); s:=t-q_char(1); {get next unoccupied cell}
  @<Ensure |trie| linked up to |s+num_ASCII_codes|@>;
  if trie_base_used(s) then goto not_found;
  for q:=qmax downto 2 do {check if state fits here}
  if trie_char(s+q_char(q))<>min_packed then goto not_found;
  goto found;
  not_found: end;
found:

@ The trie is only initialized (as a doubly linked list of empty cells) as
far as necessary.  Here we extend the initialization if necessary, and
check for overflow.

@<Ensure |trie| linked up to |s+num_ASCII_codes|@>=
if s>trie_size-num_ASCII_codes then
  overflow(trie_size:1,' pattern trie nodes');
while trie_bmax<s do
  begin incr(trie_bmax);
  trie_base_used(trie_bmax):=false;
  trie_char(trie_bmax+last_ASCII_code):=min_packed;
  trie_link(trie_bmax+last_ASCII_code):=trie_bmax+num_ASCII_codes;
  trie_back(trie_bmax+num_ASCII_codes):=trie_bmax+last_ASCII_code;
  end

@ The |unpack| procedure finds all transitions associated with the state
with base |s|, puts them into the arrays |trieq_c|, |trieq_l|, and
|trieq_r|, and sets |qmax| to one more than the number of transitions
found.  Freed cells are put at the beginning of the free list.

@p procedure unpack(@!s: trie_pointer);
var c: internal_code; @!t: trie_pointer;
begin  qmax:=1;
for c:=cmin to cmax do {search for transitions belonging to this state}
  begin  t:=s+c;
  if so(trie_char(t))=c then {found one}
    begin q_char(qmax):=c;
    q_link(qmax):=trie_link(t);
    q_outp(qmax):=trie_outp(t);
    incr(qmax);@/
    {now free trie node}
    trie_back(trie_link(0)):=t;
    trie_link(t):=trie_link(0);
    trie_link(0):=t;
    trie_back(t):=0;
    trie_char(t):=min_packed;
    end;
  end;
trie_base_used(s):=false;
end;

@ The function |new_trie_op| returns the `opcode' for the output
consisting of hyphenation value~|v|, hyphen position |d|, and next output
|n|.  The hash function used by |new_trie_op| is based on the idea that
313/510 is an approximation to the golden ratio [cf.\ {\sl The Art of
Computer Programming \bf3} (1973), 510--512]; but the choice is
comparatively unimportant in this particular application.

@p function new_trie_op(@!v: val_type; @!d: dot_type; @!n: op_type): op_type;
label exit;
var h: op_type;
begin  h:=((n+313*d+361*v) mod max_ops)+1; {trial hash location}
loop  begin if hyf_val(h)=0 then {empty position found}
    begin incr(op_count);
    if op_count=max_ops then overflow(max_ops:1,' outputs');
    hyf_val(h):=v; hyf_dot(h):=d; hyf_nxt(h):=n; new_trie_op:=h; return;
    end;
  if (hyf_val(h)=v) and (hyf_dot(h)=d) and
     (hyf_nxt(h)=n) then {already in hash table}
    begin  new_trie_op:=h; return;
    end;
  if h>1 then decr(h) @+else h:=max_ops; {try again}
  end;
exit: end;

@ @<Globals...@>=
@!pat: array[dot_type] of internal_code; {current pattern}
@!pat_len: dot_type; {pattern length}

@ Now that we have provided the necessary routines for manipulating the
dynamic packed trie, here is a procedure that inserts a pattern of length
|pat_len|, stored in the |pat| array, into the pattern trie.  It also adds
a new output.

@p procedure insert_pattern(@!val: val_type; @!dot: dot_type);
var i: dot_type; @!s, @!t: trie_pointer;
begin  i:=1;
  s:=trie_root+pat[i]; t:=trie_link(s);
  while (t>0) and (i<pat_len) do {follow existing trie}
  begin  incr(i); Incr(t)(pat[i]);
    if so(trie_char(t))<>pat[i] then
      @<Insert critical transition, possibly repacking@>;
    s:=t; t:=trie_link(s);
  end;
  q_link(1):=0; q_outp(1):=0; qmax:=1;
  while i<pat_len do {insert rest of pattern}
  begin  incr(i); q_char(1):=pat[i];
    t:=first_fit;
    trie_link(s):=t;
    s:=t+pat[i];
    incr(trie_count);
  end;
  trie_outp(s):=new_trie_op(val,dot,trie_outp(s));
end;

@ We have accessed a transition not in the trie.  We insert it, repacking
the state if necessary.

@<Insert critical transition, possibly repacking@>=
begin  if trie_char(t)=min_packed then
  begin  {we're lucky, no repacking needed}
  trie_link(trie_back(t)):=trie_link(t);
  trie_back(trie_link(t)):=trie_back(t);@/
  trie_char(t):=si(pat[i]);
  trie_link(t):=0;
  trie_outp(t):=0;
  if t>trie_max then trie_max:=t;
  end
else  begin  {whoops, have to repack}
  unpack(t-pat[i]);@/
  q_char(qmax):=pat[i];
  q_link(qmax):=0;
  q_outp(qmax):=0;@/
  t:=first_fit;
  trie_link(s):=t;
  Incr(t)(pat[i]);
  end;
incr(trie_count);
end

@* Routines for pattern count trie.
The pattern count trie is used to store the set of patterns considered in
the current pass, along with the counts of good and bad instances.  The
fields of this trie are the same as the pattern trie, except that there is
no output field, and leaf nodes are also used to store counts
(|triec_good| and |triec_bad|).  Except where noted, the following
routines are analogous to the pattern trie routines.

@<Globals...@>=
@!triec_max, @!triec_bmax, @!triec_count: triec_pointer; {same as for pattern
  trie}
@!triec_kmax: triec_pointer; {shows growth of trie during pass}
@!pat_count: integer; {number of patterns in count trie}

@ [See |init_pattern_trie|.]  The variable |triec_kmax| always contains
the size of the count trie rounded up to the next multiple of 4096, and is
used to show the growth of the trie during each pass.

@d triec_root=1

@p procedure init_count_trie;
var c: internal_code;
begin  for c:=0 to last_ASCII_code do
  begin  triec_char(triec_root+c):=si(c);@/
    triec_link(triec_root+c):=0;
    triec_back(triec_root+c):=0;
    triec_base_used(triec_root+c):=false;
  end;
  triec_base_used(triec_root):=true;
  triec_bmax:=triec_root; triec_max:=triec_root+last_ASCII_code;
  triec_count:=num_ASCII_codes; triec_kmax:=4096;@/
  triec_link(0):=triec_max+1; triec_back(triec_max+1):=0;@/
  pat_count:=0;
end;

@ [See |first_fit|.]

@p function firstc_fit: triec_pointer;
label found, not_found;
var a, @!b: triec_pointer; @!q: q_index;
begin  @<Set |b| to the count trie base location at which this state should
    be packed@>;
  for q:=1 to qmax do {pack it}
  begin  a:=b+q_char(q);@/
    triec_link(triec_back(a)):=triec_link(a);
    triec_back(triec_link(a)):=triec_back(a);@/
    triec_char(a):=si(q_char(q));
    triec_link(a):=q_link(q);
    triec_back(a):=q_back(q);
    if a>triec_max then triec_max:=a;
  end;
  triec_base_used(b):=true;
  firstc_fit:=b
end;

@ The threshold for attempting a first-fit packing is 3 transitions, which
is lower than for the pattern trie because speed is more important here.

@<Set |b| to the count trie base location...@>=
if qmax>3 then a:=triec_back(triec_max+1) @+else a:=0;
loop  begin a:=triec_link(a); b:=a-q_char(1);@/
  @<Ensure |triec| linked up to |b+num_ASCII_codes|@>;
  if triec_base_used(b) then goto not_found;
  for q:=qmax downto 2 do
  if triec_char(b+q_char(q))<>min_packed then goto not_found;
  goto found;
  not_found: end;
found:

@ @<Ensure |triec| linked up to |b+num_ASCII_codes|@>=
if b>triec_kmax-num_ASCII_codes then
  begin if triec_kmax=triec_size then
    overflow(triec_size:1,' count trie nodes');
  print(triec_kmax div 1024:1, 'K ');
  if triec_kmax>triec_size-4096 then triec_kmax:=triec_size
    else Incr(triec_kmax)(4096);
  end;
while triec_bmax<b do
  begin incr(triec_bmax);
  triec_base_used(triec_bmax):=false;
  triec_char(triec_bmax+last_ASCII_code):=min_packed;
  triec_link(triec_bmax+last_ASCII_code):=triec_bmax+num_ASCII_codes;
  triec_back(triec_bmax+num_ASCII_codes):=triec_bmax+last_ASCII_code;
  end

@ [See |unpack|.]

@p procedure unpackc(@!b: triec_pointer);
var c: internal_code; @!a: triec_pointer;
begin  qmax:=1;
for c:=cmin to cmax do {search for transitions belonging to this state}
  begin  a:=b+c;
  if so(triec_char(a))=c then {found one}
    begin q_char(qmax):=c;
    q_link(qmax):=triec_link(a);
    q_back(qmax):=triec_back(a);
    incr(qmax);@/
    triec_back(triec_link(0)):=a;
    triec_link(a):=triec_link(0);
    triec_link(0):=a; triec_back(a):=0;
    triec_char(a):=min_packed;
    end;
  end;
triec_base_used(b):=false;
end;

@ [See |insert_pattern|.]  Patterns being inserted into the count trie are
always substrings of the current word, so they are contained in the array
|word| with length |pat_len| and finishing position |fpos|.

@p function insertc_pat(@!fpos: word_index): triec_pointer;
var spos: word_index; @!a, @!b: triec_pointer;
begin  spos:=fpos-pat_len; {starting position of pattern}
  incr(spos); b:=triec_root+word[spos]; a:=triec_link(b);
  while (a>0) and (spos<fpos) do {follow existing trie}
  begin  incr(spos); Incr(a)(word[spos]);
    if so(triec_char(a))<>word[spos] then
    @<Insert critical count transition, possibly repacking@>;
    b:=a; a:=triec_link(a);
  end;
  q_link(1):=0; q_back(1):=0; qmax:=1;
  while spos<fpos do {insert rest of pattern}
  begin  incr(spos); q_char(1):=word[spos];
    a:=firstc_fit;
    triec_link(b):=a;
    b:=a+word[spos];
    incr(triec_count);
  end;
  insertc_pat:=b;
  incr(pat_count);
end;

@ @<Insert critical count transition, possibly repacking@>=
begin  if triec_char(a)=min_packed then {lucky}
  begin  triec_link(triec_back(a)):=triec_link(a);
  triec_back(triec_link(a)):=triec_back(a);
  triec_char(a):=si(word[spos]);
  triec_link(a):=0;
  triec_back(a):=0;
  if a>triec_max then triec_max:=a;
  end
else  begin  {have to repack}
  unpackc(a-word[spos]);@/
  q_char(qmax):=word[spos];
  q_link(qmax):=0;
  q_back(qmax):=0;
  a:=firstc_fit;
  triec_link(b):=a;
  Incr(a)(word[spos]);
  end;
incr(triec_count);
end

@* Input and output.
For some \PASCAL\ systems output files must be closed before the program
terminates; it may also be necessary to close input files. Since
standard \PASCAL\ does not provide for this, we use \.{WEB} macros and
will say |close_out(f)| resp.\ |close_in(f)|; these macros should not
produce errors or system messages, even if a file could not be opened
successfully.
@^system dependencies@>

@d close_out(#)==close(#) {close an output file}
@d close_in(#)==do_nothing {close an input file}

@<Globals...@>=
@!dictionary, @!patterns, @!translate, @!patout, @!pattmp: text_file;

@ When reading a line from one of the input files (|dictionary|,
|patterns|, or |translate|) the characters read from that line (padded
with blanks if necessary) are to be placed into the |buf| array. Reading
lines from the |dictionary| file should be as efficient as possible
since this is part of \.{PATGEN}'s ``inner loop''. Standard \PASCAL,
unfortunately, does not provide for this; consequently the \.{WEB} macro
|read_buf| defined below should be optimized if possible. For many
\PASCAL's this can be done with |read_ln(f,buf)| where |buf| is declared
as \PASCAL\ string (i.e., as \&{packed} \&{array} |[1..any]| \&{of}
|char|), for others a string type with dynamic length can be used.
@^inner loop@>@^system dependencies@>

@d read_buf(#)== {reads a line from input file |#| into |buf| array}
  begin buf_ptr:=0;
  while not eoln(#) do
    begin if (buf_ptr>=max_buf_len) then bad_input('Line too long');
@.Line too long@>
    incr(buf_ptr); read(#,buf[buf_ptr]);
    end;
  read_ln(#);
  while buf_ptr<max_buf_len do
    begin incr(buf_ptr); buf[buf_ptr]:=' ';
    end;
  end

@<Globals...@>=
@!buf: array[1..max_buf_len] of text_char; {array to hold lines of input}
@!buf_ptr: 0..max_buf_len; {index into |buf|}

@ When an error is caused by bad input data we say |bad_input(#)| in
order to display the contents of the |buf| array before terminating with
an error message.

@d print_buf== {print contents of |buf| array}
  begin buf_ptr:=0;
  repeat incr(buf_ptr); print(buf[buf_ptr]);
  until buf_ptr=max_buf_len;
  print_ln(' ');
  end
@d bad_input(#)==begin print_buf; error(#); end

@ The |translate| file may specify the values of \.{\\lefthyphenmin} and
\.{\\righthyphenmin} as well as the external representation and
collating sequence of the `letters' used by the language. In addition
replacements may be specified for the characters |'-'|, |'*'|, and |'.'|
representing hyphens in the word list. If the |translate| file is empty
(or does not exist) default values will be used.

@p procedure read_translate;
label done;
var c: text_char;
@!n: integer;
@!j: ASCII_code;
@!bad: boolean;
@!lower: boolean;
@!i: dot_type; @!s, @!t: trie_pointer;
begin imax:=edge_of_word;
reset(translate);
if eof(translate) then
  @<Set up default character translation tables@>
else  begin read_buf(translate); @<Set up hyphenation data@>;
  cmax:=last_ASCII_code-1;
  while not eof(translate) do @<Set up representation(s) for a letter@>;
  end;
close_in(translate);
print_ln('left_hyphen_min = ',left_hyphen_min:1,
         ', right_hyphen_min = ',right_hyphen_min:1,
         ', ',imax-edge_of_word:1,' letters');
cmax:=imax;
end;

@ @<Globals...@>=
@!imax: internal_code; {largest |internal_code| assigned so far}
@!left_hyphen_min, @!right_hyphen_min: dot_type;

@ @<Set up default...@>=
begin left_hyphen_min:=2; right_hyphen_min:=3;
for j:="A" to "Z" do
  begin incr(imax);
  c:=xchr[j+"a"-"A"]; xclass[c]:=letter_class; xint[c]:=imax;
  xext[imax]:=c;
  c:=xchr[j]; xclass[c]:=letter_class; xint[c]:=imax;
  end;
end

@ The first line of the |translate| file must contain the values
of \.{\\lefthyphenmin} and \.{\\righthyphenmin} in columns 1--2 and
3--4. In addition columns~5, 6, and~7 may (optionally) contain
replacements for the default characters |'.'|, |'-'|, and |'*'|
respectively, representing hyphens in the word list.
If the values specified for \.{\\lefthyphenmin} and \.{\\righthyphenmin}
are invalid (e.g., blank) new values are read from the terminal.

@<Set up hyphenation...@>=
bad:=false;
n:=0;
if buf[1]=' ' then do_nothing
else if xclass[buf[1]]=digit_class then n:=xint[buf[1]]@+
else bad:=true;
if xclass[buf[2]]=digit_class then n:=10*n+xint[buf[2]]@+
else bad:=true;
if (n>=1)and(n<max_dot) then left_hyphen_min:=n@+else bad:=true;
n:=0;
if buf[3]=' ' then do_nothing
else if xclass[buf[3]]=digit_class then n:=xint[buf[3]]@+
else bad:=true;
if xclass[buf[4]]=digit_class then n:=10*n+xint[buf[4]]@+
else bad:=true;
if (n>=1)and(n<max_dot) then right_hyphen_min:=n@+
else bad:=true;
if bad then
  begin bad:=false;
  repeat print('left_hyphen_min, right_hyphen_min: '); get_input(n1,n2);@/
    if (n1>=1)and(n1<max_dot)and(n2>=1)and(n2<max_dot) then
      begin left_hyphen_min:=n1; right_hyphen_min:=n2;
      end
    else  begin n1:=0;
      print_ln('Specify 1<=left_hyphen_min,right_hyphen_min<=',
                max_dot-1:1,' !');
      end;
  until n1>0;
  end;
for j:=err_hyf to found_hyf do
  begin if buf[j+4]<>' ' then xhyf[j]:=buf[j+4];
  if xclass[xhyf[j]]=invalid_class then xclass[xhyf[j]]:=hyf_class@+
  else bad:=true;
  end;
xclass['.']:=hyf_class; {in case the default has been changed}
if bad then bad_input('Bad hyphenation data')
@.Bad hyphenation data@>

@ Each following line is either a comment or specifies the external
representations for one `letter' used by the language. Comment lines
start with two equal characters (e.g., are blank) and are ignored.
Other lines contain the external representation of the lower case
version and an arbitrary number of `upper case versions' of a letter
preceded and separated by a delimiter and followed by two consecutive
delimiters; the delimiter may be any character not occurring in either
version.

@<Set up repres...@>=
begin read_buf(translate); buf_ptr:=1; lower:=true;
while not bad do {lower and then upper case version}
  begin pat_len:=0;
  repeat if buf_ptr<max_buf_len then incr(buf_ptr) @+ else bad:=true;
    if buf[buf_ptr]=buf[1] then
      if pat_len=0 then goto done
      else  begin if lower then
          begin if imax=last_ASCII_code then
            begin print_buf; overflow(num_ASCII_codes:1,' letters');
            end;
          incr(imax); xext[imax]:=xchr[pat[pat_len]];
          end;
        c:=xchr[pat[1]];
        if pat_len=1 then
          begin if xclass[c]<>invalid_class then bad:=true;
          xclass[c]:=letter_class; xint[c]:=imax;
          end
        else @<Insert a letter into pattern trie@>;
        end
    else if pat_len=max_dot then bad:=true
    else  begin incr(pat_len); pat[pat_len]:=get_ASCII(buf[buf_ptr]);
      end;
  until (buf[buf_ptr]=buf[1])or bad;
  lower:=false;
  end;
done: if bad then bad_input('Bad representation');
@.Bad representation@>
end

@ When the (lower or upper case) external representation of a letter
consists of more than one character and the corresponding |ASCII_code|
values have been placed into the |pat| array we store them in
the pattern trie.  [See |insert_pattern|.] Since this `external subtrie'
starts at |trie_link(trie_root)| it does not interfere with normal
patterns. The output field of leaf nodes contains the |internal_code|
and the link field distinguishes between lower and upper case letters.

@<Insert a letter...@>=
begin if xclass[c]=invalid_class then xclass[c]:=escape_class;
if xclass[c]<>escape_class then bad:=true;
i:=0; s:=trie_root; t:=trie_link(s);
while (t>trie_root) and (i<pat_len) do {follow existing trie}
  begin  incr(i); Incr(t)(pat[i]);
  if so(trie_char(t))<>pat[i] then
    @<Insert critical transition, possibly repacking@>
  else if trie_outp(t)>0 then bad:=true;
  s:=t; t:=trie_link(s);
  end;
if t>trie_root then bad:=true;
q_link(1):=0; q_outp(1):=0; qmax:=1;
while i<pat_len do {insert rest of pattern}
  begin  incr(i); q_char(1):=pat[i];
  t:=first_fit;
  trie_link(s):=t;
  s:=t+pat[i];
  incr(trie_count);
  end;
trie_outp(s):=imax;
if not lower then trie_link(s):=trie_root;
end

@ The |get_letter| \.{WEB} macro defined here will be used in
|read_word| and |read_patterns| to obtain the |internal_code|
corresponding to a letter externally represented by a multi-character
sequence (starting with an |escape_class| character).

@d get_letter(#)==
  begin t:=trie_root;
  loop  begin t:=trie_link(t)+xord[c];
    if so(trie_char(t))<>xord[c] then bad_input('Bad representation');
@.Bad representation@>
    if trie_outp(t)<>0 then
      begin #:=trie_outp(t); goto done;
      end;
    if buf_ptr=max_buf_len then c:=' '
    else  begin incr(buf_ptr); c:=buf[buf_ptr];
      end;
    end;
  done: end

@ In order to prepare for the output phase we store all but the last of
the \\{ASCII\_codes} of the external representation of each `lower case
letter' in the pattern count trie which is no longer used at that time.
The recursive |find_letters| procedure traverses the `external subtrie'.

@p procedure find_letters(@!b: trie_pointer; @!i: dot_type);@/
  {traverse subtries of family |b|; |i| is current depth in trie}
var c: ASCII_code; {a local variable that must be saved on recursive calls}
@!a: trie_pointer; {does not need to be saved}
@!j: dot_type; {loop index}
@!l: triec_pointer;
begin if i=1 then init_count_trie;
for c:=cmin to last_ASCII_code do {find transitions belonging to this family}
  begin a:=b+c;
  if so(trie_char(a))=c then {found one}
    begin pat[i]:=c;
    if trie_outp(a)=0 then find_letters(trie_link(a),i+1)
    else if trie_link(a)=0 then {this is a lower case letter}
      @<Insert external representation for a letter into count trie@>;
    end;
  end;
end;

@ Starting from |triec_root+trie_outp(a)| we proceed through link fields
and store all \\{ASCII\_codes} except the last one in the count trie;
the last character has already been stored in the |xext| array.

@<Insert external...@>=
begin l:=triec_root+trie_outp(a);
for j:=1 to i-1 do
  begin if triec_max=triec_size then
    overflow(triec_size:1,' count trie nodes');
  incr(triec_max); triec_link(l):=triec_max; l:=triec_max;
  triec_char(l):=si(pat[j]);
  end;
triec_link(l):=0;
end

@ During the output phase we will say |write_letter(i)(f)| and
|write(f,xext[i])| to write the lower case external representation of
the letter with internal code |i| to file |f|: |xext[i]| is the last
character of the external representation whereas the \.{WEB} macro
|write_letter| defined here writes all preceding characters (if any).

@d write_letter_end(#)==while l>0 do
  begin write(#,xchr[so(triec_char(l))]); l:=triec_link(l);
  end
@d write_letter(#)==l:=triec_link(triec_root+#); write_letter_end

@* Routines for traversing pattern tries.
At the end of a pass, we traverse the count trie using the following
recursive procedure, selecting good and bad patterns and inserting them
into the pattern trie.

@p procedure traverse_count_trie(@!b: triec_pointer; @!i: dot_type);@/
{traverse subtries of family |b|; |i| is current depth in trie}
var c: internal_code; {a local variable that must be saved on recursive calls}
    @!a: triec_pointer; {does not need to be saved}
begin
for c:=cmin to cmax do {find transitions belonging to this family}
  begin  a:=b+c;
  if so(triec_char(a))=c then {found one}
    begin  pat[i]:=c;
    if i<pat_len then traverse_count_trie(triec_link(a),i+1)
    else @<Decide what to do with this pattern@>;
    end;
  end;
end;

@ When we have come to the end of a pattern, |triec_good(a)| and
|triec_bad(a)| contain the number of times this pattern helps or hinders
the cause.  We use the counts to determine if this pattern should be
selected, or if it is hopeless, or if we can't decide yet.  In the latter
case, we set |more_to_come| true to indicate that there might still be
good patterns extending the current type of patterns.

@<Decide what to do...@>=
if good_wt*triec_good(a)<thresh then {hopeless pattern}
begin   insert_pattern(max_val,pat_dot);
  incr(bad_pat_count)
end else
if good_wt*triec_good(a)-bad_wt*triec_bad(a)>=thresh then {good pattern}
begin   insert_pattern(hyph_level,pat_dot);
  incr(good_pat_count);
  Incr(good_count)(triec_good(a));
  Incr(bad_count)(triec_bad(a));
end else
  more_to_come:=true

@ Some global variables are used to accumulate statistics about the
performance of a pass.

@<Globals...@>=
@!good_pat_count, @!bad_pat_count: integer; {number of patterns added at end
  of pass}
@!good_count, @!bad_count, @!miss_count: integer; {hyphen counts}
@!level_pattern_count: integer; {number of good patterns at level}
@!more_to_come: boolean;

@ The recursion in |traverse_count_trie| is initiated by the following
procedure, which also prints some statistics about the patterns chosen.
The ``efficiency'' is an estimate of pattern effectiveness.

@d bad_eff==(thresh/good_wt)

@p procedure collect_count_trie;
begin  good_pat_count:=0; bad_pat_count:=0;
  good_count:=0; bad_count:=0;
  more_to_come:=false;
  traverse_count_trie(triec_root,1); @/
  print(good_pat_count:1,' good and ',
    bad_pat_count:1,' bad patterns added');
  Incr(level_pattern_count)(good_pat_count);
  if more_to_come then print_ln(' (more to come)') @+else print_ln(' ');
  print('finding ',good_count:1,' good and ',bad_count:1,' bad hyphens');
  if good_pat_count>0 then
  print_ln(', efficiency = ',
    good_count/(good_pat_count+bad_count/bad_eff):1:2)
  else print_ln(' ');
  print_ln('pattern trie has ',trie_count:1,' nodes, ',@|
    'trie_max = ',trie_max:1,', ',op_count:1,' outputs');
end;

@ At the end of a level, we traverse the pattern trie and delete bad
patterns by removing their outputs.  If no output remains, the node is
also deleted.

@p function delete_patterns(@!s: trie_pointer): trie_pointer;@/
{delete bad patterns in subtrie |s|, return 0 if entire subtrie freed,
  otherwise |s|}
var c: internal_code; @!t: trie_pointer; @!all_freed: boolean;
  {must be saved on recursive calls}
    @!h, @!n: op_type; {do not need to be saved}
begin  all_freed:=true;
  for c:=cmin to cmax do {find transitions belonging to this family}
  begin  t:=s+c;
    if so(trie_char(t))=c then
    begin  @<Link around bad outputs@>;
      if trie_link(t)>0 then
        trie_link(t):=delete_patterns(trie_link(t));
      if (trie_link(t)>0) or (trie_outp(t)>0) or (s=trie_root) then
        all_freed:=false
      else
        @<Deallocate this node@>;
    end;
  end;
  if all_freed then {entire state is freed}
  begin  trie_base_used(s):=false;
    s:=0;
  end;
  delete_patterns:=s;
end;

@ @<Link around bad outputs@>=
begin  h:=0;
  hyf_nxt(0):=trie_outp(t);
  n:=hyf_nxt(0);
  while n>0 do
  begin  if hyf_val(n)=max_val then hyf_nxt(h):=hyf_nxt(n)
      else h:=n;
    n:=hyf_nxt(h);
  end;
  trie_outp(t):=hyf_nxt(0);
end

@ Cells freed by |delete_patterns| are put at the end of the free list.

@<Deallocate this node@>=
begin  trie_link(trie_back(trie_max+1)):=t;
  trie_back(t):=trie_back(trie_max+1);
  trie_link(t):=trie_max+1;
  trie_back(trie_max+1):=t;
  trie_char(t):=min_packed;@/
  decr(trie_count);
end

@ The recursion in |delete_patterns| is initiated by the following
procedure, which also prints statistics about the number of nodes deleted,
and zeros bad outputs in the hash table.  Note that the hash table may
become somewhat disorganized when more levels are added, but this defect
isn't serious.

@p procedure delete_bad_patterns;
var old_op_count: op_type;
    @!old_trie_count: trie_pointer;
    @!t: trie_pointer; @!h: op_type;
begin  old_op_count:=op_count;
  old_trie_count:=trie_count;@/
  t:=delete_patterns(trie_root);
  for h:=1 to max_ops do
  if hyf_val(h)=max_val then
  begin  hyf_val(h):=0; decr(op_count);
  end;
  print_ln(old_trie_count-trie_count:1,' nodes and ',@|
    old_op_count-op_count:1,' outputs deleted');
  qmax_thresh:=7; {pattern trie will be sparser because of deleted
    patterns}
end;

@ After all patterns have been generated, we will traverse the pattern
trie and output all patterns.  Note that if a pattern appears more than
once, only the maximum value at each position will be output.

@p procedure output_patterns(@!s: trie_pointer; @!pat_len: dot_type);@/
{output patterns in subtrie |s|; |pat_len| is current depth in trie}
var c: internal_code; {must be saved on recursive calls}
@!t: trie_pointer; @!h: op_type; @!d: dot_type;@/
@!l: triec_pointer; {for |write_letter|}
begin for c:=cmin to cmax do
  begin t:=s+c;
  if so(trie_char(t))=c then
    begin pat[pat_len]:=c;
    h:=trie_outp(t);
    if h>0 then @<Output this pattern@>;
    if trie_link(t)>0 then output_patterns(trie_link(t),pat_len+1);
    end;
  end;
end;

@ @<Output this pattern@>=
begin  for d:=0 to pat_len do hval[d]:=0;
  repeat  d:=hyf_dot(h);
    if hval[d]<hyf_val(h) then hval[d]:=hyf_val(h);
    h:=hyf_nxt(h);
  until h=0;
  if hval[0]>0 then write(patout,xdig[hval[0]]);
  for d:=1 to pat_len do
  begin  write_letter(pat[d])(patout); write(patout,xext[pat[d]]);
    if hval[d]>0 then write(patout,xdig[hval[d]]);
  end;
  write_ln(patout);
end

@* Dictionary processing routines.
The procedures in this section are the ``inner loop'' of the pattern
generation process.  To speed the program up, key parts of these routines
could be coded in machine language.
@^inner loop@>

@<Globals...@>=
@!word: array[word_index] of internal_code; {current word}
@!dots: array[word_index] of hyf_type; {current hyphens}
@!dotw: array[word_index] of digit; {dot weights}
@!hval: array[word_index] of val_type; {hyphenation values}
@!no_more: array[word_index] of boolean; {positions `knocked out'}
@!wlen: word_index; {length of current word}
@!word_wt: digit; {global word weight}
@!wt_chg: boolean; {indicates |word_wt| has changed}

@ The words in the |dictionary| consist of the `letters' used by the
language. ``Dots'' between letters can be one of four possibilities:
|'-'| indicating a hyphen, |'*'| indicating a found hyphen, |'.'|
indicating an error, or nothing; these are represented internally by the
four values |is_hyf|, |found_hyf|, |err_hyf|, and |no_hyf| respectively.
When reading a word we will, however, convert |err_hyf| into |no_hyf|
and |found_hyf| into |is_hyf| thus ignoring whether a hyphen has or
has not been found by a previous set of patterns.

@<Prepare to read dictionary@>=
xclass['.']:=invalid_class; {in case the default has been changed}
xclass[xhyf[err_hyf]]:=hyf_class; xint[xhyf[err_hyf]]:=no_hyf;
xclass[xhyf[is_hyf]]:=hyf_class; xint[xhyf[is_hyf]]:=is_hyf;
xclass[xhyf[found_hyf]]:=hyf_class; xint[xhyf[found_hyf]]:=is_hyf;

@ Furthermore single-digit word weights are allowed.  A digit at
the beginning of a word indicates a global word weight that is to be
applied to all following words (until the next global word weight).  A
digit at some intercharacter position indicates a weight for that position
only.

The |read_word| procedure scans a line of input representing a word,
and places the letters into the array |word|, with |word[1]=word[wlen]=
edge_of_word|.  The dot appearing between |word[dpos]| and |word[dpos+1]|
is placed in |dots[dpos]|, and the corresponding dot weight in
|dotw[dpos]|.

@p procedure read_word;
label done, found;
var c: text_char;
@!t: trie_pointer;
begin read_buf(dictionary);
word[1]:=edge_of_word; wlen:=1; buf_ptr:=0;
repeat incr(buf_ptr); c:=buf[buf_ptr];
  case xclass[c] of
  space_class: goto found;
  digit_class:
    if wlen=1 then {global word weight}
      begin if xint[c]<>word_wt then wt_chg:=true;
      word_wt:=xint[c];
      end
    else dotw[wlen]:=xint[c]; {dot weight}
  hyf_class: dots[wlen]:=xint[c]; {record the dot |c|}
  letter_class: {record the letter |c|}
    begin incr(wlen);
    if wlen=max_len then
      begin print_buf; overflow('word length=',max_len:1);
      end;
    word[wlen]:=xint[c]; dots[wlen]:=no_hyf; dotw[wlen]:=word_wt;
    end;
  escape_class: {record a multi-character sequence starting with |c|}
    begin incr(wlen);
    if wlen=max_len then
      begin print_buf; overflow('word length=',max_len:1);
      end;
    get_letter(word[wlen]); dots[wlen]:=no_hyf; dotw[wlen]:=word_wt;
    end;
  invalid_class: bad_input('Bad character');
@.Bad character@>
  end;
until buf_ptr=max_buf_len;
found: incr(wlen); word[wlen]:=edge_of_word;
end;

@ Here is a procedure that uses the existing patterns to hyphenate the
current word.  The hyphenation value applying between the characters
|word[dpos]| and |word[dpos+1]| is stored in |hval[dpos]|.

In addition, |no_more[dpos]| is set to |true| if this position is
``knocked out'' by either a good or bad pattern at this level.  That is,
if the pattern with current length and hyphen position is a superstring of
either a good or bad pattern at this level, then we don't need to collect
count statistics for the pattern because it can't possibly be chosen in
this pass.  Thus we don't even need to insert such patterns into the count
trie, which saves a good deal of space.

@p procedure hyphenate;
label done;
var spos, @!dpos, @!fpos: word_index;
    @!t: trie_pointer; @!h: op_type; @!v: val_type;
begin
for spos:=wlen-hyf_max downto 0 do
  begin  no_more[spos]:=false; hval[spos]:=0;
    fpos:=spos+1; t:=trie_root+word[fpos];
    repeat  h:=trie_outp(t);
      while h>0 do @<Store output |h| in the |hval| and
        |no_more| arrays, and advance |h|@>;
      t:=trie_link(t);
      if t=0 then goto done;
      incr(fpos); Incr(t)(word[fpos]);
    until so(trie_char(t))<>word[fpos];
  done:
  end;
end;

@ In order to avoid unnecessary test (and range check violations) the
globals |hyf_min|, |hyf_max|, and |hyf_len| are set up such that only
positions from |hyf_min| up to |wlen-hyf_max| of the |word| array need
to be checked, and that words with |wlen<hyf_len| need not to be checked
at all.

@<Globals...@>=
@!hyf_min, @!hyf_max, @!hyf_len: word_index; {limits for legal hyphens}

@ @<Prepare to read dictionary@>=
hyf_min:=left_hyphen_min+1; hyf_max:=right_hyphen_min+1;
hyf_len:=hyf_min+hyf_max;

@ @<Store output |h| in the |hval| and |no_more| arrays, and advance |h|@>=
begin  dpos:=spos+hyf_dot(h);
  v:=hyf_val(h);
  if (v<max_val) and (hval[dpos]<v) then hval[dpos]:=v;
  if (v>=hyph_level) then {check if position knocked out}
  if ((fpos-pat_len)<=(dpos-pat_dot))and((dpos-pat_dot)<=spos) then
    no_more[dpos]:=true;
  h:=hyf_nxt(h);
end

@ The |change_dots| procedure updates the |dots| array representing the
printing values of the hyphens.  Initially, hyphens (and correctly
found hyphens) in the word list are represented by |is_hyf| whereas
non-hyphen positions (and erroneous hyphens) are represented by |no_hyf|.
Here these values are increased by one for each hyphen found by the
current patterns, thus changing |no_hyf| into |err_hyf| and |is_hyf|
into |found_hyf|. The routine also collects statistics about the number
of good, bad, and missed hyphens.

@d incr_wt(#)==Incr(#)(dotw[dpos])

@p procedure change_dots;
var dpos: word_index;
begin  for dpos:=wlen-hyf_max downto hyf_min do
  begin if odd(hval[dpos]) then incr(dots[dpos]);
  if dots[dpos]=found_hyf then incr_wt(good_count)
  else if dots[dpos]=err_hyf then incr_wt(bad_count)
  else if dots[dpos]=is_hyf then incr_wt(miss_count);
  end;
end;

@ The following procedure outputs the word as hyphenated by the current
patterns, including any word weights. Hyphens inhibited by the values of
\.{\\lefthyphenmin} and \.{\\righthyphenmin} are output as well.

@p procedure output_hyphenated_word;
var dpos: word_index;@/
@!l: triec_pointer; {for |write_letter|}
begin if wt_chg then {output global word weight}
  begin write(pattmp,xdig[word_wt]); wt_chg:=false
  end;
for dpos:=2 to wlen-2 do
  begin write_letter(word[dpos])(pattmp); write(pattmp,xext[word[dpos]]);
  if dots[dpos]<>no_hyf then write(pattmp,xhyf[dots[dpos]]);
  if dotw[dpos]<>word_wt then write(pattmp,xdig[dotw[dpos]]);
  end;
write_letter(word[wlen-1])(pattmp); write_ln(pattmp,xext[word[wlen-1]]);
end;

@ For each dot position in the current word, the |do_word| routine first
checks to see if we need to consider it.  It might be knocked out or a dot
we don't care about.  That is, when considering hyphenating patterns, for
example, we don't need to count hyphens already found.  If a relevant dot
is found, we increment the count in the count trie for the corresponding
pattern, inserting it first if necessary.  At this point of the program
range check violations may occur if these counts are incremented beyond
|triec_max|; it would, however, be too expensive to prevent this.
@^range check violations@>

@p procedure do_word;
label continue, done;
var spos, @!dpos, @!fpos: word_index; @!a: triec_pointer;
    @!goodp: boolean;
begin  for dpos:=wlen-dot_max downto dot_min do
  begin  spos:=dpos-pat_dot;
    fpos:=spos+pat_len;
    @<Check this dot position and |goto continue| if don't care@>;
    incr(spos); a:=triec_root+word[spos];
    while spos<fpos do
    begin  {follow existing count trie}
      incr(spos);
      a:=triec_link(a)+word[spos];
      if so(triec_char(a))<>word[spos] then
      begin   {insert new count pattern}
        a:=insertc_pat(fpos);
        goto done;
      end;
    end;
  done:  if goodp then incr_wt(triec_good(a))
    @+else incr_wt(triec_bad(a));
  continue:
  end;
end;

@ The globals |good_dot| and |bad_dot| will be set to |is_hyf| and
|no_hyf|, or |err_hyf| and |found_hyf|, depending on whether the current
level is odd or even, respectively. The globals |dot_min|, |dot_max|,
and |dot_len| are analogous to |hyf_min|, |hyf_max|, and |hyf_len|
defined earlier.

@<Globals...@>=
@!good_dot, @!bad_dot: hyf_type; {good and bad hyphens at current level}
@!dot_min, @!dot_max, @!dot_len: word_index; {limits for legal dots}

@ @<Prepare to read dictionary@>=
if procesp then
  begin dot_min:=pat_dot; dot_max:=pat_len-pat_dot;
  if dot_min<hyf_min then dot_min:=hyf_min;
  if dot_max<hyf_max then dot_max:=hyf_max;
  dot_len:=dot_min+dot_max;
  if odd(hyph_level) then
    begin good_dot:=is_hyf; bad_dot:=no_hyf;
    end
  else begin good_dot:=err_hyf; bad_dot:=found_hyf;
    end;
  end;

@ If the dot position |dpos| is out of bounds, knocked out, or a ``don't
care'', we skip this position.  Otherwise we set the flag |goodp|
indicating whether this is a good or bad dot.

@<Check this dot position...@>=
if no_more[dpos] then goto continue;
if dots[dpos]=good_dot then goodp:=true else
if dots[dpos]=bad_dot then goodp:=false else goto continue;

@ If |hyphp| is set to |true|, |do_dictionary| will write out a copy of
the dictionary as hyphenated by the current set of patterns.  If |procesp|
is set to |true|, |do_dictionary| will collect pattern statistics for
patterns with length |pat_len| and hyphen position |pat_dot|, at level
|hyph_level|.

@<Globals...@>=
@!procesp, @!hyphp: boolean;
@!pat_dot: dot_type; {hyphen position, measured from beginning of pattern}
@!hyph_level: val_type; {hyphenation level}
@!filnam: packed array[1..8] of char; {for |pattmp|}

@ The following procedure makes a pass through the word list, and also
prints out statistics about number of hyphens found and storage used by
the count trie.

@p procedure do_dictionary;
begin  good_count:=0; bad_count:=0; miss_count:=0;
  word_wt:=1; wt_chg:=false;
  reset(dictionary);@/
  @<Prepare to read dictionary@>@;@/
  if procesp then
  begin  init_count_trie;
    print_ln('processing dictionary with pat_len = ',pat_len:1,
      ', pat_dot = ',pat_dot:1);
  end;
  if hyphp then
    begin filnam:='pattmp. ';
    filnam[8]:=xdig[hyph_level];
    rewrite(pattmp,filnam);
    print_ln('writing pattmp.', xdig[hyph_level]);
    end;
  @<Process words until end of file@>;@/
  close_in(dictionary);@/
  print_ln(' ');
  print_ln(good_count:1,' good, ',bad_count:1,' bad, ',
    miss_count:1,' missed');
  if (good_count+miss_count)>0 then
    print_ln((100*good_count/(good_count+miss_count)):1:2,' %, ',
      (100*bad_count/(good_count+miss_count)):1:2,' %, ',
      (100*miss_count/(good_count+miss_count)):1:2,' %');
  if procesp then
    print_ln(pat_count:1,' patterns, ',triec_count:1,
      ' nodes in count trie, ','triec_max = ',triec_max:1);
  if hyphp then close_out(pattmp);
end;

@ @<Process words...@>=
while not eof(dictionary) do
  begin read_word;
  if wlen>=hyf_len then {short words are never hyphenated}
    begin hyphenate; change_dots;
    end;
  if hyphp then if wlen>2 then output_hyphenated_word;
     {empty words are ignored}
  if procesp then if wlen>=dot_len then do_word;
  end

@* Reading patterns.
Before beginning a run, we can read in a file of existing patterns.  This
is useful for extending a previous pattern selection run to get some more
levels.  (Since these runs are quite time-consuming, it is convenient to
choose patterns one level at a time, pausing to look at the results of the
previous level, and possibly amending the dictionary.)

@p procedure read_patterns;
label done, found;
var c: text_char;
@!d: digit;
@!i: dot_type;
@!t: trie_pointer;
begin xclass['.']:=letter_class; xint['.']:=edge_of_word;
level_pattern_count:=0; max_pat:=0;
reset(patterns);
while not eof(patterns) do
  begin  read_buf(patterns);
  incr(level_pattern_count);@/
  @<Get pattern and dots and |goto found|@>;
  found: @<Insert pattern@>;
  end;
close_in(patterns);
print_ln(level_pattern_count:1,' patterns read in');@/
print_ln('pattern trie has ',trie_count:1,' nodes, ',@|
  'trie_max = ',trie_max:1,', ',op_count:1,' outputs');
end;

@ The global variable |max_pat| keeps track of the largest hyphenation
value found in any pattern.

@<Globals...@>=
@!max_pat: val_type;

@ When a new pattern has been input into |buf|, we extract the letters of
the pattern, and insert the hyphenation values (digits) into the |hval|
array.

@<Get pattern...@>=
pat_len:=0; buf_ptr:=0; hval[0]:=0;
repeat incr(buf_ptr); c:=buf[buf_ptr];
  case xclass[c] of
  space_class: goto found;
  digit_class:
    begin d:=xint[c];
    if d>=max_val then bad_input('Bad hyphenation value');
@.Bad hyphenation value@>
    if d>max_pat then max_pat:=d;
    hval[pat_len]:=d;
    end;
  letter_class:
    begin incr(pat_len); hval[pat_len]:=0; pat[pat_len]:=xint[c];
    end;
  escape_class: {record a multi-character sequence starting with |c|}
    begin incr(pat_len); hval[pat_len]:=0; get_letter(pat[pat_len]);
    end;
  hyf_class, invalid_class: bad_input('Bad character');
@.Bad character@>
  end;
until buf_ptr=max_buf_len

@ Then we insert the pattern for each non-vanishing hyphenation value.
In addition we check that |edge_of_word| (i.e., |'.'|) occurs only as
first or last character; otherwise we would have to perform a time
consuming test for the end of a word in the |hyphenate| procedure.

@<Insert pattern@>=
if pat_len>0 then {avoid spurious patterns}
  for i:=0 to pat_len do
    begin if hval[i]<>0 then insert_pattern(hval[i],i);
    if i>1 then if i<pat_len then if pat[i]=edge_of_word then
      bad_input('Bad edge_of_word');
@.Bad edge_of_word@>
    end

@* The main program.
This is where \.{PATGEN} actually starts.  We initialize the pattern trie,
get |hyph_level| and |pat_len| limits from the terminal, and generate
patterns.

@p begin initialize;
init_pattern_trie;
read_translate;
read_patterns;
procesp:=true; hyphp:=false;@/
repeat print('hyph_start, hyph_finish: '); get_input(n1,n2);@/
  if (n1>=1)and(n1<max_val)and(n2>=1)and(n2<max_val) then
    begin hyph_start:=n1; hyph_finish:=n2;
    end
  else  begin n1:=0;
    print_ln('Specify 1<=hyph_start,hyph_finish<=',max_val-1:1,' !');
    end;
until n1>0;
hyph_level:=max_pat; {in case |hyph_finish<hyph_start|}
for i:=hyph_start to hyph_finish do
  begin  hyph_level:=i; level_pattern_count:=0;
  if hyph_level>hyph_start then print_ln(' ')
  else if hyph_start<=max_pat then
    print_ln('Largest hyphenation value ',max_pat:1,
             ' in patterns should be less than hyph_start');@/
@.Largest hyphenation value@>
  repeat print('pat_start, pat_finish: '); get_input(n1,n2);@/
    if (n1>=1)and(n1<=n2)and(n2<=max_dot) then
      begin pat_start:=n1; pat_finish:=n2;
      end
    else  begin n1:=0;
      print_ln('Specify 1<=pat_start<=pat_finish<=',max_dot:1,' !');
      end;
  until n1>0;
  repeat print('good weight, bad weight, threshold: ');
    get_input(n1,n2,n3);@/
    if (n1>=1)and(n2>=1)and(n3>=1) then
      begin good_wt:=n1; bad_wt:=n2; thresh:=n3;
      end
    else  begin n1:=0;
      print_ln('Specify good weight, bad weight, threshold>=1 !');
      end;
  until n1>0;
  @<Generate a level@>;
  delete_bad_patterns;
  print_ln('total of ',level_pattern_count:1,
    ' patterns at hyph_level ',hyph_level:1);
  end;
find_letters(trie_link(trie_root),1); {prepare for output}
rewrite(patout);
output_patterns(trie_root,1);
close_out(patout);@/
@<Make final pass to hyphenate word list@>;
end_of_PATGEN:
end.

@ The patterns of a given length (at a given level) are chosen with dot
positions ordered in an ``organ-pipe'' fashion.  For example, for
|pat_len=4| we choose patterns for different dot positions in the order 2,
1, 3, 0, 4.  The variable |dot1| controls this iteration in a clever
manner.

@<Globals...@>=
@!n1, @!n2, @!n3: integer; {accumulators}
@!i: val_type; {loop index: hyphenation level}
@!j: dot_type; {loop index: pattern length}
@!k: dot_type; {loop index: hyphen position}
@!dot1: dot_type;
@!more_this_level: array[dot_type] of boolean;

@ The array |more_this_level| remembers which positions are permanently
``knocked out''.  That is, if there aren't any possible good patterns
remaining at a certain dot position, we don't need to consider longer
patterns at this level containing that position.

@<Generate a level@>=
for k:=0 to max_dot do more_this_level[k]:=true;
for j:=pat_start to pat_finish do
  begin  pat_len:=j; pat_dot:=pat_len div 2; dot1:=pat_dot*2;
  repeat pat_dot:=dot1-pat_dot; dot1:=pat_len*2-dot1-1;
    if more_this_level[pat_dot] then
      begin do_dictionary; collect_count_trie;
      more_this_level[pat_dot]:=more_to_come;
      end;
  until pat_dot=pat_len;
  for k:=max_dot downto 1 do
    if not more_this_level[k-1] then more_this_level[k]:=false;
  end

@ When all patterns have been found, the user has a chance to see what
they do.  The resulting \.{pattmp} file can be used as the new
`dictionary' if we want to continue pattern generation from this point.

@<Make final pass to hyphenate word list@>=
procesp:=false; hyphp:=true;@/
print('hyphenate word list? ');
get_input_ln(buf[1]);
if (buf[1]='Y') or (buf[1]='y') then do_dictionary

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

@* Index.
Pointers to error messages appear here together with the section numbers
where each ident\-i\-fier is used.