summaryrefslogtreecommitdiff
path: root/Master/texmf-dist/doc/eplain/base/userdef.texi
blob: dfc5fcc4497f3b39592d5fca1cb4b33d96e56602 (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
@c This is part of the Eplain manual.  Public domain.

@node User definitions
@chapter User definitions

This chapter describes definitions that are meant to be used directly
in a document.  When appropriate, ways to change the default
formatting are described in subsections.

@menu
* Diagnostics::               Tracing information.
* Rules::                     Changing the default rule dimensions.
* Citations::                 Using BibTeX and Eplain to make bibliographies.
* Displays::                  Changing the formatting of math displays.
* Time of day::               Producing the time of day.
* Lists::                     Producing numbered and unordered lists.
* Verbatim listing::          Producing text just as it appears.
* Contents::                  Making a table of contents.
* Cross-references::          Symbolic references to equations, figures, etc.
* Page references::           Symbolic references to page numbers.
* Equation references::       Symbolic references to equation numbers.
* Indexing::                  Creating and typesetting indexes.
* Justification::             Ragged left, ragged right, centered.
* Tables::                    Producing ordered tables.
* Margins::                   Changing the margins directly.
* Multiple columns::          Getting output in two columns.
* Footnotes::                 Autonumbered footnotes; changing formatting.
* Fractions::                 A better way to produce fractions in text.
* Paths::                     Allowing line breaks in pathnames.
* Logos::                     Various logos.
* Boxes::                     Producing filled or open rectangles.
* Checking for PDF output::   Checking for pdfTeX in PDF mode.
* Loading LaTeX packages::    Support for LaTeX packages under plain TeX.
@end menu


@node Diagnostics
@section Diagnostics

@cindex diagnostics
@cindex tracing
Plain @TeX{} provides the @code{\tracingall} command, to turn on the
maximum amount of tracing possible in @TeX{}.  The (usually voluminous)
output from @code{\tracingall} goes both on the terminal and into the
transcript file.
@findex tracingall
It is sometimes easier to have the output go only to the transcript
file, so you can peruse it at your leisure and not obscure other output
to the terminal.  So, Eplain provides the command @code{\loggingall}.
@findex loggingall
(For some reason, this command is available in Metafont, but not in
@TeX{}.)

It is also sometimes useful to see the complete contents of boxes. 
@code{\tracingboxes} does this.  (It doesn't affect whether or not the
contents
@findex tracingboxes
are shown on the terminal.)

You can turn off all tracing with @code{\tracingoff}.
@findex tracingoff

You can also turn logging on and off globally, so you don't have to
worry about whether or not you're inside a group at the time of command.
These variants are named @code{\gloggingall}
@findex gloggingall
and @code{\gtracingall}.
@findex gtracingall

Finally, if you write your own help messages (see @code{\newhelp}
@cindex help messages
@cindex error messages
in @cite{The @TeX{}book}), you want a convenient way to break lines in
them.  This is what @TeX{}'s @code{\newlinechar} parameter is for;
@cindex newlinechar
however, plain @TeX{} doesn't set @code{\newlinechar}.  Therefore,
Eplain defines it to be the character @code{^^J}.

For example, one of Eplain's own error messages is defined as follows:
@example
\newhelp\envhelp@{Perhaps you forgot to end the previous^^J%
   environment? I'm finishing off the current group,^^J%
   hoping that will fix it.@}%
@end example


@node Rules
@section Rules

The default dimensions of rules are defined in chapter@tie{}21 of the
@cite{The @TeX{}book}.  To sum up what is given there, the ``thickness''
of rules is
@cindex rule thickness
0.4pt by default.  Eplain defines three parameters that let you change
this dimension: @code{\hruledefaultheight}, @code{\hruledefaultdepth},
@findex hruledefaultheight
@findex hruledefaultdepth
and @code{\vruledefaultwidth}.  By default, they are defined as
@findex vruledefaultwidth
@cite{The @TeX{}book} describes.

But it would be wrong to redefine @code{\hrule} and @code{\vrule}.  For
one thing, some macros in plain @TeX{} depend on the default dimensions
being used; for another, rules are used quite heavily, and the
performance impact of making it a macro can be noticeable.  Therefore,
to take advantage of the default rule parameters, you must use
@code{\ehrule}
@findex ehrule
and @code{\evrule}.
@findex evrule


@node Citations
@section Citations

@cindex citations
@cindex bibliographies
Bibliographies are part of almost every technical document.  To handle
them easily, you need two things: a program to do the tedious
formatting, and a way to cite references by labels, rather than by
numbers.  The Bib@TeX{} program, written by Oren Patashnik, takes care
@cindex Bib@TeX{}
@cindex Patashnik, Oren
of the first item; the citation commands in @LaTeX{}, written to be used
@cindex @LaTeX{}
with Bib@TeX{}, take care of the second.  Therefore,
Eplain adopts the use of Bib@TeX{}, and virtually the same interface as
@LaTeX{}.

The general idea is that you put citation commands in the text of your
document, and commands saying where the bibliography data is.  When you
run @TeX{}, these commands produce output on the file with the same root
name as your document (by default) and the extension @file{.aux}.
@pindex .aux @r{file}
@findex jobname
Bib@TeX{} reads this file.  You should put the bibliography data in a
file or files with the extension @file{.bib}. Bib@TeX{} writes out a
file with the same root
@pindex .bib @r{file}
name as your document and extension @file{.bbl}.  Eplain reads this file
@pindex .bbl @r{file}
the next time you run your document through @TeX{}.  (It takes
multiple passes to get everything straight, because usually after seeing
your bibliography typeset, you want to make changes in the @file{.bib}
file, which means you have to run Bib@TeX{} again, which means you have
to run @TeX{} again@dots{})  An annotated example of the whole process is
given below.  

If your document has more than one bibliography---for example, if it
is a collection of papers---you can tell Eplain to use a different root
name for the @file{.bbl} file by defining the control sequence
@code{\bblfilebasename}.
@findex bblfilebasename
The default definition is simply @code{\jobname}.

See the document @cite{Bib@TeX{}ing} (whose text is in the file
@file{btxdoc.tex}, which should be in the Eplain distribution you got)
for information on how to write your @t{.bib} files.  Both the
Bib@TeX{} and the Eplain distributions contain several examples, also.

The @code{\cite}
@findex cite
command produces a citation in the text of your document.  The exact
printed form the citation will take is under your control;
@pxref{Formatting citations}.  @code{\cite} takes one
required argument, a comma-separated list of cross-reference labels
(@pxref{Cross-references}, for exactly what characters are allowed in
such labels).  Warning: spaces in this list are taken as part of the
following label name, which is probably not what you expect.
@cindex citations, undefined
The @code{\cite} command also produces a command
in the @t{.aux} file that tells Bib@TeX{} to retrieve the given reference(s)
from the @t{.bib} file.  @code{\cite} also takes one optional argument,
which you specify within square brackets, as in @LaTeX{}.  This text is
simply typeset after the citations.  (See the example below.)

Eplain can create hypertext links for citations pointing to the relevant
bibliography entries; @pxref{Citation hyperlinks}.

Another command, @code{\nocite},
@findex nocite
puts the given reference(s) into the bibliography, but produces nothing
in the text.

The @code{\bibliography}
@findex bibliography
command is next.  It serves two purposes: producing the typeset
bibliography, and telling Bib@TeX{} the root names of the @t{.bib}
files.  Therefore, the argument to @code{\bibliography} is a comma
separated list of the @t{.bib} files (without the @samp{.bib}).  Again,
spaces in this list are significant.

You tell Bib@TeX{} the particular style in which you want your
bibliography typeset with one more command:
@code{\bibliographystyle}.
@findex bibliographystyle
The argument to this is a single filename @var{style}, which tells
Bib@TeX{} to look for a file @var{style}@t{.bst}.
@pindex .bst @r{files}
See the document @cite{Designing Bib@TeX{} styles} (whose text is in the
@file{btxhak.tex}) for information on how to write your own styles.

Eplain automatically reads the citations from the @t{.aux} file when
your job starts.

If you don't want to see the messages about undefined citations, you
can say @code{\xrefwarningfalse} before making any citations.
@findex xrefwarningfalse
Eplain automatically does this if the @t{.aux} file does not exist.
You can restore the default by saying @code{\xrefwarningtrue}.

Here is a @TeX{} input file that illustrates the various commands.

@example
\input eplain                    % Reads the .aux file.
Two citations to Knuthian works:
  \cite[note]@{surreal,concrete-math@}.
\beginsection@{References.@}\par   % Title for the bibliography.
\bibliography@{knuth@}             % Use knuth.bib for the labels.
\bibliographystyle@{plain@}        % Number the references.
\end                             % End of the document.
@end example
@cindex Knuth, Donald Ervin
@cindex Graham, Ronald L.
@cindex numbered references
@cindex references, numbered

If we suppose that this file was named @file{citex.tex} and that the
bibliography data is in @file{knuth.bib} (as the @code{\bibliography}
command says), the following commands do what's required.  (@samp{$ }
represents the shell prompt.)

@example
$ tex citex       (produces undefined citation messages)
$ bibtex citex    (read knuth.bib and citex.aux, write citex.bbl)
$ tex citex       (read citex.bbl, still have undefined citations)
$ tex citex       (one more time, to resolve the references)
@end example

@pindex texi2dvi
@noindent (The @command{texi2dvi} program can help you automate this
process, @pxref{Invoking Eplain}.)

The output looks something like (because we used the @t{plain}
bibliography style):
  
@quotation
Two citations to Knuthian works: [2,1 note].

@b{References}
@tex
@frenchspacing
@end tex

[1] Ronald L. Graham, Donald E. Knuth, and Oren Patashnik.  @i{Concrete
Mathematics}. Addison-Wesley, Reading, Massachusetts, 1989.

[2] Donald E. Knuth. @i{Surreal Numbers}. Addison-Wesley, Reading,
Massachusetts, 1974.
@end quotation

See the Bib@TeX{} documentation for information on how to write the
bibliography databases, and the bibliography styles that are available.
(If you want your references printed with names, as in [Knu74], instead
of numbered, the bibliography style is @code{alpha}.)
@cindex alphanumeric references
@cindex references, alphanumeric

@menu
* Formatting citations::        Changing the way citations are printed.
* Formatting bibliographies::   Changing the way bibliographies are printed.
@end menu


@node Formatting citations
@subsection Formatting citations

@cindex citations, formatting

You may wish to change Eplain's formatting of citations; i.e., the
result of your @code{\cite} commands.  By default, the citation labels
are printed one after another, separated by commas and enclosed in
brackets, using the main text font.  Some formats require other styles,
such as superscripted labels.  You can accomodate such formats by
redefining the following macros.

@table @code
@itemx \printcitestart
@item \printcitefinish
@findex printcitestart
@findex printcitefinish
Eplain expands these macros at the begining and end of the list of
citations for each @code{\cite} command.  By default, they produce a
@samp{[} and @samp{]}, respectively.

@item \printbetweencitations
@findex printbetweencitations
If a @code{\cite} command has multiple citations, as in
@code{\cite@{acp,texbook@}}, Eplain expands this macro in between each
pair of citations.  By default, it produces a comma followed by a space.

@item \printcitenote
@findex printcitenote
This macro takes one argument, which is the optional note to the
@code{\cite} command.  If the @code{\cite} command had no note, this
macro isn't used.  Otherwise, it should print the note.  By default, the
note is preceded with a comma and a space.
@end table


Here is an example, showing you could produce citations as
superscripted labels, with the optional notes in parentheses.

@example
\def\printcitestart@{\unskip $^\bgroup@}
\def\printbetweencitations@{,@}
\def\printcitefinish@{\egroup$@}
\def\printcitenote#1@{\hbox@{\sevenrm\space (#1)@}@}
@end example


@node Formatting bibliographies
@subsection Formatting bibliographies

@cindex bibliography, formatting the

You may wish to change Eplain's formatting of the bibliography,
especially with respect to the fonts that are used.  Therefore, Eplain
provides the following control sequences:

@table @code

@item \biblabelwidth
@findex biblabelwidth
This control sequence represents a @code{\dimen} register, and its value
is the width of the widest label in the bibliography.  Although it is
unlikely you will ever want to redefine it, you might want 
to use it if you redefine @code{\biblabelprint}, below.

@item \biblabelprint
@findex biblabelprint
This macro takes one argument, the label to print.  By default, the
label is put in a box of width @code{\biblabelwidth}, and is followed by
an enspace.  When you want to change the spacing around the labels, this
is the right macro to redefine.

@item \biblabelcontents
@findex biblabelcontents
This macro also takes one argument, the label to print.  By default, the
label is printed using the font @code{\bblrm} (below), and enclosed in
brackets.  When you want to change the appearance of the label, but not
the spacing around it, this is the right macro to redefine.

@item \bblrm
@findex bblrm
@cindex bibliography fonts
The default font used for printing the bibliography.

@item \bblem
@findex bblem
The font used for printing the titles and other ``emphasized'' material.

@item \bblsc
@findex bblsc
In some styles, authors' names are printed in a caps-and-small-caps
font.  In those cases, this font is used.

@item \bblnewblock
@findex bblnewblock
This is invoked between each of the parts of a bibliography entry.  The
default is to leave some extra space between the parts; you could
redefine it to start each part on a new line (for example).  A part is
simply a main element of the entry; for example, the author is a part. 
(It was @LaTeX{} that introduced the (misleading, as far as I am
concerned) term `block' for this.)

@item \biblabelextraspace
@findex biblabelextraspace
Bibliography entries are typeset with a hanging indentation of
@code{\biblabelwidth} plus this.  The default is @code{.5em}, where the
em width is taken from the @code{\bblrm} font.  If you want to change
this, you should do it inside @code{\bblhook}.

@item \bblhook
@findex bblhook
@cindex bibliography items, extra space between
This is expanded before reading the @t{.bbl} file.  By
default, it does nothing.  You could, for example, define it to set the
bibliography fonts, or produce the heading for the references.  Two
spacing parameters must be changed inside @code{\bblhook}:
@code{\parskip}, which produces extra space between the items; and
@code{\biblabelextraspace}, which is described above.
(By the way, @code{\hookappend} won't work with @code{\bblhook}, despite
the names. Just use @code{\def}.)

@end table

If you are really desperate, you can also hand-edit the @t{.bbl} file
that Bib@TeX{} produces to do anything you wish.


@node Displays
@section Displays

@cindex displays, left-justifying
@cindex mathematics displays, formatting
@cindex left-justification of displays

By default, @TeX{} centers displayed material.  (Displayed material is
just whatever you put between @code{$$}'s---it's not necessarily
mathematics.)  Many layouts would be better served if the displayed
material was left-justified.  Therefore, Eplain provides the command
@code{\leftdisplays},
@findex leftdisplays
which indents displayed material by @code{\parindent} plus
@code{\leftskip}, plus @code{\leftdisplayindent}.
@findex leftdisplayindent

You can go back to centering displays with @code{\centereddisplays}.
@findex centereddisplays
(It is usually poor typography to have both centered and left-justified
displays in a single publication, though.)

@code{\leftdisplays} also changes the plain @TeX{} commands that deal
with alignments inside math displays,
@code{\displaylines},
@findex displaylines
@code{\eqalignno},
@findex eqalignno
and @code{\leqalignno},
@findex leqalignno
to produce left-justified text.  You can still override this formatting
by inserting @code{\hfill} glue, as explained in @cite{The @TeX{}book}.

@menu
* Formatting displays::         General formatting of displays.
@end menu


@node Formatting displays
@subsection Formatting displays

If you want some other kind of formatting, you can write a definition
of your own, analogous to @code{\leftdisplays}.  You need only make sure
that @code{\leftdisplaysetup}
@findex leftdisplaysetup
is called at the beginning of every display (presumably by invoking it
in @TeX{}'s @code{\everydisplay} parameter), and to define
@code{\generaldisplay}.
@findex generaldisplay

@code{\leftdisplays} expands the old value of @code{\everydisplay}
before calling @code{\leftdisplaysetup}, so that any changes you have made
to it won't be lost.  That old token list as available as the value of
the token register @code{\previouseverydisplay}.
@findex previouseverydisplay


@node Time of day
@section Time of day

@cindex time of day
@cindex date

@TeX{} provides the day, month, and year as numeric quantities (unless
your @TeX{} implementation is woefully deficient).  Eplain provides some
control sequences to make them a little more friendly to humans. 

@code{\monthname}
@findex monthname
produces the name of the current month, abbreviated to three letters.

@code{\fullmonthname}
@findex fullmonthname
produces the name of the current month, unabbreviated (in English).

@code{\timestring}
@findex timestring
produces the current time, as in `1:14 p.m.'

@code{\timestamp}
@findex timestamp
produces the current date and time, as in `23 Apr 64  1:14 p.m.'.
(Except the spacing is slightly different.)

@code{\today}
@findex today
produces the current date, as in `23 April 1964'.


@node Lists
@section Lists

@cindex lists
@cindex numbered lists
@cindex ordered list
@cindex unordered lists

Many documents require lists of items, either numbered or simply
enumerated.  Plain @TeX{} defines one macro to help with creating lists,
@code{\item}, but that is insufficient in many cases.  Therefore,
Eplain provides two pairs of commands:

@table @code

@itemx \numberedlist @dots{} \endnumberedlist
@item \orderedlist @dots{} \endorderedlist
@findex numberedlist
@findex endnumberedlist
@findex orderedlist
@findex endorderedlist
These commands (they are synonyms) produce a list with the items
numbered sequentially, starting from one.  A nested @code{\numberedlist}
labels the items with lowercase letters, starting with `a'.  Another
nested @code{\numberedlist} labels the items with roman numerals.  Yet
more deeply nested numbered lists label items with @samp{*}.

@item \unorderedlist @dots{} \endunorderedlist
@findex unorderedlist
@findex endunorderedlist
This produces a list with the items labelled with small black boxes
(``square bullets''). A nested @code{\unorderedlist} labels items with
em-dashes.  Doubly (and deeper) nested unordered lists label items with
`*'s.

@end table

The two kinds of lists can be nested within each other, as well.

In both kinds of lists, you begin an item with @code{\li}.
@findex li
An item may continue for several paragraphs.  Each item starts a
paragraph.

You can give @code{\li} an optional argument, a cross-reference label.
It's defined to be the ``marker'' for the current item.  This is useful
if the list items are numbered.  You can produce the value of the label
with @code{\xrefn}.  @xref{Cross-references}.

Eplain can create hypertext links for the markers produced by
@code{\xrefn} pointing to the relevant list item; @pxref{List
hyperlinks}.

You can also say @code{\listcompact}
@findex listcompact
right after @code{\numberedlist} or @code{\unorderedlist}.  The items in
the list will then not have any extra space between them
(@pxref{Formatting lists}).  You might want to do this if the items in
this particular list are short.

Here is an example:
@example
\numberedlist\listcompact
\li The first item.
\li The second item.

The second paragraph of the second item.
\endnumberedlist
@end example

@menu
* Formatting lists::            Changing how the lists look.
@end menu


@node Formatting lists
@subsection Formatting lists

@cindex lists, formatting

Several registers define the spacing associated with lists.  It is
likely that their default values won't suit your particular layout.

@table @code
@item \abovelistskipamount, \belowlistskipamount
@findex abovelistskipamount
@findex belowlistskipamount
The vertical glue inserted before and after every list, respectively.

@item \interitemskipamount
@findex interitemskipamount
The vertical glue inserted before each item except the first. 
@code{\listcompact} resets this to zero, as mentioned above.

@item \listleftindent, \listrightindent
@findex listleftindent
@findex listrightindent
@code{\listrightindent} is the amount of space by which the list is
indented on the right; i.e., it is added to @code{\rightskip}. 
@code{\listleftindent} is the amount of space, @emph{relative to}
@code{\parindent}, by which the list is indented on the left.  Why treat
the two parameters differently?  Because (a)@tie{}it is more useful to
make the list indentation depend on the paragraph indentation;
(b)@tie{}footnotes aren't formatted right if @code{\parindent} is reset
to zero.

@end table

The three vertical glues are inserted by macros, and preceded by
penalties: @code{\abovelistskip}
@findex abovelistskip
does @code{\vpenalty\abovelistpenalty}
@findex abovelistpenalty
and then @code{\vskip\abovelistskip}.  @code{\belowlistskip}
@findex belowlistskip
and @code{\interitemskip}
@findex interitemskip
are analogous.

In addition, the macro @code{\listmarkerspace}
@findex listmarkerspace
is called to separate the item label from the item text.  This is set to
@code{\enspace} by default.

If you want to change the labels on the items, you can redefine these
macros:
@code{\numberedmarker}
@findex numberedmarker
or @code{\unorderedmarker}.
@findex unorderedmarker
The following registers might be useful if you do:

@table @code
@item \numberedlistdepth, \unorderedlistdepth
@findex numberedlistdepth
@findex unorderedlistdepth
These keep track of the depth of nesting of the two kinds of lists. 

@item \itemnumber, \itemletter
@findex itemnumber
@findex itemletter
These keep track of the number of items that have been seen in the current
numbered list.  They are both integer registers.  The difference is that
@code{\itemnumber} starts at one, and @code{\itemletter} starts at 97,
i.e., lowercase `a'.

@end table

You can also redefine the control sequences that are used internally,
if you want to do something radically different:  @code{\beginlist}
@findex beginlist
is invoked to begin both kinds of lists; @code{\printitem}
@findex printitem
is invoked to print the label (and space following the label) for each
item; and @code{\endlist}
@findex endlist
is invoked to end both kinds of
lists.
@cindex item labels, changing
@cindex labels on items, changing


@node Verbatim listing
@section Verbatim listing

@cindex verbatim listing
@cindex listing files
@cindex files, verbatim listing of
It is sometimes useful to include a file verbatim in your document;
for example, part of a computer program.  The @code{\listing} 
@findex listing
command is given one argument, a filename, and produces the contents of
that file in your document.  @code{\listing} expands @code{\listingfont}
to set the current font.  The default value of @code{\listingfont}
@findex listingfont
is @code{\tt}.

You can take arbitrary actions before reading the file by defining the macro
@code{\setuplistinghook}.
@findex setuplistinghook
This is expanded just before the file is input.

If you want to have line numbers on the output, you can say
@code{\let\setuplistinghook = \linenumberedlisting}.
@findex linenumberedlisting
The line numbers are stored in the count register @code{\lineno} while
the file is being read.  You can redefine the macro
@code{\printlistinglineno} to change how they are printed.

You can produce in-line verbatim text in your document with @code{\verbatim}.
@findex verbatim
End the text with @code{|endverbatim}.  If you need a @samp{|} in the text,
double it.  If the first character of the verbatim text is a space, use
@code{| }. (@code{| } will work elsewhere in the argument, too, but
isn't necessary.)

For example:

@example
\verbatim| ||\#%&!|endverbatim
@end example

@noindent produces @code{ |\#%&!}.

Line breaks and spaces in the verbatim text are preserved.

@findex verbatimescapechar
@cindex escape character, changing verbatim
You can change the verbatim escape character from the default @samp{|}
with @code{\verbatimescapechar @var{char}}; for example, this changes
it to @samp{@@}.

@example
\verbatimescapechar \@@
@end example

@noindent The backslash is not necessary in some cases, but is in
others, depending on the catcode of the character.  The argument to
@code{\verbatimescapechar} is used as @code{\catcode `@var{char}}, so
the exact rules follow that for @code{\catcode}.

Because @code{\verbatim} must change the category code of special
characters, calling inside a macro definition of your own does not work
properly.  For example:

@example
\def\mymacro@{\verbatim &#%|endverbatim@}% Doesn't work!
@end example

To accomplish this, you must change the category codes yourself before
making the macro definition.  Perhaps @code{\uncatcodespecials} will
help you (@pxref{Category codes}).


@node Contents
@section Contents

@cindex table of contents
@cindex contents

Producing a table of contents that is both useful and aesthetic is one
of the most difficult design problems in any work.  Naturally, Eplain
does not pretend to solve the design problem.  Collecting the raw data
for a table of contents, however, is much the same across documents. 
Eplain uses an auxiliary file with extension @file{.toc}
@pindex .toc @r{file}
(and the same root name as your document) to save the information.

To write an entry for the table of contents, you say
@code{\writetocentry@{@var{part}@}@{@var{text}@}},
@findex writetocentry
where @var{part} is the type of part this entry is, e.g.,
@samp{chapter}, and @var{text} is the text of the title. 
@code{\writetocentry} puts an entry into the @t{.toc} file that looks
@findex toc@dots{}entry
like @code{\toc@var{part}entry@{@var{text}@}@{@var{page number}@}}.  The
@var{text} is written unexpanded.

@findex writenumberedtocentry
A related command, @code{\writenumberedtocentry}, takes one additional
argument, the first token of which is expanded at the point of the
@code{\writenumberedtocentry}, but the rest of the argument is not
expanded.  The usual application is when the parts of the document are
numbered.  On the other hand, the one-level expansion allows you to use
the argument for other things as well (author's names in a proceedings,
say), and not have accents or other control sequences expanded.  The
downside is that if you @emph{want} full expansion of the third
argument, you don't get it---you must expand it yourself, before you
call @code{\writenumberedtocentry}.

For example:

@example
\writenumberedtocentry@{chapter@}@{A $\sin$ wave@}@{\the\chapno@}
\writetocentry@{section@}@{A section title@}
@end example

@noindent Supposing @code{\the\chapno} expanded to @samp{3} and that the
@code{\write}'s occurred on pages eight and nine, respectively, the
above writes the following to the @t{.toc} file:

@example
\tocchapterentry@{A $\sin$ wave@}@{3@}@{8@}
\tocsectionentry@{A section title@}@{9@}
@end example

@findex readtocfile
You read the @t{.toc} file with the command @code{\readtocfile}.
Naturally, whatever @code{\toc@dots{} entry} commands that were written
to the file must be defined when @code{\readtocfile} is invoked.  Eplain
has minimal definitions for @code{\tocchapterentry},
@code{\tocsectionentry}, and @code{\tocsubsectionentry}, just to prevent
undefined control sequence errors in common cases.  They aren't suitable
for anything but preliminary proofs.

Each of @code{\writetocentry} and @code{\writenumberedtocentry} opens
the @t{.toc} file for writing, thereby deleting the information from the
previous run.  You should therefore arrange that @code{\readtocfile} be
called @emph{before} the first call to a @code{\writetoc@dots{}} macro.
@code{\readtocfile} does not itself delete the information
from the @t{.toc} file, so that you can call it several times,
e.g., to create both a short
@cindex table of contents, short
and normal table of contents.  (To produce this in particular, define
@code{\tocsectionentry} to produce nothing while you are reading
@t{.toc} file for a short table of contents (@pxref{Macro arguments}).)

On the other hand, if you don't want to rewrite the @t{.toc} file at
all, perhaps because you are only running @TeX{} on part of your
manuscript, you can set @code{\rewritetocfilefalse}.
@findex ifrewritetocfile
@findex rewritetocfile @r{(conditional)}

By default, the @file{.toc} file has the root @code{\jobname}.  If your
document has more than one contents---for example, if it is a collection
of papers, some of which have their own contents---you can tell Eplain
to use a different root name by defining the control sequence
@code{\tocfilebasename}.
@findex tocfilebasename

@cindex list of figures
@cindex list of tables
@findex definecontentsfile
In addition to the usual table of contents, you may want to have a list
of figures, list of tables, or other such contents-like list. You can do
this with @code{\definecontentsfile@{@var{abbrev}@}}.  All of the
above commands are actually a special case that Eplain predefines with

@example
\definecontentsfile@{toc@}
@end example

@noindent The @var{abbrev} is used both for the file extension and in
the control sequence names.



@node Cross-references
@section Cross-references

@cindex cross-references
It is often useful to refer the reader to other parts of your document;
but putting literal page, section, equation, or whatever numbers in the
text is certainly a bad thing.

Eplain therefore provides commands for symbolic cross-references.  It
uses an auxiliary file with extension @t{.aux}
@pindex .aux @r{file}
(and the same root name as your document) to keep track of the
information.  Therefore, it takes two passes to get the cross-references
right---one to write them out, and one to read them in.  Eplain
automatically reads the @t{.aux} file at the first reference; after
reading it, Eplain reopens it for writing.

You can control whether or not Eplain warns you about undefined
labels.  @xref{Citations}.

@cindex labels, characters valid in
Labels in Eplain's cross-reference commands can use characters of
category code eleven (letter), twelve (other), ten (space), three (math
shift), four (alignment tab), seven (superscript), or eight (subscript).
For example, @samp{(a1 $&^_} is a valid label (assuming the category
codes of plain @TeX{}), but @samp{%#\@{} has no valid characters.

You can also do symbolic cross-references for bibliographic citations
and list items.  @xref{Citations}, and @ref{Lists}.

Eplain can create hypertext links for the cross-references;
@pxref{Cross-reference hyperlinks}.

@menu
* Defining generic references::  
* Using generic references::    
@end menu


@node Defining generic references
@subsection Defining generic references

@cindex defining general references
@cindex references, defining general
@cindex cross-references, defining general

@findex definexref
Eplain provides the command @code{\definexref} for general
cross-references.  It takes three arguments: the name of the label (see
section above for valid label names), the value of the label (which can
be anything), and the ``class'' of the reference---whether it's a
section, or theorem, or what.  For example:

@example
\definexref@{sec-intro@}@{3.1@}@{section@}
@end example

@noindent Of course, the label value is usually generated by another
macro using @TeX{} count registers or some such.

@code{\definexref} doesn't actually define @var{label}; instead, it
writes out the definition to the @t{.aux} file, where Eplain will read
it on the next @TeX{} run.

The @var{class} argument is used by the @code{\ref} and @code{\refs}
commands.  See the next section.


@node Using generic references
@subsection Using generic references

@cindex defining general references
@cindex references, defining general
@cindex cross-references, defining general

To retrieve the value of the label defined via @code{\definexref} (see
the previous section), Eplain provides the following macros:

@table @code

@findex refn
@itemx \refn@{@var{label}@}
@findex xrefn
@item \xrefn@{@var{label}@}
@code{\refn} and @code{\xrefn} (they are synonyms) produce the bare
definition of @var{label}.  If @var{label} isn't defined, issue a
warning, and produce @var{label} itself instead, in typewriter.  (The
warning isn't given if @code{\xrefwarningfalse}.)
@findex xrefwarning @r{conditional}

@findex ref
@item \ref@{@var{label}@}
Given the class @var{c} for @var{label} (see the description of
@code{\definexref} in the previous section), expand the control sequence
@code{\@var{c} word} (if it's defined) followed by a tie.  Then call
@code{\refn} on @var{label}.  (Example below.)

@findex refs
@item \refs@{@var{label}@}
Like @code{\ref}, but append the letter @samp{s} to the
@code{\@dots{}word}.

@end table

The purpose of the @code{\@dots{}word} macro is to produce the word
`Section' or `Figure' or whatever that usually precedes the actual
reference number.

Here is an example:

@example
\def\sectionword@{Section@}
\definexref@{sec-intro@}@{3.1@}@{section@}
\definexref@{sec-next@}@{3.2@}@{section@}
See \refs@{sec-intro@} and \refn@{sec-next@} @dots{}
@end example

@noindent This produces `See Sections 3.1 and 3.2 @dots{}'


@node Page references
@section Page references

Eplain provides two commands for handling references to page numbers,
one for definition and one for use.

@table @code

@item \xrdef@{@var{label}@}
@findex xrdef
Define @var{label} to be the current page number.  This produces no
printed output, and ignores following spaces.

@item \xref@{@var{label}@}
@findex xref
Produce the text `p.@tie{}@var{pageno}', which is the usual form for
cross-references.  The @var{pageno} is actually @var{label}'s
definition; if @var{label} isn't defined, the text of the label itself
is printed.  The `p.@tie{}' prefix is defined by @code{\xrefpageword}.
@findex xrefpageword
Its default definition is @code{p.\thinspace}.

@end table

Eplain can create hypertext links for the page references; @pxref{Page
reference hyperlinks}.


@node Equation references
@section Equation references

@cindex equations, references to
@cindex equations, numbering
Instead of referring to pages, it's most useful if equation labels
refer to equation numbers.  Therefore, Eplain reserves a @code{\count}
register, @code{\eqnumber},
@findex eqnumber
for the current equation number, and increments it at each
numbered equation.  

Here are the commands to define equation labels and then refer to them:

@table @code

@item \eqdef@{@var{label}@}
@findex eqdef
This defines @var{label} to be the current value of @code{\eqnumber},
and, if the current context is not inner, then produces a @code{\eqno}
command.  (The condition makes it possible to use @code{\eqdef} in an
@code{\eqalignno} construction, for example.)  The text of the equation
number is produced using @code{\eqprint}.  @xref{Formatting equation
references}.

@cindex empty equation labels
@cindex labels, empty equation
@cindex equations, giving numbers to all
If @var{label} is empty, you still get an equation number (although
naturally you can't reliably refer to it).  This is useful if you want
to put numbers on all equations in your document, and you don't want to
think up unique labels.

@cindex empty equation labels, referring to
@cindex labels, empty equation, referring to
To refer to the last equation with the empty label, you just use the
empty label in one of the equation reference macros (see below).  This
can be handy when you want to refer to an equation shortly after its
definition, say, in the sentence following the displayed equation, and
do not intend to refer to the equation later.  But use this trick with
extreme caution:  if later you change the text and insert another
empty definition between the original definition and the reference,
the reference will start to refer to the new empty-labeled equation.

@item \eqdefn@{@var{label}@}
@findex eqdefn
This is like @code{\eqdef}, except it always omits the @code{\eqno}
command.  It can therefore be used in places where @code{\eqdef} can't;
for example, in a non-displayed equation.  The text of the equation
number is not produced, so you can also use it in the (admittedly
unusual) circumstance when you want to define an equation label but not
print that label.

@item \eqref@{@var{label}@}
@findex eqref
This produces a formatted reference to @var{label}.  If @var{label} is
undefined (perhaps because it is a forward reference), it just produces
the text of the label itself.  Otherwise, it calls @code{\eqprint}.

@item \eqrefn@{@var{label}@}
@findex eqrefn
This produces the cross-reference text for @var{label}.  That is, it
is like @code{\eqref}, except it doesn't call @code{\eqprint}.

@end table

@cindex equation labels, characters valid in
Equation labels can contain the same characters that are valid in
general cross-references.

Eplain can create hypertext links for the equation references;
@pxref{Equation reference hyperlinks}.


@menu
* Formatting equation references::  
* Subequation references::      
@end menu


@node Formatting equation references
@subsection Formatting equation references

@cindex equation numbers, formatting of
Both defining an equation label and referring to it should usually
produce output.  This output is produced with the @code{\eqprint} macro,
which takes one argument, the equation number being defined or referred
to.  By default, this just produces @samp{(@var{number})}, where
@var{number} is the equation number.  To produce the equation number in
a different font, or with different surrounding symbols, or whatever,
you can redefine @code{\eqprint}.
@findex eqprint
For example, the following definition would print all equation numbers
in italics.  (The extra braces define a group, to keep the font change
from affecting surrounding text.)

@example
\def\eqprint#1@{@{\it (#1)@}@}
@end example

In addition to changing the formatting of equation numbers, you might
to add more structure to the equation number; for example, you might
want to include the chapter number, to get equation numbers like
`(1.2)'.  To achieve this, you redefine @code{\eqconstruct}.
@findex eqconstruct
For example:

@example
\def\eqconstruct#1@{\the\chapternumber.#1@}
@end example

@noindent
(If you are keeping the chapter number in a count register named
@code{\chapternumber}, naturally.)

The reason for having both @code{\eqconstruct} and @code{\eqprint} may
not be immediately apparent.  The difference is that @code{\eqconstruct}
affects the text that cross-reference label is defined to be, while
@code{\eqprint} affects only what is typeset on the page.  The example
just below might help.

Usually, you want equation labels to refer to equation numbers.  But
sometimes you might want a more complicated text.  For example, you
might have an equation `(1)', and then have a variation several pages
later which you want to refer to as `(1*)'.

Therefore, Eplain allows you to give an optional argument (i.e.,
arbitrary text in square brackets) before the cross-reference label to
\eqdef.  Then, when you refer to the equation, that text is produced.
Here's how to get the example just mentioned:

@example
$$@dots{}\eqdef@{a-eq@}$$
@dots{}
$$@dots{}\eqdef[\eqrefn@{a-eq@}*]@{a-eq-var@}$$
In \eqref@{a-eq-var@}, we expand on \eqref@{a-eq@}, @dots{}
@end example

We use @code{\eqrefn} in the cross-reference text, not
@code{\eqref}, so that @code{\eqprint} is called only once.


@node Subequation references
@subsection Subequation references

@cindex equations, groups of
@cindex subequations, referring to
Eplain also provides for one level of substructure for equations.  That
is, you might want to define a related group of equations with numbers
like `2.1' and `2.2', and then be able to refer to the group as a whole:
``@dots{} in the system of equations (2)@dots{}''.

The commands to do this are @code{\eqsubdef} and
@findex eqsubdef
@code{\eqsubdefn}.
@findex eqsubdefn
They take one @var{label} argument like their counterparts above,
and generally behave in the same way.  The difference is in how they
construct the equation number: instead of using just @code{\eqnumber},
they also use another counter, @code{\subeqnumber}.
@findex subeqnumber
This counter is advanced by one at every @code{\eqsubdef} or
@code{\eqsubdefn}, and reset to zero at every @code{\eqdef} or
@code{\eqdefn}.

You use @code{\eqref} to refer to subequations as well as main
equations.

To put the two together to construct the text that the label will
produce, they use a macro @code{\eqsubreftext}.
@findex eqsubreftext
This macros takes two arguments, the ``main'' equation number (which,
because the equation label can be defined as arbitrary text, as
described in the previous section, might be anything at all) and the
``sub'' equation number (which is always just a number).  Eplain's
default definition just puts a period between them:
@example
\def\eqsubreftext#1#2@{#1.#2@}%
@end example

@noindent You can redefine @code{\eqsubreftext} to print however you
like.  For example, this definition makes the labels print as `2a',
`2b', and so on.
@example
\newcount\subref
\def\eqsubreftext#1#2@{%
  \subref = #2           % The space stops a <number>.
  \advance\subref by 96  % `a' is character code 97.
  #1\char\subref
@}
@end example

@noindent Sadly, we must define a new count register, @code{\subref},
instead of using the scratch count register @code{\count255}, because
@samp{#1} might include other macro calls which use @code{\count255}.


@node Indexing
@section Indexing

@cindex indexing
@cindex sorting an index

Eplain provides support for generating raw material for an index, and
for typesetting a sorted index. A separate program must do the actual
collection and sorting of terms, because @TeX{} itself has no support
for sorting.

Eplain can create hypertext links pointing from the index to the index
terms; @pxref{Index hyperlinks}.

@cindex URL for MakeIndex
@pindex makeindex
Eplain's indexing commands were designed to work with the program
MakeIndex, available from CTAN hosts in
@file{tex-archive/indexing/makeindex}; MakeIndex is also commonly
included in prepackaged @TeX{} distributions.  It is beyond the scope of
this manual to explain how to run MakeIndex, and all of its many
options.  See @url{http://www.ctan.org/tex-archive/indexing/makeindex/}

The basic strategy for indexing works like this:

@enumerate

@pindex .idx @r{files}
@item For a document @file{foo.tex}, Eplain's indexing commands (e.g.,
@code{\idx}; see the section `Indexing terms' below) write the raw index
material to @file{foo.idx}.

@pindex .ind @r{files}
@item MakeIndex reads @file{foo.idx}, collects and sorts the index, and
writes the result to @file{foo.ind}. 

@item Eplain reads and typesets @file{foo.ind} on a subsequent run of
@TeX{}. See the section `Typesetting an index' below.

@end enumerate

@pindex texi2dvi
@noindent The @command{texi2dvi} program can help you automate this
process, @pxref{Invoking Eplain}.

@cindex multiple indexes
@cindex indexes, multiple
@findex defineindex
If your document needs more than one index, each must have its own
file. Therefore, Eplain provides the command @code{\defineindex}, which
takes an argument that is a single letter, which replaces @samp{i} in
the filenames and in the indexing command names described below. For
example,

@example
\defineindex@{m@}
@end example

@noindent defines the command @code{\mdx} to write to the file
@file{foo.mdx}. Eplain simply does @code{\defineindex@{i@}} to define
the default commands.

@menu
* Indexing terms::          Specifying what to index.
* Typesetting an index::    Printing the sorted output.
* Customizing indexing::    Creating commands and specifying extra actions.
@end menu


@node Indexing terms
@subsection Indexing terms

@cindex indexing terms
@cindex silent indexing

Indexing commands in Eplain come in pairs: one command that only
writes the index entry to the @samp{.idx} file (see above section), and
one that also typesets the term being indexed. The former always starts
with @samp{s} (for ``silent''). In either case, the name always includes
@samp{@var{I}dx}, where @var{I} is the index letter, also described
above. Eplain defines the index @samp{i} itself, so that's what we'll
use in the names below.

@cindex subterm in indexing
The silent form of the commands take a subterm as a trailing optional
argument.  For example, @code{\sidx@{truth@}[definition of]} on page 75
makes an index entry that will eventually be typeset (by default) as

@display
truth
  definition of, 75
@end display

@cindex trailing spaces and indexing commands
@cindex spaces, trailing and indexing commands
@cindex indexing and trailing spaces
Also, the silent commands ignore trailing spaces. The non-silent ones do not.

@menu
* Indexing commands::       Making index entries.
* Modifying index entries:: Ranges, see/see also, page number typesetting.
* Proofing index terms::    Noting index entries in the margins.
@end menu


@node Indexing commands
@subsubsection Indexing commands

@cindex indexing commands
Here are the commands.

@itemize @bullet

@item
@findex sidx
@findex idx
@code{\sidx@{@var{term}@}[@var{subterm}]} makes an index entry for
@var{term}, optionally with subterm @var{subterm}.
@code{\idx@{@var{term}@}} also produces @var{term} as output. Example:

@example
\sidx@{truth@}[beauty of]
The beauty of truth is \idx@{death@}.
@end example

Subterms at the second and further levels can also be
specified in @var{subterm}, using the
@code{\idxsubentryseparator} character to separate
them.  This character is by default @samp{!}.

@item
@findex sidxname
@findex idxnameseparator
@findex idxname
@code{\sidxname@{@var{First M.}@}@{@var{von Last}@}[@var{subterm}]}
makes an index 
entry for @samp{@var{von Last}, @var{First M.}}. You can change the
@samp{, } by redefining @code{\idxnameseparator}.
@code{\idxname@{@var{First M.}@}@{@var{von Last}@}} also produces @var{First M. von
Last} as output. (These commands are useful special cases of @code{\idx}
and @code{\sidx}.) Example:

@example
\sidxname@{Richard@}@{Stark@}
\idxname@{Donald@}@{Westlake@} has written many kinds of novels, under
almost as many names.
@end example

@item
@findex sidxmarked
@findex idxmarked
@code{\sidxmarked\@var{cs}@{@var{term}@}[@var{subterm}]} makes an index
entry for @code{@var{term}[@var{subterm}]}, but @var{term} will be put
in the index as @code{\@var{cs}@{term@}}, but still sorted as just
@var{term}.  @code{\idxmarked\@var{cs}@{@var{term}@}} also typesets
@code{\@var{cs}@{term@}}.  This provides for the usual ways of changing
the typesetting of index entries. Example:

@example
\def\article#1@{``#1''@}
\sidxmarked\article@{Miss Elsa and Aunt Sophie@}
Peter Drucker's \idxmarked\article@{The Polanyis@} is a remarkable 
essay about a remarkable family.
@end example

@item
@findex idxsubmarked
@findex sidxsubmarked
@code{\sidxsubmarked@{@var{term}@}\@var{cs}@{subterm@}} makes an index
entry for @var{term}, @var{subterm} as usual, but also puts @var{subterm} in
the index as @code{\@var{cs}@{term@}}.
@code{\idxsubmarked@{@var{term}@}\@var{cs}@{subterm@}} also typesets
@code{@var{term} \@var{cs}@{subterm@}}, in the unlikely event that your
syntax is convoluted enough to make this useful. Example:

@example
\def\title#1@{@{\sl #1@}@}
\sidxsubmarked@{Anderson, Laurie@}\title@{Strange Angels@}
The \idxsubmarked@{Anderson@}\title@{Carmen@} is a strange twist.
@end example

@end itemize

@cindex index entry general sorting
@cindex sorting of index entries
The commands above rely on MakeIndex's feature for separating sorting of
an index entry's from its typesetting. You can use this directly by
specifying an index entry as @code{@var{sort}@@@var{typeset}}. For
example:

@example
\sidx@{Ap-weight@@$A_\pi$-weight@}
@end example

@noindent will sort as @code{Ap-weight}, but print with the proper math.
The @code{@@} here is MakeIndex's default character for this purpose.
See @url{http://www.ctan.org/tex-archive/indexing/makeindex/}. To make an index
entry with an @code{@@} in it, you have to escape it with a backslash;
Eplain provides no macros for doing this.

@findex afterindexterm @r{hook}
@cindex whatsits made by index entries
After any index command, Eplain runs
@code{\hookaction@{afterindexterm@}}. Because the index commands always
add a whatsit item to the current list, you may wish to preserve a
penalty or space past the new item. For example, given a conditional
@code{\if@@aftersctnhead} set true when you're at a section heading, you
could do:

@example
\hookaction@{afterindexterm@}@{\if@@aftersctnhead \nobreak \fi@}
@end example


@node Modifying index entries
@subsubsection Modifying index entries

@cindex modifying index entries' page numbers
@cindex index entries' page numbers, modifying

All the index commands described in the previous section take an initial
optional argument before the index term, which modify the index entry's
meaning in various ways.  You can specify only one of the following in
any given command, except that @code{begin} and @code{end} can be
specified together with @code{pagemarkup=@var{cs}} (separate them with
a comma without a following space, like this:
@code{[begin,pagemarkup=defn]}).

These work via MakeIndex's ``encapsulation'' feature. @xref{Customizing
indexing}, if you're not using the default characters for the
MakeIndex operators.  The other optional argument (specifying a subterm)
is independent of these.

Here are the possibilities:

@table @code

@item begin
@itemx end
@findex begin @r{for index entries}
@findex end @r{for index entries}
@cindex index entries and ranges
@cindex ranges and index entry
These mark an index entry as the beginning or end of a range. The index
entries must match exactly for MakeIndex to recognize them.
Example:

@example
\sidx[begin]@{future@}[Cohen, Leonard]
@dots{}
\sidx[end]@{future@}[Cohen, Leonard]
@end example

@noindent will typeset as something like

@display
future,
  Cohen, Leonard, 65--94
@end display

@item see
@findex see @r{for index entries}
@cindex see, and index entries
@cindex cross-referencing index entries
@cindex index entries, and cross-referencing
This marks an index entry as pointing to another; the real index term is
an additional (non-optional) argument to the command. Thus you can
anticipate a term readers may wish to look up, yet which you have
decided not to index. Example:

@example
\sidx[see]@{analysis@}[archetypal]@{archetypal criticism@}
@end example

@noindent becomes

@display
analysis,
  archetypal, @i{see} archetypal criticism
@end display

@item seealso
@findex seealso @r{for index entries}
Similar to @code{see} (the previous item), but also allows for normal
index entries of the referencing term. Example:

@example
\sidx[seealso]@{archetypal criticism@}[elements of]@{dichotomies@}
@end example

@noindent becomes

@display
archetypal criticism,
  elements of, 75, 97, 114, @i{see also} dichotomies
@end display

(Aside for the academically curious: The archetypally critical book I
took these dichotomous examples from is Laurence Berman's @cite{The
Musical Image}, which I happened to co-design and typeset.)

@item pagemarkup=@var{cs}
This puts @code{\@var{cs}} before the page number in the typeset index,
thus allowing you to underline definitive entries, italicize examples,
and the like. You do @emph{not} precede the control sequence @var{cs}
with a backslash. (That just leads to expansive difficulties.) Naturally
it is up to you to define the control sequences you want to use. Example:

@example
\def\defn#1@{@{\sl #1@}@}
\sidx[pagemarkeup=defn]@{indexing@}
@end example

@noindent becomes something like

@example
indexing, @code{\defn@{75@}}
@end example

@end table


@node Proofing index terms
@subsubsection Proofing index terms

@cindex proofing index terms
@cindex index terms, proofing
@cindex margins, index terms in

As you are reading through a manuscript, it is helpful to see what terms
have been indexed, so you can add others, catch miscellaneous errors,
etc. (Speaking from bitter experience, I can say it is extremely
error-prone to leave all indexing to the end of the writing, since it
involves adding many @TeX{} commands to the source files.)

@findex indexproofterm
@findex indexprooffont
@pindex cmtt8
So Eplain puts index terms in the margin of each page, if you
set @code{\indexproofingtrue}. It is @code{false} by default. The terms
are typeset by the macro @code{\indexproofterm}, which takes a single
argument, the term to be typeset. Eplain's definition of
@code{\indexproofterm} just puts it into an @code{\hbox}, first doing
@code{\indexprooffont}, which Eplain defines to select the font
@code{cmtt8}. With this definition long terms run off the page, but
since this is just for proofreading anyway, it seems acceptable.

@findex pageno
@findex insidemargin
@findex hoffset
@findex outsidemargin
@findex indexsetmargins
On the other hand, we certainly don't want the index term to run into
the text of the page, so Eplain uses the right-hand side of the page
rather than the left-hand page (assuming a language read left to right
here). So @code{\ifodd\pageno}, Eplain kerns by @code{\outsidemargin},
otherwise by @code{\insidemargin}. If those macros are undefined,
@code{\indexsetmargins} defines them to be one inch plus @code{\hoffset}.

@findex @@indexproof @r{insertion class}
@findex indexproofunbox
@findex makeheadline
@cindex output routine and index proofing
To get the proofing index entries on the proper page, Eplain defines a new
insertion class @code{\@@indexproof}. To unbox any index proofing
material, Eplain redefines @code{\makeheadline} to call
@code{\indexproofunbox} before the original @code{\makeheadline}. Thus,
if you have your own output routine, that redefines or doesn't use
@code{\makeheadline}, it's up to you to call @code{\indexproofunbox} at
the appropriate time.


@node Typesetting an index
@subsection Typesetting an index

@cindex typesetting an index
@cindex index typesetting
@findex readindexfile

The command @code{\readindexfile@{i@}} reads and typesets the
@file{.ind} file that MakeIndex outputs (from the @file{.idx} file which
the indexing commands in the previous sections write).  Eplain defines a
number of commands that support the default MakeIndex output.

@findex indexfilebasename
@findex jobname
More precisely, @code{\readindexfile} reads
@code{\indexfilebasename.@var{index-letter}nd}, where the
@var{index-letter} is the argument. @code{\indexfilebasename} is
@code{\jobname} by default, but if you have different indexes in
different parts of a book, you may wish to change it, just as with
bibliographies (@pxref{Citations}).

@findex begin@{theindex@}
@findex end@{theindex@}
MakeIndex was designed to work with @LaTeX{}; therefore, by default the
@file{.ind} file starts with @code{\begin@{theindex@}} and ends with
@code{\end@{theindex@}}. If no @code{\begin} has been defined, Eplain
defines one to ignore its argument and set up for typesetting the index
(see below), and also defines a @code{\end} to ignore its argument. (In
a group, naturally, since there is a primitive @code{\end}).

@findex parindent @r{in indexes}
@cindex index fonts
@findex indexfonts
@cindex double columns in indexes
Eplain calls @code{\indexfonts}, sets @code{\parindent = 0pt}, and does
@code{\doublecolumns} (@pxref{Multiple columns}) at the
@code{\begin@{theindex@}}. @code{\indexfonts} does nothing by default;
it's just there for you to override. (Indexes are usually typeset in
smaller type than the main text.)

@findex beginindex @r{hook}
It ends the setup with @code{\hookrun@{beginindex@}}, so you can
override anything you like in that hook (@pxref{Hooks}). For example:

@example
\hookaction@{beginindex@}@{\triplecolumns@}
@end example

@findex item @r{in indexes}
@findex subitem @r{in indexes}
@findex subsubitem @r{in indexes}
@cindex index entry formatting
@cindex formatting index entries
@cindex space above index entries
@cindex continued index entries
@cindex index entry continuations
MakeIndex turns each main index entry into an @code{\item}, subentries
into @code{\subitem}, and subsubentries into @code{\subsubitem}. By
default, the first line of main entries are not indented, and subentries
are indented 1em per level. Main entries are preceded by a @code{\vskip}
of @code{\aboveitemskipamount}, @code{0pt plus2pt} by default. Page
breaks are encouraged before main entries (@code{\penalty -100}), but
prohibited afterwards---Eplain has no provision for ``continued''
index entries.

All levels do the following:

@findex hangindent @r{for index entries}
@findex raggedright @r{for index entries}
@findex hyphenpenalty @r{for index entries}
@example
\hangindent = 1em
\raggedright
\hyphenpenalty = 10000
@end example

@findex indexitem @r{hook}
Each entry ends with @code{\hookrun@{indexitem@}}, so you can change any
of this. For example, to increase the allowable rag:

@example
\hookaction@{indexitem@}@{\advance\rightskip by 2em@}
@end example

@findex indexspace
@cindex index groupings
Finally, MakeIndex outputs @code{\indexspace} between each group of
entries in the @file{.ind} file. Eplain makes this equivalent to
@code{\bigbreak}.


@node Customizing indexing
@subsection Customizing indexing

@cindex customizing indexing

@findex afterindexterm
@cindex commas after index terms
@cindex after index terms
By default, MakeIndex outputs @samp{, } after each term in the index. To
change this, you can add the following to your MakeIndex style
(@file{.ist}) file:

@example
delim_0 "\\afterindexterm "
delim_1 "\\afterindexterm "
delim_2 "\\afterindexterm "
@end example

@noindent Eplain makes @code{\afterindexterm} equivalent to
@code{\quad}.

You can also change the keywords Eplain recognizes (@pxref{Modifying
index entries}):

@table @code

@item \idxrangebeginword
@findex idxrangebeginword
`begin'

@item \idxrangeendword
@findex idxrangeendword
`end'

@item \idxseecmdword
@findex idxseecmdword
`see'

@item \idxseealsocmdword
@findex idxseealsocmdword
`seealso'

@end table

You can also change the magic characters Eplain puts into the
@file{.idx} file, in case you've changed them in the @code{.ist} file:

@table @code

@item \idxsubentryseparator
@findex idxsubentryseparator
@samp{!}

@item \idxencapoperator
@findex idxencapoperator
@samp{|}

@item \idxbeginrangemark
@findex idxbeginrangemark
@samp{(}

@item \idxendrangemark
@findex idxendrangemark
@samp{)}

@end table

There is no macro for the @code{actual} (@samp{@@} by default)
character, because it's impossible to make it expand properly.

@findex idxpagenum
@cindex see also index entries and sorting
You can change the (imaginary) page number that ``see also''
entries sort as by redefining @code{\idxmaxpagenum}. This is 99999 by
default, which is one digit too many for old versions of MakeIndex.

@findex indexseeword
@findex indexseealsowords
@findex seevariant
@findex indexsee
@findex indexseealso
The words output by Eplain for ``see'' and ``see also'' index entries
are defined by @code{\indexseeword} and @code{\indexseealsowords}
respectively.  You can change the typeface used for these words by
redefining @code{\seevariant}.  And finally, the macros
@code{\indexsee} and @code{\indexseealso} actually produce the ``see
@dots{}'' entries, so you can redefine them if you want something
entirely different.  If you do redefine them, make them take two
parameters, the term being referenced and the @code{\idxmaxpagenum}
(the latter should normally be ignored).  See the example below.

@findex see @r{for index entries}
@cindex see, and index entries
@cindex cross-referencing index entries
@cindex index entries, and cross-referencing
@cindex commas in cross-referencing index entries
Unfortunately, it is impossible to reliably control the commas
produced by MakeIndex in front of ``see @dots{}'' entries in the
@file{.ind} file, either at MakeIndex level or at Eplain level.
However, the
@pindex sed
@command{sed} script named @command{trimsee}
@pindex trimsee
distributed with Eplain in the @file{test} directory can be used to
filter out these commas from the output of MakeIndex.  For example,
suppose you want the following style for your ``see @dots{}'' entries:

@display
analysis,
  archetypal (@i{see} archetypal criticism)
archetypal criticism,
  elements of, 75, 97, 114 (@i{see also} dichotomies)
@end display

@noindent You would need to redefine these macros in your @TeX{}
file:

@example
\def\indexsee#1#2@{(@{\seevariant \indexseeword\/ @}#1)@}
\def\indexseealso#1#2@{(@{\seevariant \indexseealsowords\/ @}#1)@}
@end example

@noindent and then filter out the commas in front of the ``see @dots{}''
entries by running the following command to produce the @file{.ind}
file (assuming the name of the @file{.idx} file is @file{myfile.idx}
and the @file{trimsee} script is placed in the current directory):

@example
prompt$ cat myfile.idx | makeindex | ./trimsee > myfile.ind
@end example

By default, @file{trimsee} uses default page list separators and
default ``see @dots{}'' command names.  If you set up MakeIndex to use
different page list separator or change the names of @code{\indexsee}
and @code{\indexseealso} commands, it is possible to adjust the
@file{trimsee} script through its command line options, which are the
following:

@table @option
@item -i @var{is}
Use @var{is} as a regular expression matching separator before ``see
@dots{}'' commands in the input (default: @samp{, \+}).

@item -o @var{os}
Use @var{os} as a separator to replace @var{is} before ``see @dots{}''
commands (default: @samp{ }).

@item -s @var{see}
Use @var{see} as a regular expression matching ``see @dots{}''
commands (default: @samp{\\indexsee}).

@item -h
@itemx --help
Print a usage message.

@item -v
@itemx --version
Print version.
@end table

@file{trimsee} reads input from the standard input, and directs its
output to the standard output.


@node Justification
@section Justification

@cindex centering
@cindex left-justification
@cindex right-justification
@cindex justification
Eplain defines three commands to conveniently justify multiple
lines of text: @code{\flushright}, @code{\flushleft}, and
@code{\center}.
@findex flushright
@findex flushleft
@findex center

They all work in the same way; let's take @code{\center} as the
example.  To start centering lines, you say @code{\center} inside a
group; to stop, you end the group.  Between the two commands, each
end-of-line in the input file also starts a new line in the output file.

The entire block of text is broken into paragraphs at blank lines,
so all the @TeX{} paragraph-shaping parameters apply in the usual way.
This is convenient, but it implies something else that isn't so
convenient: changes to any linespacing parameters, such as
@code{\baselineskip}, will have @emph{no effect} on the paragraph in
which they are changed.  @TeX{} does not handle linespacing changes
within a paragraph (because it doesn't know where the line breaks are
until the end of the paragraph).

The space between paragraphs is by default one blank line's worth.
You can adjust this space by assigning to @code{\blanklineskipamount};
@findex blanklineskipamount @r{in justified text}
this (vertical) glue is inserted after each blank line.

Here is an example:
@example
@{\center First line.

   Second line, with a blank line before.
@}
@end example

This produces:

@center First line.
@center
@center Second line, with a blank line before.

You may wish to use the justification macros inside of your own
macros.  Just be sure to put them in a group.  For example, here is how
a title macro might be defined:

@example
\def\title@{\begingroup\titlefont\center@}
\def\endtitle@{\endgroup@}
@end example


@node Tables
@section Tables

@cindex tables
@cindex alignments
Eplain provides a single command, @code{\makecolumns},
@findex makecolumns
to make generating one particular kind of table easier.  More ambitious
macro packages might be helpful to you for more difficult applications.
The files @file{ruled.tex} and @file{TXSruled.tex}, available from
@samp{lifshitz.ph.utexas.edu} in @file{texis/tables}, is the only one I
know of.

Many tables are homogenous, i.e., all the entries are semantically the
same.  The arrangement into columns is to save space on the page, not
to encode different meanings.  In this kind of the table, it is useful to
have the column breaks chosen automatically, so that you can add or
delete entries without worrying about the column breaks.

@code{\makecolumns} takes two arguments: the number of entries in the
table, and the number of columns to break them into.  As you can see
from the example below, the first argument is delimited by a slash, and
the second by a colon and a space (or end-of-line).  The entries for the
table then follow, one per line (not including the line with the
@code{\makecolumns} command itself).

@code{\parindent} defines the space to the left of the
table.  @code{\hsize} defines the width of the table.
So you can adjust the position of the table on the page by assignments
to these parameters, probably inside a group.

You can also control the penalty at a page break before the
@code{\makecolumns} by setting the parameter
@code{\abovecolumnspenalty}.
@findex abovecolumnspenalty
Usually, the table is preceded by some explanatory text.  You wouldn't
want a page break to occur after the text and before the table, so
Eplain sets it to @code{10000}.  But if the table produced by
@code{\makecolumns} is standing on its own, @code{\abovecolumnspenalty}
should be decreased.

If you happen to give @code{\makecolumns} a smaller number of entries
than you really have, some text beyond the (intended) end of the table
will be incorporated into the table, probably producing an error
message, or at least some strange looking entries.  And if you give
@code{\makecolumns} a larger number of entries than you really have,
some of the entries will be typeset as straight text, probably also
looking somewhat out of place.

Here is an example:
@example
% Arrange 6 entries into 2 columns:
\makecolumns 6/2: % This line doesn't have an entry.
one
two
three
four
five
six
Text after the table.
@end example

This produces `one', `two', and `three' in the first column, and
`four', `five', and `six' in the second.


@node Margins
@section Margins

@cindex margins, changing
@TeX{}'s primitives describe the type area in terms of an offset from
the upper left corner, and the width and height of the type.  Some
people prefer to think in terms of the @dfn{margins} at the top, bottom,
left, and right of the page, and most composition systems other than
@TeX{} conceive of the page laid out in this way.  Therefore, Eplain
provides commands to directly assign and increment the margins.

@table @code
@itemx \topmargin = @var{dimen}
@itemx \bottommargin = @var{dimen}
@itemx \leftmargin = @var{dimen}
@item \rightmargin = @var{dimen}
@findex topmargin
@findex bottommargin
@findex leftmargin
@findex rightmargin
These commands set the specified margin to the @var{dimen} given.
The @code{=} and the spaces around it are optional.  The control
sequences here are not @TeX{} registers, despite appearances;
therefore, commands like @code{\showthe\topmargin} will not do what you
expect.

@itemx \advancetopmargin by @var{dimen}
@itemx \advancebottommargin by @var{dimen}
@itemx \advanceleftmargin by @var{dimen}
@item \advancerightmargin by @var{dimen}
@findex advancetopmargin
@findex advancebottommargin
@findex advanceleftmargin
@findex advancerightmargin
These commands change the specified margin by the @var{dimen} given.
@end table

Regardless of whether you use the assignment or the advance commands,
Eplain always changes the type area in response, not the other margins.
For example, when @TeX{} starts, the left and right margins are both one
inch.  If you then say @code{\leftmargin = 2in}, the right margin will
remain at one inch, and the width of the lines (i.e., @code{\hsize})
@findex hsize
will decrease by one inch.

When you use any of these commands, Eplain computes the old value of
the particular margin, by how much you want to change it, and then
resets the values of @TeX{}'s primitive parameters to correspond.
Unfortunately, Eplain cannot compute the right or bottom margin without
help: you must tell it the full width and height of the final output
page.  It defines two new parameters for this:

@table @code
@item \paperheight
@findex paperheight
The height of the output page; default is 11truein.

@item \paperwidth
@findex paperwidth
The width of the output page; default is 8.5truein.
@end table

If your output page has different dimensions than this, you must
reassign to these parameters, as in

@example
\paperheight = 11truein
\paperwidth = 17truein
@end example


@node Multiple columns
@section Multiple columns

@cindex double column output
@cindex triple column output
@cindex quadruple column output
@cindex multiple column output
Eplain provides for double, triple, and quadruple column output:  say
@code{\doublecolumns},
@findex doublecolumns
@code{\triplecolumns},
@findex triplecolumns
or @code{\quadcolumns},
@findex quadcolumns
and from that point on, the manuscript will be
set in columns.  To go back to one column, say
@code{\singlecolumn}.
@findex singlecolumn

@cindex column balancing with @code{\singlecolumn}
@cindex balancing of columns with @code{\singlecolumn}
You may need to invoke @code{\singlecolumn} to balance the columns
on the last page of output.

@findex columnfill
@cindex column eject
@cindex eject in multicolumns
@findex pagetotal
To do a ``column eject'', i.e., move to the top of the next column, do
@code{\columnfill}. This does not actually force an eject, however: it
merely inserts a kern of size @code{\@@normalvsize} minus
@code{\pagetotal} (@code{\@@normalvsize} being the usual height of the
page; to implement multicolumns, Eplain multiplies @code{\vsize} itself
by the number of columns). In most circumstances, a column break will be
forced after this kern (during the column splitting operation when the
whole page is output), as desired.

@findex gutter
The columns are separated by the value of the dimen parameter
@code{\gutter}.  Default value is two picas.
@findex gutterbox
If you want to add vertical material between the columns, use 
@code{\gutterbox}. For example, to put a vertical line between columns,
define
@code{\gutterbox} as
@example
\def\gutterbox@{\vbox to \dimen0@{\vfil\hbox@{\vrule height\dimen0@}\vfil@}@}%
@end example
The dimension counter 
@code{\dimen0}
contains the height of the column.

All the @code{\@dots{}columns} macros insert the value of the glue parameter
@code{\abovecolumnskip}
@findex abovecolumnskip
before the multicolumn text, and the value of the glue parameter
@code{\belowcolumnskip}
@findex belowcolumnskip
after it.  The default value for both of these parameters is
@code{\bigskipamount}, i.e., one linespace in plain @TeX{}.

The macros take into account only the insertion classes
@cindex insertion classes
defined by plain @TeX{}; namely, footnotes and @code{\topinsert}s.  If
you have additional insertion classes, you will need to change
the implementation.

Also, Eplain makes insertions the full page width. There is no
provision for column-width insertions.


@node Footnotes
@section Footnotes

@cindex footnotes, numbered
The most common reference mark for footnotes is a raised number,
incremented on each footnote.  The @code{\numberedfootnote}
@findex numberedfootnote
macro provides this.  It takes one argument, the footnote text.

If your document uses only numbered footnotes, you could make typing
@code{\numberedfootnote} more convenient with a command such as:

@example
\let\footnote = \numberedfootnote
@end example

After doing this, you can type your footnotes as
@code{\footnote@{@var{footnote text}@}}, instead of as
@code{\numberedfootnote@{@var{footnote text}@}}.

Eplain keeps the current footnote number in the count register
@code{\footnotenumber}.  So, to reset the footnote number to zero,
as you might want to do at, for example, the beginning of a chapter, you
could say @code{\footnotenumber=0}.

Plain @TeX{} separates the footnote marker from the footnote text by
an en space (it uses the @code{\textindent} macro).  In Eplain, you can
change this space by setting the dimension register
@code{\footnotemarkseparation}.
@findex footnotemarkseparation
The default is still an en.

You can produce a space between footenotes by setting the glue
register @code{\interfootnoteskip}.
@findex interfootnoteskip
The default is zero.

@code{\parskip} is also set to zero by default before the beginning of
each footnote (but not for the text of the footnote).

You can also control footnote formatting in a more general way:
Eplain expands the token register @code{\everyfootnote}
@findex everyfootnote
before a footnote is typeset, but after the default values for all the
parameters have been established.  For example, if you want your
footnotes to be printed in seven-point type, indented by one inch, you
could say:
@example
\everyfootnote = @{\sevenrm \leftskip = 1in@}
@end example

By default, an @code{\hrule} is typeset above each group of footnotes
on a page.  You can control the dimensions of this rule by setting
the dimension registers @code{\footnoterulewidth}
@findex footnoterulewidth
and @code{\footnoteruleheight}.
@findex footnoteruleheight
The space between the rule and the first footnote on the page is
determined by the dimension register @code{\belowfootnoterulespace}.
@findex belowfootnoterulespace
If you don't want any rule at all, set @code{\footenoteruleheight=0pt},
and, most likely, @code{\belowfootnoterulespace=0pt}.  The defaults for
these parameters typeset the rule in the same way as plain @TeX{}: the
rule is 0.4 points high, 2 true inches wide, with 2.6 points below it.

The space above the rule and below the text on the page is controlled
by the glue register @code{\skip\footins}.  The default is a plain @TeX{}
@code{\bigskip}.

Eplain can create hypertext links for the footnote marks; @pxref{Footnote
hyperlinks}.



@node Fractions
@section Fractions

@cindex fractions
Exercise 11.6 of @cite{The @TeX{}book} describes a macro @code{\frac}
@findex frac
for setting fractions, but @code{\frac} never made it into plain @TeX{}.
So Eplain includes it.

@code{\frac} typesets the numerator and denominator in
@code{\scriptfont0}, slightly raised and lowered.  The numerator and
denominator are separated by a slash.  The denominator must be enclosed
in braces if it's more than one token long, but the numerator need not
be.  (This is a consequence of @code{\frac} taking delimited arguments;
see page@tie{}203 of @cite{The @TeX{}book} for an explanation of
delimited macro arguments.)

For example, @code{\frac 23/@{64@}} turns `23/64' into
@tex
\leavevmode
   \kern-.1em \raise .5ex \hbox{\the\scriptfont0 23}@comment
   \kern-.1em $/$@comment
   \kern-.15em \lower .25ex \hbox{\the\scriptfont0 64}@comment
@end tex
@ifinfo
23/64 (you can't see the difference in the Info file)@comment
@end ifinfo
.


@node Paths
@section Paths

@cindex pathnames, breaking
@cindex filenames, breaking
@cindex electronic mail addresses, breaking

When you typeset long pathnames, electronic mail addresses, or other
such ``computer'' names, you would like @TeX{} to break lines at
punctuation characters within the name, rather than trying to find
hyphenation points within the words.  For example, it would be better to
break the email address @code{letters@@alpha.gnu.ai.mit.edu} at the
@samp{@@} or a @samp{.}, rather than at the hyphenation points in
@samp{letters} and @samp{alpha}.

@findex path
If you use the @code{\path} macro to typeset the names, @TeX{} will find
these good breakpoints.  The argument to @code{\path} is delimited by
any character other other than @samp{\} which does not appear in the
name itself. 
@samp{|} is often a good choice, as in:
@example
\path|letters@@alpha.gnu.ai.mit.edu|
@end example

@findex discretionaries
You can control the exact set of characters at which breakpoints will be
allowed by calling @code{\discretionaries}.  This takes the same sort of
delimited argument; any character in the argument will henceforth be a valid
breakpoint within @code{\path}.  The default set is essentially all the
punctuation characters:
@example
\discretionaries |~!@@$%^&*()_+`-=#@{@}[]:";'<>,.?\/|
@end example

@findex specialpathdelimiters @r{(conditional)}
If for some reason you absolutely must use @code{\} as the delimiter
character for @code{\path}, you can set
@code{\specialpathdelimiterstrue}.  (Other delimiter characters can
still be used.)  @TeX{} then processes the @code{\path} argument
about four times more slowly.

@cindex URL for @file{path.sty}
The @code{\path} macro comes from @file{path.sty}, written by Nelson
Beebe and Philip Taylor and available at
@url{http://www.ctan.org/tex-archive/macros/latex/contrib/misc/path.sty}.


@node Logos
@section Logos

@cindex logos
@cindex names, of @TeX{} variants

Eplain redefines the @code{\TeX}
@findex TeX
macro of plain @TeX{} to end with @code{\null}, so that the proper
spacing is produced when @code{\TeX} is used at the end of a sentence. 
The other @dots{}@TeX{} macros listed here do this, also.

Eplain defines
@code{\AMSTeX},
@cindex AMS@TeX{}
@findex AMSTeX
@code{\BibTeX}
@cindex Bib@TeX{}
@findex BibTeX
@code{\AMSLaTeX},
@cindex AMS@LaTeX{}
@findex AMSLaTeX
@code{\LAMSTeX},
@cindex LAMS@TeX{}
@findex LAMSTeX
@code{\LaTeX}
@cindex @LaTeX{}
@findex LaTeX
@code{\MF},
@cindex Metafont
@findex MF
and @code{\SLiTeX}
@cindex SLi@TeX{}
@findex SLiTeX
to produce their respective logos.  (Sorry, the logos are not shown
here.)  Some spelling variants of these are also supported.

@cindex URL for @file{texnames.sty}
All these macros come from @file{texnames.sty}, compiled by Nelson
Beebe and available at
@url{http://www.ctan.org/tex-archive/info/biblio/texnames.sty}.


@node Boxes
@section Boxes

@cindex black boxes
@cindex rectangles
The solid rectangle that Eplain uses as a marker in unordered lists
(@pxref{Lists}) is available by itself: just say @code{\blackbox}.
@findex blackbox

You can create black boxes of arbitrary size with @code{\hrule} or
@code{\vrule}.

@cindex open boxes
@cindex boxes, open
You can also get unfilled rectangles with @code{\makeblankbox}.
@findex makeblankbox
This takes two explicit arguments: the height and depth of the rules that
define the top and bottom of the rectangle.  (The two arguments are
added to get the width of the left and right borders, so that the
thickness of the border is the same on all four sides.)  It also uses,
as implicit arguments, the dimensions of @code{\box0} to define the
dimensions of the rectangle it produces.  (The contents of @code{\box0}
are ignored.)

Here is an example.  This small raised open box is suitable for
putting next to numbers in, e.g., a table of contents.

@example
\def\openbox@{%
  \ht0 = 1.75pt \dp0 = 1.75pt \wd0 = 3.5pt
  \raise 2.75pt \makeblankbox@{.2pt@}@{.2pt@}
@}
@end example

Finally, you can put a box around arbitrary text with @code{\boxit}.
@findex boxit
This takes one argument, which must itself be a (@TeX{}) box, and puts a
printed box around it, separated by @code{\boxitspace}
@findex boxitspace
white space (3 points by default) on all four sides.  For example:

@example
\boxit@{\hbox@{This text is boxed.@}@}
@end example

The reason that the argument must be a box is that when the text is
more than one line long, @TeX{} cannot figure out the line length for
itself.  Eplain does set @code{\parindent} to zero inside @code{\boxit},
since it is very unlikely you would want indentation there.  (If you do,
you can always reset it yourself.)

@code{\boxit} uses @code{\ehrule} and @code{\evrule} so that you can
easily adjust the thicknesses of the box rules.  @xref{Rules}.


@node Checking for PDF output
@section Checking for PDF output

@cindex URL for pdf@TeX{}
@cindex PDF output
@pindex pdftex
@pindex .pdf @r{files}
pdf@TeX{} is a @TeX{} variant that can output both @file{.dvi} and
@file{.pdf} (Adobe's Portable Document Format) files (see
@url{http://www.ctan.org/tex-archive/systems/pdftex/}).  You might
sometimes want to know whether the target format is @file{.pdf} or
@file{.dvi}.  The @code{\ifpdf}
@findex ifpdf
switch can be used to detect pdf@TeX{} in PDF mode:

@example
\ifpdf
   This text is produced when pdfTeX is in PDF mode.
\else
   This text is produced when pdfTeX is in DVI mode,
   or when some program other than pdfTeX is used.
\fi
@end example

Keep in mind that @code{\ifpdf} is set based on the value of the
@code{\pdfoutput}
@findex pdfoutput
primitive of pdf@TeX{} at the time Eplain is loaded.  If you change
the value of @code{\pdfoutput} after you load Eplain, @code{\ifpdf}
will not reflect the change.

@cindex URL for @file{ifpdf.sty}
@cindex Oberdiek, Heiko
Eplain defines @code{\ifpdf} by incorporating Heiko Oberdiek's
@file{ifpdf.sty}, which is available at
@url{http://www.ctan.org/tex-archive/macros/latex/contrib/oberdiek/ifpdf.sty}.


@node Loading LaTeX packages
@section Loading @LaTeX{} packages

@cindex @LaTeX{} packages
@cindex packages, @LaTeX{}
@pindex .sty @r{files}
@pindex .cls @r{files}
Eplain provides a limited support for loading @LaTeX{} packages
(@file{.sty} files---not @file{.cls}).  This will mostly work for
packages which were designed with plain @TeX{} compatibility in mind,
which means that most @LaTeX{} packages cannot be loaded.  The
packages which are known to work are listed below (@pxref{Packages
known to work}).  If you discover a working package which is not in
the list, please report it to the Eplain mailing list
(@pxref{Introduction}).

@cindex graphics collection, @LaTeX{}
@cindex @LaTeX{} graphics collection
@pindex miniltx.tex
@cindex Carlisle, David
@cindex Rahtz, Sebastian
To set up a pseudo-@LaTeX{} environment for the packages, Eplain uses
@file{miniltx.tex}
(@url{http://www.ctan.org/tex-archive/macros/plain/graphics/miniltx.tex})
from the @LaTeX{} graphics collection, written by David Carlisle and
Sebastian Rahtz (the collection is available at
@url{http://www.ctan.org/tex-archive/macros/latex/required/graphics/}).
Eplain extends @file{miniltx.tex} to provide some additional features,
e.g., support for package options.


@menu
* The \usepackage command::           Command to load packages.
* Environment for loading packages::  Environment for the \usepackage commands.
* Packages known to work::            Supported packages.
* Packages known not to work::        Packages known not to work with Eplain.
@end menu

@node The \usepackage command
@subsection The @code{\usepackage} command

@findex usepackage
@code{\usepackage} loads a @LaTeX{} package.  Its syntax is similar to
that of @LaTeX{}'s @code{\usepackage} command:

@example
\usepackage[@var{options}]@{@var{packages}@}[@var{version}]
@end example

@noindent where @var{options} is a comma-separated list of package
options, @var{packages} is a comma-separated list of packages to load
(without the @file{.sty} suffix), and @var{version} is a package
version number given as a date in the format @samp{YYYY/MM/DD}.  If an
older version of the package is found, a warning is issued.  If
several packages are loaded within a single @code{\usepackage}
command, the @var{options} will be applied to each of the packages.
As usual, parameters in square brackets are optional and can be
omitted (together with the square brackets).

For example:

@example
\usepackage[foo,bar]@{pack1,pack2@}[2005/08/29]
@end example

@noindent will load packages @samp{pack1} and @samp{pack2}, each with
the options @samp{foo} and @samp{bar}, and will check that each of the
packages are dated 2005/08/29 or newer.


@node Environment for loading packages
@subsection Environment for loading packages

@findex beginpackages
@findex endpackages
Some packages request that certain commands are executed after all
packages have been loaded.  In @LaTeX{}, this means that the commands
are executed at the beginning of the document, after the so-called
@dfn{preamble}.  Neither plain @TeX{} nor Eplain have any kind of
preamble; therefore, Eplain requires that all packages be loaded inside
a @code{\beginpackages...\endpackages} block, for example:

@example
\beginpackages
  \usepackage[foo,bar]@{pack1@}
  \usepackage@{pack2@}
\endpackages
@end example

@noindent This requirement enables Eplain to execute the ``delayed''
commands at the end of the @code{\beginpackages...\endpackages} block.

For the same reason, it is advisable to specify only one such block
per document, just like there is only one preamble in @LaTeX{}.


@node Packages known to work
@subsection Packages known to work

@cindex @LaTeX{} packages
@cindex packages, @LaTeX{}
The following table lists packages that had been tested and are known
to work with Eplain, and locations where you can find manuals for
these packages.  Some of the short descriptions of the packages were
taken from the documentation for those packages.

@table @asis
@item autopict (@samp{2001/06/04 v1.1j Picture mode autoload file})
@pindex autopict.sty
@url{http://tug.org/eplain/ltpictur.pdf}

@cindex picture mode
@findex begin@{picture@}
@findex end@{picture@}
This is the @LaTeX{} ``picture mode'', started by
@code{\begin@{picture@}} and ended by @code{\end@{picture@}} (in
@LaTeX{}, this package is not explicitly loaded since it is part of
the @LaTeX{} kernel).  It provides commands to draw simple figures
inside your document without resorting to any external tools.

@item color (@samp{1999/02/16 v1.0i Standard LaTeX Color (DPC)})
@pindex color.sty
@itemx graphics (@samp{2001/07/07 v1.0n  Standard LaTeX Graphics (DPC,SPQR)})
@pindex graphics.sty
@itemx graphicx (@samp{1999/02/16 v1.0f  Enhanced LaTeX Graphics (DPC,SPQR)})
@pindex graphicx.sty
@url{http://www.ctan.org/tex-archive/macros/latex/required/graphics/grfguide.pdf}

@cindex graphics collection, @LaTeX{}
@cindex @LaTeX{} graphics collection
@cindex color
@cindex rotation
@cindex scaling
These packages are from the @LaTeX{} graphics collection.  They
provide commands for changing text/page colors, text rotation and
scaling, and much more.

@item psfrag (@samp{1998/04/11 v3.04 PSfrag (MCG)})
@pindex psfrag.sty
@url{http://www.ctan.org/tex-archive/macros/latex/contrib/psfrag/pfgguide.pdf}

@cindex Encapsulated PostScript
@cindex EPS
@pindex .eps @r{files}
PSfrag allows the user to precisely overlay Encapsulated PostScript
(EPS) files with arbitrary (La)@TeX{} constructions.  In order to
accomplish this, the user places a simple text ``tag'' in the graphics
file, as a ``position marker'' of sorts.  Then, using simple
(La)@TeX{} commands, the user instructs PSfrag to remove that tag from
the figure, and replace it with a properly sized, aligned, and rotated
(La)@TeX{} equation.

@item url (@samp{2005/06/27 ver 3.2 Verb mode for urls, etc.})
@pindex url.sty
@url{http://www.ctan.org/tex-archive/macros/latex/contrib/misc/url.sty}

@cindex pathnames, breaking
@cindex filenames, breaking
@cindex electronic mail addresses, breaking
This package provides a form of @code{\verbatim} that allows
line breaks at certain characters or combinations of characters,
accepts reconfiguration, and can usually be used in the argument to
another command.  It is intended for email addresses, hypertext links,
directories/paths, etc., which normally have no spaces.

Eplain can create hypertext links with the @code{\url} command;
@pxref{URL hyperlinks}.
@end table


@node Packages known not to work
@subsection Packages known not to work

@cindex @LaTeX{} packages
@cindex packages, @LaTeX{}
The following packages are known not to work with Eplain:

@table @asis
@item pict2e (@samp{2005/07/15 v0.2r Improved picture commands (HjG,RN)})
@pindex pict2e.sty
@url{http://www.ctan.org/tex-archive/macros/latex/contrib/pict2e/}

@item xcolor (@samp{2005/06/06 v2.03 LaTeX color extensions (UK)})
@pindex xcolor.sty
@url{http://www.ctan.org/tex-archive/macros/latex/contrib/xcolor/}
@end table