summaryrefslogtreecommitdiff
path: root/Master/texmf-dist/source/latex/xpackages/xbase/template.dtx
blob: 376b492993341fd21bb7596b15e1329b28ca3f3f (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
% \iffalse
%% File: template.dtx (C) Copyright 1999-2001 David Carlisle, Frank Mittelbach
%%                    (C) Copyright 2004-2009 Frank Mittelbach, LaTeX3 Project
%%
%% It may be distributed and/or modified under the conditions of the
%% LaTeX Project Public License (LPPL), either version 1.3c of this
%% license or (at your option) any later version.  The latest version
%% of this license is in the file
%%
%%    http://www.latex-project.org/lppl.txt
%%
%% This file is part of the ``xbase bundle'' (The Work in LPPL)
%% and all files in that bundle must be distributed together.
%%
%% The released version of this bundle is available from CTAN.
%%
%% -----------------------------------------------------------------------
%%
%% The development version of the bundle can be found at
%%
%%    http://www.latex-project.org/svnroot/experimental/trunk/
%%
%% for those people who are interested.
%%
%%%%%%%%%%%
%% NOTE: %%
%%%%%%%%%%%
%%
%%   Snapshots taken from the repository represent work in progress and may
%%   not work or may contain conflicting material!  We therefore ask
%%   people _not_ to put them into distributions, archives, etc. without
%%   prior consultation with the LaTeX Project Team.
%%
%% -----------------------------------------------------------------------
%%
%<*driver|package>
\RequirePackage{expl3}
%</driver|package>
%\fi
\GetIdInfo$Id: template.dtx 1670 2009-11-01 22:34:54Z will $
          {template}
%\iffalse
%<*driver>
%\fi
\ProvidesFile{\filename.\filenameext}
  [\filedate\space v\fileversion\space\filedescription]
%\iffalse
\documentclass{l3doc}
\makeatletter
 \newenvironment{decl}[1][]%
    {\par\small\addvspace{4.5ex plus 1ex}%
     \vskip -\parskip
     \ifx\relax#1\relax
        \def\@decl@date{}%
     \else
        \def\@decl@date{\NEWfeature{#1}}%
     \fi
     \noindent\hspace{-\leftmargini}%
     \begin{tabular}{|l|}\hline\ignorespaces}%
    {\\\hline\end{tabular}\nobreak\@decl@date\par\nobreak
     \vspace{2.3ex}\vskip -\parskip\@afterheading}
\makeatother

 \begin{document}
 \catcode`\_=11
 \catcode`\:=11
 \DocInput{template.dtx}
 \end{document}
%</driver>
%
%
% \fi
%
%
% \CheckSum{0}
%
% \title{The \textsf{template} package\thanks{This file
%         has version number \fileversion, last
%         revised \filedate.}}
% \author{DPC, FMi}
% \date{\filedate}
%  \maketitle
%
% \changes{0.06}{1998/12/17}{generic functions reborn as templates}
%
% \tableofcontents
%
% \section{Introduction}
% A \emph{Template} is a named `function' that has a fixed number
% of \emph{mandatory arguments} and an additional set of \emph{keys}
% or `named attributes' that are set in a `key value list'. That is,
% a comma separated  set of assignments of the form:\\
% \meta{key$_1$} |=| \meta{value$_1$} |,|
% \meta{key$_2$} |=| \meta{value$_2$} \ldots
%
% More specific instances of the template may be declared by
% specifying settings of the parameters. The key value list is parsed
% at the time the instance is declared, and an `internal' set of
% parameter assignments is passed to the template code. It is normally
% not parsed at run-time, though it is possible to enforce this
% behaviour.
%
% Templates have a \emph{type} and a \emph{name}. Templates
% of the same type have the same argument and parameter
% structure. That is, templates of the same type are expected to be
% exchangeable semantically. (However, except for checking that
% templates of the same type always have the same number of arguments
% this is not enforced by the code.)
%
% A template type is declared via the |\DeclareTemplateType|
% declaration which takes two arguments: the name for the type and the
% number of arguments a template of this type requires.
%
% Templates are declared via the |\DeclareTemplate|
% command which takes five arguments
% \begin{itemize}
% \item The \emph{type} of the template (no |\|).
% \item The \emph{name} of the template (no |\|).
% \item The number of arguments for the template (same as on type
% declaration).
% \item A list declaring the keys accepted by the template,
% with information about the action to take when the key is specified
% with a value.
% \item The code for the template. This may be arbitrary \TeX\
% code. At some point it should execute |\DoParameterAssignments|
% to run the parameter assigments.
%
% The mandatory arguments are accessed via |#1|, |#2|, \ldots
% \end{itemize}
%
%
% Each element of the key specification list is of the form:
% \begin{flushleft}
% \meta{key name} |=|
%       \meta{key type} \meta{optional default} \meta{internal code}
% \end{flushleft}
%
% The \meta{key types} are essentially specified by giving a symbolic
% representation of the assignment function to be used by \TeX.
%
% Currently the possibilities are
%
% \begin{center}\catcode`|=12
% \begin{tabular}{l|ll|l}
% key type& letter& internal code& argument form\\\hline
% Command & f\emph{n}&command name & command definition\\
% name    & n &       command name & command definition\\
% length  & l &       length register& calc length syntax\\
% fake length & L &  command name  & calc length syntax\\
% count   & c &       count register& calc count syntax\\
% fake count  & C &  command name  & calc count syntax\\
% boolean & b &       name of \verb|\newif| switch& true or false\\
% switch  & s &       \marg{true code}\marg{false code}& true or false\\
% instance& i\marg{type}& command name& instance of this \emph{type}\\
% direct  & x &       Internal code& any\\
% general & g &       general code & any
% \end{tabular}
% \end{center}
%
% In addition, any of these types may be prefixed by |+| to
% denote a global assignment (described below).
% |f| takes a digit from 0--9 to denote the number of arguments.
% |n| is in fact the same as |f0|. When an instance is declared
% The value assigned to the key should be the definition of
% the command, using |#1|\ldots|#9| to denote the specified arguments.
%
% |c| takes an internal form a count register,
%  not a \LaTeX\ counter name.
%
% For |f|, |n|, |l|, and |c|, the assignment is done twice, once
% at the time an instance is \emph{declared}. (This may involve
% using \textsf{calc} expresions. Then the `primitive assignment'
% of the value (not using calc) is copied to the internal parameter
% list, to be executed when an instance is run. Sometimes you need the
% expression to be evaluated at the time an instance is run rather
% than the time it is declared. For example it may be an expression
% involving some values that are not fixed throughout a document.
% In this case the instance declaration may give a value in the
% form |\DelayedEvaluation|\marg{calc expression}. In this case
% the value is not evaluated when the instance is declared, and
% instead the entire expression is copied to the `internal parameter
% list' and is evaluated whenever the instance is used.
%
% |L| and |C| take the same value types as |l| and |c| but the internal
% assignments are to macros not registers.
%
% Keys declared with |b| and |s| each take values either \emph{true} or
% \emph{false}. if the key zzz is declared with |b| then specifying
% |zzz=true| will essentially pass |\zzztrue| to the internal parameter
% list (although in fact |\zzztrue| need not be defined) . If instead
% zzz had been declared via |s|,  then |zzz=true| would pass the tokens
% of the \marg{true code} to the internal parameter list.
%
% If a key is specified as |x|, then when used the \emph{internal code}
% will be copied to the internal parameter lists. This code may use |#1|
% to denote the value supplied to the key in the instance declaration.
% Note that this code is \emph{only} copied at the time the instance is
% declared. It is not executed at this time. It is executed when the
% instance is executed.\footnote{Despite the question of whether or
% not x and g are still necessary these days, they have the wrong
% `names' since x is the one that is not executed during delcaration
% while g is.}
%
% If a key is declared with |g| then the code is run at the time the
% instance is declared. By default \emph{nothing} is passed to the
% internal parameter list. This code may use |#1| to denote the
% value that will be supplied when an instance is declared.
% Any code that should be run when an instance is executed should
% be explicitly passed to the internal parameter list using
% |\toks_add_right:Nn\l_TP_KV_assignments_toks{|\ldots|}|
%
% A key declared with |i|\marg{type} takes as value the name of a
% declared instance of that type. The command token associated with
% the key will store a command essentially equivalent to a call
% to |\UseInstance|\marg{type}\marg{name}, but in a slightly optimised
% internal form.
% As an exception to this rule the replacement code may be of the form
% |\UseTemplate| followed by the key settings for the template
% but without the mandatory arguments. In this case the `inner'
% instance declaration is `pre compiled' and the token assigned to
% the store the value assigned to this key will execute an instance
% of the template directly, it will not re-parse the keyword settings
% each time the instance is used.
%
% \section{Commands}
%
%
% \subsection{Template declaration commands}
%
% \begin{decl}
%  |\DeclareTemplateType| \marg{type}\marg{num}
% \end{decl}
% Declare a template type.
%
% \begin{decl}
%  |\DeclareTemplate|
%   \marg{type}\marg{tname}\marg{num}\marg{keyspec}\marg{code}
% \end{decl}
% Declare a template \meta{tname} of type \meta{type} with the set of
% keys as defined by \meta{keyspec}. From this template instances can
% be declared using |\DeclareInstance| At runtime such instances will run
% \meta{code} and expect \meta{num} mandatory arguments (same number
% for all templates of one type).\footnote{The \meta{num} argument is
% redundent as it can be deduced from the type. However, for practical
% reasons it seems better to keep that information with each
% individual template declaration.}
%
% \begin{decl}
% |\DeclareRestrictedTemplate|
% \marg{type}\marg{new-tname}\marg{old-tname}\marg{keyvals}
% \end{decl}
% Declare as new template \meta{new-tname} for type \meta{type} by
% taking template \meta{old-tname} as the basis and setting one or
% more of its keys to specific values.
%
% \begin{decl}
% |\DoParameterAssignments|
% \end{decl}
% The list of key value assignments made (and saved) during template
% declaration is evaluated at this point in the template code.
%
%
% \subsection{Instance declaration commands}
%
% \begin{decl}
% |\DeclareInstance| \marg{type}\marg{iname}\marg{tname}\marg{keyvals}
% \end{decl}
% Declare an instance of type \meta{type} named \meta{iname} build
% from using template \meta{tname} with key settings as given by
% \meta{keyvals}.
%
% \begin{decl}
% |\DeclareCollectionInstance|
% \marg{collection}\marg{type}\marg{iname}\marg{tname}\marg{keyvals}
% \end{decl}
% Same as |\DeclareInstance| except that this instance is only active
% when for the type \meta{type} the collection \meta{collection} was
% selected via |\UseCollection|. E.g., within the frontmatter one
% could make all headings behave differently by defining collection
% instances for template type `head'.
%
% \subsection{Key value commands}
%
% \begin{decl}
% |\DelayEvaluation|\marg{code}
% \end{decl}
% Used in the value spec for an instance to declare that the value
% \meta{code} should not be evaluated at declaration time but at
% run-time. Can also be used in the defaults for keys (given in square
% brackets) in the declaration of templates.
%
% \begin{decl}
% |\MultiSelection| \meta{counter} \marg{cases} \marg{else}
% \end{decl}
% Used in the value spec for an instance key to declare that the value of
% this key depends on the current setting of \meta{counter} at run-time.
% The \meta{cases} argument is a comma-separated list of ``values'',
% the \meta{else} argument a single ``value''. If at run-time
% \meta{counter} has the value $i$ then the $i$-th element of the
% \meta{cases} list is selected. If that does not exist the
% \meta{else} case is returned.
%
%
% \subsection{Processing commands}
%
% \begin{decl}
% |\UseTemplate| \marg{type}\marg{tname}\marg{keyval}
% \end{decl}
% Execute a template \meta{tname} of type  \meta{type} at run-time
% using \meta{keyvals} as the value assignments for its keys. In this
% case the keys are evaluated at run-time thus this method is far
% slower than using a predeclared instance of this template (see
% below). This command can also appear as the value for a key of type
% `i' in which case the evaluation happens at declaration time of the
% template that contains this key!
%
%
% \begin{decl}
% |\UseInstance| \marg{type}\marg{iname}
% \end{decl}
% Run the instance \meta{iname} of template type \meta{type}. If a
% collection is in force see if there is a collection instance of name
% \meta{iname} and if so run that instead.
%
% \begin{decl}
% |\UseCollection| \marg{type}\marg{collection}
% \end{decl}
% Declare that from now on (normal scoping rules) the collection
% \meta{collection} for template type \meta{type} is in force. This
% means that a call to |\UseInstance| will first check if there is a
% collection instance defined, and if so use that instance, otherwise
% use the normal instance.
%
%
% \subsection{Test commands}
%
% \begin{decl}
% |\IfExistsInstanceTF| \marg{type}\marg{iname}\marg{true}\marg{false}
% \end{decl}
% Test if for template type \meta{type} an instance with name
% \meta{iname} exists. Select \meta{true} or \meta{false} code
% accordingly.
%
%
%
% \section{Examples of template key types}
%
%  The general syntax for key specification in templates (fourth argument
%  of the command |\DeclareTemplate|) is:
%\begin{flushleft}
%| {| \\
%|  | \meta{key-name$_1$} |=|\meta{key-type$_1$}
%                            \meta{optional-default$_1$} \meta{storage-bin$_1$}|,|\\
%|  | \meta{key-name$_2$} |=|\meta{key-type$_2$}
%                            \meta{optional-default$_2$} \meta{storage-bin$_2$}|,|\\
%|     ...|\\
%| }|
%\end{flushleft}
% In this section we look at all possible key types and give examples
% for them.
%
%
% \subsection{Attributes that receive names as values}
%
%  The type |n| expects to receive a \LaTeX{} name as a value. Used,
%  for example, to specify the name of a \LaTeX{} counter to use.
%\begin{verbatim}
%  heading-id     =n                                  \heading@id,
%  counter-id     =n  [\DelayEvaluation{\heading@id}] \heading@counter,
%\end{verbatim}
% Notice the use of |\DelayEvaluation| in the default of
% |counter-id|. It is necessary to make the default the token
% |\heading@id| if we want to inherit the value from the |heading-id|
% key. Otherwise it gets value of |\heading@id| at the time the
% instance is declared.
%
%
% \subsection{Attributes that receive functions as values}
%
%
%  The type |f|\meta{num} expects a function with \meta{num} arguments
%  as a value. The arguments are denoted by |#1|, |#2|, etc. In most
%  cases either |f0| (for declarations) or |f1| (to format one argument) are
%  needed.
%\begin{verbatim}
%  initial-font   =f0            \initial@font,
%  initial-format =f1 [#1]       \initial@boxhandling,
%\end{verbatim}
%
% \subsection{Attributes that receive dimensions as values}
%
%  As far as specifying instances the |l| and |L| type behave
%  identically. They differ only in the type of internal storage-bin
%  they need: |l| expects a length register while |L| expects an
%  ordinary macro name and assigns its value via |\cs_set_nopar:Npn |.
%\begin{verbatim}
%  pre-sep        =l   \topsep,
%  post-sep       =L   \botsep,
%\end{verbatim}
%
%
%
% \subsection{Attributes that receive integers as values}
%
%  The |c| and |C| type receive integers as values. Again either of
%  them can be transparently used. In case of |c| the
%  \meta{storage-bin} has to be a \TeX{} count register not a \LaTeX{}
%  counter name, i.e., set up via |\newcount|. (\LaTeX{} counters can
%  be used as well if they are accessed via their internal name, i.e.,
%  via |\c@|\meta{\LaTeX-counter})
%\begin{verbatim}
%  pre-penalty    =c   \@beginparpenalty,
%  penalty        =C   \hmaterial@penalty,
%\end{verbatim}
%
%
%
% \subsection{Attributes that receive template instances as values}
%
%  The type |i|\marg{type} takes as value the name of a declared
%  instance of that type. The \meta{storage-bin} associated with the
%  key will store a command essentially equivalent to a call to
%  |\UseInstance|\marg{type}\marg{name}, but in a slightly optimised
%  internal form.
%
%  As an exception to this rule the replacement code may be of the form
%  |\UseTemplate| followed by the key settings for the template but
%  without the mandatory arguments. In this case the `inner' instance
%  declaration is `pre compiled' and the token assigned to the store
%  the value assigned to this key will execute an instance of the
%  template directly, it will not re-parse the keyword settings each
%  time the instance is used.
%\begin{verbatim}
%  justification-setup =i{justification} \list@justification,
%\end{verbatim}
%
%  Usage within an instance declaration is either
%\begin{verbatim}
%  justification-setup = raggedright,
%\end{verbatim}
%  i.e., name of a declared instance or a call to |\UseTemplate|
%\begin{verbatim}
%  justification-setup = \UseTemplate{justification}{TeX}
%                            { startskip = 0pt, ... },
%\end{verbatim}
%
%
%
% \subsection{Attributes that receive true or false values}
%
%  The type |s| expects the strings |true| or |false| as values. In
%  this case the declaration has no \meta{storage-bin}. Instead the
%  declaration consists of two brace groups containing code. Depending
%  on the value one of the groups gets copied verbatim into the
%  internal parameter list of the instance and gets executed at
%  run-time at the point where |\DoParameterAssignments| is seen.
%\begin{verbatim}
%  item-implicit-boolean  =s
%      { \cs_set_nopar:Npn \item@implicit@code{\item\relax} }{},
%  numbered-boolean       =b [true] @heading@nums,
%\end{verbatim}
%
%
% \subsection{Attributes that accept any value}
%
%  The type |g| is a low-level specification which contains arbitrary
%  code in place of the \meta{storage-bin}. This code is evaluated at
%  declaration time of the instance and by default \emph{nothing} is
%  passed to the internal parameter list (this has to happen explicitly
%  from within the code). |#1| may be used to access the value
%  specified.
%
%  The main purpose for this type is of historical nature (originally
%  most of the other types have been implemented internally using |g|).
%
%  The type |x| also requires code in place of the \meta{storage-bin}.
%  However with this type all of the code is copied unevaluated to the
%  internal parameter list. There are some applications for this type
%  when implementing customisable defaults. However, it is likely that
%  it will not survive a final release.
%\begin{verbatim}
%  generic-key   =g \typeout{#1},
%  extra-assigns =x \typeout{#1},
%\end{verbatim}
%
%
%
%
%
%
% \section{A complete example}
%
% The following example shows a sketch of a template for typesetting
% captions to be used as part of a larger mechanism setting whole
% floats.\footnote{I made it up while I went along so if you spot the
% ``missing brace'' or some other blunder tell me, FMi.}
%
%  We declare a template type \texttt{caption} then define an example
% template for that type and finally produce some instances from that.
%
% \subsection{Declaring the template type}
%
% To define the template type we first have to ask ourselves what
% information would be varying each time such a template is used?  A
% potential answer could be the following:
% \begin{itemize}
% \item
%   The float name, e.g., `Table' or `Fig.' etc.
% \item
%   The float
%   number e.g., `10' or `3--c' etc.
% \item
%   The actual caption text as specified in the document.
% \end{itemize}
% Since the above items would be differed in each instantiation of
% such a template we would pass them as mandatory argument to the
% template.
%
% Are there others? Possibly. Here are two more that seem to be
% useful, at least in a number of cases:
% \begin{itemize}
% \item
%   The text of the legend in document classes that distinguish
%   between caption text (heading to the figure/table) and legend
%   (explanatory material)
% \item
%   Measure to which the caption should be typeset.
% \end{itemize}
% The last one of these might need some extra explanation. Suppose a
% design requires that the caption width is decided depending on the
% width of the table of figure, e.g., the caption is supposed to
% typeset below some illustration and should not be wider than that
% illustration, or the caption is typeset aside to the illustration
% using the remaining space. In that case the process that formats the
% whole float needs to communicate with the current template to pass
% that (varying) information along. Of course, that could happen by
% using global variables, e.g., the outer process sets the measure as
% desired before calling the caption formatting template. What makes
% more sense is likely to be a matter of taste but it also has to do
% with the precise semantics of the template type. Staying with our
% example: if the the semantics of the template type \texttt{caption}
% is supposed to produce a formatted box (in \TeX{} terms) then we
% should pass the measure as an argument if we ever intend to allow
% for variations. If on the other hand the semantics are to format a
% certain set of text into the current galley (which has measure of
% its own) then a measure argument would not belong to this template
% type.
%
% Are there other variations sensible? Yes, for example, instead of
% passing a fixed string like ``Fig.'' as the first argument one could
% pass an abstract float type identifier and let the template worry to
% deduce from that information what fixed string to produce.
%
% Another question: why should we pass the fixed text (or an abstract
% identifier from which it can be deduced) and the number as separate
% arguments to the template instead of passing a combined string (like
% it is done in the |\@makecaption| command of \LaTeXe{})? Answer:
% because this allows to build templates that can individually
% manipulate both bits of information, e.g., to format the number in a
% different font, etc.
%
% So what are the conclusions of this discussion?  Defining the
% semantics of a template type is difficult and often needs several
% trials to come up with something that is covering the anticipated
% use. There is clearly not a cardinal way for defining template
% types; how the overall separation into smaller units is done is
% partly a matter of taste and partly a matter of the major layout
% characteristics that one tries to support.
%
% Returning to our example: let's assume we settle for the first four
% arguments, i.e., the calling template is responsible for setting the
% measure for the caption text if necessary.
%
% What we also have to do is to define (at least for ourselves) what
% data the arguments accept and what their semantics are. An informal
% summary of that could be the following:
% \begin{center}
% \begin{tabular}{rrl}
%  \textit{Arg} & \textit{Data Type}     & \textit{Description} \\[3pt]
%  1 & text                 & fixed float description
%  \\
%  2 & text/|\NoValue|      & float number
%  \\
%  3 & text                 & caption text
%  \\
%  4 & text/|\NoValue|      & legend text
%  \\
% \end{tabular}
% \end{center}
% The second and the fourth argument are allowed to be missing (i.e.,
% can get |\NoValue| passed as a value). Note that the empty string in
% case of a text argument is different from |\NoValue|.
%
% We further declare that it is permissible for a template of this
% type to ignore the information provided by all arguments except 3,
% i.e., the caption text.
%
% Finally the result of the template formatting should is to typeset
% text into a current galley (paragraph mode in \LaTeX{} lingua).
%
% All the above is semantic information that (at least right now) is
% not being enforced by declaring a template type (except for the
% number of arguments) but each template of a certain type is supposed
% to conform to this specification nonetheless.\footnote{To make this
% even clearer we are thinking of extending the template type
% declaration with another argument in which one has to formally or
% informally (?) specifies information like the one in the table
% above.}
%
% This finally leads to the following declaration:
%\begin{verbatim}
%\DeclareTemplateType{caption}{4}
%\end{verbatim}
%
% \subsection{Defining a first template}
%
% We start by defining a simple template of type \texttt{caption}
% which roughly formats a caption like those being presented in
% \LaTeXe{}'s article class, i.e., the caption is typeset as a
% paragraph if it is longer than a single line, otherwise it is
% centered. The legend even if present is ignored. Above and below we
% give the designer the possibility to add some space.
%
% In fact the examples is more or less identical in code to
% |\@makecaption| except that if the second argument (i.e., the
% number) is |\NoValue| it and its preceding space\footnote{For those
% who wonder: spaces are by default ignored within definitions when
% the new packages are used due to a command \texttt{\textbackslash
% InternalSyntaxOn}, do get a normal space one has to use
% \texttt{\textasciitilde} and to obtain an unbreakable space
% \texttt{\textbackslash nobreakspace}.} gets ignored.
%
% We start by declaring the template \texttt{toosimple} of type
% \texttt{caption} having four mandatory arguments (as described in
% the discussion of the template type).
%\begin{verbatim}
%\DeclareTemplate{caption}{toosimple}{4}
%\end{verbatim}
% The next argument of |\DeclareTemplate| lists all keys for the
% template. In this case we have keys for the vertical spaces above
% and below. We make them type |L| to save on registers but with a bit
% of care we could also have used scratch registers like |\@tempskipa|
% etc. Their default values are both zero.
%\begin{verbatim}
%  {
%    above-skip =L [0pt] \caption@above@skip ,
%    below-skip =L [0pt] \caption@below@skip ,
%  }
%\end{verbatim}
% The final argument of |\DeclareTemplate| contains the actual
% processing code. We start with looking at the second mandatory
% argument (caption number) to find out if it is |\NoValue| and
% depending on the result define a helper command |\caption@start|.
%\begin{verbatim}
%  {
%    \IfNoValueTF{#2}
%       { \cs_set_nopar:Npn \caption@start{#1:~} }
%       { \cs_set_nopar:Npn \caption@start{#1~#2:~} }
%\end{verbatim}
% Having dealt with the prelims we now run |\DoParameterAssigments| at
% which point the keys of the template are made available, e.g., at
% this point all those right hand containers such as
% |\caption@above@skip| get assigned the value specified in an
% instantiation of the template. (That scheme allows to do preliminary
% processing up front, e.g., defaults for the keys could be assigned
% prior to that point in which case they are overwritten if the
% template instance specifies a different value. the use of specifying
% defaults via the |[..]| syntax as done above is slightly faster at
% run-time but needs more memory.)
%\begin{verbatim}
%    \DoParameterAssigments
%\end{verbatim}
% The rest of the code should look familiar to anybody who ever looked
% at \texttt{article.cls}. The only point worth mentioning are the
% |\relax| commands after |\caption@above@skip| and
% |\caption@below@skip|. Since we have decided to use |L| as key type
% these commands are macros and not registers containing the
% dimensions as strings. This means that we have to be careful to
% ensure that \TeX{} knows where the dimension ends. In certain cases
% text following such a command might be mistaken as being part of the
% dimension (e.g., if followed by the word \texttt{plus}, etc.). In
% the code below this could only happen for the second |\vskip| but it
% is good practice to always add a terminating |\relax| to avoid such
% hidden traps.
%\begin{verbatim}
%    \vskip \caption@above@skip \relax
%    \sbox \@tempboxa {\caption@start #3}
%    \ifdim \wd\@tempboxa >\hsize
%      \caption@start #3\par
%    \else
%      \global \@minipagefalse
%      \hb@xt@\hsize{\hfil\box\@tempboxa\hfil}
%    \fi
%    \vskip \caption@below@skip \relax
%  }
%\end{verbatim}
%
% Why is the above template of not much use? Simply because it doesn't
% offer any flexibility to declare different designs. The only
% alteration offered to the designer is to modify the space above and
% below the caption, e.g., the following declaration would mimic the
% definition within the \texttt{article.cls}  class of \LaTeXe :
%\begin{verbatim}
%\DeclareInstance{caption}{article}{toosimple}
%  {
%    above-skip =  0pt,
%    below-skip = 10pt,
%  }
%\end{verbatim}
% And that's all that can be manipulated. All items that people asking
% to change, e.g., not having a colon after the number, using
% different fonts and font sizes, etc.\ are still hard-wired and thus
% inaccessible. So we have to do better if we want to make use of the
% power the template mechanism offers.
%
%
%
% \subsection{Defining a better template}
%
% First step in defining better templates is to ask ourselves a couple
% of questions:
% \begin{itemize}
% \item What are the main characteristics of the layout the template
%   is supposed to support?
% \item What are the elements that we want to allow (or can allow) the
%   designer to modify?
% \end{itemize}
%
% Take the first question first: the layout supported by the template
% of the previous section had as its main characteristics that it
% would center the caption if it would fit in a single line in the
% current measure. We could consider this being an unchangable
% characteristic of the layout this template produces (and a designer
% would need to use a different template of type \texttt{caption} if a
% design compatible with this restriction is desired) or we could try
% to make our template smarter by adding bells and wistles that allow
% the designer to say stuff like:
%\begin{verbatim}
%  one-line-format = \hfil #1 \hfil,
%\end{verbatim}
% or
%\begin{verbatim}
%  one-line-action = center,
%\end{verbatim}
% depending on how we intend to offer changing the behavior of the
% template. Like when trying to define sensible template types we have
% no single road to heaven (and probably as many to hell) --- it has a
% lot to do with how we think about design.
%
% My advice, after having tried to work with these concepts for a
% while, is to keep templates simple in so far as that most of not all
% attribute for a template should be relevant for the design. In other
% words, if you have attributes that, depending on their setting, make
% half of the other attributes not applicable then it may be
% appropriate to think about providing several templates instead. To
% give an example from \LaTeXe : instead of having |\@startsection|
% deal with both vertical heads and run-in heads provide individual
% templates. (|\@startsection| is this famous command where design
% switches are build in by making dimensions negative to signal
% something and afterwards use the absolute value.)
% Another way to look at this is to say that a template should
% normally not contain large amounts of code which is only selected in
% a subset of attribute settings.
%
% As said before there are no golden rules, it is perfectly possible
% to make hugely complicated templates that solve every possible
% aspect of layout one could think of in one go --- it is just that
% with keeping it more simple one can get the same functionality with
% less headaches for the template writer as well as the template user
% later on.
%
% Returning to our example: allowing to handle the case of a single
% line caption specially could well be considered part of the
% template. In contrast: layouts that would put the caption number
% sideways, i.e., which would need totally different internal coding
% should probably be coded as a separate template of type
% \texttt{caption}.
%
% So for our next example template we settle for the fixed caption
% text plus number (if any) being at the beginning of the variable
% caption text (coming from the document) and being together formatted
% as some sort of a pargraph. In case of the whole caption being a
% single line we allow the designer to specify how to lay it out
% (e.g., centered, flush left, etc.). If there is a legend it will get
% formatted by a vertical space followed by the legend formatted as
% another paragraph.
%
% More precisely we allow for the following bells and wistles:
%\begin{verbatim}
%\DeclareTemplate{caption}{lesssimple}{4}
%  {
%\end{verbatim}
% The designer can specify the space above and below the caption like
% we did in our first example.
%\begin{verbatim}
%   above-skip         =L           [0pt] \caption@above@skip ,
%   below-skip         =L           [0pt] \caption@below@skip ,
%\end{verbatim}
% Regarding the caption number we support the case where no number is
% present (the value being |\NoValue|) as well as the number being
% present. For both cases the designer has to specify what formatting
% should be attached. By default all is being typeset in the font the
% whole caption is presented but if there is a need for it the
% designer can use the following keys to attach special formatting
% devices to each particular item beside specifying special spacing
% information or replacing the default colon after the number with
% something else.
%\begin{verbatim}
%   number-format      =f2      [#1~#2:~] \caption@number@format,
%   nonumber-format    =f1         [#1:~] \caption@nonumber@format,
%\end{verbatim}
% If the caption is  fitting onto a single line we make it possible
% for the designer to specify how this single line should be
% positioned (the default is to center the line).
%\begin{verbatim}
%   single-line-format =f1 [\hfil#1\hfil] \caption@single@line@format,
%\end{verbatim}
% The font for the caption (including the fixed text and the number
% unless specified differently above) is going to be the one decided
% by the next key.
%\begin{verbatim}
%   caption-font       =f0  [\normalfont] \caption@font,
%\end{verbatim}
% The next attribute deserves some extra explanation: here we make use
% of an interface which is explained in more detail when we reveil the
% support for galley formatting.\footnote{Guess I have to apologize
% for the fact that i partly make use of that interface in this
% example while on other occasions (like the use of vertical spacing)
% within the example I do not---consistency around midnight is not my
% strength I fear (FMi).} In a nutshell the template type \texttt{hj}
% (hyphenation \& justification) allows one to define a) the
% justification concepts applied to the upcoming paragraphs, e.g.,
% whether they should be set flush left, adjusted, first line
% centered, etc.\ b) the linebreaking strategy used and c) the
% hyphenation rules which should apply. All this is done by selecting
% an appropriate (predefined) instance of this type as will hopefully
% become somewhat clearer in the example instances shown below.
%\begin{verbatim}
%   caption-hj-setup   =i {hj}  [default] \caption@hj@instance,
%\end{verbatim}
% In case there is a legend to format we give the designer the
% possibility to specify by how much vertical space it should be
% separated from the preceding paragraph (i.e., the caption text). The
% attributes for font and hj setup are comparable to those for the
% caption text itself (except that they will only apply to the
% legend). The only addition is the key \texttt{legend-text} which is
% allowed to take a fixed text (plus any formating and spacing for it)
% which will be added to the front of the legend in case it is
% provided at all (by default it is empty).
%\begin{verbatim}
%   legend-sep         =L           [0pt] \caption@legend@sep ,
%   legend-text        =f0             [] \caption@legend@text,
%   legend-font        =f0  [\normalfont] \caption@legend@font,
%   legend-hj-setup    =i {hj}  [default] \caption@legend@hj@instance,
%  }
%\end{verbatim}
% The actual code for the template should hold few if any
% surprises. In fact it is more or less identical to the one of the
% first template example, except that now we have now taken out some
% of the hardwired decisions and placed them into attributes.
%\begin{verbatim}
%  {
%    \IfNoValueTF{#2}
%       { \cs_set_nopar:Npn \caption@start{\caption@number@format{#1}{#2}} }
%       { \cs_set_nopar:Npn \caption@start{\caption@nonumber@format{#1}}   }
%    \DoParameterAssigments
%    \vskip \caption@above@skip \relax
%\end{verbatim}
% To properly measure the caption to determine if it fits a single
% line we have to set it in the right font, so here as well as below
% we have to apply |\caption@font|.
%\begin{verbatim}
%    \sbox \@tempboxa {\caption@font \caption@start #3}
%    \ifdim \wd\@tempboxa >\hsize
%      \begingroup
%        \caption@font \caption@hj@instance
%        \caption@start #3\par
%      \endgroup
%    \else
%      \global \@minipagefalse
%      \hb@xt@\hsize{\caption@single@line@format{\box\@tempboxa}}
%    \fi
%\end{verbatim}
% To decide whether or not we have to set any legend we have to test
% |#4| for being |\NoValue|. This part of the code was not present in
% the previous example but otherwise should be straight forward.
%\begin{verbatim}
%    \IfNoValueF{#4}
%      {
%       \vskip \caption@legend@sep \relax
%       \begingroup
%          \caption@legend@font \caption@legend@hj@instance
%          \caption@legend@text
%          #4\par
%       \endgroup
%      }
%    \vskip \caption@below@skip \relax
%  }
%\end{verbatim}
%
% I wouldn't claim the the above template is good or contains
% everything that would be desired and I'm sure that in the end we
% will have several such template for typesetting the caption part and
% perhaps decide on a different template type in the first place. So
% this is only to give a glimpse of how the template interface could
% be applied and I hope that reading it can see a) how they can apply
% it to other areas as well as see what is wrong with the example
% itself.
%
% To just note one point that i thought of being wrong after writing
% the above paragraphs: the key \texttt{single-line-format} was
% declared to be a function with one argument with the idea that
% besides specifying the single line should be centered (|\hfil|) on
% both sides, or flush left, or flush right (|\hfil| on one side) one
% could also specify something like
%\begin{verbatim}
%  single-line-format = \hspace{10pt}#1\hfil,
%\end{verbatim}
% that is a fixed indentation on the left in case where the caption is
% a single line. However, of course one can't. Or at least it is not
% safe to do so since our test in the code tests the width of the line
% without taking into account such a finite fixed space and guess what
% might happen? So in summary, flexibility needs some thought and
% often some afterthoughts as well --- happy thinking :-)
%
%
%
% \subsection{Defining a few instances}
%
% So let us conclude this example with a few sample instances. We
% start with one that repeats what current \LaTeXe{} provides in the
% article class. It shows all keys with values. However in fact only
% the first key is actually needed since all others are the same as
% the default values in the template (and of course a legend is not
% specifiable in standard \LaTeX{} coding so those settings simply do
% not apply anyway).
%\begin{verbatim}
%\DeclareInstance{caption}{article}{lesssimple}
%  {
%   above-skip         = 10pt,
%   below-skip         = 0pt,
%   number-format      = #1~#2:~,
%   nonumber-format    = #1:~,
%   single-line-format = \hfil#1\hfil,
%   caption-font       = \normalfont,
%   caption-hj-setup   = default,
%   legend-sep         = 0pt,
%   legend-text        = ,
%   legend-font        = \normalfont,
%   legend-hj-setup    = default,
%  }
%\end{verbatim}
%
% The next examples are taken from books on the shelf essentially a
% random selection I fear. This one is from \emph{Introduction to
% Database Design} by C.~J.~Date and it uses Helvetica for the caption
% text with the caption flush left, with the figure and the fixed
% string (e.g., `Fig.' in bold face) separated by a quad of space. No
% legend either so this is not set up. The \texttt{hj} instance
% \texttt{noindentflushleft} is supposed to produce a ragged right paragraph
% without any indentation. It would have to be set up elsewhere
% (instance to the template of type \texttt{hj}).
%\begin{verbatim}
%\DeclareInstance{caption}{DATE}{lesssimple}
%  {
%   above-skip         = 10pt,
%   below-skip         = 0pt,
%   number-format      = \textbf{#1~#2}\quad,
%   nonumber-format    = \textbf{#1}\quad,
%   single-line-format = #1\hfil,
%   caption-font       = \fontfamily{phv} \normalfont,
%   caption-hj-setup   = noindentflushleft,
%  }
%\end{verbatim}
%
% The final example is from the book ``Methods of Book Design'' by
% H.~Williamson which sets the caption centered if it fits a single
% line but adjusted as a paragraph without any indentation if longer
% than a single line. It uses old style numerals followed by a period
% for the number (though the example isn't quite right as i guess the
% text font used already has oldstyle numerals as default, so
% |\oldstylenums| is in fact not necessary).
%\begin{verbatim}
%\DeclareInstance{caption}{WILLIAMSON}{lesssimple}
%  {
%   above-skip         = 10pt,
%   below-skip         = 0pt,
%   number-format      = #1~\oldstylenums{#2}.~,
%   nonumber-format    = #1~,
%   single-line-format = \hfil#1\hfil,
%   caption-font       = \normalfont,
%   caption-hj-setup   = noindentadjusted,
%  }
%\end{verbatim}
%
%
%
% \section{Notes}
%
% \subsection{Note on multi-valued parameters}
%
%
%  The following code\footnote{docu taken from trial implementation in
%  xlists.dtx, FMi} implements for registers (ie L,l,C,c keys) and
%  for names (ie n key) a multi-selection mechanism of the following
%  form:
% \begin{verbatim}
%    key    = \MultiSelection \ListDepth {
%                   \DelayEvaluation {2.5em},
%                   20pt + 34pt }
%                  { \DelayEvaluation {1em} },
% \end{verbatim}
% where the first argument to |\MultiSelection| is a counter, the
% second argument is a comma separated list of values denoting the
% values for the cases 1, 2,\ldots, and the third argument contains
% the value for all other cases.
%
% The values are evaluated at declaration time in case of registers
% and therefore can contain calc expressions as well as
% |\DelayEvaluation|.
%
% Due to the implementation the case list is not allowed to have a
% trailing comma! And of course no checks are made whatsoever :-(
%
% A probably much nicer syntax would be something like this:
% \begin{verbatim}
%    key    = \MultiSelection {
%                selector = \ListDepth,
%                1        = \DelayEvaluation {2.5em},
%                2        = 20pt + 34pt,
%                else     = \DelayEvaluation {1em}
%              },
% \end{verbatim}
% but i found that too difficult to implement right now.
%
% I think it should also be considered if this kind of thing should be
% a generally available feature on all key types especially on the
% f\meta{number} ones.
%
% Anyway it is what i need for lists right now and as such it is
% sufficient.
%
%
% \subsection{Notes on template restriction}
%
% Possible semantics:
%
% a: just:-) changes the defaults  ie the new template has as
%    defaults those of its source as modified by the supplied
%    keyvals;
%
% b: similar to a: but also removes some keywords ie the new template
%    will not accept the keywods whose values are set by the suppied
%     keyvals;
%
% c: plan C.
%
%
% Towards an implementation of b: but without a restriction on what
%   keys appear where.
%
%
%
%
% \subsection{Open issues}
%
% In this section unresolved issues or ideas to think about and
% perhaps implement are collected. There is no particular order to
% them.
%
% \begin{itemize}
% \item The order of arguments in |\UseCollection| is illogical in my
%  eyes!  A collection typically modifies the behavior of several
%  types and thus should perhaps be first (as it is in the
%  |\DeclareCollectionInstance| case). Or not, or what?
%
% \item How should |\IfExistsInstanceTF| behave for Collection
%  instances? Do we need a special check for those or a default
%  action? Or do we need an additional test for the existence of
%  collection instances?
%
% \item It was suggested that the template type declaration should get
%  another argument in which (in?)formally the semantics for the
%  template types are described, e.g., data type of arguments,
%  resulting output, \ldots{} (somewhat like the description arguments
%  for functions and variables in Emacs-Lisp). The advantage being
%  that this helps employing the templates better as well as perhaps
%  guiding context sensitive editors to support the work with such
%  templates (e.g., providing help texts).
%
% \item The same might be of interest for the keys of individual
%  templates though here syntax support is already available to some
%  extend by the declaration of key types.
%
% \item There might be a need to distinguish between \TeX's dimen and
%  skip registers. Right now this is not done and both |l| and |L|
%  accepts what \LaTeX{} calls ``rubber length'' specifications.
%
% \item The type |b| can probably vanish. It is equivalent to
%  specifying the mutators of a |\newif| command in the brace groups,
%  e.g.
%\begin{verbatim}
%  numbered-boolean =b [true] @heading@nums,
%  numbered-boolean =s [true] {\@heading@numstrue}
%                             {\@heading@numsfalse},
%\end{verbatim}
%
% \item See issue raised about syntax (and semantics) for
% |\Multiselection|.
%
% \item |f0| keys should perhaps support |\UseTemplate| by replacing
% it with its internal form. or perhaps this is a rubbish idea?
%
% \item Marcin Wolinski suggested to use |\EvalOnUse| instead or in
% addition to |\DelayEvalutation|.
%
% \end{itemize}
%
% \StopEventually{}
%
% \section{Implementation}
%    \begin{macrocode}
%<*package>
\ProvidesExplPackage
  {\filename}{\filedate}{\fileversion}{\filedescription}
%    \end{macrocode}
%
%    \begin{macrocode}
\RequirePackage{expl3}
\RequirePackage{ldcsetup,xparse}
%    \end{macrocode}
%
%
% Declare a private token register for building parameter lists.
% Having the number saves a few expandafters
% (probably not needed in the end).
%    \begin{macrocode}
\toks_new:N\l_TP_KV_assignments_toks
\toks_new:N\l_TP_default_assignments_toks
%    \end{macrocode}
%
%
%
% \begin{macro}{\TP_declare_instance:Nnn}
% \begin{macro}{\TP_declare_instance:cnn}
% Declare a command name to be an instance of a template
% ie with a particular setting of the parameters.\\
% |#1| internal command name for instance to be (globally) declared\\
% |#2| template type/template name\\
% |#3| key value assignments for parameters of |#2|
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_declare_instance:Nnn #1#2#3 {
  \group_begin:
    \TP_instdecl_generate_assignments:nn {#2}{#3}
    \cs_gset_nopar:Npx #1 {
      \tl_if_eq:cNTF { TP>/#2 } \c_TP_doparameterassignments_tl
%    \end{macrocode}
%    If the body of the template consists only of the token
%    |\DoParameterAssignments|, then we insert the list of parameter
%    assignments directly. Otherwise we have push them onto the stack
%    and prepare to execute the body code (which in turn will pop them
%    again when it reaches |\DoParameterAssignments| inside).
%    \begin{macrocode}
         { \toks_use:N \l_TP_KV_assignments_toks }
         {
           \exp_not:N \TP_push_assignments:n
              {\toks_use:N\l_TP_KV_assignments_toks}
            \exp_not:c {TP>/#2}
         }
      }
  \group_end:}
\cs_generate_variant:Nn \TP_declare_instance:Nnn {cnn}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\c_TP_doparameterassignments_tl}
%    \begin{macrocode}
\tl_set:Nn \c_TP_doparameterassignments_tl {\DoParameterAssignments}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\UseTemplate}
% |{type}{templatename}{keyval}|
% Directly use a template with a particular parameter setting.
% This is also picked up if used in a nested fashion inside a parameter
% list.\\
% |#1| type of a template.\\
% |#2| name of a template.\\
% |#3| key value assignments for parameters of |#1|.
%    \begin{macrocode}
\cs_new_nopar:Npn \UseTemplate #1#2#3{
  \TP_instdecl_generate_assignments:nn {#1/#2}{#3}
  \TP_push_assignments:
  \use:c { TP>/#1/#2 }
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\DoParameterAssignments}
%    Access the parameter assignment list that was once stored in
%    |\l_TP_KV_assignments_toks| and then moved onto the
%    |\g_TP_assignments_stack_toks|.
%    \begin{macrocode}
\cs_new_nopar:Npn \DoParameterAssignments{
  \exp_after:wN
    \TP_pop_and_execute_assignments:nw
       \toks_use:N \g_TP_assignments_stack_toks \q_stop
}
%    \end{macrocode}
%
% \end{macro}
%
% \begin{macro}{\TP_pop_and_execute_assignments:nw}
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_pop_and_execute_assignments:nw#1#2\q_stop{
  \toks_gset:Nn \g_TP_assignments_stack_toks {#2}
  #1}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\g_TP_assignments_stack_toks}
%    \begin{macrocode}
\toks_new:N   \g_TP_assignments_stack_toks
\toks_gset:Nn \g_TP_assignments_stack_toks {\scan_stop:}% avoid brace loss
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_push_assignments:n}
% \begin{macro}{\TP_push_assignments:}
%   Push a list of parameter assignments onto the
%   |\g_TP_assignments_stack_toks|. As it all happens in token
%   registers |#|s need no doubling. |\TP_push_assignments:| expects
%   it to be |\l_TP_KV_assignments_toks| (needs fixing).
%    \begin{macrocode}
\cs_new:Npn \TP_push_assignments:n#1{
  \toks_gput_left:Nn\g_TP_assignments_stack_toks{{#1}}
}
\cs_new_nopar:Npn \TP_push_assignments:{
  \toks_gset:No \g_TP_assignments_stack_toks
    {\exp_after:wN
     {\toks_use:N\exp_after:wN\l_TP_KV_assignments_toks\exp_after:wN}
      \toks_use:N\g_TP_assignments_stack_toks}
}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% 
% \begin{macro}{\DeclareTemplateType}
% |{type}{nofarg}|
%    \begin{macrocode}
\cs_new_nopar:Npn \DeclareTemplateType #1#2{
  \tl_set:cn {TP@<#1>} {{}#2}}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\TP_get_csname_prefix:n}
%    |{type}| returns prefix for csnames for template type,
%    based on current collection.
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_get_csname_prefix:n #1 {
  <\exp_after:wN\exp_after:wN\exp_after:wN
   \use_i:nn
      \cs:w TP@<#1>\cs_end:>#1/
}
%    \end{macrocode}
%
% \end{macro}
%
% \begin{macro}{\TP_get_arg_count:n}
% |{type}| returns arg count for the template type.
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_get_arg_count:n #1 {
  \exp_after:wN\exp_after:wN\exp_after:wN
  \use_ii:nn
    \cs:w TP@<#1>\cs_end:
}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\DeclareTemplate}
% |{type}{templatename}{nofarg}{keywordspec}{code}|
%    \begin{macrocode}
\cs_new:Npn\DeclareTemplate #1#2#3#4#5{
  \cs_if_free:cTF{TP@<#1>}
    {\undefinedtype\DeclareTemplateType{#1}#3}
    {
      \intexpr_compare:nNnF{#3}={\TP_get_arg_count:n{#1}}
      { \BadArgCount }
    }
%    \end{macrocode}
%    Parse the key declaration, and execute the list with a suitable
%    definition of |\KV@elt|.
%    \begin{macrocode}
  \cs_set_eq:NN \KV_elt:nn \TP_templdecl_process_KV:nn
  \cs_set_nopar:Npn \KV_default_elt:n##1{
    \PackageError{template}{Missing~ =~ after~ ##1}\@ehd}
  \cs_set_eq:NN\KV@elt\KV_elt:nn
  \cs_set_eq:NN\KV@default@elt\KV_default_elt:n
  \tl_set:Nn \l_TP_curr_name_tl {#1/#2}
  \toks_clear:N\l_TP_default_assignments_toks
%    \end{macrocode}
% At this point there should be a test for which catcode regime we are
% in. We just test if spaces are ignored.
%    \begin{macrocode}
  %\intexpr_compare:nNnTF{\char_value_catcode:n{`\ }}=\c_nine
  %\KV_parse_picky_no_space_removal_no_sanitize:n
  %\KV_parse_picky_space_removal_no_sanitize:n
  \KV@parse{#4}
%    \end{macrocode}
%
%    Define the defaults: the setting for |TPD>/\l_TP_curr_name_tl| is a
%    tricky since |\l_TP_default_assignments_toks| may contain |#|. We
%    have to use an |x| expansion rather than
%    |o| since that will hide those during the assignment.
% FIX THIS (see below)!
%    \begin{macrocode}
  \cs_set_nopar:cpx { TPD>/\l_TP_curr_name_tl }
              {\toks_use:N\l_TP_default_assignments_toks}

  \tl_clear:c {TPR>/\l_TP_curr_name_tl}

  \tl_set_eq:cN {TPO>/\l_TP_curr_name_tl}\l_TP_curr_name_tl
%    \end{macrocode}
%
%    Define the template (using |\cs_new_nopar:Npn| means that one can't
%    redefine a template easily).
%    \begin{macrocode}
  \cs_generate_from_arg_count:cNnn {TP>/\l_TP_curr_name_tl}
  \cs_set:Npn {#3}{#5}
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\tl_set:cx}
% FIX this: The code above only works because in the past |\tl_set:cx| was 
%    defined as follows:
%    \begin{macrocode}
\cs_set:Npn \tl_set:cx {\exp_args:Nc  \tl_set:Nx}
%    \end{macrocode}
%    i.e., expanding the second arg at the very end.
%    This is no longer the case but for the moment I revert to the old
%    definition until the template code is fixed to not rely on  |\tl_set:cx|
%    expanding the second arg at the very last minute.
% \end{macro}
%
% \begin{macro}{\TP_templdecl_process_KV:nn}
%    The list of undefined keys and values is put in the list of the form\\
%    |\KV_elt:nn|\marg{key1}\marg{val1}%^^A
%    |\KV_elt:nn|\marg{key2}\marg{val2}\ldots\\
%    So just need to give this macro a suitable definition. We just need
%    to look at the first token of the value, to see what sort of key
%    it is, so call a helper function to split that off.
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_process_KV:nn #1#2 {%
  \cs_set_eq:NN \TP_templdecl_add_global_or_nothing: \prg_do_nothing:
  \bool_set_false:N\l_TP_global_assignment_bool
  \tl_set:Nn\l_TP_currkey_tl{#1}
  \TP_templdecl_parse_KV:N#2\q_stop}
%    \end{macrocode}
% \end{macro}
%
%
%
% \begin{macro}{\TP_templdecl_parse_KV:N}
%    Case switch on the possible key types.
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_parse_KV:N #1 {
%    \end{macrocode}
% In |#1| we have key, in |#2| the first character after the equal
% sign and in |#3| the remainder of the line. We now have to parse
% that remainder to find out if it contains a default value (in
% brackets) and then set up the key declaration needed to parse
% instance declarations. The method is similar in most cases: we call
% |\TP_parse_optional_key_default:nw| which parses for the default
% and pass it already found key name as first argument, what to do in
% the end as second argument, and the remainder delimited by |\q_stop|
% so that it becomes parseable.
%
% Note that the code in the second argument to
% |\TP_parse_optional_key_default:nw| normally calls on a macro with
% one more argument than actually provided: the reason being that the
% missing argument will be the remainder of the line (added by
% |\TP_parse_optional_key_default:nw| after the default has be
% removed (if present)).
%    \begin{macrocode}
  \cs_if_free:cTF{TP_use_arg_type_#1:w}
  {\PackageError{template}{Unknown~key~type~ (#1)~for~\l_TP_currkey_tl}\@eha}
  {\use:c{TP_use_arg_type_#1:w}}
%    \end{macrocode}
%    The |f| and |i| keys are somewhat different since there we first
%    have to parse for an additional argument (a digit in case of |f|
%    or an template type name in case of |i|):
%    \begin{macrocode}
%    \end{macrocode}
%    One more alternative: a |+| after the equal sign signals global
%    so we change |\TP_templdecl_add_global_or_nothing:| to append a
%    |\pref_global:D| to the assignment toks and then reparse the rest.
%    \begin{macrocode}
%     \cs_set_nopar:Npn  \TP_templdecl_add_global_or_nothing:
%          {\toks_put_right:Nn \l_TP_KV_assignments_toks {\pref_global:D} }
%     \TP_templdecl_parse_KV:nw{#1}#3\TP_templdecl_parse_KV:nnw
}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\l_TP_global_assignment_bool}
% For keeping track of the assignments.
%    \begin{macrocode}
\bool_new:N \l_TP_global_assignment_bool
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_use_arg_type_+:w}
%   The |+| does two things: Sets a boolean true to be used by the
%   types that can't simply be prefixed with |\pref_global:D| and
%   defines |\TP_templdecl_add_global_or_nothing:| to put the prefix
%   onto the list. After that we simply call the big switch
%   again.\footnote{It should probably all be changed to not rely on
%     the prefix working}.
%    \begin{macrocode}
\cs_new_nopar:cpn{TP_use_arg_type_+:w} {
  \bool_set_true:N\l_TP_global_assignment_bool
  \cs_set_nopar:Npn  \TP_templdecl_add_global_or_nothing:
  {\toks_put_right:Nn \l_TP_KV_assignments_toks {\pref_global:D} }
  \TP_templdecl_parse_KV:N
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_use_arg_type_l:w}
%   The |l| sets a length register. We disable the prefix and insert
%   either |\gsetlength| or |\setlength| depending on whether a |+|
%   was seen or not.
%    \begin{macrocode}
\cs_new_nopar:Npn\TP_use_arg_type_l:w {
  \TP_parse_optional_key_default:nw
  {
    \cs_set_eq:NN \TP_templdecl_add_global_or_nothing: \prg_do_nothing:
    \bool_if:NTF \l_TP_global_assignment_bool
    {\TP_templdecl_setup_register_key:Nn\gsetlength}
    {\TP_templdecl_setup_register_key:Nn\setlength}
  }
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_use_arg_type_L:w}
% The |L| sets a fake length register.
%    \begin{macrocode}
\cs_new_nopar:Npn\TP_use_arg_type_L:w {
  \TP_parse_optional_key_default:nw
  {\TP_templdecl_setup_fakeregister_key:NNn\setlength\l_tmpa_skip}
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_use_arg_type_c:w}
% The |c| sets a count register.
%    \begin{macrocode}
\cs_new_nopar:Npn\TP_use_arg_type_c:w {
  \TP_parse_optional_key_default:nw
  {
    \cs_set_eq:NN\TP_templdecl_add_global_or_nothing:\prg_do_nothing:
    \bool_if:NTF \l_TP_global_assignment_bool
    {\TP_templdecl_setup_register_key:Nn\GSetInternalCounter}
    {\TP_templdecl_setup_register_key:Nn\SetInternalCounter}
  }
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_use_arg_type_C:w}
% The |C| sets a fake count register.
%    \begin{macrocode}
\cs_new_nopar:Npn\TP_use_arg_type_C:w {
  \TP_parse_optional_key_default:nw
  {\TP_templdecl_setup_fakeregister_key:NNn
    \SetInternalCounter\l_tmpa_int}
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_use_arg_type_n:w}
% The |n| sets a token list variable.
%    \begin{macrocode}
\cs_new_nopar:Npn\TP_use_arg_type_n:w {
  \TP_parse_optional_key_default:nw
  {\TP_templdecl_setup_n_key:N}        
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_use_arg_type_f:w}
% \begin{macro}{\TP_templdecl_parse_f_arg:nw}
% The |f| defines a command with between 0 and 9 arguments.
%    \begin{macrocode}
\cs_new_nopar:Npn\TP_use_arg_type_f:w #1{
  %\TP_templdecl_parse_f_arg:nw {#1}
  \TP_parse_optional_key_default:nw{\TP_templdecl_setup_f_key:Nn{#1}}
}
%    \end{macrocode}
%    Helper for |\TP_templdecl_parse_KV:nnw|.
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_parse_f_arg:nw#1#2{
%    \end{macrocode}
%    The third argument of |\TP_templdecl_setup_f_key:Nn|, i.e., the
%    macro name, is the remaining data up to |\q_stop| which is picked up
%    by |\TP_parse_optional_key_default:nw|.
%    \begin{macrocode}
  \TP_parse_optional_key_default:nw{\TP_templdecl_setup_f_key:Nn{#1}{#2}}
}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
%
% \begin{macro}{\TP_use_arg_type_b:w}
% \begin{macro}{\TP_templdecl_setup_b_key:nn}
%   The |b| uses access to the |\if_true:| and |\if_false:|
%   primitives. Needed?
%    \begin{macrocode}
\cs_new_nopar:Npn\TP_use_arg_type_b:w {
  \TP_parse_optional_key_default:nw
  {\TP_templdecl_setup_b_key:n}
}
%    \end{macrocode}
%
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_setup_b_key:n#1{
  \cs_set_eq:cN { if#1 } \if_true:
  \TP_templdecl_define_key:n
  { \TP_templdecl_eval_b_key_value:nn {#1}{##1} }
}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\TP_templdecl_eval_b_key_value:nn}
%    Modify so the boolean does not need to have been
%    declared with |\newif|
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_eval_b_key_value:nn#1#2{
  \cs_if_free:cTF {if#2}
    { \PackageError{template}{Bad~boolean~setting~#1=#2}\@eha }
    { \tl_set_eq:cc {if_#1:}{if_#2:}
      \toks_put_right:Nf \l_TP_KV_assignments_toks
         { \tl_set_eq:cc {if_#1:}{if_#2:} }
    }
}
%    \end{macrocode}
%
% \end{macro}
%
% \begin{macro}{\TP_use_arg_type_s:w}
% \begin{macro}{\TP_templdecl_setup_s_key:n}
% The |s| chooses between true and false.
%    \begin{macrocode}
\cs_new_nopar:Npn\TP_use_arg_type_s:w {
  \TP_parse_optional_key_default:nw
  {\TP_templdecl_setup_s_key:n}
}
%    \end{macrocode}
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_setup_s_key:n #1 {
  \TP_templdecl_define_key:n
    { \TP_templdecl_eval_s_key_value:nnn{##1}#1 }
}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
%
%
%
%
%
%
% \begin{macro}{\TP_use_arg_type_i:w}
% The |i| expects an instance.
%    \begin{macrocode}
\cs_new_nopar:Npn\TP_use_arg_type_i:w #1{
  \TP_parse_optional_key_default:nw{\TP_templdecl_setup_i_key:nnn{#1}}
}
%    \end{macrocode}
%
%      declaration |hd =i{head} \fooo| \\
%      use         |hd = mine|\\
%      makes |\fooo| shorthand for |\UseInstance{head}{mine}|
%
%      also allowed: |hd = \UseTemplate{head}{...}{...}|\\
% in case you want to use an unnamed instance of type |head|
% in this place.
% \end{macro}
%
% \begin{macro}{\TP_templdecl_setup_i_key:nnn}
% MH change: do either local or global.
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_setup_i_key:nnn#1#2{
  \TP_templdecl_define_key:n
  {
    \TP_templdecl_eval_i_key_value:Nnn #2 {#1}{##1} 
  }
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_templdecl_eval_i_key_value:Nnn}
% MH change: Add extra argument for local or global.
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_eval_i_key_value:Nnn #1#2#3 {
  \tl_if_head_eq_meaning:nNTF {#3.}\UseTemplate
  {
    \iow_term:x{\token_to_str:N\UseTemplate\space seen}
%    \end{macrocode}
%
%    Code below from |\TP_templdecl_setup_f_key:Nn| (should be
%    combined and cleaned up)
%    at this point one should also check if first arg of |\UseTemplate|
%    corresponds to |#2| and if not complain (not done)
%
%    \begin{macrocode}
    {\TP_templdecl_declare_tmp_instance:nnnn #3 }
    \toks_put_right:No \l_TP_KV_assignments_toks
          { \exp_after:wN \KV@toks \exp_after:wN {\g_tmpa_tl} }
    %\TP_templdecl_add_global_or_nothing:    
    %\toks_put_right:Nn \l_TP_KV_assignments_toks
    %      { \cs_set_nopar:Npx #1{ \toks_use:N \KV@toks} }
    \bool_if:NTF \l_TP_global_assignment_bool
    {\toks_put_right:Nn \l_TP_KV_assignments_toks 
      {\cs_gset_nopar:Npx #1 { \toks_use:N \KV@toks}}
    }
    {\toks_put_right:Nn \l_TP_KV_assignments_toks 
      {\cs_set_nopar:Npx #1 { \toks_use:N \KV@toks}}
    }
  }
  {
    \TP_let_instance:Nnn#1{#2}{#3}
%    \end{macrocode}
% We want the |\cs_set_eq:Nc| hiding in |\TP_let_instance:Nnn| to expand
% fully to two csnames so we put a |\tex_romannumeral:D 0| (which in
% itself expands to nothing) in front. This expands the |\cs_set_eq:Nc| fully
% before finding out that |\cs_set_eq:NwN| is not expandable.
%    \begin{macrocode}
      \toks_put_right:Nf  \l_TP_KV_assignments_toks
        { \TP_let_instance:Nnn#1{#2}{#3} }
  }
}
%    \end{macrocode}
% \end{macro}
%
%
%
%
%
%
%
%
% \begin{macro}{\TP_use_arg_type_x:w}
% \begin{macro}{\TP_templdecl_setup_x_key:nn}
% The |x| runs internal code.
%    \begin{macrocode}
\cs_new_nopar:Npn\TP_use_arg_type_x:w {
  \TP_parse_optional_key_default:nw
  {\TP_templdecl_setup_x_key:n}
}
%    \end{macrocode}
%
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_setup_x_key:n#1{
  \TP_templdecl_define_key:n
  { \toks_put_right:Nn\l_TP_KV_assignments_toks{#1} }
}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
%
%
%
%
% \begin{macro}{\TP_use_arg_type_g:w}
% \begin{macro}{\TP_templdecl_setup_g_key:nn}
% The |g| runs any code.
%    \begin{macrocode}
\cs_new_nopar:Npn\TP_use_arg_type_g:w {
  \TP_parse_optional_key_default:nw
  {\TP_templdecl_setup_g_key:n}
}
%    \end{macrocode}
%
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_setup_g_key:n #1 {
  \TP_templdecl_define_key:n{#1}}
%    \end{macrocode}
%
% \end{macro}
% \end{macro}
%
%
%
%
% \begin{macro}{\TP_templdecl_define_key:n}
% Here we define the key in the current template. Original code from
% r522 is essentially unreadable but we keep it here until the
% internal structure is finally sorted out.
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_define_key:n#1{
   \exp_after:wN  \cs_set:Npn  \cs:w
    KV@\l_TP_curr_name_tl @\l_TP_currkey_tl
     \exp_after:wN\cs_end:
     \exp_after:wN##\exp_after:wN1\exp_after:wN{
       \exp_after:wN\TP_templdecl_remove_from_default_assignments:N
       \cs:w KV@\l_TP_curr_name_tl @\l_TP_currkey_tl
       \exp_after:wN \cs_end:
       \TP_templdecl_add_global_or_nothing:
       #1
     }
}
%    \end{macrocode}
% \end{macro}
%
%
%
%
%
%
%
%
%
%
% \begin{macro}{\TP_parse_optional_key_default:nw}
%   Look for default value. 
%    \begin{macrocode}
\cs_set:Npn \TP_ignore_leading_space_in_arg_ii:nn#1#2{
  \exp_args:Nf\TP_ignore_leading_space_in_arg_ii_aux:nn
  {\exp_not:N #2}{#1}
}
\cs_set:Npn \TP_ignore_leading_space_in_arg_ii_aux:nn#1#2{#2{#1}}


\DeclareDocumentCommand\TP_parse_optional_key_default:nw{mo}{
  \IfNoValueTF{#2}
    {\TP_templdecl_finish_key_setup:nw{#1}}
    {\TP_templdecl_finish_key_setup_with_default:nnw{#1}{#2}}
}
%\show\TP_parse_optional_key_default:nw
%\exp_args:Nc\show{\string\TP_parse_optional_key_default:nw}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_templdecl_finish_key_setup:nw}
%    After having parsed the line and not found any default value it
%    remains to actually define the key for the instance parsing by
%    executing the setup code (in |#1|) giving it |#2| (i.e., the
%    remainder of the line) as an argument.
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_finish_key_setup:nw#1#2\q_stop{
  \TP_ignore_leading_space_in_arg_ii:nn{#1}{#2}
  %%%#1{#2}
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_templdecl_finish_key_setup_with_default:nnw}
%    If there is a default the situation is more complicated since we
%    not only have to set up the key for the instance but also have to
%    add the default value to |\l_TP_default_assignments_toks| in an
%    appropriate way.
%
%    First set up the the key itself:
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_finish_key_setup_with_default:nnw#1#2#3\q_stop{
  \TP_ignore_leading_space_in_arg_ii:nn{#1}{#3}
  %%%  #1 {#3}
%    \end{macrocode}
% Now we run the new key code (which is stored in |\KV@...| hopefully)
% and give it the default found. By doing this in a group and by
% locally emptying |\l_TP_KV_assignments_toks| we will get the
% resulting assignment code into that register.
%
% (We set |\TP_templdecl_remove_from_default_assignments:N| to
% |\use_none:n| since this is a temporary operation and we don't want
% to change the default really.)
%    \begin{macrocode}
  \group_begin:
    \toks_clear:N \l_TP_KV_assignments_toks
    \cs_set_eq:NN \TP_templdecl_remove_from_default_assignments:N \use_none:n
    \use:c{KV@\l_TP_curr_name_tl @\l_TP_currkey_tl}{#2}
%    \end{macrocode}
% And now for a final trick: before closing the group again and losing
% our local changes we run |\exp_after:wN| several times to get the
% value of |\l_TP_KV_assignments_toks| into
% |\l_TP_default_assignments_toks| outside that group!
%    \begin{macrocode}
  \exp_after:wN
  \group_end:
  \exp_after:wN
  \toks_set:Nn
  \exp_after:wN
  \l_TP_default_assignments_toks
  \exp_after:wN
    { \cs:w KV@\l_TP_curr_name_tl @\l_TP_currkey_tl \exp_after:wN \cs_end:
  \exp_after:wN
      { \toks_use:N \exp_after:wN \l_TP_KV_assignments_toks
  \exp_after:wN
      }
      \toks_use:N\l_TP_default_assignments_toks
  }
}
%    \end{macrocode}
% \end{macro}
%
%
%
% \begin{macro}{\c_TP_true_tl}
%    \begin{macrocode}
\tl_new:Nn \c_TP_true_tl {true}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_templdecl_eval_s_key_value:nnn}
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_eval_s_key_value:nnn#1#2#3 {
% no error check on this yet.
  \tl_set:Nn \l_tmpa_tl {#1}
  \tl_if_eq:NNTF \l_tmpa_tl \c_TP_true_tl
     { \toks_put_right:Nn \l_TP_KV_assignments_toks {#2} }
     { \toks_put_right:Nn \l_TP_KV_assignments_toks {#3} }
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_templdecl_setup_register_key:Nnn}
% This is normally called automatically by |\DeclareTemplate|.
%
% Command for setting a template attribute whose name
% corresponds directly to a \TeX{} count or length register\\
% |#1| the function to set the value eg \cs{setlength}.\\
% |#2| key name.\\
% |#3| the register to set.
%
% This command \emph{fully evaluates} the argument at declare time,
% and assigns the value to the register. It also passes an assignment
% of the register to the final value into the parameter list for the
% template.
%
% If the value is a call to |\DelayEvaluation|, don't evaluate it now,
% just pass the whole assignment to the template. Remember to remove
% the |\DelayEvaluation|.
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_setup_register_key:Nn #1#2{
  \TP_templdecl_define_key:n{
    \tl_if_head_eq_meaning:nNTF{##1}\DelayEvaluation
    {
%    \end{macrocode}
% Old line commented out. Remove |\DelayEvaluation| and also remove
% the braces surrounding its argument.
%    \begin{macrocode}
      \toks_put_right:Nn \l_TP_KV_assignments_toks {#1#2{##1}}
      %\toks_set:No\l_tmpa_toks{\use_ii:nn ##1}
      %\toks_put_right:Nx \l_TP_KV_assignments_toks 
      %  {\exp_not:n{#1#2}{\toks_use:N \l_tmpa_toks}}
    }
%    \end{macrocode}
%
%
% check for |\MultiSelection| creeping up and if so add something like
%
% \begin{verbatim}
%  \setlength\register{\ifcase\selector \or value1 \or value2
%                       ... \else valueotherwise \fi}
% \end{verbatim}
% to |\l_TP_KV_assignments_toks|.
%
%    \begin{macrocode}
    {
      \tl_if_head_eq_meaning:nNTF{##1..}\MultiSelection
      {
        \group_begin:
          \TP_multiselection_add:nnnnnn #1#2##1
        \group_end:
%    \end{macrocode}
%
%
% there are probably better ways to do this (:-)
%
%    \begin{macrocode}
        \tl_if_in:onTF{\toks_use:N\g_TP_multiselection_toks}\DelayEvaluation
        {
          \toks_put_right:No\l_TP_KV_assignments_toks
          {
            \exp_after:wN#1\exp_after:wN#2\exp_after:wN
            {\toks_use:N\g_TP_multiselection_toks}
          }
        }
        {
          \toks_put_right:No\l_TP_KV_assignments_toks
          {
            \exp_after:wN  #2
            \exp_after:wN= \toks_use:N\g_TP_multiselection_toks\scan_stop:
          }
        }
%    \end{macrocode}
%
%
% otherwise do as before
%
%    \begin{macrocode}
      }
      {
        #1#2{##1}
        \toks_put_right:No\l_TP_KV_assignments_toks {
          \exp_after:wN #2 \exp_after:wN = \tex_the:D #2\scan_stop:
        }
      }
    }
  }
}
%    \end{macrocode}
% \end{macro}
%
%
%
%
%
%
% \begin{macro}{\DelayEvaluation}
% \begin{macro}{\MultiSelection}
%   Since we are testing explicitly for |\DelayEvaluation| and
%   |\MultiSelection| a few places we better give them unique
%   meanings!
%    \begin{macrocode}
\cs_new_nopar:Npn\DelayEvaluation #1{\use_none:n{\DelayEvaluation}#1}
\cs_new_nopar:Npn\MultiSelection  #1{\use_none:n{\MultiSelection}#1}
%    \end{macrocode}
% \end{macro}
% \end{macro}
%
% \begin{macro}{\TP_templdecl_remove_from_default_assignments:N}
%    Note: the toks register is more or less a plists and should
%    perhaps be implemented as such as this would make far more
%    readable code.
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_remove_from_default_assignments:N#1{
  \cs_set_nopar:Npn \TP_tmp:w ##1#1##2##3#1##4\q_stop{
    \l_TP_default_assignments_toks{##1##3}
  }
  \exp_after:wN \TP_tmp:w
     \toks_use:N\l_TP_default_assignments_toks #1\scan_stop:#1\q_stop}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_templdecl_setup_f_key:Nn}
%       Same for macro names. Again usually called automatically when
%       declaring a new template.\\
% |#1|   Determines how many arguments the function should have.\\
% |#2| The macro to be defined.
%
%    If the `|##1|`, the value passed as the argument of the key
%    to the macro |#2| is invoked starts with |\FunctionInstance|, then a
%    special procedure is taken. Instead of defining a macro with the
%    specified number of arguments, the paramater list of the nested
%    function instance is parsed, and |#2| is defined to be a macro
%    expanding to that instance. In this case the specified template
%    is responsible for picking up the requested number of
%    arguments. (This is \emph{not} checked.)
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_setup_f_key:Nn#1#2{
%    \end{macrocode}
%
% |##1| can either be arbitrary inline code, in which case it will be
% defined with something similar to |\newcommand[val]| so it needs to
% use |#1| -- |#val|.
%
%    define it locally here (why this, David???)
%    \begin{macrocode}
  \TP_templdecl_define_key:n
  { \TP_templdecl_define_function:NNn#1#2{##1} }
}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\TP_templdecl_define_function:NNn}
% Use number of arguments to define function.
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_define_function:NNn#1#2#3{
  \cs_generate_from_arg_count:NNnn #2 \cs_set:Npn {#1}{#3}
  \toks_put_right:Nf \l_TP_KV_assignments_toks  { 
    \cs_generate_from_arg_count:NNnn #2 \cs_set:Npn {#1}{#3}
  }
}
%    \end{macrocode}
% \end{macro}
%
%
%
% \begin{macro}{\TP_templdecl_setup_n_key:N}
% Here is the extended version that tries to deal with
% |\MultiSelection|.
%
% In case of `n' keys there is no evaluation at declaration time so it
% is not sensible to look for |\DelayEvaluation|. For this reason as
% well as for the fact that |\TP_multiselection_add:nnnnnn| above
% assumes that it deals
% with registers that can be accessed via |\toks_use:N| we have to use a
% different command to handle the |\MultiSelection| args but
% it is essentially doing the same.
%
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_setup_n_key:N#1{
  \TP_templdecl_define_key:n{
    \tl_if_head_eq_meaning:nNTF{##1..}\MultiSelection
    {
      \group_begin:
        \TP_templdecl_multiselection:nnnn ##1
      \group_end:
%    \end{macrocode}
% Extracting the correct item from the |\if_case:w| we are building
% requires a bit of care. Firstly we want to expand the appropirate
% number of times to get to the item but we also want to ensure we do
% not have any unwanted leftover |\fi:|s or other junk which is bound
% to cause errors later on. Therefore we start an |f| expansion (so we
% don't have to count |\exp_after:wN|s and then stop it again when we
% want to.
%    \begin{macrocode}
      \toks_put_right:Nx\l_TP_KV_assignments_toks {
        \exp_not:n{\tl_set:Nf #1} { \toks_use:N \g_TP_multiselection_toks}
      }
    }
    {
      \cs_set_nopar:Npn #1{##1}                      % setting it?
      \toks_put_right:Nn \l_TP_KV_assignments_toks
                          { \tl_set:Nn #1{##1} }
    }
  }
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_templdecl_multiselection:nnnn}
%   Start the |\if_case:w|.  When the item is retrieved using an |f|
%   type expansion we better stop it at the right place once we have
%   emerged on the other side of the conditional.
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_multiselection:nnnn #1#2#3#4{
  \toks_gset:Nn \g_TP_multiselection_toks {\if_case:w #2}
  \clist_map_inline:nn {#3}{ 
    \TP_multiselection_add_or_case:n {\exp_stop_f:##1} 
  }
  \toks_gput_right:Nn\g_TP_multiselection_toks {
    \else: \use_i_after_fi:nw { \exp_stop_f: #4} \fi: 
  }
}
%    \end{macrocode}
% \end{macro}
%
%
%
%
%
%
%
%
% \begin{macro}{\DeclareInstance}
% |{type}{instname}{templatename}{keyval}|
%    \begin{macrocode}
\cs_new_nopar:Npn \DeclareInstance { \DeclareCollectionInstance{} }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\DeclareCollectionInstance}
%    |{collection}{type}{instname}{templatename}{keyval}|
%    The fifth argument is picked up implicitly.
%    \begin{macrocode}
\cs_new:Npn \DeclareCollectionInstance#1#2#3#4{
  \TP_declare_instance:cnn { <#1>#2/#3 }{ #2/#4 }
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\UseCollection}
% |{type}{collection}|
%    \begin{macrocode}
\cs_new_nopar:Npn \UseCollection#1#2{
  \tl_set:cx { TP@<#1> }
    { {#2} \TP_get_arg_count:n{#1} }
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_let_instance:Nnn}
%    |\internalcommand{type}{instname}|
%
%    The way this macro is used, it must result in |\cs_set_eq:NwN| |<csname1>|
%    |<csname2>| after exactly two expansions as it is used this way
%    in |\TP_templdecl_eval_i_key_value:nnn|!
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_let_instance:Nnn#1#2#3{
  \cs_set_eq:Nc #1
  {
    \cs_if_free:cTF { \TP_get_csname_prefix:n{#2} #3 }
      { <>#2/ }
      { \TP_get_csname_prefix:n{#2} }
    #3
  }
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\UseInstance}
% |{type}{instname}|
%    \begin{macrocode}
\cs_new_nopar:Npn \UseInstance#1#2{
  \TP_let_instance:Nnn \l_tmpa_tl {#1}{#2}
  \tl_if_eq:NNTF \l_tmpa_tl \scan_stop:
     \INSTANCEundefined
     \l_tmpa_tl
}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_templdecl_declare_tmp_instance:nnnn}
%    This macro is called when we have seen a |\UseTemplate|
%    declaration as part of an |i| key value. Therefore the
%    first argument will be dropped (it contains the token
%    |\UseTemplate|) the second and third will be combined to refer to
%    the template and the fourth argument will be implictly picked up
%    by |\TP_declare_instance:Nnn|.
%    \begin{macrocode}
\cs_new:Npn \TP_templdecl_declare_tmp_instance:nnnn#1#2#3{%
  \TP_declare_instance:Nnn \g_tmpa_tl {#2/#3} }
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\ShowTemplate}
% Some extension to |\ShowTemplate| so that we also get to see the
% restrictions if any
%    \begin{macrocode}
\cs_new_nopar:Npn \ShowTemplate#1#2{
   \iow_term:x{*******~ Template:~ #1/#2~ *******}
   \iow_term:x{*}
   \iow_term:x{*~ Defaults:}
   \iow_term:x{*}
   \iow_term:x{\token_to_str:N\TPD>/#1/#2=
      \cs_meaning:c{TPD>/#1/#2}}
   \iow_term:x{*}
   \iow_term:x{*~ Restrictions:}
   \iow_term:x{*}
   \iow_term:x{\token_to_str:N\TPR>/#1/#2=
      \cs_meaning:c{TPR>/#1/#2}}
   \iow_term:x{*}
   \iow_term:x{*~ Body:}
   \iow_term:x{*}
   \cs_show:c {TP>/#1/#2}}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\ShowCollectionInstance}
%    \begin{macrocode}
\cs_new_nopar:Npn \ShowCollectionInstance#1#2#3{
   \iow_term:x{*******~ Instance:~ <#1>#2/#3~ *******}
   \iow_term:x{*}
   \cs_show:c {<#1>#2/#3}}
\cs_new_nopar:Npn \ShowInstance{\ShowCollectionInstance{}}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_templdecl_setup_fakeregister_key:NNn}
% |{setcomand}{privateregister}{key}{internalcode}|
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_templdecl_setup_fakeregister_key:NNn#1#2#3{
  \TP_templdecl_define_key:n{
    \tl_if_head_eq_meaning:nNTF{##1..}\DelayEvaluation
    {
%    \end{macrocode}
%    In the v0.08 version of \texttt{template.dtx} a
%    |\DelayEvaluation| for a faked register would simply be equiv to
%    a |\cs_set_nopar:Npn | (code is below commented out). The negative side effect
%    of this is that something like |=L| used with |\DelayEvaluation|
%    would not allow for calc syntax since it would end up as
%    |\cs_set_nopar:Npn |\allowbreak|\foo|\allowbreak|{a+b}|. The code below changes
%    this to first assign to a scratch register (at runtime) and then
%    do an |\edef|. Could be coded differently to save space (at cost
%    of time)
%    \begin{macrocode}
%       \toks_put_right:Nn \l_TP_KV_assignments_toks {\cs_set_nopar:Npn #3{##1}}
%      \toks_put_right:Nn \l_TP_KV_assignments_toks
%                         {#1#2{##1}\cs_set_nopar:Npx #3{\toks_use:N#2}}
      \toks_set:No \l_tmpa_toks {\use_ii:nn ##1}
      \toks_put_right:Nx \l_TP_KV_assignments_toks {
        \exp_not:n{#1#2}{\toks_use:N \l_tmpa_toks}
          \exp_not:n{ \cs_set_nopar:Npx #3{\toks_use:N#2} }
        
      }
    }
%    \end{macrocode}
%
%
%    Otherwise same game for fake registers except that instead of
%    passing the register to |\TP_multiselection_add:nnnnnn| we pass a
%    temp fake one and
%    doing a def instead of using |\setlength| or |\setcounter|
%
%    and i haven't done the |\DelayEvaluation| bit for that case! as
%    i'm not sure what the best approach is for those
%    things\footnote{we might disallow it for that case in general ---
%    not a nice rule but an explainable one}
%
%    \begin{macrocode}
    {
      \tl_if_head_eq_meaning:nNTF{##1..}\MultiSelection
      {
        \group_begin:
          \TP_multiselection_add:nnnnnn#1#2##1
        \group_end:
        \toks_put_right:Nx\l_TP_KV_assignments_toks
          {\exp_not:n{\cs_set_nopar:Npn #3} {\toks_use:N\g_TP_multiselection_toks}}
      }
      {
        #1#2{##1}
        \toks_put_right:Nx\l_TP_KV_assignments_toks
                    {\exp_not:n{\cs_set_nopar:Npn#3} {\toks_use:N#2}}
      }
    }
  }
}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\g_TP_multiselection_toks}
%    \begin{macrocode}
\toks_new:N \g_TP_multiselection_toks
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\TP_multiselection_add:nnnnnn}
%  \marg{operation} \marg{register} |\MultiSelection|
%  \marg{selector} \marg{case-list} \marg{else-case}
%
%  This command builds up the |\if_case:w| code from the three
%  arguments of |\MultiSelection| and stores it in
%  |\g_TP_multiselection_toks|. This code is supposed to be run in a
%  group so a) we don't have to initialise |\g_TP_multiselection_toks|
%  and b) all changes to the used registers not affecting the
%  outside. 
%
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_multiselection_add:nnnnnn #1#2#3#4#5#6{
  \toks_gset:Nn \g_TP_multiselection_toks {\if_case:w #4}
  \clist_map_inline:nn {#5}{
    \tl_if_head_eq_meaning:nNTF{##1..}\DelayEvaluation
    {
      \TP_multiselection_add_or_case:n {##1}
    }
    {
      #1#2{##1}
      \TP_multiselection_add_or_case:o { \toks_use:N #2 }
    }
  }
  \toks_gput_right:Nn \g_TP_multiselection_toks {
    \else: \use_i_after_fi:nw{#6}\fi: 
  }
}
%    \end{macrocode}
%
% \end{macro}
%
% \begin{macro}{\TP_multiselection_add_or_case:o}
%   No need to worry about where |\or:| is allowed to be added since
%   all loops in \LaTeX3 process the item outside conditionals.
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_multiselection_add_or_case:n #1 {
  \toks_gput_right:Nn \g_TP_multiselection_toks { 
    \or: \use_i_after_orelse:nw{#1} 
  }
}
\cs_generate_variant:Nn \TP_multiselection_add_or_case:n {o}
%    \end{macrocode}
% \end{macro}
%
% Since i like to set things like |item-label-text| using this
% mechanism i need to handle the `n' key specially.
%
% Actually i could have probably extended
% |\TP_templdecl_setup_f_key:nnN| thus making
% this generally available to all f\meta{number} keys but was too lazy
% (or too stupid) to get it right first time so settled for the simple
% solution.
%
% So |\TP_templdecl_parse_KV:nnw| now calls
% |\TP_templdecl_setup_n_key:nN| for the `n' key. looks like
% this thus be fixed some time soon
%
%
%
%
%
%
%
% \begin{macro}{\IfExistsInstanceTF}
%   tests that there is a \emph{default} definition
%    taken from xinitials.dtx:
%    \begin{macrocode}
\cs_new_nopar:Npn \IfExistsInstanceTF#1#2{
  \cs_if_exist:cTF{<>#1/#2}
}
%    \end{macrocode}
%
%     FMi: what happens if we are in collection FOO and there exists an
%     instance I for type T within this collection but there doesn't exist
%     an instance in the empty collection?
%
%     What would happen if \ldots\  --- not clear to me what the sematics
%     really should be. The code below is not better only different( and
%     slower).\footnote{fix semantics}
%    \begin{macrocode}
\cs_set_nopar:Npn \IfExistsInstanceTF#1#2{
  \TP_let_instance:Nnn \l_tmpa_tl {#1}{#2}
% next is not \tl_if_eq:NNTF but ...FT so done manually
  \if_meaning:w\l_tmpa_tl\scan_stop:
    \exp_after:wN\use_ii:nn
  \else:
    \exp_after:wN\use_i:nn
  \fi:}
%    \end{macrocode}
% \end{macro}
%
% \begin{macro}{\DeclareRestrictedTemplate}
% Setting it up:
%
%| \DeclareRestrictedTemplate|\\
%     |{T-type} {new-T-name} {source-T-name} {keyvals}|
%
% This uses the same code as {T-type} {source-T-name} but adds
% settings from {keyvals}
%    \begin{macrocode}
\cs_new_nopar:Npn \DeclareRestrictedTemplate#1#2#3#4{
  % CCC do we need a group here??
  \tl_set_eq:cc { TPD>/#1/#2 } { TPD>/#1/#3 }
  \tl_set_eq:cc {  TP>/#1/#2 } {  TP>/#1/#3 }
  \toks_set:Nv \l_TP_KV_assignments_toks { TPR>/ #1 / #3 }
% adds stuff to \l_TP_KV_assignments_toks
  \setkeys {\cs:w TPO>/#1/#3\cs_end:}{#4}

  \tl_set:cx { TPR>/#1/#2 }
              { \toks_use:N \l_TP_KV_assignments_toks }
  \cs_if_free:cTF { TPO>/#1/#3 }
    { \tl_set:cn {TPO>/#1/#2}{#1/#3}       }
    { \tl_set_eq:cc {TPO>/#1/#2}{TPO>/#1/#3}  }
}
%    \end{macrocode}
% \end{macro}
%
%
% Internals:
%
% \begin{macro}{\TP_instdecl_generate_assignments:nn}
%    These could probably be inlined, even when they do something!
%
%    Assumption: setkeys fully expands its first argument.
%
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_instdecl_generate_assignments:nn#1#2 {
                               % Returns to \l_TP_KV_assignments_toks
                               % the restrictions
                               % stored in the TP-structure (at present
                               % in YAM) of the template #1
    \exp_args:NNo \toks_set:No \l_TP_default_assignments_toks
                 {\cs:w TPD>/#1\cs_end:\scan_stop:\scan_stop:}
    \toks_set:Nv \l_TP_KV_assignments_toks { TPR>/ #1 }
    \setkeys { \cs:w TPO>/#1 \cs_end: }
             { #2 }            % adds stuff to \l_TP_KV_assignments_toks

% prepends stuff to \l_TP_KV_assignments_toks :
    \exp_after:wN\TP_instdecl_add_default_recurse:nn
        \toks_use:N\l_TP_default_assignments_toks

}
%    \end{macrocode}
% \end{macro}
%
%
% \begin{macro}{\TP_instdecl_add_default_recurse:nn}
%    [ 2001/06/10 Think about doing this properly with explicit plists! --- but
%    this means that one has to think about whether or not plists should be
%    implemented as token registers and not as tl vars as they are now. ]
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_instdecl_add_default_recurse:nn#1#2{
  \token_if_eq_meaning:NNF #1\scan_stop:
  {
    \l_tmpa_toks{#2}
    \tl_set:Nx \l_tmpa_tl {
      {\toks_use:N \l_tmpa_toks \toks_use:N \l_TP_KV_assignments_toks}
    }
    \l_TP_KV_assignments_toks \l_tmpa_tl
    \TP_instdecl_add_default_recurse:nn
  }
}
%    \end{macrocode}
% \end{macro}
%
%
%
% |TPD>/type/name| stores the default parameter assignments.
%
% |TPR>/type/name| stores the parameter assignments that have been
% made for a restricted template otherwise it is undefined (or |\scan_stop:|).
%
%
% |TPO>/type/name| stores the full name (i.e. as |type/name|)
% of the template a restricted
% template is coming from originally.
%
%
%
%
%  \begin{macro}{\TP_split_finite_skip_value:nnNN}
%  This macro is for use in error checking template values like
%  "text-float-sep" that can't contain infinite glue and needs the
%  shrink and/or stretch components. First argument is the skip
%  register (which is likely to be user input), second is a template
%  key name, and the last two are the \meta{dimen} registers that
%  stores the stretch and shrink components. Assignments are global.
%    \begin{macrocode}
\cs_new_nopar:Npn \TP_split_finite_skip_value:nnNN #1#2{
  \skip_split_finite_else_action:nnNN {#1} {
    \PackageError{template}{Value~ for~ key~ #2~ contains~ `fil(ll)'}
    {Only~ finite~ minus~ or~ plus~ parts~ are~ allowed~ for~ this~ key.}
  }
}
%    \end{macrocode}
%  \end{macro}
%
%
%
%
%    \begin{macrocode}
%</package>
%    \end{macrocode}
%
% \Finale
%