This file is indexed.

/usr/share/common-lisp/source/iterate/iterate.lisp is in cl-iterate 20160825-1.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453
3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539
3540
3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
3559
3560
3561
3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
3586
3587
3588
3589
3590
3591
3592
3593
3594
3595
3596
3597
3598
3599
3600
3601
3602
3603
3604
3605
3606
3607
3608
3609
3610
3611
3612
3613
3614
3615
3616
3617
3618
3619
3620
3621
3622
3623
3624
3625
3626
3627
3628
3629
3630
3631
3632
3633
3634
;;;-*- syntax:COMMON-LISP; Package: (ITERATE :use "COMMON-LISP" :colon-mode :external) -*-


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;                     ITERATE, An Iteration Macro
;;;
;;;                 Copyright 1989 by Jonathan Amsterdam
;;;         Adapted to ANSI Common Lisp in 2003 by Andreas Fuchs
;;;
;;; Permission to use, copy, modify, and distribute this software and its
;;; documentation for any purpose and without fee is hereby granted,
;;; provided that this copyright and permission notice appear in all
;;; copies and supporting documentation, and that the name of M.I.T. not
;;; be used in advertising or publicity pertaining to distribution of the
;;; software without specific, written prior permission. M.I.T. makes no
;;; representations about the suitability of this software for any
;;; purpose.  It is provided "as is" without express or implied warranty.

;;; M.I.T. DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
;;; ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
;;; M.I.T. BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
;;; ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
;;; WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
;;; ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
;;; SOFTWARE.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;  FIXES.
;;; (v. 1.2-ansi)
;;;  2004-11-30 - Joerg Hoehle: a dozen small fixes to various functions
;;;  2003-12-16 - Tested a bit more, implemented FOR-HASHTABLE and
;;;               FOR-PACKAGES (FOR-PACKAGE) iteration CLtS-style
;;;               using (with-{package,hashtable}-iterator)
;;;  2003-12-16 - ported iterate-1.2 to ANSI Common Lisp (in the form
;;;               of SBCL). Extremely untested. Works for simple
;;;               examples, though.
;;; (v. 1.2)
;;;  6/14/91  - fixed generation of previous code
;;;  5/6/91   - improved code generated for COLLECT and ADJOINING
;;;  4/10/91  - added *binding-context?* to correctly determine when inside
;;;	        a binding context
;;;  12/20/90 - fixed ,. bug in IN-HASHTABLE
;;;  3/3/91 - no longer generates loop-end and loop-step tags if they're not
;;;           used, to avoid compiler warnings from some compilers (Allegro)
;;;  3/4/91 - treat cond as a special form for allegro
;;;  (v. 1.1.1)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; OUTSTANDING PROBLEMS & QUESTIONS:
;;; - What happens if there are two contradictory declarations 
;;;   about a variable's type?  We just take the second one. CLM 
;;;   doesn't say, but presumably this is an error. Let's say it is.
;;;
;;; - Is there a more general way to do synonyms that still allows
;;;   some specificity to particular clauses?  Right now, all we allow
;;;   is for the first words of clauses to have synonyms.
;;;
;;; - We should look at function type declarations, at least at the
;;;   result type, and record them.
;;;
;;; - Consider adding an if-never keyword to find...max/min
;;;
;;; - Consider allowing accumulation variables to be generalized
;;;   variables, acceptable to setf.
;;;
;;; - Consider parsing type declarations of the form (vector * integer),
;;;   to generate types for internal variables.
;;;
;;; - Vector destructuring?
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; TO DO: 
;;;  - do I walk &optional and &key code in lambda-lists?
;;;  - try binding *macroexpand-hook* in walk
;;;  - track down PREVIOUS bug in Symbolics and sparc lucid

;;;  - reducing and accum: RESULT-TYPE
;;;  - rethink types 
;;;  - how to type result var?
;;;  - (for var concatenate (from 1 to 10) (in '(a b c)) (next (gensym)))
;;;  -       (if (< var 10) 
;;;		 (next [from-to])
;;;		 (if lst
;;;		     (next [in])
;;;		     (gensym)))
;;;  - for var choose, for var repeatedly

;;; For CL version 2:
;;;  - variable info from environments
;;;  - macro info     "     " (so we can support macrolet)
;;;  - use errors for EOF
;;;  - change WALK and FREE-VARIABLES to take symbol macros into account
;;;  - array indices are fixnums
;;;  - type REAL for extremum clauses

;;; Maybe:
;;;  - decls can appear not at top level, as long as they appear before use.
;;;  - extremum and find-extremum should do reductions when possible
;;;  - optimize collections, hashtables, packages for lispms 
;;;  - fix :using-type-of to check for supplied ???
;;;  - for-in should allow numerical keywords (from, to, etc.)...?
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; TO TEST: 
;;;  - leaving driver code where it is
;;;  - typing
;;;  - macroexpand & walk after-each
;;;  - check for duplicate keywords in defclause, defmacro-clause
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; TO DOCUMENT:
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;


(in-package #:iterate)

(declaim (declaration declare-variables))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Constants and global variables.
(defconst version "1.4" "Current version of Iterate")



(defconst standard-type-symbols ; of CLtL2
  '(array atom bignum bit bit-vector boolean character compiled-function
    complex cons double-float fixnum float function hash-table integer
    keyword list long-float nil null number package pathname random-state
    ratio rational readtable real sequence short-float signed-byte simple-array 
    simple-bit-vector simple-string simple-vector single-float standard-char
    stream string string-char symbol t unsigned-byte vector)
  "Table 4-1 of the Common Lisp Manual")


;;; These next two can be used for maximizing and minimizing.

#+nil ;; unused
(defconst smallest-number-alist
  `((fixnum . ,most-negative-fixnum)
    (float . ,most-negative-long-float)
    (long-float . ,most-negative-long-float)
    (short-float . ,most-negative-short-float)
    (double-float . ,most-negative-double-float)
    (single-float . ,most-negative-single-float)))

#+nil ;; unused
(defconst largest-number-alist
  `((fixnum . ,most-positive-fixnum)
    (float . ,most-positive-long-float)
    (long-float . ,most-positive-long-float)
    (short-float . ,most-positive-short-float)
    (double-float . ,most-positive-double-float)
    (single-float . ,most-positive-single-float)))


;;; This is like (declare (declare-variables)).

(defvar *always-declare-variables* nil)

;;; *result-var* is bound to a gensym before the clauses of an iterate
;;; form are processed.  In the generated code, the gensym is bound
;;; to nil before any other bindings are performed.  Clauses are free
;;; to generate code that sets the value of *result-var*.

(defvar *result-var*)

;;; Iterate binds *type-alist* to an alist of variables and their
;;; types before processing clauses.  It does this by looking at
;;; (declare (type ...)) forms in the clauses and recording the information
;;; there.  (Just variable type information, not function.)

(defvar *type-alist*)

;;; *declare-variables* is bound to T iff the 
;;;            (declare (iterate:declare-variables))
;;; declaration was seen at top-level, or if
;;; *always-declare-variables* is non-nil.  This indicates that variables 
;;; that haven't been declared by the user should be declared to have
;;; the appropriate types.  What "appropriate" means depends on the
;;; context. 

(defvar *declare-variables*)

;;; *clause* is bound to each entire iterate clause before the clause
;;; is processed.  Mostly for error output (see clause-error).

(defvar *clause*)

;;; *top-level?* is bound to T at top-level (i.e. before any forms that
;;; contain clauses inside them, like IF, LET, etc.) and to NIL
;;; inside such forms.  It is useful to ensure that certain forms
;;; (particularly iteration drivers) occur only at top-level.

(defvar *top-level?*)

;;; *binding-context?* a misnomer, should be named *declaration-context*, is
;;; bound to T inside a form that allows declarations (flet, labels).  We used
;;; to just see if *internal-variables* was non-nil, but that's wrong--you can
;;; be inside a binding context that binds no variables.

(defvar *binding-context?*)

;;; For the use of make-binding-internal, to pass back bindings.
;;; if-1st-time also uses it to create first-time variables.

(defvar *bindings*)


;;; This is a list of variable-lists containing the variables made by
;;; internal let's or other binding forms.  It is used to check for
;;; the error of having iterate try to bind one of these variables at
;;; top-level.  E.g.
;;;   (iterate (for i from 1 to 10)
;;;            (let ((a nil))
;;;              (collect i into a)))
;;; is an error.

(defvar *internal-variables*)


;;; For functions (like make-binding) that don't want to or can't pass
;;; declarations normally.  These are really decl-specs, not full
;;; declarations. 

(defvar *declarations*)


;;; This is how we get multiple accumulations into the same variable
;;; to come out right.  See make-accum-var-binding.
;;; It's an alist of (accum-var kind <possibly other info>).
;;; The currently used kinds are:
;;;   :collect     for collect, nconc, append, etc.
;;;   :increment   for count, sum and multiply
;;;   :max         for maximize
;;;   :min         for minimize
;;;   :if-exists   for always/never/thereis and finding such-that
;;; Note that we do not check for type conflict in the re-use of these
;;; variables.

(defvar *accum-var-alist*)

;;; Shared variables created by make-shared-binding.
;;; It's an alist of (name gensym-var <possibly other info>).
;;; Tipical use is FIRST-ITERATION-P.

(defvar *shared-bindings-alist*)

;;; Name of the block for this iterate form.  Used in generating
;;; return statements.

(defvar *block-name*)

;;; The index of standard clauses (a discrimination tree).  This is a
;;; defvar so that reloading doesn't clobber existing defs (though it
;;; will clobber those clauses that are defined in this file, of
;;; course).

(defvar *clause-info-index* (list :index))

(eval-when (:compile-toplevel)
  ;; This is so the variable has a value when we compile this file, since
  ;; the process of compilation results in actually setting things up.
  (if (not (boundp '*clause-info-index*)) 
      (setq *clause-info-index* (list :index))))


;;; An alist of lisp special forms and the functions for handling them.
;;; nil as function means leave form as-is.

(defparameter *special-form-alist* 
  '(;; First the special operators that every code walker must recognize
    (block . 		    walk-cddr) 
    (catch . 		    walk-cdr)
    (declare . 	 	    walk-declare)
    (eval-when .  	    walk-cddr)
    (flet . 		    walk-flet)
    (function . 	    walk-function)
    (go . 		    nil)
    (if . 		    walk-cdr) ; also walk test form
    (labels . 		    walk-flet)
    (let . 		    walk-let)
    (let* . 		    walk-let)
    (load-time-value .      nil)
    (locally .              walk-cdr-with-declarations)
    ;(macrolet . 	    walk-macrolet) ; uncomment to raise error
    (multiple-value-call .  walk-cdr)
    (multiple-value-prog1 . walk-cdr)
    (progn . 		    walk-progn)
    (progv . 		    walk-cdr)
    (quote . 		    nil)
    (return-from . 	    walk-cddr)
    (setq . 		    walk-setq)
    (symbol-macrolet . 	    walk-cddr-with-declarations)
    (tagbody . 		    walk-tagbody)
    (the . 		    walk-cddr)
    (throw . 		    walk-cdr) 
    (unwind-protect . 	    walk-cdr)

    ;; Next some special cases:
    ;; m-v-b is a macro, not a special form, but we want to recognize bindings.
    ;; Furthermore, Lispworks macroexpands m-v-b into some unknown m-v-BIND-call special form.
    (multiple-value-bind .  walk-multiple-value-bind)
    ;; Allegro treats cond as a special form, it does not macroexpand.
    #+allegro (cond .	    walk-cond)
    ;; Prior to 2005, CLISP expanded handler-bind into some
    ;; sys::%handler-bind syntax not declared as a special operator.
    #+clisp (handler-bind . walk-cddr) ; does not recognize clauses in handlers
    ;; A suitable generalization would be a pattern language that describes
    ;; which car/cdr are forms to be walked, declarations or structure.
    ;; Walk with-*-iterator ourselves in order to avoid macrolet warnings.
    ;; Note that walk-cddr-with-declarations won't walk the
    ;; package/hash-table descriptor argument, but it's good enough for now.
    (with-package-iterator    . walk-cddr-with-declarations)
    (with-hash-table-iterator . walk-cddr-with-declarations)

    ;; Finally some cases where code compiled from the macroexpansion
    ;; may not be as good as code compiled from the original form:
    ;; -- and iterate's own expansion becomes more readable
    (and .		    walk-cdr)
    (ignore-errors .	    walk-cdr) ; expands to handler-bind in CLISP
    (multiple-value-list .  walk-cdr)
    (multiple-value-setq .  walk-cddr)
    (nth-value .	    walk-cdr)
    (or .		    walk-cdr)
    (prog1 .		    walk-cdr)
    (prog2 .		    walk-cdr)
    (psetq . 		    walk-setq)))


;;; For clauses that are "special" in the sense that they don't conform to the
;;; keyword-argument syntax of Iterate clauses.

(defvar *special-clause-alist* nil)


;;; These two are for conserving temporaries.  *temps* is a list
;;; of temporaries that have already been created and given bindings.
;;; *temps-in-use* is a list of temporaries that are currently being used.
;;; See with-temporary, with-temporaries.
;;; This seems to stem from a time where it was more efficient to use
;;; (prog (temp)
;;;    ... (setq temp #) ; somewhere deep inside the body
;;;        (foo temp)
;;;        (bar temp)
;;;    ...)
;;; than using a local let deep inside that body, as in
;;; (tagbody ... (let ((temp #)) (foo temp) (bar temp)) ...)
;;; which may be be easier for compiler data flow and lifetime analysis.

(defvar *temps*)
(defvar *temps-in-use*)

;;; This is the environment, for macroexpand.

(defvar *env*)

;;; This is a list of information about drivers, for use by the NEXT
;;; mechanism. 

(defvar *driver-info-alist*)

;;; This is used by the PREVIOUS mechanism.

(defvar *previous-vars-alist*)


;;; Loop labels

(defvar *loop-top*)
(defvar *loop-step*)
(defvar *loop-end*)

;;; Whether a label was used, to avoid generating them.  This is so we don't
;;; get a warning from compilers that check for unused tags.

(defvar *loop-step-used?*)
(defvar *loop-end-used?*)

;;; Things that we should wrap the loop's body in

(defvar *loop-body-wrappers*)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;



(eval-when (:compile-toplevel :load-toplevel :execute)

;;; Clause-info structures, which are put in the clause index.
  (defstruct clause-info
    function
    keywords
    req-keywords
    doc-string
    generator?)

;;; Driver-info structures, for information about driver variables--used by
;;; NEXT.

  (defstruct driver-info
    next-code
    generator?
    (used nil))

;;; Previous-info structures, used by the PREVIOUS mechanism.

  (defstruct previous-info
    var
    save-info-list
    code
    (class :step))

  (defstruct save-info
    save-var
    save-vars
    iv-ref)

  )

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Macros.

(eval-when (:compile-toplevel :load-toplevel :execute)  ;; Allegro needs this 

#+nil ;; unused
(defmacro assertion (test)
  `(if (not ,test) (bug "Assertion ~a failed" ',test)))

(defmacro augment (var stuff)
  `(setf ,var (nconc ,var ,stuff)))

(defmacro prepend (stuff var)
  `(setf ,var (nconc ,stuff ,var)))

) ;end eval-when

(eval-when (:compile-toplevel :load-toplevel :execute)

(defun list-of-forms? (x)
  (and (consp x) (consp (car x))
       (not (eq (caar x) 'lambda))))

) ;end eval-when

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; SharpL. 
;;;
;;; the #L reader macro is an abbreviation for lambdas with numbered
;;; arguments, with the last argument being the greatest numbered
;;; argument that is used in the body.  Arguments which are not used
;;; in the body are (declare ignore)d.
;;;
;;; e.g. #L(list !2 !3 !5) is equivalent to:
;;;      (lambda (!1 !2 !3 !4 !5) (declare (ignore !1 !4)) (list !2 !3 !5))

(eval-when (:compile-toplevel :execute)

  (defun sharpL-reader (stream subchar n-args)
    (declare (ignore subchar))
    ;; Depending how an implementation chooses to expand `(,!1 (get-free-temp))
    ;; at read-time, it might be a macro that must be expanded before groveling
    ;; the resultant sexpr. Here it gets expanded in the null environment for
    ;; lack of anything better. If the macro is sensitive to its lexical
    ;; environment, it suggests perhaps an inappropriate use of #L.
    ;; However, to support unforseen cases, we will use the original form as
    ;; read for the resulting lambda's body. Moreover, rather than stuff new
    ;; atoms into the body which is impossible if the representation is opaque,
    ;; redirect "!" vars onto gensyms using SYMBOL-MACROLET.
    (let* ((form (read stream t nil t))
	   (refd-!vars (sort (bang-vars (macroexpand form))
                             #'< :key #'bang-var-num))
	   (bang-var-nums (mapcar #'bang-var-num refd-!vars))
	   (max-bv-num (if refd-!vars (car (last bang-var-nums)) 0)))
      (cond ((null n-args)
             (setq n-args max-bv-num))
            ((< n-args max-bv-num)
             (error "#L: digit-string ~d specifies too few arguments" n-args)))
      (let* ((all-!vars (loop for i from 1 to n-args collect (make-bang-var i)))
	     (formals (mapcar (lambda (x) (declare (ignore x)) (gensym))
                              all-!vars)))
	`#'(lambda ,formals
             ,@(let ((ignore (mapcan (lambda (!var tempvar)
                                       (unless (member !var refd-!vars)
                                         (list tempvar)))
                                     all-!vars formals)))
                 (if ignore `((declare (ignore ,@ignore)))))
             (symbol-macrolet ,(mapcan (lambda (!var tempvar)
                                         (when (member !var refd-!vars)
                                           (list (list !var tempvar))))
                                       all-!vars formals)
               ,@(if (list-of-forms? form) form (list form)))))))

  (defun make-bang-var (n)
    (intern (format nil "!~d" n)))

  (defun bang-vars (form)
    (delete-duplicates (bang-vars-1 form '()) :test #'eq))

  (defun bang-vars-1 (form vars)
    (cond
      ((consp form)
       (bang-vars-1 (cdr form)
		    (bang-vars-1 (car form) vars)))
      ((and (symbolp form) (bang-var? form)) (cons form vars))
      (t vars)))

  (defun bang-var? (sym)
    (char= (char (symbol-name sym) 0) #\!))

  (defun bang-var-num (sym)
    (let ((num (read-from-string (subseq (symbol-name sym) 1))))
      (if (not (and (integerp num) (> num 0)))
	  (error "#L: ~a is not a valid variable specifier" sym)
	  num)))

  (defun enable-sharpL-reader ()
    (set-dispatch-macro-character #\# #\L #'sharpL-reader))

  ;; According to CLHS, *readtable* must be rebound when compiling
  ;; so we are free to reassign it to a copy and modify that copy.
  (setf *readtable* (copy-readtable *readtable*))
  (enable-sharpL-reader)

  ) ; end eval-when

#|
;; Optionally set up Slime so that C-c C-c works with #L
#+#.(cl:when (cl:find-package "SWANK") '(:and))
(unless (assoc "ITERATE" swank:*readtable-alist* :test #'string=)
  (bind ((*readtable* (copy-readtable *readtable*)))
    (enable-sharpL-reader)
    (push (cons "ITERATE" *readtable*) swank:*readtable-alist*)))
;|#

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; The ITERATE macro.


(defmacro iterate (&body body)
  "Jonathan Amsterdam's powerful iteration facility"
  `(iter .,body))

(defmacro iter (&body body &environment env)
  "Jonathan Amsterdam's powerful and extensible iteration facility,
providing multiple accumulation, generators, memory of previous
iterations, over 50 clauses to start with and a Lisp-like syntax.
Evaluate (iterate:display-iterate-clauses) for an overview of clauses"
  (let* ((*env* env)
	 (*result-var* (genvar 'result))
	 (*type-alist* nil)
	 (*declare-variables* *always-declare-variables*)
	 (*bindings* nil)
	 (*internal-variables* nil)
	 (*previous-vars-alist* nil)
	 (*declarations* nil)
	 (*loop-body-wrappers* nil)
	 (*accum-var-alist* nil)
         (*shared-bindings-alist* nil)
	 (*top-level?* t)
	 (*binding-context?* nil)
	 (*temps* nil)
	 (*temps-in-use* nil)
	 (*driver-info-alist* nil)
	 (*block-name* (if (symbolp (car body))
			   (pop body)
			   nil))
	 (*loop-top* (symbol-append 'loop-top- *block-name*))
	 (*loop-step* (symbol-append 'loop-step- *block-name*))
	 (*loop-end* (symbol-append 'loop-end- *block-name*))
	 (*loop-step-used?* nil)
	 (*loop-end-used?* nil))
    (process-top-level-decls body)
    (multiple-value-bind (body decls init-code steppers final-code final-prot)
	(walk-list body)
      (multiple-value-bind (init step)
	  (insert-previous-code)
	(augment init-code init)
	(augment steppers step))
      (prepend (default-driver-code) body)
      (let ((it-bod `(block ,*block-name*
		      (tagbody
			 (progn ,.init-code)
			 ,*loop-top*
			 (progn ,.body)
			 ,.(if *loop-step-used?* (list *loop-step*))
			 (progn ,.steppers)
			 (go ,*loop-top*)
			 ,.(if *loop-end-used?* (list *loop-end*))
			 (progn ,.final-code))
		      ,(if (member *result-var* *bindings* :key #'car)
			   *result-var*
			   nil))))
	(wrap-form *loop-body-wrappers*
		   `(let* ,(nreverse *bindings*)
		     ,.(if *declarations*
			   `((declare .,*declarations*)))
		     ,.decls
		     ,(if final-prot 
			  `(unwind-protect ,it-bod .,final-prot)
			  it-bod)))))))

(defmacro defmacro-clause (clause-template &body body)
  "Create your own iterate clauses"
  (define-clause 'defmacro clause-template body nil))

(defmacro defmacro-driver (clause-template &body body)
  "Create iterators which may also be used as generators"
  (define-clause 'defmacro clause-template body t))

;;;;;;;;;;;;;;;;

(defun process-top-level-decls (clauses)
  ;; This sets *type-alist* to an alist of (var . type), and
  ;; sets *declare-variables* to t if such a declaration was seen.
  (dolist (clause clauses)
    (when (and (consp clause) (eq (car clause) 'declare))
      (dolist (spec (cdr clause))
	(cond
	 ((eq (first spec) 'declare-variables)
	  (setq *declare-variables* t))
	 ((or (eq (first spec) 'type)  ; We don't do ftypes
	      ;; FIXME recognize all shorthand type declarations
	      ;; e.g. (declare ((unsigned-byte 8) x) etc.
	      ;; -- but how to recognize type specifications?
	      (member (first spec) standard-type-symbols :test #'eq))
	  (let ((type (first spec))
		(vars (cdr spec)))
	    (if (eq type 'type)
		(setq type (pop vars)))
	    (dolist (var vars)
	      (push (cons var type) *type-alist*)))))))))


(defun default-driver-code ()
  nil)

(defun wrap-form (wrappers form)
       (if (consp wrappers)
           (wrap-form (cdr wrappers)
		      (nconc (copy-list (car wrappers))
	                     (list form)))
	   form))

(defun add-loop-body-wrapper (wrapper)
  (push wrapper *loop-body-wrappers* ))

;(defun default-driver-code ()
;  ;; Collect all non-generator code.
;  ;; [Old version: Collect all code not explicitly invoked with NEXT.]
;  (let ((code nil))
;    ;; Put list in same order as clauses
;    (setq *driver-info-alist* (nreverse *driver-info-alist*)) 
;    (dolist (entry *driver-info-alist*)
;      (let ((di (cdr entry)))
;	(when (not (driver-info-generator? di))
;	  (assert (not (driver-info-used di)))
;	  (augment code (copy-list (driver-info-next-code di))))
;	(if (and (driver-info-generator? di)
;		 (not (driver-info-used di)))
;	    (clause-warning "A generator was never used"))))
;    code))


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; The code walker.

(defun walk (form)
  ;; Returns the usual five things; body is a list of forms.
  (cond
   ((atom form) ; symbol-macrolet must not expand into Iterate clauses
    (list form))
   ((symbolp (car form))
    (cond
     ;; The ordering of these checks is such that:
     ;; 1. We handle special operators that any Common Lisp code walker
     ;;    must recognize.
     ;; 2. We handle some special cases like Allegro's cond
     ;; 3. Then we expand macros.
     ;; 4. Then only do we recognize Iterate clauses
     ;;    -- which may thus be shadowed
     ;;
     ;; Note that implementations are permitted to let SPECIAL-OPERATOR-P
     ;; return T for any macros (e.g. CLISP for WHEN). Yet they must provide
     ;; a macroexpansion for these.

     ((special-form? (car form))
      (walk-special-form form))
     ((macro-function (car form) *env*)
      ;; Some compilers (e.g. Lucid on Sparcs) treat macros differently at
      ;; compile-time; macroexpand does not expand them.  We assume that if
      ;; this happens, macroexpand's second value is nil.  
      ;;   What do we do with the form in that case?  This is actually a
      ;; very serious problem: if we don't walk it, we miss things, but if we
      ;; do walk it, we don't know how to walk it.  Right now, we don't walk
      ;; it and print out a warning.
      ;;  --Jeff Siskind says try binding *macroexpand-hook* to #'funcall.
      (multiple-value-bind (ex-form expanded?)
	  (macroexpand-1 form *env*)
	(cond
	 (expanded? (walk ex-form))
	 (t	    (clause-warning "The form ~a is a macro that won't expand. ~
  It will not be walked, which means that Iterate clauses inside it will ~
  not be seen."
				    form)
		    (list form)))))
      ((special-operator-p (car form))
       (clause-warning "Iterate does not know how to handle the special form ~s~%~
  It will not be walked, which means that Iterate clauses inside it will ~
  not be seen." form)
       (list form))
      ((starts-clause? (symbol-synonym (car form)))
       (process-clause form))     
      (t ;; Lisp function call 
       (return-code-modifying-body #'walk-arglist (cdr form)
				   #L(list (cons (car form) !1))))))
   ((lambda-expression? (car form))
    ;; Function call with a lambda in the car
    (multiple-value-bind (bod decs init step final final-prot)
	(walk-fspec (car form))
      (multiple-value-bind (abod adecs ainit astep afinal afinal-prot)
	  (walk-arglist (cdr form))
	(values (list (cons bod abod)) (nconc decs adecs) (nconc init ainit)
		(nconc step astep) (nconc final afinal) 
		(nconc final-prot afinal-prot)))))
   #+clisp ; some macros expand into ((setf foo) value other-args...)
   ;; reported by Marco Baringer on 24 Jan 2005
   ((typep form '(cons (cons (eql setf) *) *))
    (apply #'walk-cdr form))
   (t
    (clause-error "The form ~a is not a valid Lisp expression" form))))

(defun walk-list (forms)
  (walk-list-nconcing forms #'walk))

(defun walk-arglist (args)
  (let ((*top-level?* nil))
    (walk-list-nconcing args #'walk  #L(if (is-iterate-clause? !1)
					   (list (prognify !2))
					   !2))))

(defun walk-fspec (form)
  ;; Works for lambdas and function specs in flet and labels.
  ;; FORM = (LAMBDA-or-name args . body)
  ;; We only walk at the body.  The args are set up as internal variables.
  ;; Declarations are kept internal to the body.
  (let* ((args (second form))
	 (body (cddr form))
	 (*top-level?* nil)
	 (*binding-context?* t)
	 (*internal-variables* (add-internal-vars args)))
    (multiple-value-bind (bod decs init step final finalp)
	(walk-list body)
      (values `(,(first form) ,args ,.decs ,.bod) nil init step final 
	      finalp))))

(defun walk-list-nconcing (list walk-fn 
				&optional (body-during #L!2))
  (let (body-code decls init-code step-code final-code finalp-code)
    (dolist (form list)
      (declare (optimize (speed 0)))
      (multiple-value-bind (body decs init step final finalp)
	  (funcall walk-fn form)
	(augment decls decs)
	(augment init-code init)
	(augment body-code (funcall body-during form body))
	(augment step-code step)
	(augment final-code final)
	(augment finalp-code finalp)))
    (values body-code decls init-code step-code final-code
	    finalp-code)))

(defun return-code-modifying-body (f stuff mod-f)
  (declare (optimize (speed 0)))
  (multiple-value-bind (bod decs init step final finalp)
      (funcall f stuff)
    (values (funcall mod-f bod) decs init step final finalp)))


(defun add-internal-var (var)
  ;; VAR can be a symbol or a list (symbol ...).
  (cons (if (consp var) (car var) var) *internal-variables*))

(defun add-internal-vars (vars)
  ;; VARS could be a lambda-list, a list of LET bindings, or just a list of
  ;; variables; all will work.
  (nconc (lambda-list-vars vars) *internal-variables*))

(defun lambda-list-vars (lambda-list)
  ;; Return the variables in the lambda list, omitting keywords, default
  ;; values.
  (mapcan #'(lambda (thing)
	      (cond
	       ((consp thing)
		(if (consp (car thing)) ; this is a full keyword spec
		    (list (second (car thing)))
		    (list (car thing))))
	       ((not (member thing lambda-list-keywords))
		(list thing))))
	  lambda-list))


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Special forms.

(defun special-form? (symbol)
  ;; special-operator-p doesn't work in Lucid--it returns NIL for let, for
  ;; example.  Plus, we want to catch Iterate special clauses.
  (assoc symbol *special-form-alist*))

(defun walk-special-form (form)
  (let ((*clause* form)
	(func (cdr (assoc (car form) *special-form-alist*))))
    (if (null func)    ; there's nothing to transform
	(list form)
	(apply func form))))

#+nil
(defun walk-identity (&rest stuff)
  (list stuff))

(defun walk-cdr (first &rest stuff)
  ;; This is for anything where only the car isn't to be walked.
  (return-code-modifying-body #'walk-arglist stuff #L(list (cons first !1))))

(defun walk-cddr (first second &rest stuff)
  ;; This is for anything where the first two elements aren't to be walked.
  (return-code-modifying-body #'walk-arglist stuff
			      #L(list (cons first (cons second !1)))))

(defun walk-progn (progn &rest stuff)
  ;; The only difference between this and walk-cdr is that *top-level* is not
  ;; bound.  This is so macros can return PROGNs of things.  It's exactly like
  ;; the definition of "top-level" in lisp. 
  ;; (Also, just for looks, this returns nil if the progn is empty.)
  (return-code-modifying-body #'walk-list stuff 
			      #L(if (null !1)
				    nil
				    (list (cons progn !1)))))

(defun walk-setq (setq &rest things)
  ;; Walk every other thing.
  (let ((*top-level?* nil)
	(i 1)
	body-code decls init-code step-code final-code finalp-code)
    (dolist (thing things)
      (if (oddp i)
	  (push thing body-code)
	  (multiple-value-bind (body decs init step final finalp)
	      (walk thing)
	    (augment decls decs)
	    (augment init-code init)
	    (push (prognify body) body-code)
	    (augment step-code step)
	    (augment final-code final)
	    (augment finalp-code finalp)))
      (incf i))
    (values (list (cons setq (nreverse body-code)))
	    decls init-code step-code final-code finalp-code)))

(defun walk-function (function form)
  (if (lambda-expression? form)
      (return-code-modifying-body #'walk-fspec form #L(list 
						       (list function !1)))
      (list (list function form))))

(defun walk-declare (&rest declaration)
  ;; DECLARE is a declaration, and should be put in the declaration
  ;; section of the loop.  Declarations are only allowed at top-level,
  ;; except that they are allowed within binding environments, in which case
  ;; they apply only to that binding environment.
  #+ symbolics (setq declaration (copy-list declaration))
  (if (or *top-level?* *binding-context?*)
      (return-code :declarations (list declaration)) 
      (clause-error "Declarations must occur at top-level, or inside a ~
  binding context like let or multiple-value-bind.")))

(defun walk-let (let bindings &rest body)
  ;; The bindings or body may contain iterate clauses.
  ;; Important: the decls go inside this let, not at top-level.
  ;; It is an error to use a variable in the let bindings as the
  ;; target of an accumulation (i.e. INTO), because iterate will try
  ;; to make a top-level binding for that variable.  The same goes for
  ;; other variables that might be so bound.
  (let ((*top-level?* nil))
    (multiple-value-bind (binds b-decls b-init b-step b-final b-finalp)
	(walk-let-bindings let bindings)
      (let ((*binding-context?* t)
	    (*internal-variables* (add-internal-vars binds)))
	(multiple-value-bind (bod decls init step final finalp)
	    (walk-list body)
	  (return-code :declarations b-decls
		       :initial (nconc b-init init)
		       :body (list `(,let ,binds ,.decls ,.bod))
		       :step (nconc b-step step)
		       :final (nconc b-final final)
		       :final-protected (nconc b-finalp finalp)))))))

(defun walk-let-bindings (let bindings)
  (if (eq let 'let)
      (walk-list-nconcing bindings #'walk-let-binding #L(list !2))
      (walk-let*-bindings bindings)))


(defun walk-let*-bindings (bindings)
  ;; We have to do this one binding at a time, to get the variable scoping
  ;; right.
  (if (null bindings)
      nil
      (multiple-value-bind (bod decls init step final finalp)
	  (walk-let-binding (car bindings))
	(let ((*internal-variables* (add-internal-var (car bindings))))
	  (multiple-value-bind (bod1 decls1 init1 step1 final1 finalp1)
	      (walk-let*-bindings (cdr bindings))
	    (values (cons bod bod1) (nconc decls decls1) (nconc init init1)
		    (nconc step step1) (nconc final final1)
		    (nconc finalp finalp1)))))))

      
(defun walk-let-binding (binding)
  (if (consp binding)
      (multiple-value-bind (bod decls init step final finalp)
	  (walk (second binding))
	(values (list (first binding) (prognify bod)) decls init step final
		finalp))
      binding))
    
(defun walk-multiple-value-bind (mvb vars expr &rest body)
  ;; Important: decls go inside the mvb, not at top-level.  See
  ;; walk-let for binding subtleties.
  (declare (ignore mvb))
  (let ((*top-level?* nil))
    (multiple-value-bind (ebod edecls einit estep efinal efinalp)
	(walk expr)
      (let ((*binding-context?* t)
	    (*internal-variables* (add-internal-vars vars)))
	(multiple-value-bind (bod decls init step final finalp)
	    (walk-list body)
	  (return-code :declarations edecls
		       :initial (nconc einit init)
		       :body (list `(multiple-value-bind ,vars
					,(prognify ebod)
				      ,.decls ,.bod))
		       :step (nconc estep step)
		       :final (nconc efinal final)
		       :final-protected (nconc efinalp finalp)))))))

(defun walk-flet (flet bindings &rest body)
  ;; For FLET or LABELS.  We don't worry about the function bindings.
  (let ((*top-level?* nil))
    (multiple-value-bind (binds b-decls b-init b-step b-final b-finalp)
	(walk-list-nconcing bindings #'walk-fspec #L(list !2))
      (let ((*binding-context?* t))
        (multiple-value-bind (bod decls init step final finalp)
	    (walk-list body)
	  (return-code :declarations b-decls
		       :initial (nconc b-init init)
		       :body (list `(,flet ,binds ,.decls ,.bod))
		       :step (nconc b-step step)
		       :final (nconc b-final final)
		       :final-protected (nconc b-finalp finalp)))))))

(defun walk-cdr-with-declarations (first &rest stuff) ; aka walk-locally
  ;; Set *top-level?* false (via walk-arglist).
  ;; Note that when *top-level?* is false, walk won't yield declarations
  ;; because walk-declare errors out since all forms with
  ;; *declaration-context?* true keep them local (that is, in walk-let,
  ;; walk-flet and walk-multiple-value-bind b-decls/edecls are always NIL).
  ;; Ignoring code-movement issues, this approach should be fine.
  (let* ((forms (member 'declare stuff :key #L(if (consp !1) (car !1))
			:test-not #'eq))
	 (decls (ldiff stuff forms)))
    (return-code-modifying-body #'walk-arglist forms
				#L(list (cons first (nconc decls !1))))))

(defun walk-cddr-with-declarations (first second &rest stuff)
  (let* ((forms (member 'declare stuff :key #L(if (consp !1) (car !1))
			:test-not #'eq))
	 (decls (ldiff stuff forms)))
    (return-code-modifying-body #'walk-arglist forms
				#L(list (cons first (cons second (nconc decls !1)))))))

(defun walk-tagbody (tagbody &rest statements)
  (flet ((walk-statements (statements)
	   (walk-list-nconcing
	    statements
	    #L(if (atom !1) (list !1) (walk !1))
	    #'(lambda (form body)
		(cond ((atom form) body)
		      ;; wrap statements which expand into an atom
		      ((typep body '(cons atom null))
		       (list (cons 'progn body)))
		      (t body))))))
    (let ((*top-level?* nil))
      (return-code-modifying-body
       #'walk-statements statements
       #L(list (cons tagbody !1))))))

(defun walk-macrolet (form-name &rest stuff)
  (declare (ignore stuff))
  (error "~A is not permitted inside Iterate. Please ~
  refactor the Iterate form (e.g. by using ~As that wrap ~
  the ITERATE form)." form-name form-name))

#+allegro
(defun walk-cond (cond &rest stuff)
  ;; Because the allegro compiler insists on treating COND as a special form,
  ;; and because some version macroexpands (cond #) into (cond #)!
  (declare (ignore cond))
  (if (null stuff)
      nil
      (let* ((first-clause (first stuff))
	     (test (if (not (consp first-clause))
		       (error "cond clause ~a is not a list" first-clause)
		       (car first-clause)))
	     (thens (cdr first-clause))
	     (if-form (if (null thens)
			  (let ((var (gensym)))
			    `(let ((,var ,test))
			      (if ,var ,var (cond ,@(cdr stuff)))))
			  `(if ,test (progn ,@thens) (cond ,@(cdr stuff))))))
	(walk if-form))))
			    


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Processing Iterate clauses.

(defvar *initial*)
(defvar *decls*)
(defvar *step*)
(defvar *final*)
(defvar *finalp*)

(defun process-clause (clause)
  ;; This should observe the invariant that the forms it returns are
  ;; already copied from the original code, hence nconc-able.  
  (let ((*clause* clause)
	(special-func (assoc (car clause) *special-clause-alist*)))
    (if special-func
	(apply-clause-function (car clause) (cdr clause))
	(let* ((ppclause (preprocess-clause clause))
	       (info (get-clause-info ppclause)))
	  (cond
	   (info
	    (arg-check ppclause info)
	    (let ((args (cons (keywordize (first ppclause))
			      (cdr ppclause)))
		  (func (clause-info-function info)))
	      (if (macro-function func *env*)
		  (walk (macroexpand-1 (cons func args) *env*))
		  (apply-clause-function func args))))
	   (t
	    (clause-error "No iterate function for this clause; do ~
  (~S) to see the existing clauses." 'display-iterate-clauses)))))))

(defun apply-clause-function (func args)
  (let ((*initial* nil)
	(*decls* nil)
	(*step* nil)
	(*final* nil)
	(*finalp* nil))
    (declare (optimize (speed 0)))
    (multiple-value-bind (body decls init step final finalp)
	(apply func args)
      (values body 
	      (nconc *decls* decls)  
	      (nconc *initial* init)
	      (nconc *step* step)
	      (nconc *final* final)
	      (nconc *finalp* finalp)))))
  
(defun preprocess-clause (clause)
  ;; First, check for errors.
  ;; Then, turn every other symbol except the first into a keyword,
  ;; and replace synonyms occurring as the first keyword.
  (do ((cl clause (cddr cl)))
      ((null cl))
    (if (not (symbolp (car cl)))
	(clause-error "~a should be a symbol" (car cl)))
    (if (null (cdr cl))
	(clause-error "Missing value for ~a keyword" (car cl))))
  (let ((new-clause nil)
	(syn (symbol-synonym (first clause))))
    (do ((cl (cddr clause) (cddr cl)))
	((null cl))
      (push (keywordize (first cl)) new-clause)
      (push (second cl) new-clause))
    ;; Hack so that (generate ...) turns into (for ... :generate t)
    (if (eq syn 'generate)
	`(for  ,(second clause) ,.(nreverse new-clause) :generate t)
	`(,syn ,(second clause) ,.(nreverse new-clause)))))


(defun symbol-synonym (symbol)
  (or (get symbol 'synonym) symbol))

(eval-when (:compile-toplevel :load-toplevel :execute)

(defun listify (x)
  (if (listp x) x (list x)))

(defun keywordize (symbol)
  (intern (symbol-name symbol) :keyword))

);end eval-when

(defun arg-check (clause info)
  ;; Make sure that each keyword in clause is in info.
  (let ((keywords (clause-info-keywords info)))
    (do ((cl clause (cddr cl)))
	((null cl))
      (if (null (cdr cl))
	  (clause-error "Missing a value for ~a" (car cl)))
      (if (not (member (car cl) keywords :test #'eq))
	  (if (eq (car cl) :generate)
	      (if (not (clause-info-generator? info))
		  (clause-error "Clause cannot be used as a generator"))
	      (clause-error "Unknown keyword ~a" (car cl)))))))

(defun walk-expr (expr)
  ;; This isn't used by the code walker itself, but is useful for clauses that
  ;; need to walk parts of themselves.  It always returns a single expression.
  ;; The other parts are collected using globals and returned by
  ;; process-clause. 
  (multiple-value-bind (body decls init step final finalp)
      (walk expr)
    (augment *decls* decls)
    (augment *initial* init)
    (augment *step* step)
    (augment *final* final)
    (augment *finalp* finalp)
    (prognify body)))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Displaying clauses.

(defun display-iterate-clauses (&optional clause-spec)
  (fresh-line)
  (if (and clause-spec (symbolp clause-spec))
      (setq clause-spec (list clause-spec)))
  (if (member '&optional clause-spec)
      (error "Iterate: clause-spec cannot mention optional keywords"))
  (if clause-spec
      (setq clause-spec (cons (car clause-spec)
			      (mapcar #'keywordize (cdr clause-spec)))))
  (dolist (spec-entry *special-clause-alist*)
    (let ((spec-clause-kws (list (car spec-entry))))
      (if (clause-matches? clause-spec spec-clause-kws)
	  (display-clause spec-clause-kws (cdr spec-entry)))))
  (disp-std-clauses clause-spec *clause-info-index*)
  t)

(defun disp-std-clauses (clause-spec index)
  (if (index? index)
      (dolist (entry (cdr index))
	(disp-std-clauses clause-spec (cdr entry)))
      (if (clause-matches? clause-spec (clause-info-keywords index))
	  (display-clause (clause-info-keywords index)
			  (clause-info-doc-string index)))))
  
(defun display-clause (kws doc-string)
  (display-kws kws)
  (if doc-string
      (format t "~25,4t ~a~%" doc-string)
      (terpri)))


(defconst fill-col 77)

(defun display-kws (kws)
  (do* ((col 1)
	(kw-list kws (cdr kw-list))
	(kw (car kw-list) (car kw-list)))
      ((null kw-list))
    (let ((len (length (symbol-name kw))))
      (when (>= (+ col len) fill-col)
	(format t "~%~4t")
	(setq col 4))
      (if (= col 1) ; the first one--print package name
	  (format t "~s" kw)
	  (format t "~a" kw))
      (incf col len)
      (when (cdr kw-list) 
	(cond
	 ((>= (+ col 1) fill-col)
	  (format t "~%~4t")
	  (setq col 4))
	 (t
	  (format t " ")
	  (incf col)))))))
      

(defun clause-matches? (clause-spec kws)
  (or (null clause-spec)
      (every #'eq clause-spec kws)))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Indexing of clause functions.

;;; Each clause has one or more required keywords, which must
;;; appear in order, and zero or more optional keywords, which may be
;;; omitted and may appear in any order.   

;;; The first word of a clause, though used as a keyword when the
;;; clause function is called, is kept in its original package for
;;; indexing purposes.  This provides iterate's interface with the
;;; package system.

;;; Two clauses can be ambiguous when 1) they have the same list of required
;;; keywords, or 2) #1's required-list is a prefix of #2's and #1 has optional
;;; keywords which match the remaining keywords of #2's required-list.  We
;;; check for these situations and signal an error.

;;; Indexing scheme: basically a discrimination tree.  There is a tree
;;; of alists with root *clause-info-index*.

(defun get-clause-info (clause &optional (index *clause-info-index*))
  (let ((entry (cdr (index-lookup (car clause) index))))
    (if (index? entry)
	(let ((result (get-clause-info (cddr clause) entry)))
	  ;; It could be that the required part of the clause ends here.
	  (or result (get-clause-info nil entry)))
	entry)))
      

(defun is-iterate-clause? (form)
  (and (consp form)
       (symbolp (car form))
       (starts-clause? (car form))))


(defun starts-clause? (symbol)
  ;; A symbol starts a clause if it appears in the top-level index, or if it
  ;; is in the special-clause alist, or if it is GENERATE.
  ;;   This is used to distinguish the case where there's a lisp form
  ;; (in which case the symbol doesn't start a clause), versus the
  ;; situation where an erroneous clause is provided.
  (or (assoc symbol *special-clause-alist*)
      (index-lookup symbol *clause-info-index*)
      (eq symbol 'generate)))

;;; The code generated by DEFINE-CLAUSE (below) is the only code that
;;; invokes this.

(eval-when (:compile-toplevel :load-toplevel :execute)

(defun install-clause-info (req-keywords keywords function doc-string 
			    generator?)
  (install-clause-info-1 req-keywords *clause-info-index* 
			 (make-clause-info :function function
					   :keywords keywords
					   :req-keywords req-keywords
					   :doc-string doc-string
					   :generator? generator?)))


(defun install-clause-info-1 (keywords index info)  
  ;; Here, KEYWORDS is a list of the required keywords.
  ;; The basic rule here is to build indices all the way out to the
  ;; end of the list of keywords.  That way it will be necessary for
  ;; the user's clause to contain all of the required keywords.
  ;;   If index contains no entry for the first keyword, build a full
  ;; set of indices and put it in index.  
  ;;   If there is an entry and it's an index, call recursively.
  ;;   If there's an entry and it's not an index, then we have a case of
  ;; duplication or prefix.  If duplication, we replace and warn; if
  ;; prefix, we check for ambiguity, and if so, error.
  (if (null keywords)
      (ambiguity-check-index info index))
  (let ((entry (index-lookup (car keywords) index)))
    (cond
     ((null entry)
      (index-add (car keywords) (build-index (cdr keywords) info) index))
     ((index? (cdr entry))
      (install-clause-info-1 (cdr keywords) (cdr entry) info))
     ((clause-info-p (cdr entry))
      (cond
       ((null (cdr keywords))
	;; Duplication; warn if they are not completely identical.
	(unless (equal (clause-info-keywords (cdr entry))
		       (clause-info-keywords info))
	  (warn "replacing clause ~a~%with ~a"
		(clause-info-keywords (cdr entry))
		(clause-info-keywords info)))
	(setf (cdr entry) info))
       (t
	(ambiguity-check-clause (cdr entry) info 2)
	;; Replace this entry with an index.
	(let ((index2 (build-index (cdr keywords) info)))
	  (index-add nil (cdr entry) index2)
	  (setf (cdr entry) index2)))))
     (t
      (bug "install-clause-info-1: index is broken")))))
	

(defun build-index (keywords info)
  (if (null keywords)
      info
      `(:index (,(car keywords) . ,(build-index (cdr keywords) info)))))
		 
(defun index? (x)
  (and (consp x) (eq (car x) :index)))

(defun index-add (key thing index)
  (push (cons key thing) (cdr index)))

(defun index-lookup (item index)
  (assoc item (cdr index) :test #'eq))

(defun ambiguity-check-index (ci1 index)
  ;; We're trying to add CI1, and we have to check it against all the things
  ;; in INDEX.
  (dolist (entry (cdr index))
    (if (clause-info-p (cdr entry))
	(ambiguity-check-clause ci1 (cdr entry) 1)
	(ambiguity-check-index ci1 (cdr entry)))))

(defun ambiguity-check-clause (ci1 ci2 insert-n)
  ;; It is known that the required keywords of CI1 are a prefix of those
  ;; of CI2, and that we are trying to add INSERT-N (1 or 2).
  (if (ambiguous-clauses? ci1 ci2)
      (let ((kw1 (clause-info-keywords ci1))
	    (kw2 (clause-info-keywords ci2)))
	(if (= insert-n 2)
	    (rotatef kw1 kw2))
	(restart-case
            (error "Iterate: Inserting clause ~a would create ~
  an ambiguity with clause ~a"
                   kw1 kw2)
          (delete-conflict ()
            :report "Delete the original clause"
            (remove-clause kw2))))))


(defun ambiguous-clauses? (ci1 ci2)
  ;; rk1 is a prefix of rk2
  (let* ((rk1 (clause-info-req-keywords ci1))
	 (rk2 (clause-info-req-keywords ci2))
	 (rest-rk2 (nthcdr (length rk1) rk2))
	 (ok1 (cdr (member '&optional (clause-info-keywords ci1)))))
    (if (null rest-rk2)
	nil     ; Don't consider identical clauses ambiguous--that will be
		; handled elsewhere.
	(dolist (k2 rest-rk2 t)
	  (if (not (member k2 ok1))
	      (return nil))))))

	  
	  
) ;end eval-when


(defun display-index (&optional (index *clause-info-index*) (indent 0))
  ;; for debugging
  (if (not (index? index))
      (format t "~vt~a~%" indent (clause-info-keywords index))
      (dolist (entry (cdr index))
	(format t "~vt~a:~%" indent (car entry))
	(display-index (cdr entry) (+ indent 2)))))

(defun remove-clause (clause-keywords)
  ;; CLAUSE-KEYWORDS is a list that (once the symbols have been
  ;; keywordized) should be equal to some clause in the index.
 (let* ((all-keywords
	 (cons (first clause-keywords)
	       (mapcar #L(if (eq !1 '&optional) !1 (keywordize !1))
		       (rest clause-keywords))))
	(req-keywords
	 (ldiff all-keywords (member '&optional all-keywords :test #'eq))))
   (labels ((remove-clause-internal (keywords index)
	      (let ((entry (and keywords
				(index-lookup (car keywords) index))))
		(cond ((null entry)
		       (error "Clause ~a not found" clause-keywords))
		      ((clause-info-p (cdr entry))
		       (when (equal all-keywords 
				    (clause-info-keywords (cdr entry)))
			 ;; else warn that an &optional part is missing??
			 (rplacd index (delete entry (cdr index)))
			 t))
		      (t ;; an index
		       (prog1
			   (remove-clause-internal (cdr keywords) (cdr entry))
			 ;; if the index is empty, delete it too
			 (if (null (cddr entry))
			     (rplacd index (delete entry (cdr index))))))))))
     (remove-clause-internal req-keywords *clause-info-index*))))


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;  Macros and useful functions for defining new iterate clauses.

(defmacro defclause (clause-template &body body)
  (define-clause 'defun clause-template body nil))

(defmacro defclause-driver (clause-template &body body)
  (define-clause 'defun clause-template body t))


;  ;; This duplicates body, which is annoying but not serious.
;  (let* ((gen-clause-template (cons 'generate (cdr clause-template)))
;	 (for-body `((let ((generator? nil)) ,@body)))
;	 (gen-body `((let ((generator? t)) ,@body))))
;    (define-clause 'defun clause-template for-body)
;    (define-clause 'defun gen-clause-template gen-body)))

(eval-when (:compile-toplevel :load-toplevel :execute)
  (defconst sequence-keyword-list
    '(:from from :upfrom upfrom :downfrom downfrom :to to :downto downto
      :above above :below below :by (by 1) :with-index with-index))

  (defun define-clause (define-form clause-template body generator?)
    ;; CLAUSE-TEMPLATE is of the form 
    ;;  (<sym1> <spec1> ... [&optional <symk> <speck> ...] [&sequence])
    ;; The <sym> forms must be symbols (in any package); they are the
    ;; keywords for the clause. The <spec> forms are to be bound to the
    ;; values of those keywords when the clause is processed; such a
    ;; form can be either a symbol, a list (symbol initform), or a list
    ;; (symbol initform svar).  These are processed exactly as if they
    ;; were keyword specifiers.  To be precise, a pair of keyword and
    ;; value-form behaves exactly like the keyword specification
    ;; ((:keyword var) initform svar). 
    ;;   If the special symbol &sequence occurs, it must be the last
    ;; form.  It is equivalent to specifying all the sequence optional
    ;; symbols (FROM, TO, etc.), with specs of the same name (i.e. the
    ;; variable bound to the FROM keyword is "from", etc.).  There are
    ;; no defaults except that BY defaults to 1.
    ;;   The BODY is just an ordinary lisp body; it will refer to the 
    ;; value-forms in the clause template.  It should use return-code to
    ;; return the appropriate arguments.
    (if (null clause-template)
	(error "Iterate: empty clause template with body ~a" body))
    (flet ((make-keyword-spec (kw val)
	     (if (symbolp val)
		 `((,kw ,val))
		 `((,kw ,(car val)) ,@(cdr val)))))
      (let ((last (car (last clause-template))))
	(if (and (symbolp last) (string= last '&sequence))
	    (setq clause-template 
		  (nconc (butlast clause-template)
			 (if (member '&optional clause-template)
			     sequence-keyword-list
			     (cons '&optional sequence-keyword-list))))))
      (multiple-value-bind (rkws rvals okws ovals) 
	  (split-clause-template clause-template)
	(let* ((req-keywords (mapcar #'keywordize rkws))
	       (req-kws-but-first (cons (car clause-template)
					(cdr req-keywords)))
	       (opt-keywords (mapcar #'keywordize okws))
	       (keywords&opt (if opt-keywords
				 (append req-kws-but-first
					 '(&optional) opt-keywords)
				 req-kws-but-first))
	       (rkw-specs (mapcar #'make-keyword-spec req-keywords rvals))
	       (okw-specs (mapcar #'make-keyword-spec opt-keywords ovals))
	       (func-name (make-function-name rkws))
	       (doc-string (if (stringp (car body))
			       (car body)
			       nil))
	       (all-keywords (append req-keywords opt-keywords))
	       (arglist `(&key ,@rkw-specs ,@okw-specs)))
	  (if (contains-duplicates? all-keywords)
	      (error "While defining ~a: keyword list contains duplicates"
		     clause-template))
	  (if generator?
	      (augment arglist (list 'generate)))
	  ;; Actually define a named function, instead of using an
	  ;; anonymous lambda, to ensure that it gets compiled.  A
	  ;; compiler should compile a sharp-quoted lambda, but the
	  ;; Symbolics one doesn't.  Also, use the original first symbol
	  ;; of the clause for indexing.  This provides the following behavior
	  ;; re the package system: the first symbol of the user's clause
	  ;; must be eq to (hence in the same package as) the first symbol of
	  ;; the defined clause; but the packages of the other symbols don't
	  ;; matter.
	  `(eval-when (:compile-toplevel :load-toplevel :execute)
	     (,define-form ,func-name ,arglist .,body)
	     (install-clause-info ',req-kws-but-first
				  ',keywords&opt 
				  ',func-name
				  ,doc-string
				  ,generator?)
	     ',clause-template)))))

  (defun make-function-name (req-syms)
    (let ((req-string "CLAUSE-"))
      (dolist (sym req-syms)
	(setq req-string (concatenate 'string req-string (symbol-name sym) "-")))
      (gentemp req-string)))

  (defun split-clause-template (ct)
    ;; Splits template into required keywords, optional keywords and
    ;; values. 
    (let* ((opt&-list (member '&optional ct))
	   (req-list (ldiff ct opt&-list))
	   (opt-list (cdr opt&-list)))
      (if (zerop (length req-list))
	  (error "DEFCLAUSE: template ~a has no required part" ct))
      (if (oddp (length req-list))
	  (error "DEFCLAUSE: required part of template ~a is of odd length" ct))
      (if (oddp (length opt-list))
	  (error "DEFCLAUSE: optional part of template ~a is of odd length" ct))
      (multiple-value-bind (rkws rvals)
	  (split-list-odd-even req-list)
	(multiple-value-bind (okws ovals)
	    (split-list-odd-even opt-list)
	  (values rkws rvals okws ovals)))))
	

  (defun split-list-odd-even (list)
    ;; Splits list into odd- and even-numbered elements, returns
    ;; the odds and evens as two values.
    (do ((lis list (cddr lis))
	 (odds nil)
	 (evens nil))
	((null lis) (values (nreverse odds) (nreverse evens)))
      (push (car lis) odds)
      (push (cadr lis) evens)))

  (defun contains-duplicates? (list)
    (not (equal list (remove-duplicates list :test #'eq))))

  )					; end eval-when



(defmacro defsynonym (syn word)
  "Makes SYN a synonym for the existing iterate keyword WORD."
  `(eval-when (:compile-toplevel :load-toplevel :execute)
     (setf (get ',syn 'synonym) ',word)))



(defmacro defclause-sequence (element-name index-name 
			      &key access-fn size-fn
			      element-type sequence-type
			      element-doc-string index-doc-string)
  "A simple way to define a simple FOR ... &sequence clause"
  ;; Package subtlety: the FOR should be in the same package as the
  ;; element-name or index-name.
  (let* ((seq-for (if element-name 
		      (intern (symbol-name 'for) (symbol-package element-name))))
	 (seq-def (if element-name
		      `(defclause-driver (,seq-for var ,element-name seq 
						   &sequence)
			 ,element-doc-string
			 (return-sequence-code 
			  :element-var   var
			  :sequence      seq
			  :access-fn   ,access-fn
			  :size-fn     ,size-fn
			  :element-type  ,element-type
			  :sequence-type ,sequence-type))))
	 (inx-for (if index-name
		      (intern (symbol-name 'for) (symbol-package index-name))))
	 (inx-def (if index-name
		      `(defclause-driver (,inx-for var ,index-name seq 
						   &sequence)
			 ,index-doc-string
			 (cond 
			  (with-index
			   (clause-error
			    "WITH-INDEX should not be specified for this clause"))
			  (t
			   (setq with-index var)
			   (return-sequence-code
			    :sequence seq
			    :size-fn ,size-fn
			    :sequence-type ,sequence-type)))))))
    `(progn ,seq-def ,inx-def)))
			     
(defun if-1st-time (then &optional else first-time-var)
  ;; Returns 1: a form which evaluates THEN the first time through the
  ;; loop, ELSE subsequent times; 2: the variable that keeps track of
  ;; the first time.
  (let* ((var (or first-time-var 
		  (make-var-and-binding 'first-time t :type 'boolean)))
	 (code (if else
		   `(cond
		     (,var
		      (setq ,var nil)
		      ,@then)
		     (t
		      ,@else))
		   `(when ,var 
		      (setq ,var nil)
		      ,@then))))
    (values code var)))

;;; Deprecated.  Dangerous when incorrectly nested
(defmacro with-temporary (var &body body)
  (let ((old-var (gensym))
	(vars (listify var)))
    `(let ((,old-var *temps-in-use*))
       (unwind-protect
	   (let ,(mapcar #L`(,!1 (get-free-temp))
			 vars)
	     .,body)
	 (setq *temps-in-use* ,old-var)))))

#+nil ;; unused
(defmacro with-temporaries (n vlist &body body)
  (let ((old-var (gensym)))
    `(let ((,old-var *temps-in-use*))
       (unwind-protect
	   (let ((,vlist (let ((ts nil)) 
			   (dotimes (i ,n) 
			     (push (get-free-temp) ts))
			   ts)))
	      .,body)
	 (setq *temps-in-use* ,old-var)))))

(defun get-free-temp ()
  (let ((temp (some #L(if (not (member !1 *temps-in-use*)) !1)
		    *temps*)))
    (when (null temp)
      (setq temp (make-var-and-default-binding 'temp))
      (push temp *temps*))
    (push temp *temps-in-use*)
    temp))



;;;;;;;;;;;;;;;;
;;; Typing.

(defun var-type (var)
  (if (the-expression? var)
      (second var)
      (var-declaration var)))

(defun var-declaration (var)
  (cdr (assoc var *type-alist* :test #'eq)))

(defun expr-type-only (expr)
  ;; If expr is self-evaluating, return its type (using type-of);
  ;; if expr is of the form (the <type> <form>), return <type>; 
  ;; else, return nil.
  (cond 
   ((self-evaluating? expr)
    ;; Attempt to work-around (type-of 0) -> useless types like
    ;; (integer 0 0) [cmucl/sbcl], (integer 0 16777215) or BIT [clisp]
    ;; -- possibly conterproductive for (array type dim1 .. dimn) types
    (let ((type (type-of expr)))
      (if (consp type) (first type) type)))
   ((the-expression? expr)
    (second expr))
   (t nil)))

(defun expression-type (form)
  (if (symbolp form)
      (var-type form)
      (expr-type-only form)))

(defun quoted? (x)
  ;; Returns T iff x is of the form (quote ...)
  (and (consp x) (eq (car x) 'quote)))

(defun function-quoted? (x)
  ;; Returns T iff x is of the form (function ...) [same as #'(...)]
  (and (consp x) (eq (car x) 'function)))

(defun lambda-expression? (x)
  (and (consp x) (eq (car x) 'lambda)))

(defun the-expression? (x)
  (and (consp x) (eq (first x) 'the)))

(defun self-evaluating? (x)
  ;; Everything but symbols and lists are self-evaluating since CLtL2.
  ;; This differs from constantp in that it returns nil for quoted
  ;; things and defconstants.
  ;; (typep x '(and atom (or (not symbol) keyword (member t nil))))
  (and (atom x) (or (null x) (not (symbolp x)) (eq x t) (keywordp x))))

(defun constant? (x)
  ;; This differs from constantp in that it doesn't acknowledge
  ;; defconstants to be constants; the problem with so acknowledging
  ;; them is that the run-time and compile-time environments may
  ;; differ.  The things constant? returns T for are really and truly
  ;; constant everywhere.
  (or (self-evaluating? x) (quoted? x) (function-quoted? x)))

(defun duplicable? (x)
  ;; Returns T if X can be copied in code.  This returns T for symbols, on the
  ;; assumption that the copies are close enough to each other so that
  ;; updating the variable cannot occur.
  (or (numberp x) (symbolp x) (characterp x)))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Variable specifiers.  They're either a symbol, or a the-expression
;;; constaining a symbol.

(defun var-spec? (x)
  (or (the-expression? x) (symbolp x)))

(defun extract-var (var-spec)
  (if (the-expression? var-spec)
      (third var-spec)
      var-spec))

;;; Possible extension:
;;; When more than one variable can occur, we allow a single
;;; the-expression to cover them all.  Unfortunately, this makes
;;; things rather hairy--probably better to avoid it.

;(defun distribute-type-spec (x)
;  (if (and (the-expression? x) (not (symbolp (third x))))
;      (let ((type (second x))
;	    (vars (third x)))
;	(mapcar #'(lambda (v) `(the ,type ,v)) vars))
;      x))



;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Binding and destructuring.

(defun make-binding (var value &key type using-type-of)
  ;; This creates a binding of VAR to VALUE.  TYPE means declare VAR
  ;; to be of that type if it isn't declared to be a type already.
  ;; (But do so only when declare-variables has been declared.)
  ;; USING-TYPE-OF means to use the type of that form, if any.  
  ;; Specifying both keyword args is an error.
  ;;   It is okay to pass nil for VAR; in this case, nothing will
  ;; happen and nil will be returned.  This is done just to simplify
  ;; coding of clauses.
  (make-binding-internal var value t type using-type-of))

(defun make-default-binding (var &key type using-type-of)
  ;; This makes a random binding of VAR (i.e. you should not depend on
  ;; the binding's value).  It will observe TYPE and USING-TYPE-OF in
  ;; choosing a value to bind to (see the comment for make-binding).
  ;;   It is okay to pass nil for VAR; in this case, nothing will
  ;; happen and nil will be returned.  This is done just to simplify
  ;; coding of clauses.
  (make-binding-internal var nil nil type using-type-of))

(defun make-var-and-binding (string value &key type using-type-of)
  (let ((var (genvar string)))
    (make-binding-internal var value t type using-type-of)
    var))

(defun make-var-and-default-binding (string &key type using-type-of)
  (let ((var (genvar string)))
    (make-binding-internal var nil nil type using-type-of)
    var))

(defun make-accum-var-binding (var value kind &key type using-type-of)
  (make-accum-var-binding-internal var value t kind type using-type-of))

(defun make-accum-var-default-binding (var kind &key type using-type-of)
  (make-accum-var-binding-internal var nil nil kind type using-type-of))

(defun make-accum-var-binding-internal (var value value-supplied?
					kind type using-type-of)
  ;; Possibly creates a binding for an accumulation variable, like
  ;; those generated by COLLECT, MAXIMIZE, COUNT, etc.  
  ;; It checks *accum-var-alist* to see if the variable already exists.
  ;; If so, and it is of the right kind, it does not create a new
  ;; binding.  If it is of the wrong kind, an error is signalled.  If kind is
  ;; NIL, then we don't do this error check.  However, we aways check to make
  ;; sure the initial value, if supplied, is correct.
  ;;    In all cases, *internal-variables* is checked to make sure the
  ;; variable does not occur there.
  ;;    The alist entry is returned.  It can be used to store
  ;; additional info, like the end-pointer for collections.
  (let ((entry (assoc var *accum-var-alist* :test #'eq)))
    (cond
     ((null entry)
      (if value-supplied?
	  (make-binding var value :type type :using-type-of using-type-of)
	  (make-default-binding var :type type :using-type-of using-type-of))
      (setq entry (list var kind))
      (push entry *accum-var-alist*)
      entry)
     ((and kind (second entry) (not (eq (second entry) kind)))
      (clause-error "Attempt to do ~a accumulation into a variable ~
  already being used for ~a accumulation."
		    kind (second entry)))
     (t
      (if value-supplied?
	  (let ((orig-value  (second (assoc var *bindings*))))
	    (if (not (equal value orig-value))
		(clause-error "Initial values ~a and ~a are not equal ~
  for variable ~a"
			      orig-value value var))))
      (check-internal-variables var)
      entry))))

(defun make-shared-binding (var value &key type using-type-of)
  "Look up or create an alist entry keyed by var, store a gensym
   in the value and also add it as a binding. Return the entry."
  (let ((entry (assoc var *shared-bindings-alist* :test #'eq)))
    (unless entry
        (setq entry (list var (gensym (string var))))
        (push entry *shared-bindings-alist*)
        (make-binding (second entry) value :type type :using-type-of using-type-of))
    entry))

(defun make-binding-internal (var-spec value value-supplied? 
				       use-type using-type-of)
  ;; This returns T if it actually created a binding, else NIL.
  ;; Declaration and typing rules: first of all, no declaration is
  ;; generated unless *declare-variables* is T and var doesn't already
  ;; have a type declaration.  If there is no type for var, we infer
  ;; it as best we can as follows: if use-type is supplied, we use
  ;; that type.  If using-type-of is supplied, we try to determine a
  ;; type for that variable or expression (see expression-type) and
  ;; use that if we find it.  (It is erroneous to supply both use-type
  ;; and using-type-of.)  If neither is supplied, we DO NOT try to
  ;; infer the type of value--we just give up.  Otherwise, someone who
  ;; innocently did (make-binding 'foo nil) would discover that the
  ;; resulting code, if declare-variables was used, would 
  ;; have foo declared to be of type symbol (since, in Lucid at least,
  ;; (type-of nil) == symbol).  Note that we do not check for a type
  ;; conflict between a supplied type and the existing type; the
  ;; existing type just wins.
  ;;
  ;;   The var can actually be of the form (the <type> var).
  (let ((var (extract-var var-spec)))
    (cond
     ((null var-spec)
      nil)
     ((not (symbolp var))
      (clause-error "The variable ~a is not a symbol" var))
     (t
      (let* ((existing-type (var-type var-spec))
	     (declared? (var-declaration var))
	     (type (or existing-type
		       use-type
		       (if using-type-of (expression-type using-type-of)))))
	(if (or declared? (and *declare-variables* type))
	    ;; We only have to be concerned about getting value to be
	    ;; the right type if there will actually be a declaration
	    ;; for var.  This will be either when there is an existing
	    ;; declaration, or when *declare-variables* is true and
	    ;; there is some type.
	    (setq value (make-initial-value value value-supplied? type)))
	(if (and (not declared?) *declare-variables* type)
	    (push `(type ,type ,var) *declarations*))
	(add-binding var value)
      t)))))


(defun make-initial-value (value value-supplied? type)
  ;; This should really be done by trying to coerce, then trapping the error,
  ;; because the subtype checks aren't really right--nil, for instance, is a
  ;; subtype of anything, but you can't coerce anything to it.  (Sure, we
  ;; check for nil explicitly, but there are other things like it.)  Yet if we
  ;; omit the subtype tests currently, how will we know that we can convert
  ;; nil to a vector?
  (cond
   ((null type)
    value)
   (value-supplied?
    (if (self-evaluating? value)
	(coerce value type)
	`(the ,type ,value)))
   ((or (subtypep 'number type) (subtypep type 'number))
    (coerce 0 type))
   ((or (subtypep 'sequence type) (subtypep 'symbol type)
	(subtypep type 'sequence) (subtypep type 'symbol))
    (coerce nil type))
   ((subtypep type 'character)
    (coerce (code-char 0) type)) ; Neither #\Null nor #\Nul are valid characters.
   (t 
    (clause-warning 
     "Cannot supply an initial value for type ~s; using NIL."
     type)
    nil)))

(defun add-binding (var value)
  (cond
   ((var-binding var)
    (clause-error "Duplicate variable: ~a" var))
   (t
    (check-internal-variables var)
    (push (list var value) *bindings*))))

(defun check-internal-variables (var)
  (if (internal-variable? var)
      (clause-error 
       "The variable ~a, which Iterate would like to bind, already has a ~
  binding in a context internal to the iterate form.  Give the variable ~
  another name." var)))

(defun internal-variable? (var)
  (member var *internal-variables* :test #'eq))

;  (some #L(if (symbolp !1) 
;	      (eq var !1) 
;	      (member var !1 :test #'eq))
;	*internal-variables*))

(defun var-binding (var)
  (car (member var *bindings* :test #'eq :key #'car)))



;;;;;;;;;;;;;;;;;;
;;; Destructuring.

;;; Where destructuring happens:
;;;  WITH (bind)
;;;  FOR...INIT...THEN (setq)
;;;  FOR...FIRST...THEN (setq)
;;;  FOR...= (setq)
;;;  FOR...IN-FILE (setq)
;;;  FOR...IN-STREAM (setq)
;;;  FOR...IN-HASHTABLE (setq)
;;;  FOR...IN-PACKAGE (setq)
;;;  element-var of sequence & list drivers (setq)


(defun make-destructuring-bindings (template value 
				    &key type using-type-of)
  (cond
   ((null template)
    (clause-error "Can't bind to NIL: ~a" value))
   ((var-spec? template)
    (make-binding template value :type type :using-type-of using-type-of))
   ((atom template)
    (clause-error "Invalid binding form: ~a" template))
   ((eq (car template) 'values)
    (clause-error "Cannot perform multiple-value destructuring in ~
  this context"))
   (t
    (let ((var (make-var-and-binding 'temp value)))
      (push var *temps*)  ; so that others can benefit
      (do-destructuring-bindings template var)))))


(defun do-destructuring-bindings (template value)
  (cond
   ((null template)
    nil)
   ((var-spec? template)
    (make-binding template value)
    nil)
   ((atom template)
    (clause-error "Invalid binding form: ~a" template))
   ((eq (car template) 'values)
    (clause-error "Multiple-value destructuring cannot be nested"))
   (t
    (nconc (do-destructuring-bindings (car template) `(car ,value))
	   (do-destructuring-bindings (cdr template) `(cdr ,value))))))

(defun extract-vars (template)
  ;; Like extract-var, but will work with a destructuring template as well.
  ;; Returns a list of variables.
  (cond
   ((null template)
    nil)
   ((var-spec? template)
    (list (extract-var template)))
   ((not (consp template))
    (clause-error "Invalid binding form: ~a" template))
   ((eq (car template) 'values)
    (mapcan #'extract-vars (cdr template)))
   (t
    (nconc (extract-vars (car template))
	   (extract-vars (cdr template))))))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Dsetq.

(defmacro dsetq (template value)
  "Destructuring assignment; supports both
(VALUES ...) for destructuring a multiple-value form and
NIL as a variable name, meaning to ignore that position,
e.g. (DSETQ (VALUES (a . b) nil c) form)"
  ;; This macro can be used outside an Iterate form. 
  ;; The semantics are that if you say (DSETQ (A B) A), then b will get its
  ;; value from the original A.
  (do-dsetq template value nil))

  
(defun do-dsetq (template value &optional (bindings? t) type)
  (cond
   ((null template)
    (dsetq-error "Can't bind to nil"))
   ((var-spec? template) ; not only (symbolp template)
    (if bindings?
	(make-default-binding template :type type))
    `(setq ,(extract-var template) ,value))
   ((and (consp template) (eq (car template) 'values))
    ;; Just do a simple check for the most common errors.  There's no way we
    ;; can catch all problems.
    (if (or (atom value) (member (car value) '(car cdr cdar caar aref get)))
	(dsetq-error "Multiple values make no sense for this expression" )
	(make-mv-dsetqs (cdr template) value bindings?)))
   (t
    (let ((temp (gensym "DSETQ")))
      `(let ((,temp ,value))
	 ,.(if (and type *declare-variables*) `((declare (type ,type ,temp))))
	 ,.(make-dsetqs template temp bindings?)
	 ,temp)))))

(defun make-dsetqs (template value bindings?)
  (cond 
   ((null template)
    nil)
   ((var-spec? template)
    (if bindings?
	(make-default-binding template))
    `((setq ,(extract-var template) ,value)))
   ((atom template)
    (dsetq-error "Invalid binding form: ~a" template))
   ((eq (car template) 'values)
    (dsetq-error "Multiple-value destructuring cannot be nested"))
   (t
    (nconc (make-dsetqs (car template) `(car ,value) bindings?)
	   (make-dsetqs (cdr template) `(cdr ,value) bindings?)))))

(defun make-mv-dsetqs (templates value bindings?)
  (let ((temps '()) (vars '()) (tplates '()))
    (declare (type list temps vars tplates))
    (dolist (tp templates)
      (cond
       ((and tp (var-spec? tp)) ; either var or (the type var)
	(push nil tplates)
	(push nil temps)
	(push (extract-var tp) vars)
	(if bindings?
	    (make-default-binding tp)))
       (t ; either NIL or destructuring template
	(let ((temp (gensym "VALUE")))
	  (push tp tplates)
	  (push temp temps)
	  (push temp vars)))))
    (setq temps (nreverse temps))
    (setq vars (nreverse vars))
    (setq tplates (nreverse tplates))
    (let ((mv-setq `(multiple-value-setq ,vars ,value))
	  ;; Remove, don't delete. Bug
	  ;; reported by Francois Ren'e Rideau on 2005-11-01
	  (temp-vars (remove nil temps)))
      (if (null temp-vars)
	  mv-setq
	  `(let ,temp-vars
	     (declare (ignorable .,temp-vars)) ; in case of NIL template
	     ,mv-setq
	     ,.(mapcan #L(make-dsetqs !1 !2 bindings?)
		       tplates temps)
	     ,(car vars))))))

(defun dsetq-error (format-string &rest args)
  (if (in-iterate?)
      (apply #'clause-error format-string args)
      (apply #'error (concatenate 'string "DSETQ: " format-string) args)))

(defun in-iterate? ()
  (boundp '*result-var*))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Free variables; checking for local bindings.

(defun local-binding-check (form)
  (when *internal-variables* ; else no need to extract free variables
    (let ((vars (remove-if-not #'internal-variable? (free-variables form))))
      (if vars
	  (clause-error "The variable~p ~{~a~^, ~} ~:[is~;are~] bound in a context internal to ~
  the Iterate form.~%~
  This part of the clause will be moved outside the body of the loop, so it ~
  must not contain anything that depends on the body."
			(length vars) vars (rest vars))))))


(defun free-variables (form)
  ;; This will return a list of the (lexically) free variables in FORM.  It
  ;; will never return anything that is not a free variable (except for not
  ;; processing MACROLET), but it may not get all of them. 
  (delete-duplicates (free-vars form nil) :test #'eq))

(defun free-vars (form bound-vars)
  ;; To compute the variables that are free in a form, we have to walk it,
  ;; keeping track of what variables are bound.
  (cond
   ((constantp form)
    nil)
   ((symbolp form)
    (if (not (member form bound-vars :test #'eq))
	(list form)))
   ((atom form)
    nil)
   ((symbolp (car form))
    (cond
     ((or (special-operator-p (car form)) 
	  ;; Lucid doesn't think that these are special forms
	  ;; and we need to handle declarations:
	  (member (car form) '(declare multiple-value-bind
			       flet labels let let*) :test #'eq))
      (case (car form)
	((catch if locally multiple-value-call multiple-value-prog1
	  progn progv setq tagbody throw unwind-protect)
	    (free-vars-list (cdr form) bound-vars))
	((block eval-when return-from the)
	    (free-vars-list (cddr form) bound-vars))
	(multiple-value-bind
	    (free-vars-list (cddr form) (append (cadr form) bound-vars)))
	(function
	    (free-vars-fspec (second form) bound-vars))
	((flet labels macrolet)
	    (nconc (mapcan #L(free-vars-fspec !1 bound-vars)
			   (second form))
		   (free-vars-list (cddr form) bound-vars)))
	((let symbol-macrolet)
	    (let* ((bindings (second form))
		   (body (cddr form))
		   (vars (mapcar #L(if (consp !1) (car !1) !1)
				 bindings)))
	      (nconc (mapcan #L(if (consp !1)
				   (free-vars (second !1) bound-vars)
				   nil)
			     bindings)
		     (free-vars-list body (append vars bound-vars)))))
	(let*
	    (let* ((bindings (second form))
		   (body (cddr form))
		   (free-vars nil))
	      (dolist (binding bindings)
		(if (consp binding)
		    (augment free-vars (free-vars (second binding) 
						  bound-vars)))
		(push (if (consp binding) (car binding) binding) bound-vars))
	      (nconc free-vars (free-vars-list body bound-vars))))
	(otherwise
	    nil)))
     ((macro-function (car form) *env*)
      (free-vars (macroexpand-1 form *env*) bound-vars))
     (t ; function call
      (free-vars-list (cdr form) bound-vars))))
   ((and (consp (car form)) (eq (caar form) 'lambda))
    (nconc (free-vars-fspec (car form) bound-vars)
	   (free-vars-list (cdr form) bound-vars)))
   (t
    (error "The form ~a is not a valid Lisp expression" form))))

(defun free-vars-list (list bound-vars)
  (mapcan #L(free-vars !1 bound-vars)
	  list))

(defun free-vars-fspec (fspec bound-vars)
  ;; FSPEC is either: a symbol, or
  ;; (<name-or-lambda> (<vars>) . body), or
  ;; (SETF <symbol>)
  (if (or (symbolp fspec) (eq (car fspec) 'setf))
      nil
      (free-vars-list (cddr fspec) (append (second fspec) bound-vars))))


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Functions that return code.

(defun return-code (&key declarations initial body step final final-protected)
  (values body declarations initial step final final-protected))

(defmacro return-driver-code (&key variable initial declarations body step
				   final final-protected next)
  ;; This assumes there is a local var called 'generate'
  (let ((btemp (gensym))
	(ntemp (gensym)))
    `(let ((,btemp ,body)
	   (,ntemp ,next))
      (add-driver-info ,variable ,ntemp generate)
      (if (not generate)
	  (augment ,btemp ,ntemp))
      (values ,btemp ,declarations ,initial ,step ,final ,final-protected))))

(defun add-driver-info (var-template next-code generator?)
  ;; VAR-TEMPLATE could be a single var-spec or a destructuring template.
  ;; Copy the code--the original could be nconc'ed.
  (let ((vars (extract-vars var-template))
	(di (make-driver-info :next-code (copy-list next-code)
			      :generator? generator?)))
    (register-previous-code vars next-code :next)
    (push (cons vars di) *driver-info-alist*)))

(defmacro return-sequence-code (&key element-var sequence access-fn
				     size-fn element-type sequence-type)
  ;; This assumes all the sequence keywords will be in the lexical
  ;; environment. 
  `(return-seq-code
    :element-var ,element-var
    :sequence ,sequence
    :access-fn ,access-fn
    :size-fn ,size-fn
    :element-type ,element-type
    :sequence-type ,sequence-type
    :from from :upfrom upfrom :to to :downto downto :above above :below below
    :downfrom downfrom :by by
    :with-index with-index
    :generate generate))

(defun return-seq-code (&key element-var sequence access-fn size-fn
			     element-type sequence-type
			     from upfrom to downto above below downfrom 
			     with-index (by 1) generate)
  ;; element-var might involve destructuring; the others won't.  If
  ;; access-fn is NIL, don't generate element-accessing code at all.
  (top-level-check)
  (check-sequence-keywords from upfrom downfrom to downto above below t)
  (let* ((index-var-spec (or with-index (genvar 'index))) 
	 (index-var (extract-var index-var-spec))
	 (seq-var (if (or access-fn (not (symbolp sequence)))
		      (make-var-and-default-binding 'sequence
						    :type sequence-type)))
	 (seq-code (or seq-var sequence))
	 (step-var (if (not (constant? by))
		       (make-var-and-default-binding 'step :type 'fixnum)))
	 (step (or step-var by))
	 (step-func (if (or downto downfrom above) '- '+))
	 (test-func (cond
		     (to '>)
		     ((or downto downfrom) '<)
		     (below '>=)
		     (above '<=)
		     (t '>=)))
	 (size-code (make-application size-fn seq-code))
	 (limit-value (cond
		       ((or to below))
		       ((or downto above))
		       (downfrom 0)
		       (t size-code)))
	 (limit-var (if (not (numberp limit-value)) 
			(make-var-and-default-binding 'limit :type 'fixnum)))
	 (limit-code (or limit-var limit-value))
	 (other-func (if (eq step-func '-) '+ '-))
	 (initial-value (eval-const-expr
			 (cond
			  ((or from upfrom downfrom)
			   `(,other-func ,(or from upfrom downfrom) ,step))
			  ((or downto above)
			   (if (eql step 1) size-code `(+ ,size-code (1- ,step))))
			  (t `(- ,step)))))
	 (access-code (if (null access-fn)
			  nil
			  (make-application access-fn seq-code index-var)))
	 (step-code `(setq ,index-var (,step-func ,index-var ,step)))
	 (setqs	(if access-fn (do-dsetq element-var access-code 
					t element-type)))
	 (test `(if (,test-func ,index-var ,limit-code) (go ,*loop-end*))))
    (make-default-binding index-var-spec :type 'fixnum)
    (setq *loop-end-used?* t)
    (return-driver-code
     :initial (nconc (if seq-var `((setq ,seq-var ,sequence)))
		     (if step-var `((setq ,step-var ,by)))
		     (if limit-var `((setq ,limit-var ,limit-value)))
		     (if index-var `((setq ,index-var ,initial-value))))
     :next (list step-code test setqs)
     ;; say (list nil ...) in case element-var = VALUES
     :variable (list nil element-var index-var))))

(defun check-sequence-keywords (from upfrom downfrom to downto above below
				known-limits? &aux count)

  ;; If the limits aren't known, the possibilities are: FROM; UPFROM;
  ;; DOWNFROM; TO; BELOW; or FROM and exactly one of TO, DOWNTO, ABOVE and
  ;; BELOW.
  ;; If the limits are known: you also have DOWNTO; ABOVE; and nothing.
  (if (or (and upfrom downfrom)
	  (and (or upfrom downfrom) (or from to downto above below)))
      (clause-error "UPFROM or DOWNFROM must occur alone"))
  (if (> (setq count (count-if #'identity (list to downto above below))) 1)
      (clause-error "Use at most one of TO, DOWNTO, ABOVE and BELOW"))
  (if (not known-limits?)
      ;; eliminate the cases DOWNTO, ABOVE, and nothing.
      (if (and (not (or from upfrom downfrom))
	       (or downto above (zerop count)))
	  (clause-error "Illegal set of sequence keywords"))))

(defun eval-const-expr (expr)
  ;; This is very simple: if expr is a list, and all the args are constants,
  ;; it will evaluate it; else it will just return it.
  (if (and (consp expr) (every #'constantp (cdr expr)))
      (eval expr)
      expr))

(defun make-funcall (fn &rest args)
  ;; This should be used when FN is something the user has written in a
  ;; clause. 
  #+symbolics (setq args (copy-list args))
  (cond
   ((or (quoted? fn) (function-quoted? fn))
    `(,(second fn) ,@args))
   ((lambda-expression? fn)
    `(,fn ,@args))
   ;;((functionp fn) `(funcall ,fn ,@args)) ; same treatment as default case
   (t
    `(funcall ,fn ,@args))))

(defun make-application (fn &rest args)
  ;; Use this when FN is given in the implementation code.
  #+ symbolics (setq args (copy-list args))
  (cond
   ((or (symbolp fn) (lambda-expression? fn))
    `(,fn ,@args))
   ((function-quoted? fn)
    `(,(second fn) ,@args))
   ((and (consp fn) (eq (car fn) 'subst))
    (apply-subst-expr fn args))
   ((functionp fn) `(funcall ,fn ,@args)) ;; Siskind's patch for compiled fns
   (t
    (clause-error "~a should denote a function, but it doesn't" fn))))
      
(defun apply-subst-expr (subst-expr args)
  (let ((params (second subst-expr))
	(body (cddr subst-expr)))
    (prognify (sublis (pairlis params args) body))))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;   Clauses   ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Special clauses.  These must return freshly consed lists that are
;;; nconcable. 

(defmacro def-special-clause (name arglist &body body)
  `(progn
     (defun ,name ,arglist .,body)
     (install-special-clause-function ',name
				      ,(if (stringp (car body))
					   (car body)))))

(defun install-special-clause-function (symbol &optional doc-string)
  ;; Put it at the end, if not already present.
  (let ((entry (assoc symbol *special-clause-alist*)))
    (if (null entry)
	(augment *special-clause-alist* (list (cons symbol doc-string)))
	(setf (cdr entry) doc-string))
    symbol))

;;; (INITIALLY &rest)
(def-special-clause initially (&rest forms)
  "Lisp forms to execute before loop starts"
  (mapc #'local-binding-check forms)
  (return-code :initial (copy-list forms)))

;;; (AFTER-EACH &rest)
(def-special-clause after-each (&rest forms)
  "Lisp forms to execute after each iteration"
  (mapc #'local-binding-check forms)
  (return-code :step (walk-list forms)))

;;; (ELSE &rest)
(def-special-clause else (&rest forms)
  "Lisp forms to execute if the loop is never entered"
  (mapc #'local-binding-check forms)
  (let ((flag (make-var-and-binding 'else t :type 'boolean)))
    (return-code :final `((when ,flag
			    .,(walk-list forms)))
                 :body (list `(setq ,flag nil)))))

;;; (FINALLY &rest)
(def-special-clause finally (&rest forms)
  "Lisp forms to execute after loop ends"
  (mapc #'local-binding-check forms)
  (return-code :final (copy-list forms)))

;;; (FINALLY-PROTECTED &rest)
(def-special-clause finally-protected (&rest forms)
  "Lisp forms in an UNWIND-PROTECT after loop ends"
  (mapc #'local-binding-check forms)
  (return-code :final-protected (copy-list forms)))

;;; (IF-FIRST-TIME then &optional else)
(def-special-clause if-first-time (then &optional else)
  "Evaluate branch depending on whether this clause is met for the first time"
  (return-code :body (list
		      (if-1st-time (list (walk-expr then))
				   (if else (list (walk-expr else)))))))

;;; (FIRST-TIME-P)
(def-special-clause FIRST-TIME-P ()
  "True when evaluated for the first time"
  (return-code :body (list (if-1st-time '(t)))))

;;; (FIRST-ITERATION-P)
(def-special-clause FIRST-ITERATION-P ()
  "True within first iteration through the body"
  ;; Like (with ,var = t) (after-each (setq ,var nil))
  ;; except all these clauses shares a single binding.
  (let* ((entry (make-shared-binding 'first-iteration t :type 'boolean))
         (step-body nil)
         (first-usage (not (cddr entry)))
         (var (second entry)))
    (when first-usage
      (setf step-body (list `(setf ,var nil)))
      (setf (cddr entry) (list t)))
    (return-code :body `(,var)
                 :step step-body)))

;;; (IN &body)
(def-special-clause in (block-name &rest forms)
  "Process forms in a named Iterate block"
  ;; VALUE: depends on forms
  (if (eq block-name *block-name*)
      (walk-list forms)
      `((in ,block-name ,.(copy-list forms)))))

;;; (NEXT var)
(def-special-clause next (var &optional (n 1))
  "Explicitly step a driver variable"
  ;; VALUE: var, after stepping.
  ;; Enclose the returned code in a PROGN so that the variable reference isn't
  ;; confusable with a tag (since the code might appear within a tagbody).
  ;; The PROGN is also necessary so that spliced-in save code will not result
  ;; in extra forms, for cases when the NEXT appears as an argument.
  (let ((entry (assoc var *driver-info-alist* :test #'member)))
    (if (or (null entry) (not (driver-info-generator? (cdr entry))))
	(clause-error "Variable is not associated with a generator")
	(let* ((vars (car entry))
	       (di (cdr entry))
	       (code (copy-list (driver-info-next-code di))))
	  (if (internal-variable? var)
	      (clause-error "The variable ~a is bound in a context internal ~
  to the Iterate form. ~
  It cannot be stepped at this point in the code." var))
	  (if (some #'internal-variable? vars)
	      (clause-error "Some of the variables ~a, which will be stepped ~
  when this clause is executed, are bound in a context internal to the Iterate ~
  form, so ~a cannot be stepped at this point in the code." vars var))
	  (setf (driver-info-used di) t)
	  (register-previous-code vars code :next)
	  (return-code :body (make-next-code var code n))))))


(defun make-next-code (var code n)
  ;; Construct the body carefully (avoid backquote), ensuring that CODE,
  ;; and not a copy, appears in it.
  (if (eql n 1)
      (let ((var-code (if (eq var (var-value-returned code))
			  ()
			  (list var))))
	;; This var-value-returned optimization benefits
	;; FOR IN-VECTOR/SEQUENCE/STRING.
	;; Too small a benefit in light of current compilers?
	(list (cons 'progn (nconc code var-code))))
      (let ((i (genvar 'next)))
	(list (list* 'dotimes (list i n var) `(declare (ignorable ,i)) code)))))


(defun var-value-returned (forms)
  ;; If the result of evaluating FORMS would be the value of some variable,
  ;; then that variable is returned; else NIL.
  ;;  We only check for progns, setqs and raw variables.
  (let ((form (car (last forms))))
    (cond
     ((symbolp form)
      form)
     ((atom form)
      nil)
     ((eq (car form) 'setq)
      (second (last form 3)))		; support degenerated (setq)
     ((eq (car form) 'progn)
      (var-value-returned (cdr form)))
     (t
      nil))))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Iteration-driving clauses.

(defsynonym as for)

(defsynonym generating generate)

(defclause (repeat n)
  "Repeat the loop some number of times"
  (top-level-check)
  (let* ((c-type (or (expression-type n) 'fixnum))
	 (count-var (make-var-and-default-binding 'count :type c-type)))
    (setq *loop-end-used?* t)
    (return-code :initial `((setq ,count-var ,n))
		 :body `((if (<= ,count-var 0) (go ,*loop-end*)))
		 :step `((setq ,count-var (1- ,count-var))))))


;;; (FOR &sequence)
(defclause-driver (for var-spec &sequence)
  "Numbers"
  (top-level-check)
  (if with-index
      (clause-error "WITH-INDEX should not be specified for this clause"))
  (check-sequence-keywords from upfrom downfrom to downto above below nil)
  (make-default-binding var-spec :type 'number)
  (let* ((var (extract-var var-spec))
	 (initial (or from upfrom downfrom 0))
	 (limit (or to downto above below))
	 (step-func (if (or downfrom downto above)
			'-
			'+))
	 (test-func (cond
		     (to '>)
		     (downto '<)
		     (below '>=)
		     (above '<=)))
	 (limit-var (if (and limit (not (constant? limit)))
			(make-var-and-default-binding 
			 'limit
			 :using-type-of (if (expression-type limit)
					    limit
					    var))))
	 (step-var (if (not (constantp by)) 
		       (make-var-and-default-binding 'step
						     :using-type-of by)))
	 (step-thing (or step-var by))
	 (limit-code (or limit-var limit))
	 (init-val (eval-const-expr
		    (list (if (eq step-func '+) '- '+) initial step-thing)))
	 (test (if limit
		   (progn (setq *loop-end-used?* t)
			  `((if (,test-func ,var ,limit-code) 
				(go ,*loop-end*))))
		   nil))
	 (next `((setq ,var (,step-func ,var ,step-thing)) .,test)))
    (return-driver-code :initial `(,.(if limit-var
					 `((setq ,limit-var ,limit)))
				   ,.(if step-var
					 `((setq ,step-var ,by)))
				   (setq ,var ,init-val))
			:next next
			:variable var)))


;;;;;;;;;;;;;;;;;;;;;;;
;;; Sequence iteration

;;; (FOR ON &optional BY)
(defclause-driver (for var on list &optional by (step ''cdr))
  "Sublists of a list"
  (top-level-check)
  (let* ((list-var (make-var-and-default-binding 'list))
	 ;; Handle dotted lists, so type declaration is not possible
	 (setqs (do-dsetq var list-var t 'list))
	 (test `(if (atom ,list-var) (go ,*loop-end*))))
    (setq *loop-end-used?* t)
    (return-driver-code :initial `((setq ,list-var ,list))
			:next (list test
				    setqs
				    (generate-function-step-code 
				     list-var step))
			:variable var)))

;;; (FOR IN &optional BY)
(defclause-driver (for var in list &optional by (step ''cdr))
  "Elements of a list"
  (top-level-check)
  (let* ((on-var (make-var-and-default-binding 'list :type 'list))
	 (setqs (do-dsetq var `(car ,on-var)))
	 (test `(if (endp ,on-var) (go ,*loop-end*))))
    (setq *loop-end-used?* t)
    (return-driver-code :initial `((setq ,on-var ,list))
			:next (list test
				    setqs
				    (generate-function-step-code on-var step))
			:variable var)))


(defun generate-function-step-code (var step) 
  ;; If the stepping function is quoted or sharp-quoted, we don't need to make
  ;; a variable for it.  The two constant cases are distinguished solely for
  ;; compilers too stupid to compile (funcall 'cdr foo) the same as (cdr foo).
  ;; (Really, for cosmetics--there probably are no such stupid compilers.)
  (cond
   ((quoted? step)
    `(setq ,var (,(second step) ,var)))
   ((function-quoted? step)
    `(setq ,var (funcall ,step ,var)))
   (t
    (let ((step-var (make-var-and-binding 'step step :type 'function)))
      `(setq ,var (funcall ,step-var ,var))))))


;;; (FOR IN-VECTOR &sequence)
(defclause-sequence in-vector index-of-vector
  ;; This observes fill-pointers.
  :access-fn 'aref
  :size-fn 'length
  :sequence-type 'vector
  :element-doc-string "Elements of a vector"
  :index-doc-string "Indices of a vector")

;;; (FOR IN-SEQUENCE)
(defclause-sequence in-sequence index-of-sequence
  ;; This observes fill pointers, and works for any sequence.
  :access-fn 'elt
  :size-fn 'length
  :sequence-type 'sequence
  :element-doc-string "Elements of a sequence (vector or list)"
  :index-doc-string "Indices of a sequence (vector or list)")

;;; (FOR IN-STRING)
(defclause-sequence in-string index-of-string
  :access-fn 'char
  :size-fn 'length
  :sequence-type 'string
  :element-type 'character
  :element-doc-string "Characters in a string"
  :index-doc-string "Indices of a string")


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Hash-table, Packages and Streams

;;; (FOR IN-HASHTABLE)
(defclause-driver (for key-val-vars in-hashtable table)
  "Elements and keys of a hashtable"
  (top-level-check)
  (unless (consp key-val-vars)
    (clause-error "~a should be a list of up to two variables: the first ~
  for the keys, the second for the values." key-val-vars))
  (let* ((iterator (gensym "HASH-TABLE-ITERATOR-"))
	 (more?    (gensym))
	 (var-spec `(values ,more? .,key-val-vars))
	 (setqs    (do-dsetq var-spec `(,iterator)))
	 (test     `(if (not ,more?) (go ,*loop-end*))))
    ;; FIXME 2004-11-11 destructure only after termination test
    (setq *loop-end-used?* t)
    (add-loop-body-wrapper `(with-hash-table-iterator (,iterator ,table)))
    (return-driver-code :next (list setqs test)
			:variable var-spec)))

;;; (FOR IN-PACKAGES &optional HAVING-ACCESS)
(defclause-driver (for sym-access-pkg-vars in-packages pkgs &optional having-access (sym-types '(:external :internal :inherited)))
  "Symbols and their access-types in packages"
  ;;defclause-driver has the benefit over defmacro-driver of less code walking
  (top-level-check)
  (unless (and (listp sym-access-pkg-vars) ; empty list is allowed (count)
	       (every #'symbolp sym-access-pkg-vars))
    (clause-error "~a should be a list of up to three variables: the symbol, ~
  the access type and the home package." sym-access-pkg-vars))
  (unless (consp sym-types)
    (clause-error "~s should be a list of symbols indicating the symbols' ~
  access types." sym-types))
  (let* ((iterator (gensym "PACKAGE-ITERATOR-"))
	 (more?    (gensym))
	 (var-spec `(values ,more? .,sym-access-pkg-vars))
	 (setqs    (do-dsetq var-spec `(,iterator)))
	 (test     `(if (not ,more?) (go ,*loop-end*))))
    (setq *loop-end-used?* t)
    (add-loop-body-wrapper `(with-package-iterator (,iterator ,pkgs .,sym-types)))
    (return-driver-code :next (list setqs test)
			:variable var-spec)))

;;; (FOR IN-PACKAGE &optional EXTERNAL-ONLY)
(defmacro-driver (for var in-package pkg &optional external-only (ext nil))
  "Symbols accessible in a package"
  `(,(if generate 'generate 'for) (,var) in-packages ,pkg having-access
	 ,(if ext '(:external) '(:external :internal :inherited))))

;;; (FOR IN-FILE &optional USING)
(defclause-driver (for var in-file filename &optional using (reader '#'read))
  "Forms in a file"
  (top-level-check)
  (return-stream-driver-code var filename reader :file generate))

;;; (FOR IN-STREAM &optional USING)
(defclause-driver (for var in-stream stream &optional using (reader '#'read))
  "Forms in a stream (which will be closed at the end)"
  (top-level-check)
  (return-stream-driver-code var stream reader :stream generate))

(defun return-stream-driver-code (var thing reader stream-or-file generate)
  (let* ((evar (extract-var var))
	 (type (or (var-type evar) t))
	 (stream-var (make-var-and-binding 'stream nil))
	 (set-var (if (and (var-spec? var)
			   (subtypep 'symbol type))
		      ;; We can use the given variable directly if no
		      ;; destructuring is required, and if the type of the
		      ;; variable can hold a symbol (since we use a gensym for
		      ;; the eof-marker).
		      evar
		      (genvar 'element)))
	 (setq (cond ((eq set-var evar)
		      (make-default-binding var) ())
		     (t (make-default-binding set-var)
			(list (do-dsetq var set-var)))))
	 (eof (gensym "EOF")))
    (setq *loop-end-used?* t)
    (return-driver-code 
     :initial (if (eq stream-or-file :file)
		  `((setq ,stream-var (open ,thing :direction :input)))
		  `((setq ,stream-var ,thing)))
     :next `((if (eq (setq ,set-var ,(make-funcall
				      reader stream-var nil `',eof))
		     ',eof) (go ,*loop-end*))
	     .,setq)
     :final-protected `((if (streamp ,stream-var)
			    (close ,stream-var)))
     :variable var)))
  
  
;;; (FOR NEXT)
(defclause-driver (for var next next)
  "General driver; VAR is set to value of NEXT"
  (return-driver-code :variable var
		      :next (list (do-dsetq var (walk-expr next)))))
  
;;; (FOR DO-NEXT)
(defclause-driver (for var do-next next)
  "General driver; VAR must be set in DO-NEXT"
    (do-dsetq var '(list)) ; for effect only, to make var known
    ;; We can't use (make-destructuring-bindings var) here because
    ;; we support the (values ...) template,
    ;; to maintain the documented equivalence with FOR ... NEXT.
    (return-driver-code
     :variable var
     :next (mapcar #'walk-expr (if (list-of-forms? next)
				   (copy-list next)
				   (list next)))))

; No NEXT:
; LOOP-TOP: SET
;          (if test (go LOOP-END))
;          STEP
;
; NEXT:
;	...
; LOOP-TOP ...
;	[next] SET; (if test (go LOOP-END)); STEP


;(FOR var FROM n) => (initially (setq var (- n 1)))
;                    (FOR var NEXT (1+ var))
;
;(FOR var FROM n TO m) => (initially (setq var (- n 1)) (setq limit (- m 1)))
;                         (FOR var NEXT (if (> var limit) (finish) (1+ var))
;
;
;(FOR var ON list)  =>    (initially (setq temp list))
;                         (FOR var NEXT (if (atom temp)
;					   (finish)
;					   (progn (setq temp (cdr temp))
;						  temp)))
;
;(FOR var IN list) =>    (initially (setq temp list))
;			(FOR var NEXT (if (endp temp)
;					  (finish)
;					  (pop temp)))
;
;(FOR var IN-VECT v) =>  (initially (setq index -1) (setq len (1- (length v))))
;			(FOR var NEXT (if (>= index len) (finish))
;			              (setq index (1+ index))
;				      (aref v index))
;

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Variable binding and setting; pseudo-drivers.

;;; (WITH &optional =)
(defclause (with var &optional = (value nil supplied?))
  "Bind a variable"
  ;; Special case: if value is not supplied, var can be a list of
  ;; variables, all bound defaultly.
  (if (not supplied?)
      (mapc #'make-default-binding (if (var-spec? var) (list var) var))
      (make-destructuring-bindings var value))
  (return-code)) ; nothing to return

;;; (FOR INITIALLY THEN)
(defclause (for var initially initial then then)
  "Set var initially, then on subsequent iterations"
  ;; This is a pseudo-driver: it doesn't work with NEXT.
  ;; Set var in initialization code, then set it in the step section on
  ;; subsequent iterations.  
  (top-level-check)
  (let* ((initial-setq (list (do-dsetq var initial)))
	 (then-setq (list (do-dsetq var (walk-expr then) nil))))
    (register-previous-code (extract-vars var) then-setq :initial)
    (return-code :initial initial-setq
		 :step then-setq)))

;;; (FOR =)
(defclause (for var = expr)
  "Set a variable on each iteration"
  ;; Set var each time through the loop.
  ;; VALUE: primary value of expr.
  (let ((vars (extract-vars var))
	(code (list (do-dsetq var (walk-expr expr)))))
    (register-previous-code vars code :next)
    (return-code :body code)))


;;; (FOR FIRST THEN)
(defclause (for var first first-expr then then-expr)
  "Set var on first, and then on subsequent iterations"
  ;; Set var in the loop, but differently the first time.  Most
  ;; inefficient of the three.
  ;; VALUE: primary value of first- or then-expr.
  (let* ((first-setq (list (do-dsetq var (walk-expr first-expr))))
	 (then-setq  (list (do-dsetq var (walk-expr then-expr) nil))))
    (register-previous-code (extract-vars var) then-setq :initial)
    (return-code :body (list (if-1st-time first-setq then-setq)))))


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Reducers.

(defun return-reduction-code (&key identity operation external-op? variable
				   expression test type using-type-of
				   accum-kind)
  ;;  A reduction is an iteration pattern in which a value is accumulated
  ;;(into VARIABLE) by repeatedly applying a binary OPERATION to the 
  ;;variable and an EXPRESSION.  The first time, the operation is applied
  ;;to the IDENTITY and the expression.
  ;;  Some other options allow for a wider range of patterns.  If TEST
  ;;is present, the result will only be accumulated on each iteration if
  ;;it succeeds. 
  ;;  TYPE is the type of the accumulation variable.
  ;;  ACCUM-KIND is the kind of accumulation this is--:increment, :max,
  ;;etc.  If NIL, then it matches any kind.
  ;; VALUE: the value accumulated so far.
  (setq variable (or variable *result-var*))
  (let* ((var (extract-var variable))
	 (expr (walk-expr expression))
	 (test-expr (if test (walk-expr test)))
	 (op-expr (if external-op?
		      (make-funcall operation var expr)
		      (make-application operation var expr)))
	 (update-code `(setq ,var ,op-expr)))
    (make-accum-var-binding variable identity accum-kind 
			    :type type :using-type-of using-type-of)
    (return-code :body (if test
			   `((if ,test-expr ,update-code ,var))
			   (list update-code)))))

(defsynonym count counting)

;;; (COUNTING &optional INTO)
(defclause (counting expr &optional into var)
  "Increment a variable if expression is non-nil"
  (return-reduction-code :identity 0
			 :operation '(subst (var expr) (1+ var))
			 :expression nil
			 :test expr
			 :variable var
			 :type 'fixnum
			 :accum-kind :increment))

;;; (SUM &optional INTO)
(defclause (sum expr &optional into var)
  "Sum into a variable"
  (return-reduction-code :identity 0
			 :operation '+
			 :expression expr
			 :test nil
			 :variable var
			 :type 'number
			 :accum-kind :increment))

(defsynonym summing sum)

;;; (MULTIPLY &optional INTO)
(defclause (multiply expr &optional into var)
  "Multiply into a variable"
  (return-reduction-code :identity 1
			 :operation '*
			 :expression expr
			 :test nil
			 :variable var
			 :type 'number
			 :accum-kind :increment))

(defsynonym multiplying multiply)


;;; (REDUCING BY &optional INITIAL-VALUE INTO)
(defclause (reducing expr by op &optional initial-value (init-val nil iv?)
		                          into var-spec)
  "Generalized reduction"
  ;; VALUE: the value accumulated so far.
  ;; If we don't know the initial value, we can't use RETURN-REDUCTION-CODE.
  ;; We have to be inefficient and do something different the first time.
  ;; Also, we have to share the first-time-var in case of multiple reductions
  ;; into the same variable.
  (cond
   (iv?
    (local-binding-check init-val)
    (return-reduction-code :identity init-val
			   :operation op
			   :external-op? t
			   :expression expr
			   :test nil
			   :variable var-spec
			   :type (expr-type-only op)
			   :accum-kind nil))  ; matches anything
   (t
    (setq expr (walk-expr expr))
    (setq var-spec (or var-spec *result-var*))
    (let* ((var (extract-var var-spec))
	   (entry (make-accum-var-default-binding var-spec nil
						  :using-type-of expr))
	   (prev-first-time-var (third entry)))
      (multiple-value-bind (update-code first-time-var)
	  (if-1st-time 
	   `((setq ,var ,expr))
	   `((setq ,var ,(make-funcall op var expr)))
	   prev-first-time-var)
	(if (null prev-first-time-var)
	    (setf (cddr entry) (list first-time-var)))
	(return-code :body (list update-code)))))))


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Extrema.

;;; (MAXIMIZE &optional INTO)
(defclause (maximize expr &optional into var)
  "Maximize value of an expression"
  (return-extremum-code expr var 'max))

(defsynonym maximizing maximize)

;;; (MINIMIZE &optional INTO)
(defclause (minimize expr &optional into var)
  "Minimize value of an expression"
  (return-extremum-code expr var 'min))

(defsynonym minimizing minimize)


(defun return-extremum-code (expr var-spec operation)
  ;; If we know the extremal value for the type of var, we COULD generate
  ;; a reduction...but don't right now, because it complicates
  ;; multiple accumulation.
  ;;  In order to accomodate multiple maxmins into the same variable, 
  ;; we store the first-time-variable in the accum-var-alist entry and
  ;; reuse it.  We have to do it this way, testing the var each time
  ;; through the loop, because due to conditionalization we don't know
  ;; if any of the first-time code will be executed.
  ;; VALUE: extremum so far.
  (setq expr (walk-expr expr))
  (let* ((m-var-spec (or var-spec *result-var*))
	 (m-var (extract-var m-var-spec))
	 (entry (make-accum-var-default-binding m-var-spec 
						(if (eq operation 'min)
						    :min :max)
						:using-type-of expr))
	 (prev-first-time-var (third entry)))
    (multiple-value-bind (update-code first-time-var)
	(if-1st-time 
	 `((setq ,m-var ,expr))
	 `((setq ,m-var (,operation ,m-var ,expr)))
	 prev-first-time-var)
      (if (null prev-first-time-var)
	  (setf (cddr entry) (list first-time-var)))
      (return-code :body (list update-code)))))


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Control flow.

;;; (FIMISH)
(defmacro finish ()
  "Leave the loop gracefully, executing the epilogue"
  (setq *loop-end-used?* t)
  `(go ,*loop-end*))

;;; (TERMINATE)
(defmacro terminate () ; recommended for use with FOR ... NEXT
  "Use within FOR ... DO-/NEXT clause to end the iteration"
  '(finish))

;;; (NEXT-ITERATION)
(defmacro next-iteration ()
  "Begin the next iteration"
  (setq *loop-step-used?* t)
  `(go ,*loop-step*))

;;; (LEAVE &optional)
(defmacro leave (&optional value)
  "Exit the loop without running the epilogue code"
  `(return-from ,*block-name* ,value))

;;; (WHILE)
(defclause (while expr)
  "Exit loop if test is nil"
  (setq *loop-end-used?* t)
  (return-code :body `((if (not ,(walk-expr expr)) (go ,*loop-end*)))))

;;; (UNTIL)
(defclause (until expr)
  "Exit loop if test is non-nil"
  (setq *loop-end-used?* t)
  (return-code :body `((if ,(walk-expr expr) (go ,*loop-end*)))))


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Aggregated Boolean tests.

;; Use same :if-exists kind of accumulation as finding ... such-that
;; so the clauses can be used together.

;;; (ALWAYS)
(defclause (always expr)
  "Return last value iff expression is always non-nil"
  ;; VALUE: primary value of expr
  (setq expr (walk-expr expr))
  (let ((var *result-var*))
    (make-accum-var-binding var t :if-exists)
    (return-code :body `((or (setq ,var ,expr) 
			     (return-from ,*block-name* nil))))))

;;; (NEVER)
(defclause (never expr)
  "Return T iff expression is never non-nil"
  ;; VALUE: always nil
  (setq expr (walk-expr expr))
  (let ((var *result-var*))
    ;; Do not use :type 'symbol so as be compatible with ALWAYS
    (make-accum-var-binding var t :if-exists)
    (return-code :body `((if ,expr (return-from ,*block-name* nil))))))


;;; (THEREIS)
(defclause (thereis expr)
  "Return value of expression as soon as it is non-nil"
  ;; VALUE: always nil
  (setq expr (walk-expr expr))
  (let ((var *result-var*))
    (make-accum-var-default-binding var :if-exists)
    (return-code :body `((if (setq ,var ,expr) 
			     (return-from ,*block-name* ,var))))))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Finders.

;;; (FINDING SUCH-THAT &optional INTO ON-FAILURE)
(defclause (finding expr such-that test &optional into var-spec
						  on-failure fval)
  "Return expression when test is non-nil"
  ;; VALUE: undefined.
  (setq expr (walk-expr expr))
  (setq test (walk-expr test))
  (local-binding-check fval)
  (setq var-spec (or var-spec *result-var*))
  (setq *loop-end-used?* t)
  (let ((var (extract-var var-spec)))
    (make-accum-var-binding var-spec fval :if-exists :using-type-of fval) 
    (if (function-quoted? test)
	(if (duplicable? expr)
	    (return-code :body `((when ,(make-funcall test expr)
				   (setq ,var ,expr)
				   (go ,*loop-end*))))
	    (let ((temp-var (gensym "FINDING")))
	      (return-code :body `((let ((,temp-var ,expr))
				     (when ,(make-funcall test temp-var)
				       (setq ,var ,temp-var)
				       (go ,*loop-end*)))))))
	(return-code :body `((when ,test
			       (setq ,var ,expr)
			       (go ,*loop-end*)))))))

;;; (FINDING MAXIMIZING &optional INTO)
(defclause (finding expr maximizing max-expr &optional into variable)
  "Return value which maximizes expression"
  (return-find-extremum-code expr max-expr variable :max))

;;; (FINDING MINIMIZING &optional INTO)
(defclause (finding expr minimizing min-expr &optional into variable)
  "Return value which minimizes expression"
  (return-find-extremum-code expr min-expr variable :min))

(defun return-find-extremum-code (expr m-expr var kind)
  ;; VALUE: expr corresponding to max/min-expr so far.
  ;; Variable can be a list of two variables, in which case the first
  ;; is used for the expr and the second for the extremum.
  ;; The update code looks something like this:
  ;; When m-expr is not a function:
  ;;     (setq temp m-expr)
  ;;     (cond
  ;;      ((> temp m-var)
  ;;       (setq m-var temp)
  ;;       (setq expr-var expr))
  ;;      (t expr-var))
  ;;
  ;; When m-expr is a function:
  ;;     (setq temp2 expr)
  ;;     (setq temp (funcall m-expr temp2)) ;; or (m-expr temp2)
  ;;     (cond 
  ;;      ((> temp m-var)
  ;;       (setq m-var temp)
  ;;       (setq expr-var temp2))
  ;;      (t expr-var))
  ;;
  (setq expr (walk-expr expr))
  (setq m-expr (walk-expr m-expr))
  (let* ((function? (function-quoted? m-expr))
	 (temp-var (make-var-and-default-binding 'temp :using-type-of 
						 (if (not function?) m-expr)))
	 (temp-var-2 (if (and function? (not (duplicable? expr)))
			 (make-var-and-default-binding 'temp
						       :using-type-of expr)))
	 (test (if (eq kind :max) '> '<))
	 expr-var m-var)
    (cond
     ((null var)   
      ;; no var means return expr as a result
      (setq expr-var *result-var*)
      (setq m-var (genvar kind)))
     ((var-spec? var)
      ;; a single var-spec means set expr to that var
      (setq expr-var var)
      (setq m-var (genvar kind)))
     ((and (consp var) (= (length var) 2) (every #'var-spec? var))
      ;; a two-element list means set expr to 1st, m to 2nd
      (setq expr-var (first var))
      (setq m-var (second var)))
     (t
      (clause-error "The value for INTO, ~a, should be a variable specifier ~
  or a list of two variable specifiers." var)))
    (make-default-binding expr-var :using-type-of expr)
    (make-accum-var-default-binding m-var kind :using-type-of m-expr)
    (setq expr-var (extract-var expr-var))
    (setq m-var (extract-var m-var))
    (let* ((expr-code (or temp-var-2 expr))
	   (esetq-code (if temp-var-2 `((setq ,temp-var-2 ,expr))))
	   (m-code (if function?
		       (make-funcall m-expr expr-code)
		       m-expr)))
      (return-code :body `(,.esetq-code
			   (setq ,temp-var ,m-code)
			   ,(if-1st-time 
			     `((setq ,m-var ,temp-var)
			       (setq ,expr-var ,expr-code))
			     `((cond
				((,test ,temp-var ,m-var)
				 (setq ,m-var ,temp-var)
				 (setq ,expr-var ,expr-code))
				(t ,expr-var)))))))))
				 

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Collectors.

    
(defun return-collection-code (&key variable expression 
				    start-operation end-operation
				    one-element
				    test
				    (place 'end) (result-type 'list))
  ;; VALUE: the list so far.
  ;; Remove the "maybe quoted" idiom from documentation & code in the next release
  (when (quoted? result-type) (setq result-type (second result-type)))
  (when (quoted? place) (setq place (second place)))
  (let ((place-string (locally (declare (optimize safety)) (symbol-name place))))
    (cond
     ((string= place-string '#:end)
      (setq place 'end))
     ((or (string= place-string '#:start)
	  (string= place-string '#:beginning))
      (setq place 'start))
     (t 
      (clause-error "~a is neither 'start', 'beginning' nor 'end'" place))))
  (let* ((collect-var-spec (or variable *result-var*))
	 (collect-var (extract-var collect-var-spec))
	 (entry (make-accum-var-binding collect-var-spec nil :collect
		 :type (if (eq result-type 'list) 'list
			 `(or list ,result-type))))
	 (end-pointer (third entry))
	 (prev-result-type (fourth entry)))
    (cond
     ((null end-pointer)
      (if (eq place 'end)
	  (setq end-pointer (make-var-and-binding 'end-pointer nil 
						  :type 'list)))
      (setf (cddr entry) (list end-pointer result-type)))
     (t
      (if (not (equal result-type prev-result-type))
	  (clause-error "Result type ~a doesn't match ~a" 
			result-type prev-result-type))))
    (let* ((expr (walk-expr expression))
	   (op-expr 
	    (if (eq place 'start)
		(if (null start-operation)
		    expr
		    (make-application start-operation expr collect-var))
		(if (null end-operation)
		    expr
		    (make-application end-operation collect-var expr)))))
      (if (eq place 'start)
          (return-code :body `((setq ,collect-var ,op-expr))
                       :final (unless (eq result-type 'list)
                                `((setq ,collect-var
                                        (coerce ,collect-var ',result-type)))))
	  (with-temporary temp-var
	    ;; In the update code, must test if collect-var is null to allow
	    ;; for other clauses to collect into same var.  This code
	    ;; is a tad bummed, but probably more for looks than real
	    ;; efficiency.
	    (let* ((update-code `(if ,collect-var
				     (setf (cdr ,end-pointer) ,temp-var)
				     (setq ,collect-var ,temp-var)))
		   (main-code (cond
			       ((not one-element)
				`((if (setq ,temp-var ,op-expr)
				      (setq ,end-pointer 
					    (last ,update-code)))))
			       (test
				`((when ,(make-application test
							   collect-var expr)
				      (setq ,temp-var ,op-expr)
				      (setq ,end-pointer ,update-code))))
			       (t
				`((setq ,temp-var ,op-expr)
				  (setq ,end-pointer ,update-code))))))
				
	      (return-code 
	       ;; Use a progn so collect-var isn't mistaken for a tag.
	       :body `((progn ,.main-code ,collect-var))
	       :final (if (eq result-type 'list)
			  nil
			  `((setq ,collect-var 
				  (coerce ,collect-var ',result-type)))))))))))


;;; (COLLECT &optional INTO AT RESULT-TYPE)
(defclause (collect expr &optional into var at (place 'end) 
		    		   result-type (type 'list))
  "Collect into a list"
  (return-collection-code
   :variable var
   :expression expr
   :one-element t
   :start-operation 'cons 
   :end-operation '(subst (var expr) (list expr))
   :place place
   :result-type type))

(defsynonym collecting collect)

;;; (ADJOINING &optional INTO AT TEST RESULT-TYPE)
(defclause (adjoining expr &optional into var
				     at (place 'end)
				     test (test '#'eql)
				     result-type (type 'list))
  "Adjoin into a list (tests for membership first)"
  (if (duplicable? expr)
      (return-collection-code
       :variable var
       :expression expr
       :start-operation `(subst (expr var) (adjoin expr var :test ,test))
       :test `(subst (var expr) (not (member expr var :test ,test)))
       :end-operation '(subst (var expr) (list expr))
       :one-element t
       :result-type type
       :place place)
      (with-temporary temp
	(return-collection-code
	 :variable var
	 :expression expr
	 :start-operation `(subst (expr var)
			    (progn ,temp ; silence unused variable warning
			     (adjoin expr var :test ,test)))
	 :test `(subst (var expr)
		 (progn
		   (setq ,temp expr)
		   (not (member ,temp var :test ,test))))
	 :end-operation `(subst (var expr) (list ,temp))
	 :one-element t
	 :result-type type
	 :place place))))



;;; (NCONCING &optional INTO AT)
(defclause (nconcing expr &optional into var at (place 'end))
  "Nconc into a list"
  (return-collection-code
   :variable var
   :expression expr
   :start-operation 'nconc
   :place place
   :one-element nil))
   
;;; (APPENDING &optional INTO AT)
(defclause (appending expr &optional into var at (place 'end))
  "Append into a list"
  (return-collection-code
   :variable var
   :expression expr
   :start-operation 'append
   :end-operation '(subst (var expr) (copy-list expr))
   :place place
   :one-element nil))

;;; (UNIONING &optional INTO AT TEST)
(defclause (unioning expr &optional into var at (place 'end) 
		                    test (test '#'eql))
  "Union into a list"
  ;; Can't use UNION because it says nothing about the order.
  (return-collection-code
    :variable var
    :expression expr
    :start-operation `(subst (expr var)
			(nconc (delete-if #L(member !1 var :test ,test)
					  (copy-list expr))
			       var))
    :end-operation `(subst (var expr) 
		      (delete-if #L(member !1 var :test ,test)
				 (copy-list expr)))
    :place place
    :one-element nil))

;;; (NUNIONING &optional INTO AT TEST)
(defclause (nunioning expr &optional into var at (place 'end) 
		                    test (test '#'eql))
  "Union into a list, destructively"
  ;; Can't use NUNION because it says nothing about the order.
  (return-collection-code
    :variable var
    :expression expr
    :start-operation `(subst (expr var)
			(nconc (delete-if #L(member !1 var :test ,test)
					  expr)
			       var))
    :end-operation `(subst (var expr) 
		      (delete-if #L(member !1 var :test ,test)
				 expr))
    :place place
    :one-element nil))


;;; (ACCUMULATE BY &optional INITIAL-VALUE INTO)
(defclause (accumulate expr by op &optional initial-value init-val 
		                            into var-spec)
  "Generalized accumulation"
  ;; VALUE: the value accumulated so far.
  ;; This is just like REDUCING except, 1. the args to OP are in the other
  ;; order, and 2. if no initial value is supplied, NIL is used. 
  (local-binding-check init-val)
  (setq var-spec (or var-spec *result-var*))
  ;; ignore the THE expression--it was a bad idea
  (if (the-expression? op) 
      (setq op (third op)))
  (let* ((var (extract-var var-spec))
	 (op-expr (make-funcall op (walk-expr expr) var)))
    (make-accum-var-binding var-spec init-val nil :type nil)
    (return-code :body `((setq ,var ,op-expr)))))

(defsynonym accumulating accumulate)

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; The PREVIOUS mechanism.

;;; It makes no sense to save local vars, so this is not as complex as I had
;;; thought.  There is one list: an alist of top-level vars and their info
;;; (*previous-vars-alist*).  Also, I now insist that the default value be
;;; fixed at the initialization section of the loop, so the old *unset*
;;; implementation is unnecessary.
;;;   However, generators complicate things.  In the absence of a generator,
;;; the save code can go in the step portion of the loop; but if there is a
;;; generator, the best we can do is use a flag for the first time.

;;; (FOR PREVIOUS &optional INITIALLY BACK)
(defclause (for pvar-spec previous var &optional
		initially (default nil default?) back (n-expr 1))
  "Previous value of a variable"
  ;; Set each save variable to the default in the initialization.
  (top-level-check)
  (if (not (constantp n-expr))
      (clause-error "~a should be a compile-time constant" n-expr))

  (let ((pvar (extract-var pvar-spec))
	(n    (eval n-expr))) ; Is this okay? It should be.
    (if (not (and (integerp n) (> n 0)))
	(clause-error "~a should be a positive integer" n-expr)
	;; Here, n is a positive integer.
	(let* ((p-i (intern-previous-info var))
	       (init-val (make-initial-value default default? (var-type var)))
	       (temp (if (not (duplicable? init-val))
			 (make-var-and-default-binding
			  'temp :using-type-of init-val)))
	       (iv-ref (or temp init-val))
	       (save-vars (cons pvar (make-save-vars var (1- n))))
	       (inits (mapcar #L`(setq ,!1 ,iv-ref) save-vars)))
	  (if temp (push `(setq ,temp ,init-val) inits))
	  (make-default-binding pvar-spec)
	  (push (make-save-info :save-var pvar
				:iv-ref iv-ref
				:save-vars save-vars)
		(previous-info-save-info-list p-i))
	  (return-code :initial inits)))))

(defun register-previous-code (vars code class)
  ;; It's important for this that code is never copied; we keep a pointer to
  ;; it. 
  (dolist (var (listify vars))
    (let ((p-i (intern-previous-info var)))
      (setf (previous-info-class p-i) class)
      (push (cons code (last code)) (previous-info-code p-i)))))

(defun intern-previous-info (var)
  ;; If VAR already has a previous-info structure, return it; else
  ;; create a new one, put it where it belongs, and return it.
  ;;   Make sure that if VAR is itself a save-var, the new record goes after
  ;; the one for VAR's var, so that the previous code is generated before it
  ;; is itself considered update code for another previous splicing.
  (or (cdr (assoc var *previous-vars-alist*))
      (let* ((p-i (make-previous-info :var var))
	     (place (member var *previous-vars-alist* 
			    :test #'is-save-var)))
	(if (null place)
	    (push (cons var p-i) *previous-vars-alist*)
	    (push (cons var p-i) (cdr place)))
	p-i)))

(defun is-save-var (var entry)
  (member var (previous-info-save-info-list (cdr entry))
	  :key #'save-info-save-var))

(defun make-save-vars (var n)
  (let ((list nil)
	(string (format nil "SAVE-~a-" var)))
    (dotimes (i n)
      (let ((svar (make-var-and-default-binding string :using-type-of var)))
	(push svar list)))
    list))

(defun insert-previous-code ()
  ;; For each variable that requires a previous value, get all the update code
  ;; for that variable and splice in code that will remember the previous
  ;; values for the desired number of iterations.  Return code to put in the
  ;; init and step sections of the loop.
  ;; There are three situations here: 
  ;; 1. Variable has its initial value at the beginning of the loop, or gets
  ;;    its initial value in a different place than where it is updated.  In
  ;;    this case, we can put the save code just before each update of the
  ;;    variable.  Applicable clauses are: FOR-PREVIOUS, FOR-INITIALLY-THEN,
  ;;    and FOR-FIRST-THEN. (class :INITIAL)
  ;; 2. The variable is updated somewhere inside the loop, and the update also
  ;;    gives it its first value.  We use another, internal save variable,
  ;;    which is set to the variable after each update.  This is for FOR-= and
  ;;    driver clauses when NEXT is used.(class :NEXT)
  ;; 3. Variable is a driver with no NEXT.  We can put the update in the step
  ;;    portion of the loop, since we know the update code occurs at the
  ;;    beginning. (class :STEP)
  ;; Note that (3) is really an optimization of (2), and we could perform such
  ;; an optimization more generally if we could show that a variable in class
  ;; (2) was always updated before being used.  Right now, we don't bother.
  ;;  *** (3) is no longer done because driver code stays where the driver is.
  ;;  We could try to detect that the driver is at the beginning, but don't
  ;;  for now.
  (let ((init-code nil)
	(step-code nil)
	(pv-list *previous-vars-alist*))
    ;; Step through this manually, because it may be that we add to it in
    ;; the process, and we must make sure that we don't cdr till we have to. 
    (loop
     (if (null pv-list) (return))
     (let* ((entry (car pv-list))
	    (var (car entry))
	    (p-i (cdr entry))
	    (save-info-list (previous-info-save-info-list p-i))
	    (code-list (previous-info-code p-i))
	    (class (previous-info-class p-i)))
       (if save-info-list
	   (if (and (null code-list) (not (eq class :step)))
	       (clause-error "Cannot obtain previous values of ~a" var)
	       (let ((prev-code (if (not (eq class :next))
				    (mapcan #L(make-prev-code var !1)
					    save-info-list))))
		 (case class
;;;;;;		   (:step (augment step-code prev-code))
		   (:initial (splice-in-code prev-code nil code-list))
		   ((:next :step) (augment init-code
				   (do-extra-save-var-hack var save-info-list
							   code-list)))
		   (otherwise (bug "unknown class ~a" class)))))))
     (setq pv-list (cdr pv-list)))
    (values init-code step-code)))

(defun do-extra-save-var-hack (var save-info-list code-list)
  (let ((init-code nil)
	(prev-code nil)
	(post-code nil))
    (dolist (s-i save-info-list)
      (let* ((extra-save-var (make-post-save-var var))
	     (prev (make-prev-code extra-save-var s-i :next)))
	(augment init-code `((setq ,extra-save-var ,(save-info-iv-ref s-i))))
	(augment post-code `((setq ,extra-save-var ,var)))
	(augment prev-code prev)))
    (splice-in-code prev-code post-code code-list)
    init-code))
			
(defun make-post-save-var (var)
  (make-var-and-default-binding (format nil "POST-SAVE-~a-" var) 
				:using-type-of var))


(defun make-prev-code (set-var s-i &optional (class :initial))
  (let ((prev (make-save-previous-code set-var (save-info-save-vars s-i))))
    (register-previous-code (save-info-save-var s-i) prev class)
    prev))

(defun make-save-previous-code (var save-vars)
  ;; The first save-var is the furthest back.
  (if (null (cdr save-vars))
      `((setq ,(car save-vars) ,var))
      (cons `(setq ,(first save-vars) ,(second save-vars))
	    (make-save-previous-code var (cdr save-vars)))))

(defun splice-in-code (prev-code post-code code-list)
  ;; Put PREV-CODE in at the first cons cell of CODE, and POST-CODE at the
  ;; last cons cell.  Both PREV-CODE and POST-CODE are single forms.
  ;; Some list splicing here--danger.  It's crucial that
  ;; CODE actually appears in the code to be generated.
  ;;  Can't use prognify here, because other people might have pointers to
  ;;  this code, and when prognify takes the car it ruins that.
  (setq prev-code (add-progn prev-code))
  (setq post-code (add-progn post-code))
  (dolist (code code-list)
    (let* ((first-cons-cell (car code))
	   (last-cons-cell (cdr code)))
      (when post-code
;;;	(format t "Splicing ~a after ~a~%" post-code last-cons-cell)
	(setf (cdr last-cons-cell) (cons post-code (cdr last-cons-cell))))
      (when prev-code
;;;	(format t "Splicing ~a before ~a~%" prev-code first-cons-cell)
	(let ((new-start (cons (car first-cons-cell) (cdr first-cons-cell))))
	  (setf (car first-cons-cell) prev-code)
	  (setf (cdr first-cons-cell) new-start))))))

(defun add-progn (forms)
  ;; If more than one form, cons the progn in; else do nothing.
  (cond
   ((null forms)
    nil)
  ((and (listp (car forms)) (not (lambda-expression? (car forms))))
   (cons 'progn forms))
  (t
   forms)))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Miscellaneous.

;; unused
(defun at-top-level? ()
  *top-level?*)

(defun top-level-check ()
  (if (not *top-level?*)
      (clause-error "Clause can occur only at top-level")))

(defun prognify (forms)
  ;; If more than one form, and the first is a list, then insert a PROGN.
  ;; Be careful to not copy forms.
  (if (cdr forms)
      (if (and (listp (car forms)) (not (eq (caar forms) 'lambda)))
	  (cons 'progn forms)
	  forms)
      (car forms)))

(defun clause-error (format-string &rest args)
  (apply #'error
	 (concatenate 'string 
		      "Iterate~@[, in ~a~]:~%" format-string)
	 (and (boundp' *clause*) *clause*)
	 args))

(defun clause-warning (format-string &rest args)
  (let ((*print-pretty* t))
    (apply #'warn
	   (concatenate 'string 
			"Iterate~@[, in clause ~a~]:~%" format-string)
	   (and (boundp' *clause*) *clause*)
	   args)))


(defun bug (format-string &rest args)
  (apply #'format 
	 *error-output*
	 (concatenate 'string "Bug in Iterate: " format-string)
	 args))

;;; I need something that's a cross between gensym and gentemp...

(defvar *genvar-counter* 0)

(defun genvar (&optional (string "TEMP"))
  (prog1 (make-symbol (format nil "~a~d" string *genvar-counter*))
	 (incf *genvar-counter*)))
    

(defun symbol-append (&rest syms)
  (intern (apply #'concatenate 'string (mapcar #'symbol-name syms))))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Debugging.

#|
(defun run-test ()
  (with-open-file (ifile "/wh/jba/Lisp/test-iter.lisp" :direction :input)
    (loop
      (let ((form (read ifile nil :eof)))
	(if (eq form :eof) (return-from run-test nil))
	(print form)
	(format t "==>~%")
	(print (eval form))
	(format t "~%--------------------~2%")))))

(defun expand-test ()
  (with-open-file (ifile "test-iter.lisp" :direction :input)
    (loop
      (let ((form (read ifile nil :eof)))
	(if (eq form :eof) (return-from expand-test nil))
	(print form)
	(format t "==>~%")
	(print (macroexpand-1 form))
	(format t "~%--------------------~2%")))))

(defmacro me (x)
  `(progn (setq *print-pretty* t) (macroexpand-1 ',x)))
|#


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Junk.


;;;;;;; For Gnu Emacs ;;;;;;;
;;; Local variables:
;;; version-control: t
;;; kept-new-versions: 5
;;; kept-old-versions: 0
;;; end: