File: Prolog.st

package info (click to toggle)
gnu-smalltalk 3.2.4-2.1
  • links: PTS, VCS
  • area: main
  • in suites: jessie, jessie-kfreebsd
  • size: 32,688 kB
  • ctags: 14,104
  • sloc: ansic: 87,424; sh: 22,729; asm: 8,465; perl: 4,513; cpp: 3,548; xml: 1,669; awk: 1,581; yacc: 1,357; makefile: 1,237; lisp: 855; lex: 843; sed: 258; objc: 124
file content (3254 lines) | stat: -rw-r--r-- 84,180 bytes parent folder | download | duplicates (6)
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
"======================================================================
|
|   Prolog interpreter written in Smalltalk
|
|
 ======================================================================"


"======================================================================
|
| Written by Aoki Atsushi and Nishihara Satoshi.
| Modified by Paolo Bonzini (removed GUI).
|
| This file is part of GNU Smalltalk.
|
| GNU Smalltalk is free software; you can redistribute it and/or modify it
| under the terms of the GNU General Public License as published by the Free
| Software Foundation; either version 2, or (at your option) any later version.
| 
| GNU Smalltalk is distributed in the hope that it will be useful, but WITHOUT
| ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
| FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
| details.
| 
| You should have received a copy of the GNU General Public License along with
| GNU Smalltalk; see the file COPYING.  If not, write to the Free Software
| Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  
|
 ======================================================================"

Object subclass: #PrologEntity
	instanceVariableNames: ''
	classVariableNames: ''
	poolDictionaries: ''
	category: 'Examples-Prolog'!

PrologEntity subclass: #PrologList
	instanceVariableNames: 'carPart cdrPart '
	classVariableNames: 'PrologDotPairPrintHorizontalLevel PrologDotPairPrintVerticalLevel '
	poolDictionaries: ''
	category: 'Examples-Prolog'!

PrologList subclass: #PrologBody
	instanceVariableNames: ''
	classVariableNames: ''
	poolDictionaries: ''
	category: 'Examples-Prolog'!

PrologList subclass: #PrologClause
	instanceVariableNames: ''
	classVariableNames: ''
	poolDictionaries: ''
	category: 'Examples-Prolog'!

PrologClause subclass: #PrologResolveClause
	instanceVariableNames: ''
	classVariableNames: ''
	poolDictionaries: ''
	category: 'Examples-Prolog'!

PrologList subclass: #PrologDefinition
	instanceVariableNames: ''
	classVariableNames: ''
	poolDictionaries: ''
	category: 'Examples-Prolog'!

PrologEntity subclass: #PrologObject
	instanceVariableNames: 'source object '
	classVariableNames: ''
	poolDictionaries: ''
	category: 'Examples-Prolog'!

Object subclass: #PrologScanner
	instanceVariableNames: 'source mark token tokenType endChar '
	classVariableNames: 'EndChar ScanningTable'
	poolDictionaries: ''
	category: 'Examples-Prolog'!

PrologScanner subclass: #PrologParser
	instanceVariableNames: 'prevMark prevToken prevTokenType failBlock '
	classVariableNames: ''
	poolDictionaries: ''
	category: 'Examples-Prolog'!

PrologEntity subclass: #PrologString
	instanceVariableNames: 'string '
	classVariableNames: ''
	poolDictionaries: ''
	category: 'Examples-Prolog'!

PrologList subclass: #PrologStructure
	instanceVariableNames: ''
	classVariableNames: ''
	poolDictionaries: ''
	category: 'Examples-Prolog'!

PrologString subclass: #PrologSymbol
	instanceVariableNames: ''
	classVariableNames: 'PrologCut PrologFail PrologSelf PrologSend PrologSymbolTable PrologTrue PrologVar '
	poolDictionaries: ''
	category: 'Examples-Prolog'!

PrologList subclass: #PrologTerms
	instanceVariableNames: ''
	classVariableNames: ''
	poolDictionaries: ''
	category: 'Examples-Prolog'!

PrologString subclass: #PrologVariable
	instanceVariableNames: ''
	classVariableNames: 'PrologVariableCounter PrologVariableTable '
	poolDictionaries: ''
	category: 'Examples-Prolog'!

Object subclass: #PrologInterpreter
	instanceVariableNames: 'systemPredicates userPredicates status definition question questionEnv clause clauseEnv queue queueEnv envCounter valueEnv unbindList cutBack backTrack resolveAction definitionStack tracePredicates traceCounter textValue textCollector verbose listValue predicate '
	classVariableNames: 'SystemPredicates '
	poolDictionaries: ''
	category: 'Examples-Prolog'!



!Object methodsFor: 'prolog'!

car
    self == nil ifTrue: [^nil].
    self error: 'send message car to atom'!

cdr
    self == nil ifTrue: [^nil].
    self error: 'send message cdr to atom'!

cons: anObject 
    ^PrologList car: self cdr: anObject!

consp
    ^false!

isPrologEntity
    self == nil ifTrue: [^true].
    ^self isKindOf: Number!

isPrologVariable
    ^false!

printPrologOn: aStream 
    self == nil
	ifTrue: 
	    [aStream nextPutAll: '[]'.
	    ^self].
    (self isKindOf: Number)
	ifTrue: 
	    [self printOn: aStream.
	    ^self].
    aStream nextPut: ${.
    self printOn: aStream.
    aStream nextPut: $}!

printPrologOn: aStream level: anInteger 
    self printPrologOn: aStream!

printPrologString
    | aStream |
    aStream := WriteStream on: (String new: 20).
    self printPrologOn: aStream.
    ^aStream contents! !


!PrologEntity class methodsFor: 'copyright'!

copyright
    ^'Copyright (C) 1995-1998 AOKI Atsushi, All Rights Reserved.'!

system
    ^'Goodies'!

version
    ^'003'! !

!PrologEntity methodsFor: 'testing'!

isPrologEntity
    ^true! !



!PrologList class methodsFor: 'class initialization'!

initialize
    "PrologList initialize"

    PrologDotPairPrintVerticalLevel := 10.
    PrologDotPairPrintHorizontalLevel := 100! !

!PrologList class methodsFor: 'copyright'!

copyright
    ^'Copyright (C) 1995-1998 AOKI Atsushi, All Rights Reserved.'!

system
    ^'Goodies'!

version
    ^'003'! !

!PrologList class methodsFor: 'instance creation'!

car: carObject cdr: cdrObject 
    ^super new car: carObject cdr: cdrObject!

list: anArray
    | size list |
    size := anArray size.
    list := nil.
    size
	to: 1
	by: -1
	do: [:i | list := self car: (anArray at: i) cdr: list].
    ^list! !

!PrologList methodsFor: 'accessing'!

car
    ^carPart!

car: carObject 
    carPart := carObject!

cdr
    ^cdrPart!

cdr: cdrObject 
    cdrPart := cdrObject!

nth: anInteger 
    | count list |
    anInteger <= 0 ifTrue: [^self].
    count := 1.
    list := self.
    [list consp]
	whileTrue: 
	    [count >= anInteger ifTrue: [^list car].
	    count := count + 1.
	    list := list cdr].
    ^nil! !

!PrologList methodsFor: 'converting'!

asPrologList
    | list new tail |
    new := self car cons: nil.
    tail := new.
    list := self cdr.
    [list consp]
	whileTrue: 
	    [tail cdr: (list car cons: nil).
	    tail := tail cdr.
	    list := list cdr].
    tail cdr: list.
    ^new! !

!PrologList methodsFor: 'enumerating'!

do: aBlock
    | list |
    list := self.
    [list consp] whileTrue: [
	aBlock value: list car.
	list := list cdr]! !

!PrologList methodsFor: 'functions'!

append: aPrologDotPair 
    (cdrPart consp)
	ifFalse: [^carPart cons: aPrologDotPair].
    ^carPart cons: (cdrPart append: aPrologDotPair)!

arity
    ^2!

assoc: anObject 
    | list assoc |
    list := self.
    [list consp]
	whileTrue: 
	    [assoc := list car.
	    anObject = assoc car ifTrue: [^assoc].
	    list := list cdr].
    ^nil!

functor
    ^PrologSymbol fromString: '.'!

length
    | list count |
    list := self.
    count := 0.
    [list consp]
	whileTrue: 
	    [count := count + 1.
	    list := list cdr].
    ^count!

member: anObject 
    | list |
    list := self.
    [list consp]
	whileTrue: 
	    [anObject = list car ifTrue: [^list].
	    list := list cdr].
    ^nil!

nconc: aPrologDotPair 
    | list |
    list := self.
    [list consp]
	whileTrue: [(list cdr consp)
		ifTrue: [list := list cdr]
		ifFalse: 
		    [list cdr: aPrologDotPair.
		    ^self]].
    ^aPrologDotPair!

reverse
    | list revlist mark |
    list := self.
    revlist := nil.
    [list consp]
	whileTrue: 
	    [revlist == nil
		ifTrue: [revlist := mark := list car cons: revlist]
		ifFalse: [revlist := list car cons: revlist].
	    list := list cdr].
    mark cdr: list.
    ^revlist!

structureList
    "disassemble prolog structure of myself into a list."
    ^self functor cons: ((self car) cons: ((self cdr) cons: nil))! !

!PrologList methodsFor: 'printing'!

prettyPrintPrologOn: aStream 
    | head body list |
    head := self car.
    body := self cdr.
    head printPrologOn: aStream.
    body ~~ nil
	ifTrue: 
	    [aStream nextPutAll: ' :- '.
	    list := body.
	    aStream nl; tab.
	    [list cdr consp]
		whileTrue: 
		    [list ~~ body
			ifTrue: 
			    [aStream nextPutAll: ', '.
			    aStream nl; tab].
		    list car printPrologOn: aStream.
		    list := list cdr].
	    list ~~ self
		ifTrue: 
		    [aStream nextPutAll: ', '.
		    aStream nl; tab].
	    list car printPrologOn: aStream].
    aStream nextPut: $.!

prettyPrintPrologString
    | aStream |
    aStream := WriteStream on: (String new: 20).
    self prettyPrintPrologOn: aStream.
    ^aStream contents!

printOn: aStream 
    aStream nextPutAll: self class printString.
    aStream nextPutAll: '('.
    aStream nextPutAll: self printPrologString.
    aStream nextPutAll: ')'!

printPrologOn: aStream 
    self printPrologOn: aStream level: 1!

printPrologOn: aStream cdr: tail level: anInteger 
    | d count |
    d := tail.
    count := 1.
    [d consp]
	whileTrue: 
	    [count >= PrologDotPairPrintHorizontalLevel
		ifTrue: 
		    [aStream nextPutAll: ' ... ]'.
		    ^self].
	    aStream nextPut: $,.
	    d car consp
		ifTrue: [d car printPrologOn: aStream level: anInteger + 1]
		ifFalse: [d car printPrologOn: aStream].
	    "d car printPrologOn: aStream level: anInteger + 1."
	    count := count + 1.
	    d := d cdr].
    d isNil
	ifTrue: [aStream nextPut: $]]
	ifFalse: 
	    [aStream nextPut: $|.
	    d printPrologOn: aStream.
	    aStream nextPut: $]]!

printPrologOn: aStream level: anInteger 
    anInteger > PrologDotPairPrintVerticalLevel
	ifTrue: 
	    [aStream nextPutAll: ' ... '.
	    ^self].
    aStream nextPutAll: '['.
    carPart consp
	ifTrue: [carPart printPrologOn: aStream level: anInteger + 1]
	ifFalse: [carPart printPrologOn: aStream].
    self
	printPrologOn: aStream
	cdr: cdrPart
	level: anInteger! !

!PrologList methodsFor: 'private'!

car: carObject cdr: cdrObject 
    carPart := carObject.
    cdrPart := cdrObject! !

!PrologList methodsFor: 'testing'!

= anObject 
    anObject consp ifFalse: [^false].
    self car = anObject car ifTrue: [^self cdr = anObject cdr].
    ^false!

consp
    ^true! !


PrologList initialize!

!PrologBody class methodsFor: 'copyright'!

copyright
    ^'Copyright (C) 1995-1998 AOKI Atsushi, All Rights Reserved.'!

system
    ^'Goodies'!

version
    ^'003'! !

!PrologBody class methodsFor: 'instance creation'!

fromList: aPrologDotPair 
    aPrologDotPair consp ifFalse: [^aPrologDotPair].
    ^super new fromList: aPrologDotPair!

fromReverseList: aPrologDotPair 
    aPrologDotPair consp ifFalse: [^aPrologDotPair].
    ^super new fromReverseList: aPrologDotPair!

structure: aPrologStructure next: link 
    ^super new structure: aPrologStructure next: link! !

!PrologBody methodsFor: 'printing'!

prettyPrintPrologOn: aStream 
    | list |
    list := self.
    aStream nl; tab.
    [list cdr consp]
	whileTrue: 
	    [list ~~ self
		ifTrue: 
		    [aStream nextPutAll: ', '.
		    aStream nl; tab].
	    list car printPrologOn: aStream.
	    list := list cdr].
    list ~~ self
	ifTrue: 
	    [aStream nextPutAll: ', '.
	    aStream nl; tab].
    list car printPrologOn: aStream!

printPrologOn: aStream 
    | list |
    list := self.
    [list cdr consp]
	whileTrue: 
	    [list ~~ self ifTrue: [aStream nextPutAll: ', '].
	    list car printPrologOn: aStream.
	    list := list cdr].
    list ~~ self ifTrue: [aStream nextPutAll: ', '].
    list car printPrologOn: aStream!

printPrologOn: aStream level: anInteger
    self printPrologOn: aStream! !

!PrologBody methodsFor: 'private'!

fromList: aPrologDotPair 
    ^self fromReverseList: aPrologDotPair reverse!

fromReverseList: aPrologDotPair 
    | list body mark |
    list := aPrologDotPair.
    body := nil.
    [list consp]
	whileTrue: 
	    [body == nil
		ifTrue: [body := mark := self class structure: list car next: body]
		ifFalse: [body := self class structure: list car next: body].
	    list := list cdr].
    mark cdr: list.
    ^body!

structure: aPrologStructure next: link 
    carPart := aPrologStructure.
    cdrPart := link! !



!PrologClause class methodsFor: 'copyright'!

copyright
    ^'Copyright (C) 1995-1998 AOKI Atsushi, All Rights Reserved.'!

system
    ^'Goodies'!

version
    ^'003'! !

!PrologClause class methodsFor: 'instance creation'!

head: aPrologStructure body: aPrologBody 
    ^super new head: aPrologStructure body: aPrologBody! !

!PrologClause methodsFor: 'accessing'!

body
    ^cdrPart!

body: aPrologBody 
    cdrPart := aPrologBody!

head
    ^carPart!

head: aPrologStructure 
    carPart := aPrologStructure! !

!PrologClause methodsFor: 'printing'!

prettyPrintPrologOn: aStream 
    | head body |
    head := self head.
    body := self body.
    head printPrologOn: aStream.
    body ~~ nil
	ifTrue: 
	    [aStream nextPutAll: ' :- '.
	    body prettyPrintPrologOn: aStream].
    aStream nextPut: $.!

prettyPrintPrologString
    | aStream |
    aStream := WriteStream on: (String new: 20).
    self prettyPrintPrologOn: aStream.
    ^aStream contents!

printPrologOn: aStream 
    | head body |
    head := self head.
    body := self body.
    aStream nextPut: $(.
    head printPrologOn: aStream.
    body == nil
	ifFalse: 
	    [aStream nextPutAll: ', '.
	    body printPrologOn: aStream].
    aStream nextPut: $)!

printPrologOn: aStream level: anInteger
    self printPrologOn: aStream! !

!PrologClause methodsFor: 'private'!

head: aPrologStructure body: aPrologBody 
    self head: aPrologStructure.
    self body: aPrologBody! !


!PrologClause methodsFor: 'polymorphism'!

isResolveClause
    ^false! !

!PrologResolveClause methodsFor: 'polymorphism'!

printPrologOn: aStream 
    | head body |
    head := self head.
    body := self body.
    aStream nextPutAll: '?- '.
    head printPrologOn: aStream.
    body ~~ nil
	ifTrue: 
	    [aStream nextPutAll: ', '.
	    body printPrologOn: aStream].
    aStream nextPut: $.!

isResolveClause
    ^true! !

!PrologDefinition class methodsFor: 'copyright'!

copyright
    ^'Copyright (C) 1995-1998 AOKI Atsushi, All Rights Reserved.'!

system
    ^'Goodies'!

version
    ^'003'! !

!PrologDefinition class methodsFor: 'instance creation'!

clause: aPrologClause next: link 
    ^super new clause: aPrologClause next: link!

fromList: aPrologDotPair 
    aPrologDotPair consp ifFalse: [^aPrologDotPair].
    ^super new fromList: aPrologDotPair!

fromReverseList: aPrologDotPair 
    aPrologDotPair consp ifFalse: [^aPrologDotPair].
    ^super new fromReverseList: aPrologDotPair! !

!PrologDefinition methodsFor: 'private'!

clause: aPrologClause next: link 
    carPart := aPrologClause.
    cdrPart := link!

fromList: aPrologDotPair 
    ^self fromReverseList: aPrologDotPair reverse!

fromReverseList: aPrologDotPair 
    | list definition |
    list := aPrologDotPair.
    definition := nil.
    [list consp]
	whileTrue: 
	    [definition := self class clause: list car next: definition.
	    list := list cdr].
    ^definition! !



!PrologObject class methodsFor: 'copyright'!

copyright
    ^'Copyright (C) 1995-1998 AOKI Atsushi, All Rights Reserved.'!

system
    ^'Goodies'!

version
    ^'003'! !

!PrologObject class methodsFor: 'instance creation'!

readFrom: aStream 
    | buffer char |
    buffer := WriteStream on: (String new: 20).
    
    [char := aStream next.
    char = $}]
	whileFalse: 
	    [char == nil ifTrue: [self error:
		    'Syntax error near ${ unmatched $}\-- end of file --' withCRs].
	    buffer nextPut: char].
    ^buffer contents!

source: aString object: anObject 
    ^super new source: aString object: anObject! !

!PrologObject methodsFor: 'accessing'!

object
    ^object!

object: anObject
    object := anObject!

source
    ^source!

source: aString
    source := aString! !

!PrologObject methodsFor: 'printing'!

printOn: aStream 
    aStream nextPutAll: self class printString.
    aStream nextPutAll: '('.
    aStream nextPutAll: self object printString.
    aStream nextPutAll: ')'!

printPrologOn: aStream 
    aStream nextPut: ${.
    aStream nextPutAll: self source.
    aStream nextPut: $}!

printPrologOn: aStream level: anInteger
    self printPrologOn: aStream! !

!PrologObject methodsFor: 'private'!

source: aString object: anObject 
    self source: aString.
    self object: anObject! !

!PrologObject methodsFor: 'testing'!

= anObject 
    anObject class = self class ifFalse: [^false].
    ^self object = anObject object! !



!PrologScanner class methodsFor: 'class initialization'!

initialize
    "PrologScanner initialize"

    | newTable |
    newTable := Array new: 256 withAll: #xBinary.
    newTable atAll: #(9 10 12 13 32 ) put: #xDelimiter.
    newTable atAll: ($0 asInteger to: $9 asInteger) put: #xDigit.
    newTable atAll: ($A asInteger to: $Z asInteger) put: #xVariable.
    newTable at: $~ asInteger put: #xVariable.
    newTable atAll: ($a asInteger to: $z asInteger) put: #xSymbol.
    128 to: 256 do: [:i | newTable at: i put: #xSymbol].
    #($! $: $* $/ $\ $> $< $= $_) do: [:each | newTable at: each asInteger put: #xSymbol].
    newTable at: $^ asInteger put: #eof.
    newTable at: $" asInteger put: #xDoubleQuote.
    newTable at: $$ asInteger put: #xDollar.
    newTable at: $' asInteger put: #xSingleQuote.
    newTable at: $( asInteger put: #leftParenthesis.
    newTable at: $) asInteger put: #rightParenthesis.
    newTable at: $. asInteger put: #period.
    newTable at: $: asInteger put: #xColon.
    newTable at: $? asInteger put: #xColon.
    newTable at: $; asInteger put: #semicolon.
    newTable at: $[ asInteger put: #leftBracket.
    newTable at: $] asInteger put: #rightBracket.
    newTable at: ${ asInteger put: #leftBrace.
    newTable at: $} asInteger put: #rightBrace.
    newTable at: $, asInteger put: #comma.
    newTable at: $| asInteger put: #verticalBar.
    newTable at: $+ asInteger put: #xSign.
    newTable at: $- asInteger put: #xSign.
    newTable at: $% asInteger put: #xComment.
    ScanningTable := newTable.
    EndChar := $^! !

!PrologScanner class methodsFor: 'copyright'!

copyright
    ^'Copyright (C) 1995-1998 AOKI Atsushi, All Rights Reserved.'!

system
    ^'Goodies'!

version
    ^'003'! !

!PrologScanner class methodsFor: 'instance creation'!

new
    ^super new initScanner! !

!PrologScanner methodsFor: 'accessing'!

tableAt: char
    | index |
    index := char asInteger.
    ^index = 0
	ifFalse: [ScanningTable at: index]
	ifTrue: [#xDelimiter]! !

!PrologScanner methodsFor: 'error handling'!

error: labelString with: contentsString
    "(PrologScanner new) error: 'error!' with: 'show must go on'."

    | handler |
    self error: contentsString! !

!PrologScanner methodsFor: 'initialize-release'!

initScanner
    endChar := EndChar!

on: inputStream 
    source := inputStream.
    mark := source position! !

!PrologScanner methodsFor: 'private'!

nextChar
    | char |
    source atEnd ifTrue: [ ^endChar ].
    char := source next.
    char = Character cr
	ifTrue: 
	    [char := Character nl. source peekFor: char].
    ^char!

peekChar
    | char |
    char := source peek.
    char = Character cr ifTrue: [char := Character nl].
    char == nil ifTrue: [char := endChar].
    ^char!

unNextChar
    source skip: -1! !

!PrologScanner methodsFor: 'scanning'!

multiChar: type 
    self perform: type!

nextToken
    | char |
    mark := source position.
    char := self peekChar.
    tokenType := self tableAt: char asInteger.
    [tokenType == #xDelimiter]
	whileTrue: 
	    [self nextChar.
	    char := self peekChar.
	    tokenType := self tableAt: char asInteger].
    (tokenType at: 1) = $x
	ifTrue:[self multiChar: tokenType]
	ifFalse:[self singleChar: tokenType].
    ^token!

singleChar: type 
    self nextChar.
    token := type.
    tokenType == #leftBrace ifFalse: [^self].
    tokenType := #object.
    token := PrologObject readFrom: source!

unNextToken
    source position: mark!

xBinary
    self error: 'Syntax error ' , source peek printString , '\' withCRs , source upToEnd!

xColon
    | char |
    source next.
    char := source peek.
    char = $-
	ifTrue: 
	    [tokenType := #neck.
	    self singleChar: tokenType]
	ifFalse: 
	    [self unNextToken.
	    tokenType := #symbol.
	    token := PrologSymbol readFrom: source]!

xComment
    | char |
    [(char := self nextChar) = Character nl]
	whileFalse: [char == endChar
		ifTrue: 
		    [tokenType := #eof.
		    ^self]].
    self nextToken!

xDigit
    tokenType := #number.
    token := Number readFrom: source!

xDollar
    self xBinary!

xDoubleQuote
    tokenType := #string.
    token := PrologString readFrom: source!

xSign
    | char sign |
    sign := self nextChar.
    char := self peekChar.
    char isDigit
	ifTrue: 
	    [tokenType := #number.
	    token := Number readFrom: source.
	    sign == $- ifTrue: [token := token negated]]
	ifFalse: 
	    [self unNextChar.
	    tokenType := #symbol.
	    token := PrologSymbol readFrom: source]!

xSingleQuote
    tokenType := #symbol.
    token := PrologSymbol readFrom: source!

xSymbol
    tokenType := #symbol.
    token := PrologSymbol readFrom: source!

xVariable
    tokenType := #variable.
    token := PrologVariable readFrom: source! !


PrologScanner initialize!

!PrologParser class methodsFor: 'copyright'!

copyright
    ^'Copyright (C) 1995-1998 AOKI Atsushi, All Rights Reserved.'!

system
    ^'Goodies'!

version
    ^'003'! !

!PrologParser methodsFor: 'parsing'!

parse: sourceStream 
    | label string |
    ^self parse: sourceStream
	ifFail: 
	    [:errorMessage | 
	    label := errorMessage , ' near ' , token printString.
	    string := source upToEnd.
	    string size > 100 ifTrue: [string := string copyFrom: 1 to: 100].
	    self error: label with: (string = ''
			ifTrue: ['-- end of file --']
			ifFalse: ['--> ' , string])]!

parse: sourceStream ifFail: aBlock
    | result |
    self init: sourceStream ifFail: aBlock.
    result := self scan.
    ^result! !

!PrologParser methodsFor: 'private'!

compileAndEvaluate: string 
    ^Behavior
	evaluate: string
	ifError: []!

init: sourceStream ifFail: aBlock 
    super on: sourceStream.
    failBlock := aBlock.
    PrologVariable setZero! !

!PrologParser methodsFor: 'scan'!

scan
    source atEnd ifTrue: [^#eof].
    self nextToken.
    tokenType == #eof ifTrue: [^#eof].
    tokenType == #neck ifTrue: [^self scanClause: PrologResolveClause]. "resolve clause"
    self unNextToken.
    ^self scanClause: PrologClause!

scanBody
    | list |
    list := nil.
    [tokenType ~~ #eof]
	whileTrue: 
	    [list := self scanStructure cons: list.
	    self nextToken.
	    tokenType == #rightParenthesis ifTrue: [^PrologBody fromReverseList: list].
	    tokenType == #period ifTrue: [^PrologBody fromReverseList: list].
	    tokenType ~~ #comma ifTrue: [failBlock value: 'Syntax error']].
    failBlock value: 'Unexpected eof'!

scanClause: class
    | head |
    head := self scanStructure.
    self nextToken.
    tokenType == #neck ifTrue: [^class head: head body: self scanBody].
    tokenType == #comma ifTrue: [^class head: head body: self scanBody].
    tokenType == #period ifTrue: [^class head: head body: nil].
    tokenType == #rightParenthesis ifTrue: [^class head: head body: nil].
    self unNextToken.
    failBlock value: 'Syntax error'!

scanExpression
    | symbol |
    self nextToken.
    (tokenType == #eof or: [tokenType == #period])
	ifTrue: [^nil].
    tokenType == #number ifTrue: [^token].
    tokenType == #string ifTrue: [^token].
    tokenType == #object ifTrue: [^PrologObject source: token object: (self compileAndEvaluate: token)].
    tokenType == #leftBracket ifTrue: [^self scanList].
    tokenType == #leftParenthesis ifTrue: [^self scanClause: PrologClause].
    (tokenType == #symbol or: [tokenType == #variable])
	ifTrue: 
	    [symbol := token.
	    self nextToken.
	    tokenType == #leftParenthesis
		ifTrue: 
		    [self unNextToken.
		    self unNextToken.
		    ^self scanStructure]
		ifFalse: 
		    [self unNextToken.
		    ^symbol]].
    self unNextToken.
    failBlock value: 'Syntax error'!

scanList
    | expression |
    self nextToken.
    tokenType == #comma ifTrue: [self nextToken].
    tokenType == #neck ifTrue: [self nextToken].
    tokenType == #rightBracket ifTrue: [^nil].
    tokenType == #leftBracket ifTrue: [^self scanList cons: self scanList].
    tokenType == #verticalBar
	ifTrue: 
	    [expression := self scanExpression.
	    self nextToken.
	    tokenType == #rightBracket
		ifTrue: [^expression]
		ifFalse: [failBlock value: 'Syntax error']].
    self unNextToken.
    expression := self scanExpression.
    ^expression cons: self scanList!

scanStructure
    | functor terms |
    functor := self nextToken.
    (tokenType == #symbol or: [tokenType == #variable])
	ifTrue: 
	    [terms := self scanTerms.
	    ^PrologStructure functor: functor terms: terms].
    failBlock value: 'Syntax error'!

scanTerms
    | list |
    self nextToken.
    tokenType == #leftParenthesis
	ifTrue: 
	    [self nextToken.
	    (tokenType == #verticalBar or: [tokenType == #rightParenthesis])
		ifTrue:
		    [tokenType == #rightParenthesis
			ifTrue: [^nil].
		    list := self scanExpression.
		    self nextToken.
		    tokenType == #rightParenthesis
			ifTrue: [^list]
			ifFalse: [failBlock value: 'Syntax error']]
		ifFalse: [self unNextToken].
	    list := nil.
	    [tokenType ~~ #eof]
		whileTrue: 
		    [list := self scanExpression cons: list.
		    self nextToken.
		    token == #rightParenthesis ifTrue: [^PrologTerms fromReverseList: list].
		    tokenType == #verticalBar
			ifTrue:
			    [list := list reverse.
			    list := list nconc: self scanExpression.
			    self nextToken.
			    tokenType == #rightParenthesis
				ifTrue: [^PrologTerms fromList: list]
				ifFalse: [failBlock value: 'Syntax error']].
		    tokenType ~~ #comma ifTrue: [failBlock value: 'Syntax error']].
	    failBlock value: 'Unexpected eof']
	ifFalse: 
	    [self unNextToken.
	    ^nil]! !

!PrologParser methodsFor: 'scanning'!

nextToken
    prevMark := mark.
    prevToken := token.
    prevTokenType := tokenType.
    ^super nextToken!

unNextToken
    super unNextToken.
    mark := prevMark.
    token := prevToken.
    tokenType := prevTokenType! !



PrologString class instanceVariableNames: 'charMap '!

!PrologString class methodsFor: 'accessing'!

charMap: map
    charMap := map!

charMapAt: char
    | index |
    index := char asInteger.
    ^index = 0
	ifTrue: [false]
	ifFalse: [charMap at: index]! !

!PrologString class methodsFor: 'copyright'!

copyright
    ^'Copyright (C) 1995-1998 AOKI Atsushi, All Rights Reserved.'!

system
    ^'Goodies'!

version
    ^'003'! !

!PrologString class methodsFor: 'instance creation'!

fromString: aString 
    ^super new string: aString!

readFrom: aStream 
    | buffer char string |
    buffer := WriteStream on: (String new: 20).
    char := aStream next.
    char = $" ifTrue: [
	[char := aStream peek.
	char ~~ nil]
	    whileTrue: 
		[char = $"
		    ifTrue: 
			[aStream next.
			char := aStream peek.
			char = $" ifFalse: [^self fromString: buffer contents]].
		buffer nextPut: aStream next]].
    string := aStream upToEnd.
    string size > 100 ifTrue: [string := string copyFrom: 1 to: 100].
    self error: 'Syntax error near $" unmatched $"\' withCRs , (string = ''
		    ifTrue: ['-- end of file --']
		    ifFalse: ['--> ' , string])! !

!PrologString methodsFor: 'accessing'!

at: index
    ^string at: index!

at: index put: char
    ^string at: index put: char!

size
    ^string size!

string
    ^string!

string: aString
    string := aString! !

!PrologString methodsFor: 'comparing'!

< aPrologString 
    ^self string < aPrologString string!

<= aPrologString 
    ^self string <= aPrologString string!

> aPrologString 
    ^self string > aPrologString string!

>= aPrologString 
    ^self string >= aPrologString string!

hash
    ^self asString hash! !

!PrologString methodsFor: 'converting'!

asString
    ^self string! !

!PrologString methodsFor: 'enumerating'!

do: aBlock
    ^self asString do: aBlock! !

!PrologString methodsFor: 'printing'!

printOn: aStream 
    aStream nextPutAll: self class printString.
    aStream nextPutAll: '('.
    aStream nextPutAll: self asString.
    aStream nextPutAll: ')'!

printPrologOn: aStream 
    | i length x |
    aStream nextPut: $".
    i := 0.
    length := string size.
    [(i := i + 1) <= length]
	whileTrue: 
	    [aStream nextPut: (x := string at: i).
	    x == $" ifTrue: [aStream nextPut: x]].
    aStream nextPut: $"!

printPrologOn: aStream level: anInteger 
    self printPrologOn: aStream! !

!PrologString methodsFor: 'testing'!

= anObject 
    anObject class = self class ifFalse: [^false].
    ^self string = anObject string! !



!PrologStructure class methodsFor: 'copyright'!

copyright
    ^'Copyright (C) 1995-1998 AOKI Atsushi, All Rights Reserved.'!

system
    ^'Goodies'!

version
    ^'003'! !

!PrologStructure class methodsFor: 'instance creation'!

functor: aPrologSymbol terms: aPrologTerms 
    ^super new functor: aPrologSymbol terms: aPrologTerms! !

!PrologStructure methodsFor: 'accessing'!

arity
    ^self terms length!

functor
    ^carPart!

functor: aPrologSymbol 
    carPart := aPrologSymbol!

nthTerm: anInteger 
    ^cdrPart nth: anInteger!

terms
    ^cdrPart!

terms: aPrologTerms 
    cdrPart := aPrologTerms! !

!PrologStructure methodsFor: 'functions'!

structureList
    "disassemble prolog structure of myself into a list."
    ^(self functor) cons: self terms asPrologList! !

!PrologStructure methodsFor: 'printing'!

printPrologOn: aStream 
    | functor terms |
    functor := self functor.
    terms := self terms.
    functor printPrologOn: aStream.
    terms == nil
	ifFalse:
	    [(terms consp)
		ifTrue: [terms printPrologOn: aStream]
		ifFalse:
		    [aStream nextPutAll: '(|'.
		    terms printPrologOn: aStream.
		    aStream nextPut: $)]]!

printPrologOn: aStream level: anInteger
    self printPrologOn: aStream! !

!PrologStructure methodsFor: 'private'!

functor: aPrologSymbol terms: aPrologTerms 
    self functor: aPrologSymbol.
    self terms: aPrologTerms! !



!PrologSymbol class methodsFor: 'class initialization'!

initialize
    "PrologSymbol initialize"

    | newMap |
    newMap := Array new: 256 withAll: false.
    newMap atAll: ($0 asInteger to: $9 asInteger)
	put: true.
    newMap atAll: ($A asInteger to: $Z asInteger)
	put: true.
    newMap atAll: ($a asInteger to: $z asInteger)
	put: true.
    128 to: 256 do: [:i | newMap at: i put: true].
    #($+ $- $! $: $* $/ $\ $> $< $= $_) do: [:each | newMap at: each asInteger put: true].
    self charMap: newMap.

    PrologSymbolTable := Dictionary new.
    PrologCut := self install: '!'.
    PrologTrue := self install: 'true'.
    PrologFail := self install: 'fail'.
    PrologSend := self install: 'send'.
    PrologVar := self install: 'var'.
    PrologSelf := self install: 'self'! !

!PrologSymbol class methodsFor: 'constants'!

cut
    ^PrologCut! !

!PrologSymbol class methodsFor: 'copyright'!

copyright
    ^'Copyright (C) 1995-1998 AOKI Atsushi, All Rights Reserved.'!

system
    ^'Goodies'!

version
    ^'003'! !

!PrologSymbol class methodsFor: 'instance creation'!

install: aString 
    | symbol key |
    symbol := PrologSymbolTable at: aString ifAbsent: [nil].
    symbol == nil
	ifTrue: 
	    [key := self fromString: aString.
	    symbol := self fromString: aString.
	    PrologSymbolTable at: key put: symbol].
    ^symbol!

readFrom: aStream 
    | buffer char |
    buffer := WriteStream on: (String new: 20).
    char := aStream peek.
    char == $'
	ifTrue: 
	    [aStream next.
	    
	    [char := aStream peek.
	    char ~~ nil]
		whileTrue: 
		    [char = $'
			ifTrue: 
			    [aStream next.
			    char := aStream peek.
			    char = $' ifFalse: [^self install: buffer contents]].
		    buffer nextPut: aStream next].
	self error: 'Syntax error near $'' unmatched $''\-- end of file --' withCRs].
    (self expect: '=..' on: aStream)
	ifTrue: ["Non standard (or ad hoc) parsing patterns."
	    ^self install: '=..'].
    [char ~~ nil and: [self charMapAt: char]]
	whileTrue: 
	    [buffer nextPut: aStream next.
	    char := aStream peek].
    ^self install: buffer contents! !

!PrologSymbol class methodsFor: 'private'!

expect: aString on: aStream
    "If aStream contains aString at the current position, then return true and set the position of aStream to the next char of the string.
    else return false and rewind the position."

    | pos string |
    pos := aStream position.
    string := String new.
    aString size timesRepeat: [
	aStream atEnd ifFalse: [string := string , (String with: aStream next)]].
    aString = string
	ifTrue: [^true]
	ifFalse: [
	    aStream position: pos.
	    ^false]! !

!PrologSymbol methodsFor: 'accessing'!

arity
    ^0!

functor
    ^self! !

!PrologSymbol methodsFor: 'printing'!

printPrologOn: aStream 
    | flag firstChar i length x |
    flag := false.
    self do: [:each | (self class charMapAt: each)
	    ifFalse: [flag := true]].
    string isEmpty
	ifTrue: 
	    [aStream nextPutAll: ''''.
	    aStream nextPutAll: '''']
	ifFalse: 
	    [firstChar := string at: 1.
	    ((firstChar >= $A and: [firstChar <= $Z])
		or: [flag])
		ifTrue: 
		    [aStream nextPutAll: ''''.
		    i := 0.
		    length := string size.
		    [(i := i + 1) <= length]
			whileTrue: 
			    [aStream nextPut: (x := string at: i).
			    x == $' ifTrue: [aStream nextPut: x]].
		    aStream nextPutAll: '''']
		ifFalse: 
		    [i := 0.
		    length := string size.
		    [(i := i + 1) <= length]
			whileTrue: 
			    [aStream nextPut: (x := string at: i).
			    x == $' ifTrue: [aStream nextPut: x]]]]!

printPrologOn: aStream level: anInteger 
    self printPrologOn: aStream! !

!PrologSymbol methodsFor: 'testing'!

isBuiltInPredicate
    self isPrologCut ifTrue: [^true].
    self isPrologTrue ifTrue: [^true].
    self isPrologFail ifTrue: [^true].
    self isPrologSend ifTrue: [^true].
    self isPrologVar ifTrue: [^true].
    ^false!

isPrologCut
    ^self = PrologCut!

isPrologFail
    ^self = PrologFail!

isPrologSelf
    ^self = PrologSelf!

isPrologSend
    ^self = PrologSend!

isPrologTrue
    ^self = PrologTrue!

isPrologVar
    ^self = PrologVar! !


PrologSymbol initialize!

!PrologTerms class methodsFor: 'copyright'!

copyright
    ^'Copyright (C) 1995-1998 AOKI Atsushi, All Rights Reserved.'!

system
    ^'Goodies'!

version
    ^'003'! !

!PrologTerms class methodsFor: 'instance creation'!

fromList: aPrologDotPair 
    ^super new fromList: aPrologDotPair!

fromReverseList: aPrologDotPair 
    ^super new fromReverseList: aPrologDotPair!

term: term next: link 
    ^super new term: term next: link! !

!PrologTerms methodsFor: 'printing'!

printPrologOn: aStream 
    | list |
    aStream nextPut: $(.
    list := self.
    [list cdr consp]
	whileTrue: 
	    [list ~~ self ifTrue: [aStream nextPut: $,].
	    list car printPrologOn: aStream.
	    list := list cdr].
    list ~~ self ifTrue: [aStream nextPut: $,].
    list car printPrologOn: aStream.
    list cdr isNil
	ifTrue: [aStream nextPut: $)]
	ifFalse:
	    [aStream nextPut: $|.
	    list cdr printPrologOn: aStream.
	    aStream nextPut: $)]!

printPrologOn: aStream level: anInteger
    self printPrologOn: aStream! !

!PrologTerms methodsFor: 'private'!

fromList: aPrologDotPair 
    ^self fromReverseList: aPrologDotPair reverse!

fromReverseList: aPrologDotPair 
    | list terms mark |
    list := aPrologDotPair.
    terms := nil.
    [list consp]
	whileTrue: 
	    [terms == nil
		ifTrue: [terms := mark := self class term: list car next: terms]
		ifFalse: [terms := self class term: list car next: terms].
	    list := list cdr].
    mark cdr: list.
    ^terms!

term: anObject next: link 
    carPart := anObject.
    cdrPart := link! !



!PrologVariable class methodsFor: 'class initialization'!

initialize
    "PrologVariable initialize"

    | newMap |
    newMap := Array new: 256 withAll: false.
    newMap atAll: ($0 asInteger to: $9 asInteger)
	put: true.
    newMap atAll: ($A asInteger to: $Z asInteger)
	put: true.
    newMap atAll: ($a asInteger to: $z asInteger)
	put: true.
    newMap at: $~ asInteger put: true.
    self charMap: newMap.
    self setZero.
    PrologVariableTable := Dictionary new! !

!PrologVariable class methodsFor: 'copyright'!

copyright
    ^'Copyright (C) 1995-1998 AOKI Atsushi, All Rights Reserved.'!

system
    ^'Goodies'!

version
    ^'003'! !

!PrologVariable class methodsFor: 'instance creation'!

install: aString 
    | variable key |
    variable := PrologVariableTable at: aString ifAbsent: [nil].
    variable == nil
	ifTrue: 
	    [key := aString.
	    variable := self fromString: aString.
	    PrologVariableTable at: key put: variable].
    ^variable!

readFrom: aStream 
    | buffer char |
    buffer := WriteStream on: (String new: 20).
    char := aStream peek.
    (char ~~ nil and: [char = $~])
	ifTrue: 
	    [aStream next.
	    self countUp.
	    ^self install: '~' , PrologVariableCounter printString].
    [char ~~ nil and: [ self charMapAt: char]]
	whileTrue: 
	    [buffer nextPut: aStream next.
	    char := aStream peek].
    ^self install: buffer contents! !

!PrologVariable class methodsFor: 'private'!

countUp
    PrologVariableCounter := PrologVariableCounter + 1!

setZero
    PrologVariableCounter := 0! !

!PrologVariable methodsFor: 'printing'!

printPrologOn: aStream 
    (self asString at: 1)
	= $~
	ifTrue: [aStream nextPut: $~]
	ifFalse: [aStream nextPutAll: self asString]!

printPrologOn: aStream level: anInteger
    self printPrologOn: aStream! !

!PrologVariable methodsFor: 'testing'!

isPrologVariable
    ^true! !


PrologVariable initialize!

!PrologInterpreter class methodsFor: 'class initialization'!

flushOthers
    "PrologInterpreter flushOthers."

    self flushSystemPredicates!

flushSystemPredicates
    "PrologInterpreter flushSystemPredicates."

    SystemPredicates := nil! !

!PrologInterpreter class methodsFor: 'copyright'!

copyright
    ^'Copyright (C) 1995-1998 AOKI Atsushi, All Rights Reserved.'!

system
    ^'Goodies'!

version
    ^'003'! !

!PrologInterpreter class methodsFor: 'examples'!

example01
    "PrologInterpreter example01."

    self example: '

    ?- remove.       % remove all predicates in PrologDataBase.
    likes(john,mary).    % assert fact.
    likes(john,wine).    % assert fact.
    likes(mary,wine).    % assert fact.
    likes(mary,john).    % assert fact.
    ?- likes(X,Y).	   % question goal.
    ?- likes(john,X), likes(mary,X). % question goal.

    '!

example02
    "PrologInterpreter example02."

    self example: '

    ?- remove.       % remove all predicates in PrologDataBase.
    on(hen,cat).
    on(cat,dog).
    on(dog,donkey).
    above(X,Y) :-
	on(X,Y).
    above(X,Y) :-
	on(X,Z), above(Z,Y).
    ?- on(X,dog).
    ?- above(X,dog).

    '!

example03
    "PrologInterpreter example03."

    self example: '

    ?- remove.    % remove all predicates in PrologDataBase.
    hanoi(N) :-    % This is Hanoi Tower Prolgram.
	move(N,left,right,center).
	move(0,X,Y,Z) :- !.
    move(N,A,B,C) :-
	-(N,1,M),
	move(M,A,C,B),
	inform(A,B),
	move(M,C,B,A).
    inform(X,Y) :-
	write([move,disc,from,X,to,Y]),
	nl.
    ?- hanoi(3).     % question goal.

    '!

example04
    "PrologInterpreter example04."

    | string prolog result |
    self example: '?- append(X,Y,[a,b,c,d]).'!

example05
    "PrologInterpreter example05."

    self example: '

    ?- send(123,+,[456],X).   % X := 123 + 456.

    '!

example06
    "PrologInterpreter example06."

    self example: '

    ?- is(X,+(3,4)).
    ?- is(X,F(3,4)).

    '!

example: string
    ^PrologInterpreter new
	textCollector: Transcript;
	refute: string action: 
	    [:answer | 
	    answer keys asSortedCollection
		do: 
		    [:s | 
		    Transcript show: s.
		    Transcript show: ' = '.
		    Transcript show: (answer at: s) printPrologString.
		    Transcript nl]. false]! !

!PrologInterpreter class methodsFor: 'instance creation'!

new
    ^super new initialize! !

!PrologInterpreter class methodsFor: 'public access'!

refute: stringOrStream 
    ^self new refute: stringOrStream!

refute: stringOrStream action: aBlock 
    ^self new refute: stringOrStream action: aBlock! !

!PrologInterpreter methodsFor: 'accessing'!

textCollector
    ^textCollector!

textCollector: aTextCollector 
    textCollector := aTextCollector! !

!PrologInterpreter methodsFor: 'binding and unbinding'!

bind: x env: xEnv and: y env: yEnv 
    | list |
    list := (self fetchValue: y env: yEnv) cons: valueEnv.
    list := (x cons: list) cons: xEnv cdr. 
    xEnv cdr: list. 
    unbindList := xEnv cons: unbindList!

binding: x env: xEnv 
    | assocList |
    assocList := xEnv cdr.
    assocList == nil ifTrue: [^nil].
    ^assocList assoc: x!

fetchValue: x env: xEnv 
    | xx xxEnv assoc |
    xx := x.
    xxEnv := xEnv.
    [true]
	whileTrue: 
	    [valueEnv := xxEnv.
	    xx isPrologVariable
		ifTrue: 
		    [assoc := self binding: xx env: xxEnv.
		    assoc == nil ifTrue: [^xx].
		    assoc := assoc cdr.
		    xx := assoc car.
		    xxEnv := assoc cdr]
		ifFalse: [^xx]]!

noValue: x env: xEnv 
    | assoc |
    x isPrologVariable
	ifTrue: 
	    [assoc := self binding: x env: xEnv.
	    assoc == nil ifTrue: [^true].
	    assoc := assoc cdr.
	    ^self noValue: assoc car env: assoc cdr].
    ^false!

nullEnv
    envCounter := envCounter + 1.
    ^envCounter cons: nil!

unbindFrom: start to: end 
    | list env assocList |
    list := start.
    [list ~~ end]
	whileTrue: 
	    [env := list car.
	    assocList := env cdr.
	    assocList car cdr cdr: nil.
	    env cdr: assocList cdr.
	    list := list cdr]! !

!PrologInterpreter methodsFor: 'copying'!

shallowCopy
    super shallowCopy.
    textValue := nil.
    listValue := nil.
    predicate := nil! !

!PrologInterpreter methodsFor: 'initialize-release'!

initialize
    systemPredicates := Dictionary new.
    userPredicates := Dictionary new.
    tracePredicates := Dictionary new.
    textCollector := Transcript.
    verbose := false.
    self makeSystemPredicates! !

!PrologInterpreter methodsFor: 'kernel predicates'!

builtInCut
    backTrack := cutBack car.
    clause := clause cdr.
    status := #loop!

builtInFail
    status := #back!

builtInPredicate: functor 
    functor isPrologCut ifTrue: [^self builtInCut].
    functor isPrologTrue ifTrue: [^self builtInTrue].
    functor isPrologFail ifTrue: [^self builtInFail].
    functor isPrologSend ifTrue: [^self builtInSend].
    functor isPrologVar ifTrue: [^self builtInVar].
    self error: 'Unexpected built-in predicate'!

builtInSend
    | list receiverSymbol selectorSymbol argumentList unifyTerm result |
    list := self expression: clause car cdr env: clauseEnv.
    receiverSymbol := list car.
    list := list cdr.
    selectorSymbol := list car.
    list := list cdr.
    argumentList := list car.
    list := list cdr.
    list == nil
	ifTrue: [unifyTerm := nil]
	ifFalse: [list cdr == nil
		ifTrue: [unifyTerm := clause car cdr nth: 4]
		ifFalse: 
		    [status := #back.
		    ^self]].
    result := self
		receiver: receiverSymbol
		selector: selectorSymbol
		arguments: argumentList.
    result = PrologSymbol cut
	ifTrue: 
	    [self builtInCut.
	    status := #back.
	    ^self].
    unifyTerm isNil
	ifTrue: 
	    [result = false ifFalse: [result := true].
	    result
		ifTrue: 
		    [clause := clause cdr.
		    status := #loop.
		    ^self]
		ifFalse: 
		    [status := #back.
		    ^self]]
	ifFalse: [(self
		unify: unifyTerm
		env: clauseEnv
		and: result
		env: self nullEnv)
		ifTrue: 
		    [clause := clause cdr.
		    status := #loop.
		    ^self]
		ifFalse: 
		    [status := #back.
		    ^self]].
    ^self!

builtInTrue
    clause := clause cdr.
    status := #loop!

builtInVar
    | var |
    var := clause car cdr car.
    (self noValue: var env: clauseEnv)
	ifTrue: 
	    [clause := clause cdr.
	    status := #loop]
	ifFalse: [status := #back]!

call: aPrologStructure 
    | structure functor |
    aPrologStructure cdr == nil
	ifTrue: 
	    [self callVariable: aPrologStructure car.
	    ^self].
    structure := self expression: aPrologStructure env: clauseEnv.
    (self
	unify: aPrologStructure
	env: clauseEnv
	and: structure
	env: clauseEnv)
	ifFalse: [self error: 'Unexpected unify structure'].
    functor := structure car.
    functor isPrologVariable
	ifTrue: 
	    [status := #back.
	    ^self].
    clause := clause cdr.
    clause := structure cons: clause.
    status := #loop!

callVariable: aPrologVariable 
    | horn functor |
    horn := self expression: aPrologVariable env: clauseEnv.
    (self
	unify: aPrologVariable
	env: clauseEnv
	and: horn
	env: clauseEnv)
	ifFalse: [self error: 'Unexpected unify horn clause'].
    horn consp ifFalse: [horn := PrologStructure functor: horn terms: nil].
    horn car consp ifFalse: [horn := PrologClause head: horn body: nil].
    horn := PrologClause head: horn car body: (PrologBody fromList: horn cdr).
    functor := horn car car.
    functor isPrologVariable
	ifTrue: 
	    [status := #back.
	    ^self].
    clause := clause cdr.
    horn := horn reverse.
    [horn consp]
	whileTrue: 
	    [clause := horn car cons: clause.
	    horn := horn cdr].
    status := #loop!

receiver: receiverSymbol selector: selectorSymbol arguments: argumentList 
    | receiver size selector arguments list result index |
    ((receiverSymbol isKindOf: PrologSymbol)
	and: [receiverSymbol isPrologSelf])
	ifTrue: [receiver := self]
	ifFalse: [receiver := receiverSymbol].
    (receiver isKindOf: PrologObject)
	ifTrue: [receiver := receiver object].
    size := selectorSymbol size.
    selector := String new: size.
    1 to: size do: [:i | selector at: i put: (selectorSymbol at: i)].
    selector := selector asSymbol.
    list := argumentList.
    list == nil
	ifTrue: 
	    [arguments := Array new.
	    result := receiver perform: selector]
	ifFalse: 
	    [size := list length.
	    arguments := Array new: size.
	    1 to: size
		do: 
		    [:i | 
		    arguments at: i put: ((list car isKindOf: PrologObject)
			    ifTrue: [list car object]
			    ifFalse: [list car]).
		    list := list cdr].
	    result := receiver perform: selector withArguments: arguments].
    ((result = true or: [result = false])
	or: [result isPrologEntity])
	ifTrue: [result := result yourself]
	ifFalse: 
	    [list := PrologList car: receiverSymbol cdr: argumentList.
	    index := (Array with: receiver)
			, arguments findFirst: [:each | each = result].
	    index = 0
		ifTrue: [result := PrologObject source: result printString object: result]
		ifFalse: [result := list nth: index]].
    ^result! !

!PrologInterpreter methodsFor: 'outputting'!

outputAnswer: dict 
    | anArray string assoc associations |
    associations := OrderedCollection new.
    dict associationsDo: [:association | associations add: association].
    anArray := associations asSortedCollection.
    1 to: anArray size do: [:i | 
	assoc := anArray at: i.
	i = 1
	    ifTrue: [string := '']
	    ifFalse: [string := ',\' withCRs].
	string := string , assoc key.
	string := string , ' = '.
	string := string , assoc value printPrologString.
	string := string , ' '.
	textCollector show: string]!

outputTime: msec 
    | goal string |
    verbose
	ifTrue: 
	    [goal := envCounter - 1.
	    string := '<'.
	    string := string , msec printString , ' milliseconds, '.
	    string := string , goal printString , ' goals'.
	    string := string , '>\' withCRs.
	    textCollector show: string asText]!

outputVariables: aDictionary
    | bool |
    self outputAnswer: aDictionary.
    bool := self confirm: 'All right ?'.
    bool
	ifTrue: [textCollector nl]
	ifFalse: [textCollector show: ';\' withCRs].
    ^bool! !

!PrologInterpreter methodsFor: 'private'!

acceptWith: aText
    "force to regist aText as a contents."

    self contents: aText.
    textValue := aText.
    self changed: #clearUserEdits!

associations: aCollection
    "by nishis, 1998/04/12 07:34"

    | anOrderedCollection |
    anOrderedCollection := OrderedCollection new: aCollection size.
    aCollection associationsDo: [:association | anOrderedCollection add: association].
    ^ anOrderedCollection!

deallocateEnv: env
    | assocList assoc nextEnv |  
    assocList := env cdr.
    [assocList consp]
	whileTrue: 
	    [assoc := assocList car.
	    nextEnv := assoc cdr cdr.
	    assoc cdr cdr: nil.
	    nextEnv consp ifTrue: [self deallocateEnv: nextEnv].
	    assocList := assocList cdr]!

getCondition
    | condition |
    condition := Array new: 14.
    condition at: 1 put: status.
    condition at: 2 put: definition.
    condition at: 3 put: question.
    condition at: 4 put: questionEnv.
    condition at: 5 put: clause.
    condition at: 6 put: clauseEnv.
    condition at: 7 put: queue.
    condition at: 8 put: queueEnv.
    condition at: 9 put: valueEnv.
    condition at: 10 put: unbindList.
    condition at: 11 put: cutBack.
    condition at: 12 put: backTrack.
    condition at: 13 put: resolveAction.
    condition at: 14 put: definitionStack.
    ^condition!

makeSystemPredicates
    SystemPredicates isNil
	ifTrue: 
	    [self systemPredicatesNo0.
	    self systemPredicatesNo1.
	    self systemPredicatesNo2.
	    self systemPredicatesNo3.
	    self systemPredicatesNo4.
	    self systemPredicatesNo5.
	    self systemPredicatesNo6.
	    self systemPredicatesNo7.
	    self systemPredicatesNo8.
	    self systemPredicatesNo9.
	    SystemPredicates := systemPredicates]
	ifFalse: [systemPredicates := SystemPredicates]!

putCondition: condition 
    status := condition at: 1.
    definition := condition at: 2.
    question := condition at: 3.
    questionEnv := condition at: 4.
    clause := condition at: 5.
    clauseEnv := condition at: 6.
    queue := condition at: 7.
    queueEnv := condition at: 8.
    valueEnv := condition at: 9.
    unbindList := condition at: 10.
    cutBack := condition at: 11.
    backTrack := condition at: 12.
    resolveAction := condition at: 13.
    definitionStack := condition at: 14!

systemPredicatesNo0
    "PrologInterpreter flushSystemPredicates."

    self systemReconsult: (ReadStream on: '
	! :- builtin.
	true :- builtin.
	fail :- builtin.
	var(X) :- builtin.
	send(X,Y,Z) :- bulitin.
	send(X,Y,Z,A) :- bulitin.
    ')!

systemPredicatesNo1
    "PrologInterpreter flushSystemPredicates."

    self systemReconsult: (ReadStream on: '
	repeat.
	repeat :- repeat.
	nonvar(X) :- var(X), !, fail.
	nonvar(X).
	integer(X) :- send(self,integer:,[X]).
	float(X) :- send(self,float:,[X]).
	double(X) :- send(self,double:,[X]).
	fraction(X) :- send(self,fraction:,[X]).
	number(X) :- send(self,number:,[X]).
	symbol(X) :- send(self,symbol:,[X]).
	string(X) :- send(self,string:,[X]).
	list(X) :- send(self,list:,[X]).
	dotp(X) :- send(self,dotp:,[X]).
	atom(X) :- symbol(X).
	atom(X) :- nonvar(X), =(X,[]).
	atom(X) :- string(X).
	atomic(X) :- atom(X).
	atomic(X) :- number(X).
	structure(X) :- nonvar(X), not(atomic(X)).
    ')!

systemPredicatesNo2
    "PrologInterpreter flushSystemPredicates."

    self systemReconsult: (ReadStream on: '
	==(X,Y) :- send(X,=,[Y]).
	\==(X,Y) :- ==(X,Y), !, fail.
	\==(X,Y).
	=(X,X).
	\=(X,Y) :- =(X,Y), !, fail.
	\=(X,Y).
	>(X,Y) :- send(X,>,[Y]).
	>=(X,Y) :- send(X,>=,[Y]).
	<(X,Y) :- send(X,<,[Y]).
	=<(X,Y) :- send(X,<=,[Y]).
    ')!

systemPredicatesNo3
    "PrologInterpreter flushSystemPredicates."

    self systemReconsult: (ReadStream on: '
	+(X,Y,Z) :- send(X,+,[Y],Z).
	-(X,Y,Z) :- send(X,-,[Y],Z).
	*(X,Y,Z) :- send(X,*,[Y],Z).
	//(X,Y,Z) :- send(X,//,[Y],Z).
	/(X,Y,Z) :- send(X,/,[Y],Z).
	\\(X,Y,Z) :- send(X,\\,[Y],Z).
	is(Z,+(X,Y)) :- nonvar(Z), nonvar(X), nonvar(Y), send(X,+,[Y],Z).
	is(Z,+(X,Y)) :- var(Z), nonvar(X), nonvar(Y), send(X,+,[Y],Z).
	is(Z,+(X,Y)) :- var(X), nonvar(Y), nonvar(Z), send(Z,-,[Y],X).
	is(Z,+(X,Y)) :- var(Y), nonvar(Z), nonvar(X), send(Z,-,[X],Y).
	is(Z,-(X,Y)) :- nonvar(Z), nonvar(X), nonvar(Y), send(X,-,[Y],Z).
	is(Z,-(X,Y)) :- var(Z), nonvar(X), nonvar(Y), send(X,-,[Y],Z).
	is(Z,-(X,Y)) :- var(X), nonvar(Y), nonvar(Z), send(Z,+,[Y],X).
	is(Z,-(X,Y)) :- var(Y), nonvar(Z), nonvar(X), send(X,-,[Z],Y).
	is(Z,*(X,Y)) :- nonvar(Z), nonvar(X), nonvar(Y), send(X,*,[Y],Z).
	is(Z,*(X,Y)) :- var(Z), nonvar(X), nonvar(Y), send(X,*,[Y],Z).
	is(Z,*(X,Y)) :- var(X), nonvar(Y), nonvar(Z), send(Z,/,[Y],X).
	is(Z,*(X,Y)) :- var(Y), nonvar(Z), nonvar(X), send(Z,/,[X],Y).
	is(Z,/(X,Y)) :- nonvar(Z), nonvar(X), nonvar(Y), send(X,/,[Y],Z).
	is(Z,/(X,Y)) :- var(Z), nonvar(X), nonvar(Y), send(X,/,[Y],Z).
	is(Z,/(X,Y)) :- var(X), nonvar(Y), nonvar(Z), send(Z,*,[Y],X).
	is(Z,/(X,Y)) :- var(Y), nonvar(Z), nonvar(X), send(X,/,[Z],Y).
	is(X,Y) :- =(X,Y).
    ')!

systemPredicatesNo4
    "PrologInterpreter flushSystemPredicates."

    self systemReconsult: (ReadStream on: '
	listing :- send(self,userListing,[]).
	listing(X) :- send(self,userListing:,[X]).
	systemListing :- send(self,systemListing,[]).
	systemListing(X) :- send(self,systemListing:,[X]).
	consult(X) :- nonvar(X), send(self,consultFile:,[X]).
	reconsult(X) :- nonvar(X), send(self,reconsultFile:,[X]).
	saving :- send(self,saving,[]).
	saving(X) :- send(self,saving:,[X]).
	userPredicates(X) :- send(self,userPredicates,[],X).
	systemPredicates(X) :- send(self,systemPredicates,[],X).
	predicates([X|Y]) :- userPredicates(X), systemPredicates(Y).
	functor(T,F,A) :- nonvar(T), !, send(self,functorArityOf:,[T],[F|A]).
	functor(T,F,A) :- number(F), !, =(0,A),=(T,F).
	functor(T,F,A) :- atom(F), =<(0,A), ''~addvar''([F],A,L), =..(T,L).
	''~addvar''(L,0,M) :- !, =(L,M).
	''~addvar''(L,NVars,M) :- -(NVars, 1, N), append(L,[FreeV],LV), ''~addvar''(LV,N,M).
	arg(Nth,S,T) :- integer(Nth), <(0,Nth), structure(S), =..(S,[F|L]), nth(L,Nth,T).
	=..(X,Y) :- send(self,univ:,[[''X''|''Y'']]).
	name(X,Y) :- atomic(X), list(Y), !, send(self,symToList:,[X],Y).
	name(X,Y) :- atomic(X), !, send(self,symToStr:,[X],Y).
	name(X,Y) :- var(X), !, nonvar(Y), send(self, strToSym:,[Y],X).
	remove :- send(self,remove,[]).
	remove(X) :- send(self,remove:,[X]).
	clause(X) :- send(self,clauseSet:,[X]), repeat, send(self,clause:,[X],X).
	asserta(X) :- send(self,asserta:,[X]).
	assert(X) :- send(self,assertz:,[X]).
	assertz(X) :- send(self,assertz:,[X]).
	retract(X) :- repeat, send(self,retract:,[X],X).
    ')!

systemPredicatesNo5
    "PrologInterpreter flushSystemPredicates."

    self systemReconsult: (ReadStream on: '
	call(G) :- G.
	not(G) :- G, !, fail.
	not(G).
	or(X,Y) :- call(X).
	or(X,Y) :- call(Y).
	and(X,Y) :- call(X), call(Y).
    ')!

systemPredicatesNo6
    "PrologInterpreter flushSystemPredicates."

    self systemReconsult: (ReadStream on: '
	write(X) :- send(self,write:,[X]).
	nl :- send(self,nl,[]).
	tab(X) :- number(X), send(self,tab:,[X]).
	clear :- send(self,clear,[]).
    ')!

systemPredicatesNo7
    "PrologInterpreter flushSystemPredicates."

    self systemReconsult: (ReadStream on: '
	clock(X) :- send({Time},millisecondClockValue,[],X).
	verbose(X) :- send(self,verbose:,[X]).
	gc :- send(self,gc,[]).
	inspect(X) :- send(X,inspect,[]).
	spy(X) :- send(self,spy:,[X]).
	nospy(X) :- send(self,nospy:,[X]).
	trace :- send(self,trace,[]).
	notrace :- send(self,notrace,[]).
    ')!

systemPredicatesNo8
    "PrologInterpreter flushSystemPredicates."

    self systemReconsult: (ReadStream on: '
	append([],X,X).
	append([A|X],Y,[A|Z]) :- append(X,Y,Z).
	member(X,[X|Y]).
	member(X,[Y|Z]) :- member(X,Z).
	reverse([],[]).
	reverse([H|T],L) :- reverse(T,Z), append(Z,[H],L).
	length(X,Y) :- send(self,length:,[X],Y).
	nth([X|Y],1,Z) :- !, =(X,Z).
	nth([X|Y],N,Z) :- -(N,1,PN), nth(Y,PN,Z).
	printlist(L) :- send(self,listPrint:,[L]).
	lispAppend(X,Y,Z) :- send(X,append:,[Y],Z).
	lispReverse(X,Y) :- send(X,reverse,[],Y).
	lispMember(X,Y) :- send(Y,member:,[X],A), \=(A,[]).
	lispMember(X,Y,Z) :- send(Y,member:,[X],Z).
	lispAssoc(X,Y) :- send(Y,assoc:,[X],A), \=(A,[]).
	lispAssoc(X,Y,Z) :- send(Y,assoc:,[X],Z).
	lispNconc(X,Y,Z) :- send(X,nconc:,[Y],Z).
    ')!

systemPredicatesNo9
    "PrologInterpreter flushSystemPredicates."

    self systemReconsult: (ReadStream on: '
	%
	%    User System Predicates
	%
    ')! !

!PrologInterpreter methodsFor: 'public accessing'!

refute: stringOrStream
    ^self refute: stringOrStream action: [:answer | ^answer]!

refute: stringOrStream action: aBlock 
    | stream |
    (stringOrStream isKindOf: Stream)
	ifTrue: [stream := ReadStream on: stringOrStream contents]
	ifFalse: [stream := ReadStream on: stringOrStream].
    ^self consult: stream action: aBlock! !

!PrologInterpreter methodsFor: 'representation'!

collectVariables
    | dict | 
    dict := Dictionary new.
    self collectVariables: question to: dict.
    ^dict!

collectVariables: x to: dict
    | key value |  
    (x isPrologVariable and: [(x at: 1) ~= $~])
	ifTrue:
	    [key := String fromString: x printPrologString.
	    (dict at: key ifAbsent: []) ~~ nil
		ifTrue: [^self]
		ifFalse: 
		    [value := self represent: x env: questionEnv.
		    dict at: key put: value]].
    (x consp)
	ifFalse: [^self].
    self collectVariables: x car to: dict.
    self collectVariables: x cdr to: dict!

expression: x env: xEnv 
    | assoc a d |
    x isPrologVariable
	ifTrue: 
	    [assoc := self binding: x env: xEnv.
	    assoc == nil ifTrue: [^x].
	    assoc := assoc cdr.
	    ^self expression: assoc car env: assoc cdr].
    (x consp) ifFalse: [^x].
    a := self expression: x car env: xEnv.
    d := self expression: x cdr env: xEnv.
    ^x class car: a cdr: d!

represent: x env: xEnv 
    | assoc a d |
    x isPrologVariable
	ifTrue: 
	    [assoc := self binding: x env: xEnv.
	    assoc == nil ifTrue: [^self variableRepresent: x env: xEnv].
	    assoc := assoc cdr.
	    ^self represent: assoc car env: assoc cdr].
    (x consp) ifFalse: [^x].
    a := self represent: x car env: xEnv.
    d := self represent: x cdr env: xEnv.
    ^x class car: a cdr: d!

variableRepresent: x env: xEnv 
    ^PrologVariable install: x string , xEnv car printString! !

!PrologInterpreter methodsFor: 'resolution'!

resolve: goal 
    ^self resolve: goal action: nil!

resolve: goal action: actionBlock
    question := clause := goal.
    actionBlock == nil
	ifTrue: [resolveAction := [:dict | self outputVariables: dict]]
	ifFalse: [resolveAction := actionBlock].
    
    self resolveInitialize.
    self resolveLoop.
    ^self resolveTerminate!

resolveInitialize
    status := #loop.
    envCounter := 0.
    questionEnv := clauseEnv := self nullEnv.
    queue := queueEnv := valueEnv := nil.
    unbindList := cutBack := backTrack := nil.
    definitionStack := nil.
    traceCounter := 0!

resolveLoop
    | totalTime time answer |
    totalTime := 0.
    time := Time millisecondClockValue.
    [true]
	whileTrue: 
	    [status == #loop ifTrue: [self loop].
	    status == #next ifTrue: [self next].
	    status == #back ifTrue: [self back].
	    status == #succ
		ifTrue: 
		    [time := Time millisecondClockValue - time.
		    self outputTime: (totalTime := totalTime + time).
		    answer := self collectVariables.
		    answer isEmpty ifTrue: [^true].
		    (resolveAction value: answer)
			ifTrue: [^true]
			ifFalse: 
			    [status := #back.
			    time := Time millisecondClockValue]].
	    status == #fail
		ifTrue: 
		    [time := Time millisecondClockValue - time.
		    self outputTime: (totalTime := totalTime + time).
		    ^false]]!

resolveTerminate
    self deallocateEnv: questionEnv.
    status == #succ
	ifTrue: 
	    [textCollector show: 'yes'.
	    textCollector nl.
	    ^true].
    status == #fail
	ifTrue: 
	    [textCollector show: 'no'.
	    textCollector nl.
	    ^false].
    self error: 'Unexpected status'! !

!PrologInterpreter methodsFor: 'resolve modules'!

back
    | array |
    backTrack == nil
	ifTrue: 
	    [status := #fail.
	    ^self].
    array := backTrack car.
    backTrack := backTrack cdr.
    clause := array at: 1.
    clauseEnv := array at: 2.
    queue := array at: 3.
    queueEnv := array at: 4.
    cutBack := array at: 5.
    definition := array at: 6.
    array := array at: 7.
    self unbindFrom: unbindList to: array.
    unbindList := array.
    status := #next!

loop
    | structure functor |
    clause == nil
	ifTrue: 
	    [queue == nil
		ifTrue: 
		    [status := #succ.
		    ^self].
	    clause := queue car.
	    clauseEnv := queueEnv car.
	    queue := queue cdr.
	    queueEnv := queueEnv cdr.
	    cutBack := cutBack cdr.
	    status := #loop.
	    ^self].
    structure := clause car.
    structure consp
	ifFalse: 
	    [structure := PrologStructure functor: structure terms: nil.
	    clause car: structure].
    functor := structure car.
    functor isPrologVariable
	ifTrue: 
	    [self call: clause car.
	    ^self].
    functor isBuiltInPredicate
	ifTrue: 
	    [self builtInPredicate: functor.
	    ^self].
    definition := userPredicates at: functor ifAbsent: [systemPredicates at: functor
		    ifAbsent: 
			[status := #back.
			^self]].
    status := #next!

next
    | definitionEnv saveBackTrack array |
    definitionEnv := self nullEnv.
    definition cdr == nil
	ifTrue: 
	    [(self
		unify: clause car cdr
		env: clauseEnv
		and: definition car car cdr
		env: definitionEnv)
		ifFalse: 
		    [status := #back.
		    ^self].
	    queue := clause cdr cons: queue.
	    queueEnv := clauseEnv cons: queueEnv.
	    clause := definition car cdr.
	    clauseEnv := definitionEnv.
	    cutBack := backTrack cons: cutBack.
	    status := #loop.
	    ^self].
    saveBackTrack := backTrack.
    array := Array new: 7.
    array at: 1 put: clause.
    array at: 2 put: clauseEnv.
    array at: 3 put: queue.
    array at: 4 put: queueEnv.
    array at: 5 put: cutBack.
    array at: 6 put: definition cdr.
    array at: 7 put: unbindList.
    backTrack := array cons: saveBackTrack.
    (self
	unify: clause car cdr
	env: clauseEnv
	and: definition car car cdr
	env: definitionEnv)
	ifFalse: 
	    [status := #back.
	    ^self].
    queue := clause cdr cons: queue.
    queueEnv := clauseEnv cons: queueEnv.
    clause := definition car cdr.
    clauseEnv := definitionEnv.
    cutBack := saveBackTrack cons: cutBack.
    status := #loop! !

!PrologInterpreter methodsFor: 'system predicates'!

asserta: aPrologClause 
    | horn def functor |
    horn := aPrologClause.
    horn consp ifFalse: [horn := PrologStructure functor: horn terms: nil].
    horn car consp ifFalse: [horn := PrologClause head: horn body: nil].
    horn := PrologClause head: horn car body: (PrologBody fromList: horn cdr).
    functor := horn car car.
    def := userPredicates at: functor ifAbsent: [nil].
    def == nil
	ifTrue: 
	    [def := PrologDefinition fromList: (horn cons: nil).
	    userPredicates at: functor put: def]
	ifFalse: 
	    [def := PrologDefinition fromList: (horn cons: def).
	    userPredicates at: functor put: def].
    ^true!

assertz: aPrologClause 
    | horn def functor |
    horn := aPrologClause.
    horn consp ifFalse: [horn := PrologStructure functor: horn terms: nil].
    horn car consp ifFalse: [horn := PrologClause head: horn body: nil].
    horn := PrologClause head: horn car body: (PrologBody fromList: horn cdr).
    functor := horn car car.
    def := userPredicates at: functor ifAbsent: [nil].
    def == nil
	ifTrue: 
	    [def := PrologDefinition fromList: (horn cons: nil).
	    userPredicates at: functor put: def]
	ifFalse: [def nconc: (PrologDefinition fromList: (horn cons: nil))].
    ^true!

clause: aPrologClause 
    | count horn def result |
    count := 0.
    horn := aPrologClause.
    horn consp
	ifFalse: 
	    [horn := PrologStructure functor: horn terms: nil.
	    count := count + 1].
    horn car consp
	ifFalse: 
	    [horn := PrologClause head: horn body: nil.
	    count := count + 1].
    horn := PrologClause head: horn car body: (PrologBody fromList: horn cdr).
    def := definitionStack car.
    [def consp]
	whileTrue: [(self
		unify: horn
		env: self nullEnv
		and: def car
		env: self nullEnv)
		ifTrue: 
		    [result := def car.
		    count timesRepeat: [result := result car].
		    def := def cdr.
		    definitionStack car: def.
		    ^result]
		ifFalse: 
		    [def := def cdr.
		    definitionStack car: def]].
    definitionStack := definitionStack cdr.
    ^PrologSymbol cut!

clear
    textCollector clear.
    ^true!

consultFile: fileName 
    | aFileStream |
    (fileName respondsTo: #asString)
	ifFalse: [^false].
    (File name: fileName asString) exists
	ifTrue: 
	    [textCollector show: '<consult from ' , fileName asString , '>\' withCRs.
	    aFileStream := FileStream open: fileName asString mode: FileStream read.
	    self consult: aFileStream action: nil.
	    aFileStream close.
	    ^true]
	ifFalse: [^false]!

dotp: x 
    ^x consp!

double: x
    ^x isKindOf: Float!

float: x
    ^x isKindOf: Float!

fraction: x
    ^x isKindOf: Fraction!

functorArityOf: aPrologStructure 
    aPrologStructure isNil ifTrue: [^nil cons: 0].
    (self number: aPrologStructure)
	ifTrue: [^aPrologStructure cons: 0].
    (aPrologStructure respondsTo: #functor)
	ifFalse: [^nil].
    ^aPrologStructure functor cons: aPrologStructure arity!

gc
    ObjectMemory compact.
    Transcript nl; show: 'garbage collecting: '.
    ^true!

integer: x
    ^x isKindOf: Integer!

length: aPrologDotPair 
    aPrologDotPair consp ifFalse: [^0].
    ^aPrologDotPair length!

list: x 
    x == nil ifTrue: [^true].
    ^self dotp: x!

listPrint: aPrologDotPair 
    | list |
    aPrologDotPair consp ifFalse: [^false].
    list := aPrologDotPair.
    [list consp]
	whileTrue: 
	    [textCollector show: list car printPrologString , ' '.
	    list := list cdr].
    ^true!

nl
    textCollector nl.
    ^true!

nospy: aPrologSymbol 
    | def |
    def := tracePredicates at: aPrologSymbol ifAbsent: [nil].
    def == nil ifTrue: [^false].
    userPredicates at: aPrologSymbol put: def.
    tracePredicates removeKey: aPrologSymbol.
    ^true!

notrace
    userPredicates associationsDo: [:assoc | self nospy: assoc key].
    ^true!

number: x
    ^x isKindOf: Number!

reconsultFile: fileName 
    | aFileStream |
    (fileName respondsTo: #asString)
	ifFalse: [^false].
    (File name: fileName asString) exists
	ifTrue: 
	    [textCollector show: '<reconsult from ' , fileName asString , '>\' withCRs.
	    aFileStream := FileStream open: fileName asString mode: FileStream read.
	    self reconsult: aFileStream action: nil.
	    aFileStream close.
	    ^true]
	ifFalse: [^false]!

remove
    userPredicates keys do: 
	[:aPrologSymbol | 
	userPredicates removeKey: aPrologSymbol ifAbsent: [].
	tracePredicates removeKey: aPrologSymbol ifAbsent: []].
    ^true!

remove: aPrologSymbol
    userPredicates removeKey: aPrologSymbol ifAbsent: [^false].
    tracePredicates removeKey: aPrologSymbol ifAbsent: [].
    ^true!

retract: aPrologClause 
    | count horn def functor prev result |
    count := 0.
    horn := aPrologClause.
    horn consp
	ifFalse: 
	    [horn := PrologStructure functor: horn terms: nil.
	    count := count + 1].
    horn car consp
	ifFalse: 
	    [horn := PrologClause head: horn body: nil.
	    count := count + 1].
    horn := PrologClause head: horn car body: (PrologBody fromList: horn cdr).
    functor := horn car car.
    prev := def := userPredicates at: functor ifAbsent: [^PrologSymbol cut].
    [def consp]
	whileTrue: [(self
		unify: horn
		env: self nullEnv
		and: def car
		env: self nullEnv)
		ifTrue: 
		    [result := def car.
		    count timesRepeat: [result := result car].
		    prev == def
			ifTrue: 
			    [def cdr isNil
				ifTrue: [userPredicates removeKey: functor ifAbsent: [nil]]
				ifFalse: [userPredicates at: functor put: def cdr].
			    ^result]
			ifFalse: 
			    [prev cdr: def cdr.
			    ^result]]
		ifFalse: 
		    [prev := def.
		    def := def cdr]].
    ^PrologSymbol cut!

saving
    self saveOn: self saveFileName.
    ^true!

saving: aPrologSymbol 
    | def |
    def := tracePredicates at: aPrologSymbol ifAbsent: [userPredicates at: aPrologSymbol ifAbsent: []].
    def == nil ifTrue: [^false].
    self saveOn: self saveFileName.
    ^true!

spy: aPrologSymbol 
    | def reverseClone tracedef |
    def := userPredicates at: aPrologSymbol ifAbsent: [nil].
    def == nil ifTrue: [^false].
    (tracePredicates at: aPrologSymbol ifAbsent: [nil]) isNil ifFalse: [^true].
    tracePredicates at: aPrologSymbol put: def.
    reverseClone := nil.
    [def consp]
	whileTrue: 
	    [reverseClone := def car cons: reverseClone.
	    def := def cdr].
    tracedef := nil.
    [reverseClone consp]
	whileTrue: 
	    [tracedef := (self traceFailClause: reverseClone car car)
			cons: tracedef.
	    tracedef := (self traceExitClause: reverseClone car)
			cons: tracedef.
	    reverseClone cdr consp
		ifTrue: [tracedef := (self traceRedoClause: reverseClone car car)
				cons: tracedef]
		ifFalse: [tracedef := (self traceCallClause: reverseClone car car)
				cons: tracedef].
	    reverseClone := reverseClone cdr].
    userPredicates at: aPrologSymbol put: (PrologDefinition fromList: tracedef).
    ^true!

string: x
    ^x class == PrologString!

strToSym: listOrString 
    | stream string token s |
    listOrString consp
	ifTrue: 
	    [s := WriteStream on: (String new: 16).
	    listOrString do: [:char | s nextPut: (Character value: char)].
	    string := s contents]
	ifFalse: [string := listOrString string].
    stream := ReadStream on: string.
    token := (PrologScanner new on: stream) nextToken.
    ((self number: token)
	and: [stream atEnd])
	ifTrue: [^token]
	ifFalse: [string = '[]'
		ifTrue: [^nil]
		ifFalse: [^PrologSymbol install: string]]!

symbol: x
    ^x class == PrologSymbol!

symToList: numOrSym 
    | pstring |
    pstring := self symToStr: numOrSym.
    ^PrologList list: pstring string asByteArray!

symToStr: numOrSym 
    numOrSym isNil ifTrue: [^PrologString fromString: '[]'].
    (self number: numOrSym)
	ifTrue: [^PrologString fromString: numOrSym printString].
    ^PrologString fromString: numOrSym string!

systemListing
    | predicateName |
    (self associations: systemPredicates) asSortedCollection
	do: 
	    [:assoc | 
	    predicateName := assoc key.
	    ((predicateName respondsTo: #asString)
		and: [predicateName string isEmpty not and: [predicateName string first = $~]])
		ifFalse: [self systemListing: predicateName]].
    ^true!

systemListing: aPrologSymbol
    | def |
    def := systemPredicates at: aPrologSymbol ifAbsent: [nil].
    def == nil ifTrue: [^false].
    [def consp]
	    whileTrue: 
		[textCollector show: def car prettyPrintPrologString , '\' withCRs.
		def := def cdr].
    ^true!

systemPredicates
    | collection list |
    collection := (self associations: systemPredicates) asSortedCollection.
    list := nil.
    collection reverseDo: [:each | ((each key respondsTo: #asString)
	    and: [each key string isEmpty not and: [each key string first = $~]])
	    ifTrue: ['not adding: invisible predicate' yourself]
	    ifFalse: [list := each key cons: list]].
    ^list!

tab: aNumber 
    | spaces |
    (aNumber isKindOf: Number)
	ifFalse: [^false].
    spaces := String new.
    aNumber asInteger timesRepeat: [spaces := spaces , ' '].
    textCollector show: spaces.
    ^true!

trace
    userPredicates associationsDo: [:assoc | self spy: assoc key].
    ^true!

univ: aPrologList 
    | termv listv termValue termEnv listVal listEnv functor functorEnv terms newterms newStruct car t list |
    termv := PrologVariable install: aPrologList car string.
    listv := PrologVariable install: aPrologList cdr string.
    termValue := self fetchValue: termv env: clauseEnv.
    termEnv := valueEnv.
    listVal := self fetchValue: listv env: clauseEnv.
    listEnv := valueEnv.
    termValue isPrologVariable
	ifTrue: 
	    ["construct a term from fixed length list."
	    listVal isPrologVariable ifTrue: [^false].
	    listVal consp ifFalse: [^false].
	    functor := self fetchValue: listVal car env: listEnv.
	    functorEnv := valueEnv.
	    terms := self fetchValue: listVal cdr env: listEnv.
	    listEnv := valueEnv.
	    (self number: functor)
		ifTrue: 
		    [terms isNil ifFalse: [^false].
		    self
			bind: termValue
			env: termEnv
			and: functor
			env: listEnv.
		    ^true].
	    functor consp ifTrue: ["It's a structure or a list"
		^false].
	    terms isNil
		ifTrue: 
		    [self
			bind: termValue
			env: termEnv
			and: functor
			env: functorEnv.
		    ^true].
	    terms consp ifFalse: ["Not a list, but an illegal dot pair."
		^false].
	    newterms := nil.
	    [terms isNil]
		whileFalse: 
		    [car := terms car.
		    terms := self fetchValue: terms cdr env: listEnv.
		    terms isPrologVariable ifTrue: ["The length of the list has not been fixed yet."
			^false].
		    t := PrologTerms car: car cdr: nil.
		    newterms isNil
			ifTrue: [newterms := t]
			ifFalse: [newterms := newterms nconc: t]].
	    newStruct := PrologStructure functor: functor terms: newterms.
	    ^self
		unify: termValue
		env: termEnv
		and: newStruct
		env: listEnv]
	ifFalse: 
	    ["disasemble a term into a list"
	    termValue consp
		ifTrue: ["It's a list or a structure."
		    list := termValue structureList]
		ifFalse: ["primitive data like symbol, number, nil, or string."
		    list := termValue cons: nil].
	    ^self
		unify: list
		env: termEnv
		and: listVal
		env: listEnv]!

userListing
    | predicateName |
    ((self associations: userPredicates) asSortedCollection)
	do: 
	    [:assoc | 
	    predicateName := assoc key.
	    self userListing: predicateName].
    ^true!

userListing: aPrologSymbol 
    | def |
    def := userPredicates at: aPrologSymbol ifAbsent: [nil].
    def == nil ifTrue: [^false].
    [def consp]
	whileTrue: 
	    [textCollector show: def car prettyPrintPrologString , '\' withCRs.
	    def := def cdr].
    ^true!

userPredicates
    | collection list |
    collection := (self associations: userPredicates) asSortedCollection.
    list := nil.
    collection reverseDo: [:each | ((each key respondsTo: #string)
	    and: [each key string isEmpty not and: [each key string first = $~]])
	    ifTrue: ['not adding: invisible predicate' yourself]
	    ifFalse: [list := each key cons: list]].
    ^list!

verbose: aPrologSymbol 
    aPrologSymbol isPrologTrue
	ifTrue: [verbose := true]
	ifFalse: [verbose := false].
    ^true!

write: anObject 
    (anObject respondsTo: #asString)
	ifTrue: [textCollector show: anObject asString]
	ifFalse: [textCollector show: anObject printPrologString].
    ^true! !

!PrologInterpreter methodsFor: 'system support'!

clauseSet: aPrologClause 
    | horn functor def |
    horn := aPrologClause.
    horn consp ifFalse: [horn := PrologStructure functor: horn terms: nil].
    horn car consp ifFalse: [horn := PrologClause head: horn body: nil].
    horn := PrologClause head: horn car body: (PrologBody fromList: horn cdr).
    functor := horn car car.
    def := userPredicates at: functor ifAbsent: [^false].
    definitionStack := def cons: definitionStack.
    ^true!

consult: readStream action: aBlock
    | condition parser node hornClause program functor stream result |
    condition := self getCondition.
    parser := PrologParser new.
    result := true.
    [node := parser parse: readStream.
    node == #eof]
	whileFalse: 
	    [hornClause := node.
	    node isResolveClause
		ifTrue: 
		    [stream := WriteStream on: (String new: 20).
		    hornClause printPrologOn: stream.
		    textCollector show: stream contents.
		    textCollector nl.
		    result := self resolve: hornClause action: aBlock]
		ifFalse: 
		    [functor := hornClause car car.
		    program := tracePredicates at: functor ifAbsent: [userPredicates at: functor ifAbsent: []].
		    program == nil
			ifTrue: 
			    [program := PrologDefinition fromList: (hornClause cons: nil).
			    userPredicates at: functor put: program]
			ifFalse: [program nconc: (hornClause cons: nil)]]].
    self putCondition: condition.
    ^result!

reconsult: readStream action: aBlock
    | condition newPredicates parser node hornClause program functor stream result |
    condition := self getCondition.
    newPredicates := Dictionary new.
    parser := PrologParser new.
    result := true.
    [node := parser parse: readStream.
    node == #eof]
	whileFalse: 
	    [hornClause := node.
	    node isResolveClause
		ifTrue: 
		    [stream := WriteStream on: (String new: 20).
		    hornClause printPrologOn: stream.
		    textCollector show: stream contents.
		    textCollector nl.
		    result := self resolve: hornClause action: aBlock]
		ifFalse: 
		    [functor := hornClause car car.
		    program := newPredicates at: functor ifAbsent: [].
		    program == nil
			ifTrue: 
			    [program := PrologDefinition fromList: (hornClause cons: nil).
			    newPredicates at: functor put: program]
			ifFalse: [program nconc: (hornClause cons: nil)].
		    userPredicates at: functor put: program]].
    newPredicates keys
	do: [:eachPredicate |
	    userPredicates at: eachPredicate put: (newPredicates at: eachPredicate).
	    tracePredicates removeKey: eachPredicate ifAbsent: []].
    self putCondition: condition.
    ^result!

saveFileName
    ^'prolog.db'!

saveOn: fileName 
    | aFileStream def |
    aFileStream := FileStream open: fileName asString mode: FileStream write.
    (self associations: userPredicates) asSortedCollection
	do: 
	    [:assoc | 
	    def := assoc value.
	    [def consp]
		whileTrue: 
		    [aFileStream nextPutAll: def car prettyPrintPrologString , '\' withCRs.
		    def := def cdr]].
    aFileStream close!

saveOn: fileName predicateName: aPrologSymbol 
    | aFileStream def |
    aFileStream := FileStream open: fileName asString mode: FileStream write.
    def := userPredicates at: aPrologSymbol ifAbsent: [].
    def == nil ifFalse: [[def consp]
	    whileTrue: 
		[aFileStream nextPutAll: def car prettyPrintPrologString , '\' withCRs.
		def := def cdr]].
    aFileStream close!

systemConsult: readStream 
    | condition parser node hornClause program functor |
    condition := self getCondition.
    parser := PrologParser new.
    [node := parser parse: readStream.
    node == #eof]
	whileFalse: 
	    [hornClause := node.
	    node isResolveClause
		ifTrue: [self resolve: hornClause]
		ifFalse: 
		    [functor := hornClause car car.
		    program := systemPredicates at: functor ifAbsent: [].
		    program == nil
			ifTrue: 
			    [program := PrologDefinition fromList: (hornClause cons: nil).
			    systemPredicates at: functor put: program]
			ifFalse: [program nconc: (hornClause cons: nil)]]].
    self putCondition: condition.
    ^true!

systemReconsult: readStream 
    | condition newPredicates parser node hornClause program functor |
    condition := self getCondition.
    newPredicates := Dictionary new.
    parser := PrologParser new.
    [node := parser parse: readStream.
    node == #eof]
	whileFalse: 
	    [hornClause := node.
	    node isResolveClause
		ifTrue: [self resolve: hornClause]
		ifFalse: 
		    [functor := hornClause car car.
		    program := newPredicates at: functor ifAbsent: [].
		    program == nil
			ifTrue: 
			    [program := PrologDefinition fromList: (hornClause cons: nil).
			    newPredicates at: functor put: program]
			ifFalse: [program nconc: (hornClause cons: nil)].
		    systemPredicates at: functor put: program]].
    newPredicates keys do: [:eachPredicate | systemPredicates at: eachPredicate put: (newPredicates at: eachPredicate)].
    self putCondition: condition.
    ^true!

trace: para head: head arguments: terms 
    | headString numberString structure arguString |
    headString := (self expression: head env: clauseEnv) printPrologString.
    para = 0
	ifTrue: 
	    [traceCounter := traceCounter + 1.
	    numberString := String new: traceCounter withAll: $|.
	    structure := PrologStructure functor: head car terms: terms.
	    arguString := (self expression: structure env: clauseEnv) printPrologString.
	    headString := headString , ' ~ ' , arguString.
	    textCollector show: numberString , ' CALL : ' , headString , '\' withCRs.
	    ^self].
    para = 1
	ifTrue: 
	    [traceCounter := traceCounter + 1.
	    numberString := String new: traceCounter withAll: $|.
	    structure := PrologStructure functor: head car terms: terms.
	    arguString := (self expression: structure env: clauseEnv) printPrologString.
	    headString := headString , ' ~ ' , arguString.
	    textCollector show: numberString , ' REDO : ' , headString , '\' withCRs.
	    ^self].
    para = 2
	ifTrue: 
	    [numberString := String new: traceCounter withAll: $|.
	    textCollector show: numberString , ' FAIL : ' , headString , '\' withCRs.
	    traceCounter := traceCounter - 1.
	    ^self].
    para = 3
	ifTrue: 
	    [numberString := String new: traceCounter withAll: $|.
	    textCollector show: numberString , ' EXIT : ' , headString , '\' withCRs.
	    ^self]!

traceCallClause: head
    ^self traceClause: head flag: 0!

traceClause: head flag: anInteger 
    | arguVar headStruct failStruct traceStruct |
    arguVar := PrologVariable install: 'Arguments'.
    headStruct := PrologStructure functor: head car terms: arguVar.
    failStruct := PrologStructure functor: (PrologSymbol install: 'fail')
		terms: nil.
    traceStruct := arguVar cons: nil.
    traceStruct := head cons: traceStruct.
    traceStruct := anInteger cons: traceStruct.
    traceStruct := traceStruct cons: nil.
    traceStruct := (PrologSymbol install: 'trace:head:arguments:')
		cons: traceStruct.
    traceStruct := (PrologSymbol install: 'self')
		cons: traceStruct.
    traceStruct := PrologTerms fromList: traceStruct.
    traceStruct := PrologStructure functor: (PrologSymbol install: 'send')
		terms: traceStruct.
    anInteger = 3 ifTrue: [^PrologClause head: headStruct body: (PrologBody fromList: (traceStruct cons: nil))].
    ^PrologClause head: headStruct body: (PrologBody fromList: (traceStruct cons: (failStruct cons: nil)))!

traceExitClause: exitClause
    | traceExitClause reverseClone| 
    traceExitClause := self traceExitClauseAux: exitClause car.
    traceExitClause := traceExitClause cdr.
    reverseClone := exitClause reverse.
    [reverseClone consp]
	whileTrue:
	    [traceExitClause := reverseClone car cons: traceExitClause.
	    reverseClone := reverseClone cdr].
    ^PrologClause head: traceExitClause car body: (PrologBody fromList: traceExitClause cdr)!

traceExitClauseAux: head
    ^self traceClause: head flag: 3!

traceFailClause: head
    ^self traceClause: head flag: 2!

traceRedoClause: head
    ^self traceClause: head flag: 1! !

!PrologInterpreter methodsFor: 'unification'!

unify: x env: xEnv and: y env: yEnv 
    | xx yy assoc |
    xx := x.
    yy := y.
    [true]
	whileTrue: 
	    [xEnv == yEnv ifTrue: [x = y ifTrue: [^true]].
	    xx isPrologVariable ifTrue: [(assoc := self binding: xx env: xEnv) ~~ nil
		    ifTrue: 
			[valueEnv := xEnv.
			assoc := assoc cdr.
			xx := self fetchValue: assoc car env: assoc cdr.
			^self
			    unify: xx
			    env: valueEnv
			    and: yy
			    env: yEnv]
		    ifFalse: 
			[yy isPrologVariable ifTrue: [(assoc := self binding: yy env: yEnv) ~~ nil
				ifTrue: 
				    [valueEnv := yEnv.
				    assoc := assoc cdr.
				    yy := self fetchValue: assoc car env: assoc cdr.
				    ^self
					unify: xx
					env: xEnv
					and: yy
					env: valueEnv]].
			self
			    bind: xx
			    env: xEnv
			    and: yy
			    env: yEnv.
			^true]].
	    yy isPrologVariable
		ifTrue: 
		    [(assoc := self binding: yy env: yEnv) ~~ nil
			ifTrue: 
			    [valueEnv := yEnv.
			    assoc := assoc cdr.
			    yy := self fetchValue: assoc car env: assoc cdr.
			    ^self
				unify: xx
				env: xEnv
				and: yy
				env: valueEnv].
		    self
			bind: yy
			env: yEnv
			and: xx
			env: xEnv.
		    ^true].
	    xx consp ifFalse: [^xx = yy].
	    yy consp ifFalse: [^yy = xx].
	    (self
		unify: xx car
		env: xEnv
		and: yy car
		env: yEnv)
		ifFalse: [^false].
	    xx := xx cdr.
	    yy := yy cdr]! !