summaryrefslogtreecommitdiff
path: root/lisp/play/gomoku.el
blob: 1cd1f81b6f86c7439408cea0c206cfb563c6bd29 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
;;; gomoku.el --- Gomoku game between you and Emacs  -*- lexical-binding:t -*-

;; Copyright (C) 1988, 1994, 1996, 2001-2014 Free Software Foundation,
;; Inc.

;; Author: Philippe Schnoebelen <phs@lsv.ens-cachan.fr>
;; Maintainer: emacs-devel@gnu.org
;; Adapted-By: ESR, Daniel Pfeiffer <occitan@esperanto.org>
;; Keywords: games

;; This file is part of GNU Emacs.

;; GNU Emacs 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 3 of the License, or
;; (at your option) any later version.

;; GNU Emacs 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 Emacs.  If not, see <http://www.gnu.org/licenses/>.

;;; Commentary:

;; RULES:
;;
;; Gomoku is a game played between two players on a rectangular board.  Each
;; player, in turn, marks a free square of its choice. The winner is the first
;; one to mark five contiguous squares in any direction (horizontally,
;; vertically or diagonally).
;;
;; I have been told that, in "The TRUE Gomoku", some restrictions are made
;; about the squares where one may play, or else there is a known forced win
;; for the first player. This program has no such restriction, but it does not
;; know about the forced win, nor do I.
;; See http://renju.nu/r1rulhis.htm for more information.


;; There are two main places where you may want to customize the program: key
;; bindings and board display. These features are commented in the code. Go
;; and see.


;; HOW TO USE:
;;
;; The command "M-x gomoku" displays a
;; board, the size of which depends on the size of the current window. The
;; size of the board is easily modified by giving numeric arguments to the
;; gomoku command and/or by customizing the displaying parameters.
;;
;; Emacs plays when it is its turn. When it is your turn, just put the cursor
;; on the square where you want to play and hit RET, or X, or whatever key you
;; bind to the command gomoku-human-plays. When it is your turn, Emacs is
;; idle: you may switch buffers, read your mail, ... Just come back to the
;; *Gomoku* buffer and resume play.


;; ALGORITHM:
;;
;; The algorithm is briefly described in section "THE SCORE TABLE". Some
;; parameters may be modified if you want to change the style exhibited by the
;; program.

;;; Code:

(defgroup gomoku nil
  "Gomoku game between you and Emacs."
  :prefix "gomoku-"
  :group 'games)
;;;
;;; GOMOKU MODE AND KEYMAP.
;;;
(defcustom gomoku-mode-hook nil
  "If non-nil, its value is called on entry to Gomoku mode.
One useful value to include is `turn-on-font-lock' to highlight the pieces."
  :type 'hook
  :group 'gomoku)

;;;
;;; CONSTANTS FOR BOARD
;;;

(defconst gomoku-buffer-name "*Gomoku*"
  "Name of the Gomoku buffer.")

;; You may change these values if you have a small screen or if the squares
;; look rectangular, but spacings SHOULD be at least 2 (MUST BE at least 1).

(defconst gomoku-square-width 4
  "Horizontal spacing between squares on the Gomoku board.")

(defconst gomoku-square-height 2
  "Vertical spacing between squares on the Gomoku board.")

(defconst gomoku-x-offset 3
  "Number of columns between the Gomoku board and the side of the window.")

(defconst gomoku-y-offset 1
  "Number of lines between the Gomoku board and the top of the window.")


(defvar gomoku-mode-map
  (let ((map (make-sparse-keymap)))

    ;; Key bindings for cursor motion.
    (define-key map "y" 'gomoku-move-nw)		    ; y
    (define-key map "u" 'gomoku-move-ne)		    ; u
    (define-key map "b" 'gomoku-move-sw)		    ; b
    (define-key map "n" 'gomoku-move-se)		    ; n
    (define-key map "h" 'backward-char)			    ; h
    (define-key map "l" 'forward-char)			    ; l
    (define-key map "j" 'gomoku-move-down)		    ; j
    (define-key map "k" 'gomoku-move-up)		    ; k

    (define-key map [kp-7] 'gomoku-move-nw)
    (define-key map [kp-9] 'gomoku-move-ne)
    (define-key map [kp-1] 'gomoku-move-sw)
    (define-key map [kp-3] 'gomoku-move-se)
    (define-key map [kp-4] 'backward-char)
    (define-key map [kp-6] 'forward-char)
    (define-key map [kp-2] 'gomoku-move-down)
    (define-key map [kp-8] 'gomoku-move-up)

    (define-key map "\C-n" 'gomoku-move-down)		    ; C-n
    (define-key map "\C-p" 'gomoku-move-up)		    ; C-p

    ;; Key bindings for entering Human moves.
    (define-key map "X" 'gomoku-human-plays)		    ; X
    (define-key map "x" 'gomoku-human-plays)		    ; x
    (define-key map " " 'gomoku-human-plays)		    ; SPC
    (define-key map "\C-m" 'gomoku-human-plays)		    ; RET
    (define-key map "\C-c\C-p" 'gomoku-human-plays)	    ; C-c C-p
    (define-key map "\C-c\C-b" 'gomoku-human-takes-back)    ; C-c C-b
    (define-key map "\C-c\C-r" 'gomoku-human-resigns)	    ; C-c C-r
    (define-key map "\C-c\C-e" 'gomoku-emacs-plays)	    ; C-c C-e

    (define-key map [kp-enter] 'gomoku-human-plays)
    (define-key map [insert] 'gomoku-human-plays)
    (define-key map [down-mouse-1] 'gomoku-click)
    (define-key map [drag-mouse-1] 'gomoku-click)
    (define-key map [mouse-1] 'gomoku-click)
    (define-key map [down-mouse-2] 'gomoku-click)
    (define-key map [mouse-2] 'gomoku-mouse-play)
    (define-key map [drag-mouse-2] 'gomoku-mouse-play)

    (define-key map [remap previous-line] 'gomoku-move-up)
    (define-key map [remap next-line] 'gomoku-move-down)
    (define-key map [remap move-beginning-of-line] 'gomoku-beginning-of-line)
    (define-key map [remap move-end-of-line] 'gomoku-end-of-line)
    (define-key map [remap undo] 'gomoku-human-takes-back)
    (define-key map [remap advertised-undo] 'gomoku-human-takes-back)
    map)

  "Local keymap to use in Gomoku mode.")


(defvar gomoku-emacs-won ()
  "For making font-lock use the winner's face for the line.")

(defface gomoku-O
    '((((class color)) (:foreground "red" :weight bold)))
  "Face to use for Emacs's O."
  :group 'gomoku)

(defface gomoku-X
    '((((class color)) (:foreground "green" :weight bold)))
  "Face to use for your X."
  :group 'gomoku)

(defvar gomoku-font-lock-keywords
  '(("O" . 'gomoku-O)
    ("X" . 'gomoku-X)
    ("[-|/\\]" 0 (if gomoku-emacs-won 'gomoku-O 'gomoku-X)))
  "Font lock rules for Gomoku.")

;; This one is for when they set view-read-only to t: Gomoku cannot
;; allow View Mode to be activated in its buffer.
(define-derived-mode gomoku-mode special-mode "Gomoku"
  "Major mode for playing Gomoku against Emacs.
You and Emacs play in turn by marking a free square.  You mark it with X
and Emacs marks it with O.  The winner is the first to get five contiguous
marks horizontally, vertically or in diagonal.
\\<gomoku-mode-map>
You play by moving the cursor over the square you choose and hitting \\[gomoku-human-plays].

Other useful commands:\n
\\{gomoku-mode-map}"
  (gomoku-display-statistics)
  (make-local-variable 'font-lock-defaults)
  (setq font-lock-defaults '(gomoku-font-lock-keywords t)
	buffer-read-only t)
  (add-hook 'post-command-hook #'gomoku--intangible nil t))

;;;
;;; THE BOARD.
;;;

;; The board is a rectangular grid. We code empty squares with 0, X's with 1
;; and O's with 6.  The rectangle is recorded in a one dimensional vector
;; containing padding squares (coded with -1).  These squares allow us to
;; detect when we are trying to move out of the board.  We denote a square by
;; its (X,Y) coords, or by the INDEX corresponding to them in the vector.  The
;; leftmost topmost square has coords (1,1) and index gomoku-board-width + 2.
;; Similarly, vectors between squares may be given by two DX, DY coords or by
;; one DEPL (the difference between indexes).

(defvar gomoku-board-width nil
  "Number of columns on the Gomoku board.")

(defvar gomoku-board-height nil
  "Number of lines on the Gomoku board.")

(defvar gomoku-board nil
  "Vector recording the actual state of the Gomoku board.")

(defvar gomoku-vector-length nil
  "Length of `gomoku-board' vector.")

(defvar gomoku-draw-limit nil
  ;; This is usually set to 70% of the number of squares.
  "After how many moves will Emacs offer a draw?")


(defun gomoku-xy-to-index (x y)
  "Translate X, Y cartesian coords into the corresponding board index."
  (+ (* y gomoku-board-width) x y))

(defun gomoku-index-to-x (index)
  "Return corresponding x-coord of board INDEX."
  (% index (1+ gomoku-board-width)))

(defun gomoku-index-to-y (index)
  "Return corresponding y-coord of board INDEX."
  (/ index (1+ gomoku-board-width)))

(defun gomoku-init-board ()
  "Create the `gomoku-board' vector and fill it with initial values."
  (setq gomoku-board (make-vector gomoku-vector-length 0))
  ;; Every square is 0 (i.e. empty) except padding squares:
  (let ((i 0) (ii (1- gomoku-vector-length)))
    (while (<= i gomoku-board-width)	; The squares in [0..width] and in
      (aset gomoku-board i  -1)		;    [length - width - 1..length - 1]
      (aset gomoku-board ii -1)		;    are padding squares.
      (setq i  (1+ i)
	    ii (1- ii))))
  (let ((i 0))
    (while (< i gomoku-vector-length)
      (aset gomoku-board i -1)		; and also all k*(width+1)
      (setq i (+ i gomoku-board-width 1)))))

;;;
;;; THE SCORE TABLE.
;;;

;; Every (free) square has a score associated to it, recorded in the
;; GOMOKU-SCORE-TABLE vector. The program always plays in the square having
;; the highest score.

(defvar gomoku-score-table nil
  "Vector recording the actual score of the free squares.")


;; The key point point about the algorithm is that, rather than considering
;; the board as just a set of squares, we prefer to see it as a "space" of
;; internested 5-tuples of contiguous squares (called qtuples).
;;
;; The aim of the program is to fill one qtuple with its O's while preventing
;; you from filling another one with your X's. To that effect, it computes a
;; score for every qtuple, with better qtuples having better scores. Of
;; course, the score of a qtuple (taken in isolation) is just determined by
;; its contents as a set, i.e. not considering the order of its elements. The
;; highest score is given to the "OOOO" qtuples because playing in such a
;; qtuple is winning the game. Just after this comes the "XXXX" qtuple because
;; not playing in it is just losing the game, and so on. Note that a
;; "polluted" qtuple, i.e. one containing at least one X and at least one O,
;; has score zero because there is no more any point in playing in it, from
;; both an attacking and a defending point of view.
;;
;; Given the score of every qtuple, the score of a given free square on the
;; board is just the sum of the scores of all the qtuples to which it belongs,
;; because playing in that square is playing in all its containing qtuples at
;; once. And it is that function which takes into account the internesting of
;; the qtuples.
;;
;; This algorithm is rather simple but anyway it gives a not so dumb level of
;; play. It easily extends to "n-dimensional Gomoku", where a win should not
;; be obtained with as few as 5 contiguous marks: 6 or 7 (depending on n !)
;; should be preferred.


;; Here are the scores of the nine "non-polluted" configurations.  Tuning
;; these values will change (hopefully improve) the strength of the program
;; and may change its style (rather aggressive here).

(defconst gomoku-nil-score	  7  "Score of an empty qtuple.")
(defconst gomoku-Xscore	 15  "Score of a qtuple containing one X.")
(defconst gomoku-XXscore	400  "Score of a qtuple containing two X's.")
(defconst gomoku-XXXscore     1800  "Score of a qtuple containing three X's.")
(defconst gomoku-XXXXscore  100000  "Score of a qtuple containing four X's.")
(defconst gomoku-Oscore	 35  "Score of a qtuple containing one O.")
(defconst gomoku-OOscore	800  "Score of a qtuple containing two O's.")
(defconst gomoku-OOOscore    15000  "Score of a qtuple containing three O's.")
(defconst gomoku-OOOOscore  800000  "Score of a qtuple containing four O's.")

;; These values are not just random: if, given the following situation:
;;
;;			  . . . . . . . O .
;;			  . X X a . . . X .
;;			  . . . X . . . X .
;;			  . . . X . . . X .
;;			  . . . . . . . b .
;;
;; you want Emacs to play in "a" and not in "b", then the parameters must
;; satisfy the inequality:
;;
;;		   6 * gomoku-XXscore > gomoku-XXXscore + gomoku-XXscore
;;
;; because "a" mainly belongs to six "XX" qtuples (the others are less
;; important) while "b" belongs to one "XXX" and one "XX" qtuples.  Other
;; conditions are required to obtain sensible moves, but the previous example
;; should illustrate the point. If you manage to improve on these values,
;; please send me a note. Thanks.


;; As we chose values 0, 1 and 6 to denote empty, X and O squares, the
;; contents of a qtuple are uniquely determined by the sum of its elements and
;; we just have to set up a translation table.

(defconst gomoku-score-trans-table
  (vector gomoku-nil-score gomoku-Xscore gomoku-XXscore gomoku-XXXscore gomoku-XXXXscore 0
	  gomoku-Oscore    0	   0	   0	    0	      0
	  gomoku-OOscore   0	   0	   0	    0	      0
	  gomoku-OOOscore  0	   0	   0	    0	      0
	  gomoku-OOOOscore 0	   0	   0	    0	      0
	  0)
  "Vector associating qtuple contents to their score.")


;; If you do not modify drastically the previous constants, the only way for a
;; square to have a score higher than gomoku-OOOOscore is to belong to a "OOOO"
;; qtuple, thus to be a winning move. Similarly, the only way for a square to
;; have a score between gomoku-XXXXscore and gomoku-OOOOscore is to belong to a "XXXX"
;; qtuple. We may use these considerations to detect when a given move is
;; winning or losing.

(defconst gomoku-winning-threshold gomoku-OOOOscore
  "Threshold score beyond which an Emacs move is winning.")

(defconst gomoku-losing-threshold gomoku-XXXXscore
  "Threshold score beyond which a human move is winning.")


(defun gomoku-strongest-square ()
  "Compute index of free square with highest score, or nil if none."
  ;; We just have to loop other all squares. However there are two problems:
  ;; 1/ The SCORE-TABLE only gives correct scores to free squares. To speed
  ;;	up future searches, we set the score of padding or occupied squares
  ;;	to -1 whenever we meet them.
  ;; 2/ We want to choose randomly between equally good moves.
  (let ((score-max 0)
	(count	   0)			; Number of equally good moves
	(square	   (gomoku-xy-to-index 1 1)) ; First square
	(end	   (gomoku-xy-to-index gomoku-board-width gomoku-board-height))
	best-square score)
    (while (<= square end)
      (cond
       ;; If score is lower (i.e. most of the time), skip to next:
       ((< (aref gomoku-score-table square) score-max))
       ;; If score is better, beware of non free squares:
       ((> (setq score (aref gomoku-score-table square)) score-max)
	(if (zerop (aref gomoku-board square)) ; is it free ?
	    (setq count 1		       ; yes: take it !
		  best-square square
		  score-max   score)
	    (aset gomoku-score-table square -1))) ; no: kill it !
       ;; If score is equally good, choose randomly. But first check freedom:
       ((not (zerop (aref gomoku-board square)))
	(aset gomoku-score-table square -1))
       ((zerop (random (setq count (1+ count))))
	(setq best-square square
	      score-max	  score)))
      (setq square (1+ square)))	; try next square
    best-square))

;;;
;;; INITIALIZING THE SCORE TABLE.
;;;

;; At initialization the board is empty so that every qtuple amounts for
;; gomoku-nil-score. Therefore, the score of any square is gomoku-nil-score times the number
;; of qtuples that pass through it. This number is 3 in a corner and 20 if you
;; are sufficiently far from the sides. As computing the number is time
;; consuming, we initialize every square with 20*gomoku-nil-score and then only
;; consider squares at less than 5 squares from one side. We speed this up by
;; taking symmetry into account.
;; Also, as it is likely that successive games will be played on a board with
;; same size, it is a good idea to save the initial SCORE-TABLE configuration.

(defvar gomoku-saved-score-table nil
  "Recorded initial value of previous score table.")

(defvar gomoku-saved-board-width nil
  "Recorded value of previous board width.")

(defvar gomoku-saved-board-height nil
  "Recorded value of previous board height.")


(defun gomoku-init-score-table ()
  "Create the score table vector and fill it with initial values."
  (if (and gomoku-saved-score-table	; Has it been stored last time ?
	   (= gomoku-board-width  gomoku-saved-board-width)
	   (= gomoku-board-height gomoku-saved-board-height))
      (setq gomoku-score-table (copy-sequence gomoku-saved-score-table))
      ;; No, compute it:
      (setq gomoku-score-table
	    (make-vector gomoku-vector-length (* 20 gomoku-nil-score)))
      (let (i j maxi maxj maxi2 maxj2)
	(setq maxi  (/ (1+ gomoku-board-width) 2)
	      maxj  (/ (1+ gomoku-board-height) 2)
	      maxi2 (min 4 maxi)
	      maxj2 (min 4 maxj))
	;; We took symmetry into account and could use it more if the board
	;; would have been square and not rectangular !
	;; In our case we deal with all (i,j) in the set [1..maxi2]*[1..maxj] U
	;; [maxi2+1..maxi]*[1..maxj2]. Maxi2 and maxj2 are used because the
	;; board may well be less than 8 by 8 !
	(setq i 1)
	(while (<= i maxi2)
	  (setq j 1)
	  (while (<= j maxj)
	    (gomoku-init-square-score i j)
	    (setq j (1+ j)))
	  (setq i (1+ i)))
	(while (<= i maxi)
	  (setq j 1)
	  (while (<= j maxj2)
	    (gomoku-init-square-score i j)
	    (setq j (1+ j)))
	  (setq i (1+ i))))
      (setq gomoku-saved-score-table  (copy-sequence gomoku-score-table)
	    gomoku-saved-board-width  gomoku-board-width
	    gomoku-saved-board-height gomoku-board-height)))

(defun gomoku-nb-qtuples (i j)
  "Return the number of qtuples containing square I,J."
  ;; This function is complicated because we have to deal
  ;; with ugly cases like 3 by 6 boards, but it works.
  ;; If you have a simpler (and correct) solution, send it to me. Thanks !
  (let ((left  (min 4 (1- i)))
	(right (min 4 (- gomoku-board-width i)))
	(up    (min 4 (1- j)))
	(down  (min 4 (- gomoku-board-height j))))
    (+ -12
       (min (max (+ left right) 3) 8)
       (min (max (+ up down) 3) 8)
       (min (max (+ (min left up) (min right down)) 3) 8)
       (min (max (+ (min right up) (min left down)) 3) 8))))

(defun gomoku-init-square-score (i j)
  "Give initial score to square I,J and to its mirror images."
  (let ((ii (1+ (- gomoku-board-width i)))
	(jj (1+ (- gomoku-board-height j)))
	(sc (* (gomoku-nb-qtuples i j) (aref gomoku-score-trans-table 0))))
    (aset gomoku-score-table (gomoku-xy-to-index i  j)	sc)
    (aset gomoku-score-table (gomoku-xy-to-index ii j)	sc)
    (aset gomoku-score-table (gomoku-xy-to-index i  jj) sc)
    (aset gomoku-score-table (gomoku-xy-to-index ii jj) sc)))

;;;
;;; MAINTAINING THE SCORE TABLE.
;;;

;; We do not provide functions for computing the SCORE-TABLE given the
;; contents of the BOARD. This would involve heavy nested loops, with time
;; proportional to the size of the board. It is better to update the
;; SCORE-TABLE after each move. Updating needs not modify more than 36
;; squares: it is done in constant time.

(defun gomoku-update-score-table (square dval)
  "Update score table after SQUARE received a DVAL increment."
  ;; The board has already been updated when this function is called.
  ;; Updating scores is done by looking for qtuples boundaries in all four
  ;; directions and then calling update-score-in-direction.
  ;; Finally all squares received the right increment, and then are up to
  ;; date, except possibly for SQUARE itself if we are taking a move back for
  ;; its score had been set to -1 at the time.
  (let* ((x    (gomoku-index-to-x square))
	 (y    (gomoku-index-to-y square))
	 (imin (max -4 (- 1 x)))
	 (jmin (max -4 (- 1 y)))
	 (imax (min 0 (- gomoku-board-width x 4)))
	 (jmax (min 0 (- gomoku-board-height y 4))))
    (gomoku-update-score-in-direction imin imax
				      square 1 0 dval)
    (gomoku-update-score-in-direction jmin jmax
				      square 0 1 dval)
    (gomoku-update-score-in-direction (max imin jmin) (min imax jmax)
				      square 1 1 dval)
    (gomoku-update-score-in-direction (max (- 1 y) -4
					   (- x gomoku-board-width))
				      (min 0 (- x 5)
					   (- gomoku-board-height y 4))
				      square -1 1 dval)))

(defun gomoku-update-score-in-direction (left right square dx dy dval)
  "Update scores for all squares in the qtuples starting between the LEFTth
square and the RIGHTth after SQUARE, along the DX, DY direction, considering
that DVAL has been added on SQUARE."
  ;; We always have LEFT <= 0, RIGHT <= 0 and DEPL > 0 but we may very well
  ;; have LEFT > RIGHT, indicating that no qtuple contains SQUARE along that
  ;; DX,DY direction.
  (cond
   ((> left right))			; Quit
   (t					; Else ..
    (let (depl square0 square1 square2 count delta)
      (setq depl    (gomoku-xy-to-index dx dy)
	    square0 (+ square (* left depl))
	    square1 (+ square (* right depl))
	    square2 (+ square0 (* 4 depl)))
      ;; Compute the contents of the first qtuple:
      (setq square square0
	    count  0)
      (while (<= square square2)
	(setq count  (+ count (aref gomoku-board square))
	      square (+ square depl)))
      (while (<= square0 square1)
	;; Update the squares of the qtuple beginning in SQUARE0 and ending
	;; in SQUARE2.
	(setq delta (- (aref gomoku-score-trans-table count)
		       (aref gomoku-score-trans-table (- count dval))))
	(cond ((not (zerop delta))	; or else nothing to update
	       (setq square square0)
	       (while (<= square square2)
		 (if (zerop (aref gomoku-board square)) ; only for free squares
		     (aset gomoku-score-table square
			   (+ (aref gomoku-score-table square) delta)))
		 (setq square (+ square depl)))))
	;; Then shift the qtuple one square along DEPL, this only requires
	;; modifying SQUARE0 and SQUARE2.
	(setq square2 (+ square2 depl)
	      count   (+ count (- (aref gomoku-board square0))
			 (aref gomoku-board square2))
	      square0 (+ square0 depl)))))))

;;;
;;; GAME CONTROL.
;;;

;; Several variables are used to monitor a game, including a GAME-HISTORY (the
;; list of all (SQUARE . PREVSCORE) played) that allows to take moves back
;; (anti-updating the score table) and to compute the table from scratch in
;; case of an interruption.

(defvar gomoku-game-in-progress nil
  "Non-nil if a game is in progress.")

(defvar gomoku-game-history nil
  "A record of all moves that have been played during current game.")

(defvar gomoku-number-of-moves nil
  "Number of moves already played in current game.")

(defvar gomoku-number-of-human-moves nil
  "Number of moves already played by human in current game.")

(defvar gomoku-emacs-played-first nil
  "Non-nil if Emacs played first.")

(defvar gomoku-human-took-back nil
  "Non-nil if Human took back a move during the game.")

(defvar gomoku-human-refused-draw nil
  "Non-nil if Human refused Emacs offer of a draw.")

(defvar gomoku-emacs-is-computing nil
  ;; This is used to detect interruptions. Hopefully, it should not be needed.
  "Non-nil if Emacs is in the middle of a computation.")


(defun gomoku-start-game (n m)
  "Initialize a new game on an N by M board."
  (setq gomoku-emacs-is-computing t)	; Raise flag
  (setq gomoku-game-in-progress t)
  (setq gomoku-board-width   n
	gomoku-board-height  m
	gomoku-vector-length (1+ (* (+ m 2) (1+ n)))
	gomoku-draw-limit    (/ (* 7 n m) 10))
  (setq gomoku-emacs-won	     nil
	gomoku-game-history	     nil
	gomoku-number-of-moves	     0
	gomoku-number-of-human-moves 0
	gomoku-emacs-played-first    nil
	gomoku-human-took-back	     nil
	gomoku-human-refused-draw    nil)
  (gomoku-init-display n m)		; Display first: the rest takes time
  (gomoku-init-score-table)		; INIT-BOARD requires that the score
  (gomoku-init-board)			;   table be already created.
  (setq gomoku-emacs-is-computing nil))

(defun gomoku-play-move (square val &optional dont-update-score)
  "Go to SQUARE, play VAL and update everything."
  (setq gomoku-emacs-is-computing t)	; Raise flag
  (cond ((= 1 val)			; a Human move
	 (setq gomoku-number-of-human-moves (1+ gomoku-number-of-human-moves)))
	((zerop gomoku-number-of-moves)	; an Emacs move. Is it first ?
	 (setq gomoku-emacs-played-first t)))
  (setq gomoku-game-history
	(cons (cons square (aref gomoku-score-table square))
	      gomoku-game-history)
	gomoku-number-of-moves (1+ gomoku-number-of-moves))
  (gomoku-plot-square square val)
  (aset gomoku-board square val)	; *BEFORE* UPDATE-SCORE !
  (if dont-update-score nil
      (gomoku-update-score-table square val) ; previous val was 0: dval = val
      (aset gomoku-score-table square -1))
  (setq gomoku-emacs-is-computing nil))

(defun gomoku-take-back ()
  "Take back last move and update everything."
  (setq gomoku-emacs-is-computing t)
  (let* ((last-move (car gomoku-game-history))
	 (square (car last-move))
	 (oldval (aref gomoku-board square)))
    (if (= 1 oldval)
	(setq gomoku-number-of-human-moves (1- gomoku-number-of-human-moves)))
    (setq gomoku-game-history	 (cdr gomoku-game-history)
	  gomoku-number-of-moves (1- gomoku-number-of-moves))
    (gomoku-plot-square square 0)
    (aset gomoku-board square 0)	; *BEFORE* UPDATE-SCORE !
    (gomoku-update-score-table square (- oldval))
    (aset gomoku-score-table square (cdr last-move)))
  (setq gomoku-emacs-is-computing nil))

;;;
;;; SESSION CONTROL.
;;;

(defvar gomoku-number-of-emacs-wins 0
  "Number of games Emacs won in this session.")

(defvar gomoku-number-of-human-wins 0
  "Number of games you won in this session.")

(defvar gomoku-number-of-draws 0
  "Number of games already drawn in this session.")


(defun gomoku-terminate-game (result)
  "Terminate the current game with RESULT."
  (message
   (cond
    ((eq result 'emacs-won)
     (setq gomoku-number-of-emacs-wins (1+ gomoku-number-of-emacs-wins))
     (cond ((< gomoku-number-of-moves 20)
	    "This was a REALLY QUICK win.")
	   (gomoku-human-refused-draw
	    "I won...  Too bad you refused my offer of a draw!")
	   (gomoku-human-took-back
	    "I won...  Taking moves back will not help you!")
	   ((not gomoku-emacs-played-first)
	    "I won...  Playing first did not help you much!")
	   ((and (zerop gomoku-number-of-human-wins)
		 (zerop gomoku-number-of-draws)
		 (> gomoku-number-of-emacs-wins 1))
	    "I'm becoming tired of winning...")
	   ("I won.")))
    ((eq result 'human-won)
     (setq gomoku-number-of-human-wins (1+ gomoku-number-of-human-wins))
     (concat "OK, you won this one."
	     (cond
	      (gomoku-human-took-back
	       "  I, for one, never take my moves back...")
	      (gomoku-emacs-played-first
	       ".. so what?")
	      ("  Now, let me play first just once."))))
    ((eq result 'human-resigned)
     (setq gomoku-number-of-emacs-wins (1+ gomoku-number-of-emacs-wins))
     "So you resign.  That's just one more win for me.")
    ((eq result 'nobody-won)
     (setq gomoku-number-of-draws (1+ gomoku-number-of-draws))
     (concat "This is a draw.  "
	     (cond
	      (gomoku-human-took-back
	       "I, for one, never take my moves back...")
	      (gomoku-emacs-played-first
	       "Just chance, I guess.")
	      ("Now, let me play first just once."))))
    ((eq result 'draw-agreed)
     (setq gomoku-number-of-draws (1+ gomoku-number-of-draws))
     (concat "Draw agreed.  "
	     (cond
	      (gomoku-human-took-back
	       "I, for one, never take my moves back...")
	      (gomoku-emacs-played-first
	       "You were lucky.")
	      ("Now, let me play first just once."))))
    ((eq result 'crash-game)
     "Sorry, I have been interrupted and cannot resume that game...")))
  (gomoku-display-statistics)
  ;;(ding)
  (setq gomoku-game-in-progress nil))

(defun gomoku-crash-game ()
  "What to do when Emacs detects it has been interrupted."
  (setq gomoku-emacs-is-computing nil)
  (gomoku-terminate-game 'crash-game)
  (sit-for 4)				; Let's see the message
  (gomoku-prompt-for-other-game))

;;;
;;; INTERACTIVE COMMANDS.
;;;

;;;###autoload
(defun gomoku (&optional n m)
  "Start a Gomoku game between you and Emacs.

If a game is in progress, this command allows you to resume it.
If optional arguments N and M are given, an N by M board is used.
If prefix arg is given for N, M is prompted for.

You and Emacs play in turn by marking a free square.  You mark it with X
and Emacs marks it with O.  The winner is the first to get five contiguous
marks horizontally, vertically or in diagonal.

You play by moving the cursor over the square you choose and hitting
\\<gomoku-mode-map>\\[gomoku-human-plays].

This program actually plays a simplified or archaic version of the
Gomoku game, and ought to be upgraded to use the full modern rules.

Use \\[describe-mode] for more info."
  (interactive (if current-prefix-arg
		   (list (prefix-numeric-value current-prefix-arg)
			 (eval (read-minibuffer "Height: ")))))
  ;; gomoku-switch-to-window, but without the potential call to gomoku
  ;; from gomoku-prompt-for-other-game.
  (if (get-buffer gomoku-buffer-name)
      (switch-to-buffer gomoku-buffer-name)
    (when gomoku-game-in-progress
      (setq gomoku-emacs-is-computing nil)
      (gomoku-terminate-game 'crash-game)
      (sit-for 4)
      (or (y-or-n-p "Another game? ") (error "Chicken!")))
    (switch-to-buffer gomoku-buffer-name)
    (gomoku-mode))
  (cond
   (gomoku-emacs-is-computing
    (gomoku-crash-game))
   ((or (not gomoku-game-in-progress)
	(<= gomoku-number-of-moves 2))
    (let ((max-width (gomoku-max-width))
	  (max-height (gomoku-max-height)))
      (or n (setq n max-width))
      (or m (setq m max-height))
      (cond ((< n 1)
	     (error "I need at least 1 column"))
	    ((< m 1)
	     (error "I need at least 1 row"))
	    ((> n max-width)
	     (error "I cannot display %d columns in that window" n)))
      (if (and (> m max-height)
	       (not (eq m gomoku-saved-board-height))
	       ;; Use EQ because SAVED-BOARD-HEIGHT may be nil
	       (not (y-or-n-p (format "Do you really want %d rows? " m))))
	  (setq m max-height)))
    (message "One moment, please...")
    (gomoku-start-game n m)
    (if (y-or-n-p "Do you allow me to play first? ")
	(gomoku-emacs-plays)
	(gomoku-prompt-for-move)))
   ((y-or-n-p "Shall we continue our game? ")
    (gomoku-prompt-for-move))
   (t
    (gomoku-human-resigns))))

(defun gomoku-emacs-plays ()
  "Compute Emacs next move and play it."
  (interactive)
  (gomoku-switch-to-window)
  (cond
   (gomoku-emacs-is-computing
    (gomoku-crash-game))
   ((not gomoku-game-in-progress)
    (gomoku-prompt-for-other-game))
   (t
    (message "Let me think...")
    (let (square score)
      (setq square (gomoku-strongest-square))
      (cond ((null square)
	     (gomoku-terminate-game 'nobody-won))
	    (t
	     (setq score (aref gomoku-score-table square))
	     (gomoku-play-move square 6)
	     (cond ((>= score gomoku-winning-threshold)
		    (setq gomoku-emacs-won t) ; for font-lock
		    (gomoku-find-filled-qtuple square 6)
		    (gomoku-terminate-game 'emacs-won))
		   ((zerop score)
		    (gomoku-terminate-game 'nobody-won))
		   ((and (> gomoku-number-of-moves gomoku-draw-limit)
			 (not gomoku-human-refused-draw)
			 (gomoku-offer-a-draw))
		    (gomoku-terminate-game 'draw-agreed))
		   (t
		    (gomoku-prompt-for-move)))))))))

;; For small square dimensions this is approximate, since though measured in
;; pixels, event's (X . Y) is a character's top-left corner.
(defun gomoku-click (click)
  "Position at the square where you click."
  (interactive "e")
  (and (windowp (posn-window (setq click (event-end click))))
       (numberp (posn-point click))
       (select-window (posn-window click))
       (setq click (posn-col-row click))
       (gomoku-goto-xy
	(min (max (/ (+ (- (car click)
			   gomoku-x-offset
			   1)
			(window-hscroll)
			gomoku-square-width
			(% gomoku-square-width 2)
			(/ gomoku-square-width 2))
		     gomoku-square-width)
		  1)
	     gomoku-board-width)
	(min (max (/ (+ (- (cdr click)
			   gomoku-y-offset
			   1)
                        (count-lines (point-min) (window-start))
			gomoku-square-height
			(% gomoku-square-height 2)
			(/ gomoku-square-height 2))
		     gomoku-square-height)
		  1)
	     gomoku-board-height))))

(defun gomoku-mouse-play (click)
  "Play at the square where you click."
  (interactive "e")
  (if (gomoku-click click)
      (gomoku-human-plays)))

(defun gomoku-human-plays ()
  "Signal to the Gomoku program that you have played.
You must have put the cursor on the square where you want to play.
If the game is finished, this command requests for another game."
  (interactive)
  (gomoku-switch-to-window)
  (cond
   (gomoku-emacs-is-computing
    (gomoku-crash-game))
   ((not gomoku-game-in-progress)
    (gomoku-prompt-for-other-game))
   (t
    (let (square score)
      (setq square (gomoku-point-square))
      (cond ((null square)
	     (error "Your point is not on a square.  Retry!"))
	    ((not (zerop (aref gomoku-board square)))
	     (error "Your point is not on a free square.  Retry!"))
	    (t
	     (setq score (aref gomoku-score-table square))
	     (gomoku-play-move square 1)
	     (cond ((and (>= score gomoku-losing-threshold)
			 ;; Just testing SCORE > THRESHOLD is not enough for
			 ;; detecting wins, it just gives an indication that
			 ;; we confirm with GOMOKU-FIND-FILLED-QTUPLE.
			 (gomoku-find-filled-qtuple square 1))
		    (gomoku-terminate-game 'human-won))
		   (t
		    (gomoku-emacs-plays)))))))))

(defun gomoku-human-takes-back ()
  "Signal to the Gomoku program that you wish to take back your last move."
  (interactive)
  (gomoku-switch-to-window)
  (cond
   (gomoku-emacs-is-computing
    (gomoku-crash-game))
   ((not gomoku-game-in-progress)
    (message "Too late for taking back...")
    (sit-for 4)
    (gomoku-prompt-for-other-game))
   ((zerop gomoku-number-of-human-moves)
    (message "You have not played yet...  Your move?"))
   (t
    (message "One moment, please...")
    ;; It is possible for the user to let Emacs play several consecutive
    ;; moves, so that the best way to know when to stop taking back moves is
    ;; to count the number of human moves:
    (setq gomoku-human-took-back t)
    (let ((number gomoku-number-of-human-moves))
      (while (= number gomoku-number-of-human-moves)
	(gomoku-take-back)))
    (gomoku-prompt-for-move))))

(defun gomoku-human-resigns ()
  "Signal to the Gomoku program that you may want to resign."
  (interactive)
  (gomoku-switch-to-window)
  (cond
   (gomoku-emacs-is-computing
    (gomoku-crash-game))
   ((not gomoku-game-in-progress)
    (message "There is no game in progress"))
   ((y-or-n-p "You mean, you resign? ")
    (gomoku-terminate-game 'human-resigned))
   ((y-or-n-p "You mean, we continue? ")
    (gomoku-prompt-for-move))
   (t
    (gomoku-terminate-game 'human-resigned)))) ; OK. Accept it

;;;
;;; PROMPTING THE HUMAN PLAYER.
;;;

(defun gomoku-prompt-for-move ()
  "Display a message asking for Human's move."
  (message (if (zerop gomoku-number-of-human-moves)
	       "Your move?  (Move to a free square and hit X, RET ...)"
	       "Your move?")))

(defun gomoku-prompt-for-other-game ()
  "Ask for another game, and start it."
  (if (y-or-n-p "Another game? ")
      (gomoku gomoku-board-width gomoku-board-height)
    (error "Chicken!")))

(defun gomoku-offer-a-draw ()
  "Offer a draw and return t if Human accepted it."
  (or (y-or-n-p "I offer you a draw.  Do you accept it? ")
      (not (setq gomoku-human-refused-draw t))))

;;;
;;; DISPLAYING THE BOARD.
;;;

(defun gomoku-max-width ()
  "Largest possible board width for the current window."
  (1+ (/ (- (window-width)
	    gomoku-x-offset gomoku-x-offset 1)
	 gomoku-square-width)))

(defun gomoku-max-height ()
  "Largest possible board height for the current window."
  (1+ (/ (- (window-height)
	    gomoku-y-offset gomoku-y-offset 2)
	 ;; 2 instead of 1 because WINDOW-HEIGHT includes the mode line !
	 gomoku-square-height)))

(defun gomoku-point-y ()
  "Return the board row where point is."
  (1+ (/ (- (count-lines (point-min) (point))
            gomoku-y-offset (if (bolp) 0 1))
         gomoku-square-height)))

(defun gomoku-point-square ()
  "Return the index of the square point is on."
  (gomoku-xy-to-index (1+ (/ (- (current-column) gomoku-x-offset)
                             gomoku-square-width))
                      (gomoku-point-y)))

(defun gomoku-goto-square (index)
  "Move point to square number INDEX."
  (gomoku-goto-xy (gomoku-index-to-x index) (gomoku-index-to-y index)))

(defun gomoku-goto-xy (x y)
  "Move point to square at X, Y coords."
  (goto-char (point-min))
  (forward-line (+ gomoku-y-offset (* gomoku-square-height (1- y))))
  (move-to-column (+ gomoku-x-offset (* gomoku-square-width (1- x)))))

(defun gomoku-plot-square (square value)
  "Draw 'X', 'O' or '.' on SQUARE depending on VALUE, leave point there."
  (or (= value 1)
      (gomoku-goto-square square))
  (let ((inhibit-read-only t))
    (insert (cond ((= value 1) ?X)
                  ((= value 6) ?O)
                  (?.)))
    (and (zerop value)
	 (add-text-properties
	  (1- (point)) (point)
	  '(mouse-face highlight help-echo "mouse-2: play at this square")))
    (delete-char 1)
    (backward-char 1))
  (sit-for 0))	; Display NOW

(defun gomoku-init-display (n m)
  "Display an N by M Gomoku board."
  (buffer-disable-undo (current-buffer))
  (let ((inhibit-read-only t)
	(point (point-min)) opoint
	(i m) j x)
    ;; Try to minimize number of chars (because of text properties)
    (setq tab-width
	  (if (zerop (% gomoku-x-offset gomoku-square-width))
	      gomoku-square-width
	    (max (/ (+ (% gomoku-x-offset gomoku-square-width)
		       gomoku-square-width 1) 2) 2)))
    (erase-buffer)
    (insert-char ?\n gomoku-y-offset)
    (while (progn
	     (setq j n
		   x (- gomoku-x-offset gomoku-square-width))
	     (while (>= (setq j (1- j)) 0)
               (insert-char ?\t (/ (- (setq x (+ x gomoku-square-width))
                                      (current-column))
                                   tab-width))
               (insert-char ?\s (- x (current-column)))
	       (and (zerop j)
		    (= i (- m 2))
		    (progn
		      (while (>= i 3)
			(append-to-buffer (current-buffer) opoint (point))
			(setq i (- i 2)))
		      (goto-char (point-max))))
	       (setq point (point))
	       (insert ?.)
	       (add-text-properties
		point (point)
		'(mouse-face highlight
		  help-echo "mouse-2: play at this square")))
	     (> (setq i (1- i)) 0))
      (if (= i (1- m))
	  (setq opoint point))
      (insert-char ?\n gomoku-square-height))
    (insert-char ?\n))
  (gomoku-goto-xy (/ (1+ n) 2) (/ (1+ m) 2)) ; center of the board
  (sit-for 0))                               ; Display NOW

(defun gomoku-display-statistics ()
  "Obnoxiously display some statistics about previous games in mode line."
  ;; Update mode line only if Gomoku buffer is current (Bug#12771).
  (when (string-equal (buffer-name) gomoku-buffer-name)
    ;; We store this string in the mode-line-process local variable.
    ;; This is certainly not the cleanest way out ...
    (setq mode-line-process
	  (format ": won %d, lost %d%s"
		  gomoku-number-of-human-wins
		  gomoku-number-of-emacs-wins
		  (if (zerop gomoku-number-of-draws)
		      ""
		    (format ", drew %d" gomoku-number-of-draws))))
    (force-mode-line-update)))

(defun gomoku-switch-to-window ()
  "Find or create the Gomoku buffer, and display it."
  (interactive)
  (if (get-buffer gomoku-buffer-name)       ; Buffer exists:
      (switch-to-buffer gomoku-buffer-name) ;   no problem.
    (if gomoku-game-in-progress
        (gomoku-crash-game))            ;   buffer has been killed or something
    (switch-to-buffer gomoku-buffer-name)   ; Anyway, start anew.
    (gomoku-mode)))

;;;
;;; CROSSING WINNING QTUPLES.
;;;

;; When someone succeeds in filling a qtuple, we draw a line over the five
;; corresponding squares. One problem is that the program does not know which
;; squares ! It only knows the square where the last move has been played and
;; who won. The solution is to scan the board along all four directions.

(defun gomoku-find-filled-qtuple (square value)
  "Return t if SQUARE belongs to a qtuple filled with VALUEs."
  (or (gomoku-check-filled-qtuple square value 1 0)
      (gomoku-check-filled-qtuple square value 0 1)
      (gomoku-check-filled-qtuple square value 1 1)
      (gomoku-check-filled-qtuple square value -1 1)))

(defun gomoku-check-filled-qtuple (square value dx dy)
  "Return t if SQUARE belongs to a qtuple filled  with VALUEs along DX, DY."
  (let ((a 0) (b 0)
	(left square) (right square)
	(depl (gomoku-xy-to-index dx dy)))
    (while (and (> a -4)		; stretch tuple left
		(= value (aref gomoku-board (setq left (- left depl)))))
      (setq a (1- a)))
    (while (and (< b (+ a 4))		; stretch tuple right
		(= value (aref gomoku-board (setq right (+ right depl)))))
      (setq b (1+ b)))
    (cond ((= b (+ a 4))		; tuple length = 5 ?
	   (gomoku-cross-qtuple (+ square (* a depl)) (+ square (* b depl))
				dx dy)
	   t))))

(defun gomoku-cross-qtuple (square1 square2 dx dy)
  "Cross every square between SQUARE1 and SQUARE2 in the DX, DY direction."
  (save-excursion			; Not moving point from last square
    (let ((depl (gomoku-xy-to-index dx dy))
	  (inhibit-read-only t))
      ;; WARNING: this function assumes DEPL > 0 and SQUARE2 > SQUARE1
      (while (/= square1 square2)
	(gomoku-goto-square square1)
	(setq square1 (+ square1 depl))
	(cond
	  ((= dy 0)			; Horizontal
	   (forward-char 1)
	   (insert-char ?- (1- gomoku-square-width) t)
	   (delete-region (point) (progn
				    (skip-chars-forward " \t")
				    (point))))
	  ((= dx 0)			; Vertical
	   (let ((n 1)
		 (column (current-column)))
	     (while (< n gomoku-square-height)
	       (setq n (1+ n))
	       (forward-line 1)
	       (indent-to column)
	       (insert ?|))))
	  ((= dx -1)			; 1st Diagonal
	   (indent-to (prog1 (- (current-column) (/ gomoku-square-width 2))
			(forward-line (/ gomoku-square-height 2))))
	   (insert ?/))
	  (t				; 2nd Diagonal
	   (indent-to (prog1 (+ (current-column) (/ gomoku-square-width 2))
			(forward-line (/ gomoku-square-height 2))))
	   (insert ?\\))))))
  (sit-for 0))				; Display NOW

;;;
;;; CURSOR MOTION.
;;;

(defvar-local gomoku--last-pos 0)

(defconst gomoku--intangible-chars "- \t\n|/\\\\")

(defun gomoku--intangible ()
  (when (or (eobp)
            (save-excursion
              (not (zerop (skip-chars-forward gomoku--intangible-chars)))))
    (if (<= gomoku--last-pos (point))   ;Moving forward.
        (progn
          (skip-chars-forward gomoku--intangible-chars)
          (when (eobp)
            (skip-chars-backward gomoku--intangible-chars)
            (forward-char -1)))
      (skip-chars-backward gomoku--intangible-chars)
      (if (bobp)
          (skip-chars-forward gomoku--intangible-chars)
        (forward-char -1))))
  (setq gomoku--last-pos (point)))

;; previous-line and next-line don't work right with intangible newlines
(defun gomoku-move-down ()
  "Move point down one row on the Gomoku board."
  (interactive)
  (when (< (gomoku-point-y) gomoku-board-height)
    (let ((column (current-column)))
      (forward-line gomoku-square-height)
      (move-to-column column))))

(defun gomoku-move-up ()
  "Move point up one row on the Gomoku board."
  (interactive)
  (when (> (gomoku-point-y) 1)
    (let ((column (current-column)))
      (forward-line (- gomoku-square-height))
      (move-to-column column))))

(defun gomoku-move-ne ()
  "Move point North East on the Gomoku board."
  (interactive)
  (gomoku-move-up)
  (forward-char))

(defun gomoku-move-se ()
  "Move point South East on the Gomoku board."
  (interactive)
  (gomoku-move-down)
  (forward-char))

(defun gomoku-move-nw ()
  "Move point North West on the Gomoku board."
  (interactive)
  (gomoku-move-up)
  (backward-char))

(defun gomoku-move-sw ()
  "Move point South West on the Gomoku board."
  (interactive)
  (gomoku-move-down)
  (backward-char))

(defun gomoku-beginning-of-line ()
  "Move point to first square on the Gomoku board row."
  (interactive)
  (move-to-column gomoku-x-offset))

(defun gomoku-end-of-line ()
  "Move point to last square on the Gomoku board row."
  (interactive)
  (move-to-column (+ gomoku-x-offset
		     (* gomoku-square-width (1- gomoku-board-width)))))

(provide 'gomoku)

;;; gomoku.el ends here