Source

org-drill / org-drill.el

   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
;;; org-drill.el - Self-testing with org-learn
;;;
;;; Author: Paul Sexton <eeeickythump@gmail.com>
;;; Version: 1.6
;;; Repository at http://bitbucket.org/eeeickythump/org-drill/
;;;
;;;
;;; Synopsis
;;; ========
;;;
;;; Uses the spaced repetition algorithm in `org-learn' to conduct interactive
;;; "drill sessions", where the material to be remembered is presented to the
;;; student in random order. The student rates his or her recall of each item,
;;; and this information is fed back to `org-learn' to schedule the item for
;;; later revision.
;;;
;;; Each drill session can be restricted to topics in the current buffer
;;; (default), one or several files, all agenda files, or a subtree. A single
;;; topic can also be drilled.
;;;
;;; Different "card types" can be defined, which present their information to
;;; the student in different ways.
;;;
;;; See the file README.org for more detailed documentation.


(eval-when-compile (require 'cl))
(eval-when-compile (require 'hi-lock))
(require 'org)
(require 'org-learn)


(defgroup org-drill nil
  "Options concerning interactive drill sessions in Org mode (org-drill)."
  :tag "Org-Drill"
  :group 'org-link)



(defcustom org-drill-question-tag
  "drill"
  "Tag which topics must possess in order to be identified as review topics
by `org-drill'."
  :group 'org-drill
  :type 'string)



(defcustom org-drill-maximum-items-per-session
  30
  "Each drill session will present at most this many topics for review.
Nil means unlimited."
  :group 'org-drill
  :type '(choice integer (const nil)))



(defcustom org-drill-maximum-duration
  20
  "Maximum duration of a drill session, in minutes.
Nil means unlimited."
  :group 'org-drill
  :type '(choice integer (const nil)))


(defcustom org-drill-failure-quality
  2
  "If the quality of recall for an item is this number or lower,
it is regarded as an unambiguous failure, and the repetition
interval for the card is reset to 0 days.  By default this is
2. For Mnemosyne-like behaviour, set it to 1.  Other values are
not really sensible."
  :group 'org-drill
  :type '(choice (const 2) (const 1)))


(defcustom org-drill-leech-failure-threshold
  15
  "If an item is forgotten more than this many times, it is tagged
as a 'leech' item."
  :group 'org-drill
  :type '(choice integer (const nil)))


(defcustom org-drill-leech-method
  'skip
  "How should 'leech items' be handled during drill sessions?
Possible values:
- nil :: Leech items are treated the same as normal items.
- skip :: Leech items are not included in drill sessions.
- warn :: Leech items are still included in drill sessions,
  but a warning message is printed when each leech item is
  presented."
  :group 'org-drill
  :type '(choice (const 'warn) (const 'skip) (const nil)))


(defface org-drill-visible-cloze-face
  '((t (:foreground "darkseagreen")))
  "The face used to hide the contents of cloze phrases."
  :group 'org-drill)


(defface org-drill-visible-cloze-hint-face
  '((t (:foreground "dark slate blue")))
  "The face used to hide the contents of cloze phrases."
  :group 'org-drill)


(defcustom org-drill-use-visible-cloze-face-p
  nil
  "Use a special face to highlight cloze-deleted text in org mode
buffers?"
  :group 'org-drill
  :type 'boolean)


(defface org-drill-hidden-cloze-face
  '((t (:foreground "deep sky blue" :background "blue")))
  "The face used to hide the contents of cloze phrases."
  :group 'org-drill)


(defcustom org-drill-new-count-color
  "royal blue"
  "Foreground colour used to display the count of remaining new items
during a drill session."
  :group 'org-drill
  :type 'color)

(defcustom org-drill-mature-count-color
  "green"
  "Foreground colour used to display the count of remaining mature items
during a drill session. Mature items are due for review, but are not new."
  :group 'org-drill
  :type 'color)

(defcustom org-drill-failed-count-color
  "red"
  "Foreground colour used to display the count of remaining failed items
during a drill session."
  :group 'org-drill
  :type 'color)

(defcustom org-drill-done-count-color
  "sienna"
  "Foreground colour used to display the count of reviewed items
during a drill session."
  :group 'org-drill
  :type 'color)


(setplist 'org-drill-cloze-overlay-defaults
          '(display "[...]"
                    face org-drill-hidden-cloze-face
                    window t))


(defvar org-drill-cloze-regexp
  ;; ver 1   "[^][]\\(\\[[^][][^]]*\\]\\)"
  ;; ver 2   "\\(\\[.*?\\]\\|^[^[[:cntrl:]]*?\\]\\|\\[.*?$\\)"
  ;; ver 3!  "\\(\\[.*?\\]\\|\\[.*?[[:cntrl:]]+.*?\\]\\)"
  "\\(\\[[[:cntrl:][:graph:][:space:]]*?\\)\\(\\||.+?\\)\\(\\]\\)")

(defvar org-drill-cloze-keywords
  `((,org-drill-cloze-regexp
     (1 'org-drill-visible-cloze-face nil)
     (2 'org-drill-visible-cloze-hint-face t)
     (3 'org-drill-visible-cloze-face nil)
     )))


(defcustom org-drill-card-type-alist
  '((nil . org-drill-present-simple-card)
    ("simple" . org-drill-present-simple-card)
    ("twosided" . org-drill-present-two-sided-card)
    ("multisided" . org-drill-present-multi-sided-card)
    ("multicloze" . org-drill-present-multicloze)
    ("spanish_verb" . org-drill-present-spanish-verb))
  "Alist associating card types with presentation functions. Each entry in the
alist takes the form (CARDTYPE . FUNCTION), where CARDTYPE is a string
or nil, and FUNCTION is a function which takes no arguments and returns a
boolean value."
  :group 'org-drill
  :type '(alist :key-type (choice string (const nil)) :value-type function))


(defcustom org-drill-spaced-repetition-algorithm
  'sm5
  "Which SuperMemo spaced repetition algorithm to use for scheduling items.
Available choices are SM2 and SM5."
  :group 'org-drill
  :type '(choice (const 'sm2) (const 'sm5)))

(defcustom org-drill-add-random-noise-to-intervals-p
  nil
  "If true, the number of days until an item's next repetition
will vary slightly from the interval calculated by the SM2
algorithm. The variation is very small when the interval is
small, and scales up with the interval. The code for calculating
random noise is adapted from Mnemosyne."
  :group 'org-drill
  :type 'boolean)

(defcustom org-drill-cram-hours
  12
  "When in cram mode, items are considered due for review if
they were reviewed at least this many hours ago."
  :group 'org-drill
  :type 'integer)


(defvar *org-drill-session-qualities* nil)
(defvar *org-drill-start-time* 0)
(defvar *org-drill-new-entries* nil)
(defvar *org-drill-mature-entries* nil)
(defvar *org-drill-failed-entries* nil)
(defvar *org-drill-again-entries* nil)
(defvar *org-drill-done-entries* nil)
(defvar *org-drill-cram-mode* nil
  "Are we in 'cram mode', where all items are considered due
for review unless they were already reviewed in the recent past?")



;;;; Utilities ================================================================


(defun free-marker (m)
  (set-marker m nil))


(defmacro pop-random (place)
  (let ((idx (gensym)))
    `(if (null ,place)
         nil
       (let ((,idx (random (length ,place))))
         (prog1 (nth ,idx ,place)
           (setq ,place (append (subseq ,place 0 ,idx)
                                (subseq ,place (1+ ,idx)))))))))


(defun shuffle-list (list)
  "Randomly permute the elements of LIST (all permutations equally likely)."
  ;; Adapted from 'shuffle-vector' in cookie1.el
  (let ((i 0)
	j
	temp
	(len (length list)))
    (while (< i len)
      (setq j (+ i (random (- len i))))
      (setq temp (nth i list))
      (setf (nth i list) (nth j list))
      (setf (nth j list) temp)
      (setq i (1+ i))))
  list)


(defun time-to-inactive-org-timestamp (time)
  (format-time-string
   (concat "[" (substring (cdr org-time-stamp-formats) 1 -1) "]")
   time))



(defmacro with-hidden-cloze-text (&rest body)
  `(progn
     (org-drill-hide-clozed-text)
     (unwind-protect
         (progn
           ,@body)
       (org-drill-unhide-clozed-text))))


(defun org-drill-days-since-last-review ()
  "Nil means a last review date has not yet been stored for
the item.
Zero means it was reviewed today.
A positive number means it was reviewed that many days ago.
A negative number means the date of last review is in the future --
this should never happen."
  (let ((datestr (org-entry-get (point) "DRILL_LAST_REVIEWED")))
    (when datestr
      (- (time-to-days (current-time))
         (time-to-days (apply 'encode-time
                              (org-parse-time-string datestr)))))))


(defun org-drill-hours-since-last-review ()
  "Like `org-drill-days-since-last-review', but return value is
in hours rather than days."
  (let ((datestr (org-entry-get (point) "DRILL_LAST_REVIEWED")))
    (when datestr
      (floor
       (/ (- (time-to-seconds (current-time))
             (time-to-seconds (apply 'encode-time
                                     (org-parse-time-string datestr))))
          (* 60 60))))))


(defun org-drill-entry-p ()
  "Is the current entry a 'drill item'?"
  (or (org-entry-get (point) "LEARN_DATA")
      ;;(assoc "LEARN_DATA" (org-entry-properties nil))
      (member org-drill-question-tag (org-get-local-tags))))


(defun org-part-of-drill-entry-p ()
  "Is the current entry either the main heading of a 'drill item',
or a subheading within a drill item?"
  (or (org-drill-entry-p)
      ;; Does this heading INHERIT the drill tag
      (member org-drill-question-tag (org-get-tags-at))))


(defun org-drill-goto-drill-entry-heading ()
  "Move the point to the heading which hold the :drill: tag for this
drill entry."
  (unless (org-at-heading-p)
    (org-back-to-heading))
  (unless (org-part-of-drill-entry-p)
    (error "Point is not inside a drill entry"))
  (while (not (org-drill-entry-p))
    (unless (org-up-heading-safe)
      (error "Cannot find a parent heading that is marked as a drill entry"))))



(defun org-drill-entry-leech-p ()
  "Is the current entry a 'leech item'?"
  (and (org-drill-entry-p)
       (member "leech" (org-get-local-tags))))


(defun org-drill-entry-due-p ()
  (cond
   (*org-drill-cram-mode*
    (let ((hours (org-drill-hours-since-last-review)))
      (and (org-drill-entry-p)
           (or (null hours)
               (>= hours org-drill-cram-hours)))))
   (t
    (let ((item-time (org-get-scheduled-time (point))))
      (and (org-drill-entry-p)
           (or (not (eql 'skip org-drill-leech-method))
               (not (org-drill-entry-leech-p)))
           (or (null item-time)
               (not (minusp             ; scheduled for today/in future
                     (- (time-to-days (current-time))
                        (time-to-days item-time))))))))))


(defun org-drill-entry-new-p ()
  (and (org-drill-entry-p)
       (let ((item-time (org-get-scheduled-time (point))))
         (null item-time))))



(defun org-drill-entry-last-quality ()
  (let ((quality (org-entry-get (point) "DRILL_LAST_QUALITY")))
    (if quality
        (string-to-number quality)
      nil)))


;;; SM2 Algorithm =============================================================


(defun determine-next-interval-sm2 (last-interval n ef quality of-matrix)
  "Arguments:
- LAST-INTERVAL -- the number of days since the item was last reviewed.
- N -- the number of times the item has been successfully reviewed
- EF -- the 'easiness factor'
- QUALITY -- 0 to 5
- OF-MATRIX -- a matrix of values, used by SM5 but not by SM2.

Returns a list: (INTERVAL N EF OFMATRIX), where:
- INTERVAL is the number of days until the item should next be reviewed
- N is incremented by 1.
- EF is modified based on the recall quality for the item.
- OF-MATRIX is not modified."
  (assert (> n 0))
  (assert (and (>= quality 0) (<= quality 5)))
  (if (<= quality org-drill-failure-quality)
      ;; When an item is failed, its interval is reset to 0,
      ;; but its EF is unchanged
      (list -1 1 ef of-matrix)
    ;; else:
    (let* ((next-ef (modify-e-factor ef quality))
           (interval
            (cond
             ((<= n 1) 1)
             ((= n 2)
              (cond
               (org-drill-add-random-noise-to-intervals-p
                (case quality
                  (5 6)
                  (4 4)
                  (3 3)
                  (2 1)
                  (t -1)))
               (t 6)))
             (t (ceiling (* last-interval next-ef))))))
      (list (round
             (if org-drill-add-random-noise-to-intervals-p
                 (+ last-interval (* (- interval last-interval)
                                     (org-drill-random-dispersal-factor)))
               interval))
            (1+ n) next-ef of-matrix))))


;;; SM5 Algorithm =============================================================

;;; From http://www.supermemo.com/english/ol/sm5.htm
(defun org-drill-random-dispersal-factor ()
  (let ((a 0.047)
        (b 0.092)
        (p (- (random* 1.0) 0.5)))
    (flet ((sign (n)
                 (cond ((zerop n) 0)
                       ((plusp n) 1)
                       (t -1))))
      (/ (+ 100 (* (* (/ -1 b) (log (- 1 (* (/ b a ) (abs p)))))
                   (sign p)))
         100))))


(defun inter-repetition-interval-sm5 (last-interval n ef &optional of-matrix)
  (let ((of (get-optimal-factor n ef of-matrix)))
    (if (= 1 n)
	of
      (* of last-interval))))


(defun determine-next-interval-sm5 (last-interval n ef quality of-matrix)
  (assert (> n 0))
  (assert (and (>= quality 0) (<= quality 5)))
  (let ((next-ef (modify-e-factor ef quality))
        (interval nil))
    (setq of-matrix
          (set-optimal-factor n next-ef of-matrix
                              (modify-of (get-optimal-factor n ef of-matrix)
                                         quality org-learn-fraction))
          ef next-ef)

    (cond
     ;; "Failed" -- reset repetitions to 0,
     ((<= quality org-drill-failure-quality)
      (list -1 1 ef of-matrix))      ; Not clear if OF matrix is supposed to be
                                     ; preserved
     ;; For a zero-based quality of 4 or 5, don't repeat
     ((and (>= quality 4)
           (not org-learn-always-reschedule))
      (list 0 (1+ n) ef of-matrix))     ; 0 interval = unschedule
     (t
      (setq interval (inter-repetition-interval-sm5
                      last-interval n ef of-matrix))
      (if org-drill-add-random-noise-to-intervals-p
          (setq interval (+ last-interval
                            (* (- interval last-interval)
                               (org-drill-random-dispersal-factor)))))
      (list (round interval) (1+ n) ef of-matrix)))))


;;; Essentially copied from `org-learn.el', but modified to
;;; optionally call the SM2 function above.
(defun org-drill-smart-reschedule (quality)
  (interactive "nHow well did you remember the information (on a scale of 0-5)? ")
  (let* ((learn-str (org-entry-get (point) "LEARN_DATA"))
	 (learn-data (or (and learn-str
			      (read learn-str))
			 (copy-list initial-repetition-state)))
	 closed-dates)
    (setq learn-data
          (case org-drill-spaced-repetition-algorithm
            (sm5 (determine-next-interval-sm5 (nth 0 learn-data)
                                              (nth 1 learn-data)
                                              (nth 2 learn-data)
                                              quality
                                              (nth 3 learn-data)))
            (sm2 (determine-next-interval-sm2 (nth 0 learn-data)
                                              (nth 1 learn-data)
                                              (nth 2 learn-data)
                                              quality
                                              (nth 3 learn-data)))))
    (org-entry-put (point) "LEARN_DATA" (prin1-to-string learn-data))
    (cond
     ((= 0 (nth 0 learn-data))
      (org-schedule t))
     ((minusp (first learn-data))
      (org-schedule nil (current-time)))
     (t
      (org-schedule nil (time-add (current-time)
				  (days-to-time (nth 0 learn-data))))))))


(defun org-drill-hypothetical-next-review-date (quality)
  (let* ((learn-str (org-entry-get (point) "LEARN_DATA"))
	 (learn-data (or (and learn-str
			      (read learn-str))
			 (copy-list initial-repetition-state)))
	 closed-dates)
    (setq learn-data
          (case org-drill-spaced-repetition-algorithm
            (sm5 (determine-next-interval-sm5 (nth 0 learn-data)
                                              (nth 1 learn-data)
                                              (nth 2 learn-data)
                                              quality
                                              (nth 3 learn-data)))
            (sm2 (determine-next-interval-sm2 (nth 0 learn-data)
                                              (nth 1 learn-data)
                                              (nth 2 learn-data)
                                              quality
                                              (nth 3 learn-data)))))
    (cond
     ((not (plusp (nth 0 learn-data)))
      0)
     (t
      (nth 0 learn-data)))))


(defun org-drill-reschedule ()
  "Returns quality rating (0-5), or nil if the user quit."
  (let ((ch nil)
        (input nil)
        (next-review-date-3 (org-drill-hypothetical-next-review-date 3))
        (next-review-date-4 (org-drill-hypothetical-next-review-date 4))
        (next-review-date-5 (org-drill-hypothetical-next-review-date 5)))
    (save-excursion
      (while (not (memq ch '(?q ?e ?0 ?1 ?2 ?3 ?4 ?5)))
        (setq input (read-key-sequence
                     (if (eq ch ??)
                         (format "0-2 Means you have forgotten the item.
3-5 Means you have remembered the item.

0 - Completely forgot.
1 - Even after seeing the answer, it still took a bit to sink in.
2 - After seeing the answer, you remembered it.
3 - It took you awhile, but you finally remembered. (+%s days)
4 - After a little bit of thought you remembered. (+%s days)
5 - You remembered the item really easily. (+%s days)

How well did you do? (0-5, ?=help, e=edit, t=tags, q=quit)"
                                 next-review-date-3
                                 next-review-date-4
                                 next-review-date-5)
                       "How well did you do? (0-5, ?=help, e=edit, q=quit)")))
        (cond
         ((stringp input)
          (setq ch (elt input 0)))
         ((and (vectorp input) (symbolp (elt input 0)))
          (case (elt input 0)
            (up (ignore-errors (forward-line -1)))
            (down (ignore-errors (forward-line 1)))
            (left (ignore-errors (backward-char)))
            (right (ignore-errors (forward-char)))
            (prior (ignore-errors (scroll-down))) ; pgup
            (next (ignore-errors (scroll-up)))))  ; pgdn
         ((and (vectorp input) (listp (elt input 0))
               (eventp (elt input 0)))
          (case (car (elt input 0))
            (wheel-up (ignore-errors (mwheel-scroll (elt input 0))))
            (wheel-down (ignore-errors (mwheel-scroll (elt input 0)))))))
        (if (eql ch ?t)
            (org-set-tags-command))))
    (cond
     ((and (>= ch ?0) (<= ch ?5))
      (let ((quality (- ch ?0))
            (failures (org-entry-get (point) "DRILL_FAILURE_COUNT")))
        (save-excursion
          (org-drill-smart-reschedule quality))
        (push quality *org-drill-session-qualities*)
        (cond
         ((<= quality org-drill-failure-quality)
          (when org-drill-leech-failure-threshold
            (setq failures (if failures (string-to-number failures) 0))
            (org-set-property "DRILL_FAILURE_COUNT"
                              (format "%d" (1+ failures)))
            (if (> (1+ failures) org-drill-leech-failure-threshold)
                (org-toggle-tag "leech" 'on))))
         (t
          (let ((scheduled-time (org-get-scheduled-time (point))))
            (when scheduled-time
              (message "Next review in %d days"
                       (- (time-to-days scheduled-time)
                          (time-to-days (current-time))))
              (sit-for 0.5)))))
        (org-set-property "DRILL_LAST_QUALITY" (format "%d" quality))
        (org-set-property "DRILL_LAST_REVIEWED"
                          (time-to-inactive-org-timestamp (current-time)))
        quality))
     ((= ch ?e)
      'edit)
     (t
      nil))))


(defun org-drill-hide-all-subheadings-except (heading-list)
  "Returns a list containing the position of each immediate subheading of
the current topic."
  (let ((drill-entry-level (org-current-level))
        (drill-sections nil)
        (drill-heading nil))
    (org-show-subtree)
    (save-excursion
      (org-map-entries
       (lambda ()
         (when (= (org-current-level) (1+ drill-entry-level))
           (setq drill-heading (org-get-heading t))
           (unless (member drill-heading heading-list)
             (hide-subtree))
           (push (point) drill-sections)))
       "" 'tree))
    (reverse drill-sections)))



(defun org-drill-presentation-prompt (&rest fmt-and-args)
  (let* ((item-start-time (current-time))
         (input nil)
         (ch nil)
         (last-second 0)
         (prompt
          (if fmt-and-args
              (apply 'format
                     (first fmt-and-args)
                     (rest fmt-and-args))
            (concat "Press key for answer, "
                    "e=edit, t=tags, s=skip, q=quit."))))
    (setq prompt
          (format "%s %s %s %s %s"
                  (propertize
                   (number-to-string (length *org-drill-done-entries*))
                   'face `(:foreground ,org-drill-done-count-color)
                   'help-echo "The number of items you have reviewed this session.")
                  (propertize
                   (number-to-string (+ (length *org-drill-again-entries*)
                                        (length *org-drill-failed-entries*)))
                   'face `(:foreground ,org-drill-failed-count-color)
                   'help-echo (concat "The number of items that you failed, "
                                      "and need to review again."))
                  (propertize
                   (number-to-string (length *org-drill-mature-entries*))
                   'face `(:foreground ,org-drill-mature-count-color)
                   'help-echo "The number of old items due for review.")
                  (propertize
                   (number-to-string (length *org-drill-new-entries*))
                   'face `(:foreground ,org-drill-new-count-color)
                   'help-echo (concat "The number of new items that you "
                                      "have never reviewed."))
                  prompt))
    (if (and (eql 'warn org-drill-leech-method)
             (org-drill-entry-leech-p))
        (setq prompt (concat
                      (propertize "!!! LEECH ITEM !!!
You seem to be having a lot of trouble memorising this item.
Consider reformulating the item to make it easier to remember.\n"
                                  'face '(:foreground "red"))
                      prompt)))
    (while (memq ch '(nil ?t))
      (setq ch nil)
      (while (not (input-pending-p))
        (message (concat (format-time-string
                          "%M:%S " (time-subtract
                                   (current-time) item-start-time))
                         prompt))
        (sit-for 1))
      (setq input (read-key-sequence nil))
      (if (stringp input) (setq ch (elt input 0)))
      (if (eql ch ?t)
          (org-set-tags-command)))
    (case ch
      (?q nil)
      (?e 'edit)
      (?s 'skip)
      (otherwise t))))


(defun org-pos-in-regexp (pos regexp &optional nlines)
  (save-excursion
    (goto-char pos)
    (org-in-regexp regexp nlines)))


(defun org-drill-hide-clozed-text ()
  (save-excursion
    (while (re-search-forward org-drill-cloze-regexp nil t)
      ;; Don't hide org links, partly because they might contain inline
      ;; images which we want to keep visible
      (unless (org-pos-in-regexp (match-beginning 0)
                                 org-bracket-link-regexp 1)
        (org-drill-hide-matched-cloze-text)))))


(defun org-drill-hide-matched-cloze-text ()
  "Hide the current match with a 'cloze' visual overlay."
  (let ((ovl (make-overlay (match-beginning 0) (match-end 0))))
    (overlay-put ovl 'category
                 'org-drill-cloze-overlay-defaults)
    (when (find ?| (match-string 0))
      (overlay-put ovl
                   'display
                   (format "[...%s]"
                           (substring-no-properties
                            (match-string 0)
                            (1+ (position ?| (match-string 0)))
                            (1- (length (match-string 0)))))))))


(defun org-drill-unhide-clozed-text ()
  (save-excursion
    (dolist (ovl (overlays-in (point-min) (point-max)))
      (when (eql 'org-drill-cloze-overlay-defaults (overlay-get ovl 'category))
        (delete-overlay ovl)))))



;;; Presentation functions ====================================================

;; Each of these is called with point on topic heading.  Each needs to show the
;; topic in the form of a 'question' or with some information 'hidden', as
;; appropriate for the card type. The user should then be prompted to press a
;; key. The function should then reveal either the 'answer' or the entire
;; topic, and should return t if the user chose to see the answer and rate their
;; recall, nil if they chose to quit.

(defun org-drill-present-simple-card ()
  (with-hidden-cloze-text
   (org-drill-hide-all-subheadings-except nil)
   (org-display-inline-images t)
   (org-cycle-hide-drawers 'all)
   (prog1 (org-drill-presentation-prompt)
     (org-show-subtree))))


(defun org-drill-present-two-sided-card ()
  (with-hidden-cloze-text
   (let ((drill-sections (org-drill-hide-all-subheadings-except nil)))
     (when drill-sections
       (save-excursion
         (goto-char (nth (random (min 2 (length drill-sections)))
                         drill-sections))
         (org-show-subtree)))
     (org-display-inline-images t)
     (org-cycle-hide-drawers 'all)
     (prog1
         (org-drill-presentation-prompt)
       (org-show-subtree)))))



(defun org-drill-present-multi-sided-card ()
  (with-hidden-cloze-text
   (let ((drill-sections (org-drill-hide-all-subheadings-except nil)))
     (when drill-sections
       (save-excursion
         (goto-char (nth (random (length drill-sections)) drill-sections))
         (org-show-subtree)))
     (org-display-inline-images t)
     (org-cycle-hide-drawers 'all)
     (prog1
         (org-drill-presentation-prompt)
       (org-show-subtree)))))


(defun org-drill-present-multicloze ()
  (let ((item-end nil)
        (match-count 0)
        (body-start (or (cdr (org-get-property-block))
                        (point))))
    (org-drill-hide-all-subheadings-except nil)
    (save-excursion
      (outline-next-heading)
      (setq item-end (point)))
    (save-excursion
      (goto-char body-start)
      (while (re-search-forward org-drill-cloze-regexp item-end t)
        (incf match-count)))
    (when (plusp match-count)
      (save-excursion
        (goto-char body-start)
        (re-search-forward org-drill-cloze-regexp
                           item-end t (1+ (random match-count)))
        (org-drill-hide-matched-cloze-text)))
    (org-display-inline-images t)
    (org-cycle-hide-drawers 'all)
    (prog1 (org-drill-presentation-prompt)
      (org-show-subtree)
      (org-drill-unhide-clozed-text))))


(defun org-drill-present-spanish-verb ()
  (let ((prompt nil)
        (reveal-headings nil))
    (with-hidden-cloze-text
     (case (random 6)
       (0
        (org-drill-hide-all-subheadings-except '("Infinitive"))
        (setq prompt
              (concat "Translate this Spanish verb, and conjugate it "
                      "for the *present* tense.")
              reveal-headings '("English" "Present Tense" "Notes")))
       (1
        (org-drill-hide-all-subheadings-except '("English"))
        (setq prompt (concat "For the *present* tense, conjugate the "
                             "Spanish translation of this English verb.")
              reveal-headings '("Infinitive" "Present Tense" "Notes")))
       (2
        (org-drill-hide-all-subheadings-except '("Infinitive"))
        (setq prompt (concat "Translate this Spanish verb, and "
                             "conjugate it for the *past* tense.")
              reveal-headings '("English" "Past Tense" "Notes")))
       (3
        (org-drill-hide-all-subheadings-except '("English"))
        (setq prompt (concat "For the *past* tense, conjugate the "
                             "Spanish translation of this English verb.")
              reveal-headings '("Infinitive" "Past Tense" "Notes")))
       (4
        (org-drill-hide-all-subheadings-except '("Infinitive"))
        (setq prompt (concat "Translate this Spanish verb, and "
                             "conjugate it for the *future perfect* tense.")
              reveal-headings '("English" "Future Perfect Tense" "Notes")))
       (5
        (org-drill-hide-all-subheadings-except '("English"))
        (setq prompt (concat "For the *future perfect* tense, conjugate the "
                             "Spanish translation of this English verb.")
              reveal-headings '("Infinitive" "Future Perfect Tense" "Notes"))))
     (org-cycle-hide-drawers 'all)
     (prog1
         (org-drill-presentation-prompt prompt)
       (org-drill-hide-all-subheadings-except reveal-headings)))))



(defun org-drill-entry ()
  "Present the current topic for interactive review, as in `org-drill'.
Review will occur regardless of whether the topic is due for review or whether
it meets the definition of a 'review topic' used by `org-drill'.

Returns a quality rating from 0 to 5, or nil if the user quit, or the symbol
EDIT if the user chose to exit the drill and edit the current item.

See `org-drill' for more details."
  (interactive)
  (org-drill-goto-drill-entry-heading)
  ;;(unless (org-part-of-drill-entry-p)
  ;;  (error "Point is not inside a drill entry"))
  ;;(unless (org-at-heading-p)
  ;;  (org-back-to-heading))
  (let ((card-type (org-entry-get (point) "DRILL_CARD_TYPE"))
        (cont nil))
    (save-restriction
      (org-narrow-to-subtree)
      (org-show-subtree)
      (org-cycle-hide-drawers 'all)

      (let ((presentation-fn (cdr (assoc card-type org-drill-card-type-alist))))
        (cond
         (presentation-fn
          (setq cont (funcall presentation-fn)))
         (t
          (error "Unknown card type: '%s'" card-type))))

      (cond
       ((not cont)
        (message "Quit")
        nil)
       ((eql cont 'edit)
        'edit)
       ((eql cont 'skip)
        'skip)
       (t
        (save-excursion
          (org-drill-reschedule)))))))


;; (defun org-drill-entries (entries)
;;   "Returns nil, t, or a list of markers representing entries that were
;; 'failed' and need to be presented again before the session ends."
;;   (let ((again-entries nil))
;;     (setq *org-drill-done-entry-count* 0
;;           *org-drill-pending-entry-count* (length entries))
;;     (if (and org-drill-maximum-items-per-session
;;              (> (length entries)
;;                 org-drill-maximum-items-per-session))
;;         (setq entries (subseq entries 0
;;                               org-drill-maximum-items-per-session)))
;;     (block org-drill-entries
;;       (dolist (m entries)
;;         (save-restriction
;;           (switch-to-buffer (marker-buffer m))
;;           (goto-char (marker-position m))
;;           (setq result (org-drill-entry))
;;           (cond
;;            ((null result)
;;             (message "Quit")
;;             (return-from org-drill-entries nil))
;;            ((eql result 'edit)
;;             (setq end-pos (point-marker))
;;             (return-from org-drill-entries nil))
;;            (t
;;             (cond
;;              ((< result 3)
;;               (push m again-entries))
;;              (t
;;               (decf *org-drill-pending-entry-count*)
;;               (incf *org-drill-done-entry-count*)))
;;             (when (and org-drill-maximum-duration
;;                        (> (- (float-time (current-time)) *org-drill-start-time*)
;;                           (* org-drill-maximum-duration 60)))
;;               (message "This drill session has reached its maximum duration.")
;;               (return-from org-drill-entries nil))))))
;;       (or again-entries
;;           t))))


(defun org-drill-entries-pending-p ()
  (or *org-drill-again-entries*
      (and (not (org-drill-maximum-item-count-reached-p))
           (not (org-drill-maximum-duration-reached-p))
           (or *org-drill-new-entries*
               *org-drill-failed-entries*
               *org-drill-mature-entries*
               *org-drill-again-entries*))))


(defun org-drill-pending-entry-count ()
  (+ (length *org-drill-new-entries*)
     (length *org-drill-failed-entries*)
     (length *org-drill-mature-entries*)
     (length *org-drill-again-entries*)))


(defun org-drill-maximum-duration-reached-p ()
  "Returns true if the current drill session has continued past its
maximum duration."
  (and org-drill-maximum-duration
       *org-drill-start-time*
       (> (- (float-time (current-time)) *org-drill-start-time*)
          (* org-drill-maximum-duration 60))))


(defun org-drill-maximum-item-count-reached-p ()
  "Returns true if the current drill session has reached the
maximum number of items."
  (and org-drill-maximum-items-per-session
       (>= (length *org-drill-done-entries*)
           org-drill-maximum-items-per-session)))


(defun org-drill-pop-next-pending-entry ()
  (cond
   ;; First priority is items we failed in a prior session.
   ((and *org-drill-failed-entries*
         (not (org-drill-maximum-item-count-reached-p))
         (not (org-drill-maximum-duration-reached-p)))
    (pop-random *org-drill-failed-entries*))
   ;; Next priority is newly added items, and items which
   ;; are not new and were not failed when they were last
   ;; reviewed.
   ((and (or *org-drill-new-entries*
             *org-drill-mature-entries*)
         (not (org-drill-maximum-item-count-reached-p))
         (not (org-drill-maximum-duration-reached-p)))
    (if (< (random (+ (length *org-drill-new-entries*)
                      (length *org-drill-mature-entries*)))
           (length *org-drill-new-entries*))
        (pop-random *org-drill-new-entries*)
      ;; else
      (pop-random *org-drill-mature-entries*)))
   ;; After all the above are done, last priority is items
   ;; that were failed earlier THIS SESSION.
   (*org-drill-again-entries*
    (pop-random *org-drill-again-entries*))
   (t
    nil)))


(defun org-drill-entries ()
  "Returns nil, t, or a list of markers representing entries that were
'failed' and need to be presented again before the session ends."
  (block org-drill-entries
    (while (org-drill-entries-pending-p)
      (setq m (org-drill-pop-next-pending-entry))
      (unless m
        (error "Unexpectedly ran out of pending drill items"))
      (save-excursion
        (switch-to-buffer (marker-buffer m))
        (goto-char m)
        (setq result (org-drill-entry))
        (cond
         ((null result)
          (message "Quit")
          (return-from org-drill-entries nil))
         ((eql result 'edit)
          (setq end-pos (point-marker))
          (return-from org-drill-entries nil))
         ((eql result 'skip)
          nil)                          ; skip this item
         (t
          (cond
           ((<= result org-drill-failure-quality)
            (push m *org-drill-again-entries*))
           (t
            (push m *org-drill-done-entries*)))))))))



(defun org-drill-final-report ()
  (read-char-exclusive
   (format
    "%d items reviewed
%d items awaiting review (%s, %s, %s)
Session duration %s

Recall of reviewed items:
 Excellent (5):     %3d%%   |   Near miss (2):     %3d%%
 Good (4):          %3d%%   |   Failure (1):       %3d%%
 Hard (3):          %3d%%   |   Total failure (0): %3d%%

You successfully recalled %d%% of reviewed items (quality > %s)
Session finished. Press a key to continue..."
    (length *org-drill-done-entries*)
    (org-drill-pending-entry-count)
    (propertize
     (format "%d failed"
             (+ (length *org-drill-failed-entries*)
                (length *org-drill-again-entries*)))
     'face `(:foreground ,org-drill-failed-count-color))
    (propertize
     (format "%d old"
             (length *org-drill-mature-entries*))
     'face `(:foreground ,org-drill-mature-count-color))
    (propertize
     (format "%d new"
             (length *org-drill-new-entries*))
     'face `(:foreground ,org-drill-new-count-color))
    (format-seconds "%h:%.2m:%.2s"
                    (- (float-time (current-time)) *org-drill-start-time*))
    (round (* 100 (count 5 *org-drill-session-qualities*))
           (max 1 (length *org-drill-session-qualities*)))
    (round (* 100 (count 2 *org-drill-session-qualities*))
           (max 1 (length *org-drill-session-qualities*)))
    (round (* 100 (count 4 *org-drill-session-qualities*))
           (max 1 (length *org-drill-session-qualities*)))
    (round (* 100 (count 1 *org-drill-session-qualities*))
           (max 1 (length *org-drill-session-qualities*)))
    (round (* 100 (count 3 *org-drill-session-qualities*))
           (max 1 (length *org-drill-session-qualities*)))
    (round (* 100 (count 0 *org-drill-session-qualities*))
           (max 1 (length *org-drill-session-qualities*)))
    (round (* 100 (count-if (lambda (qual)
                              (> qual org-drill-failure-quality))
                            *org-drill-session-qualities*))
           (max 1 (length *org-drill-session-qualities*)))
    org-drill-failure-quality
    )))



(defun org-drill (&optional scope)
  "Begin an interactive 'drill session'. The user is asked to
review a series of topics (headers). Each topic is initially
presented as a 'question', often with part of the topic content
hidden. The user attempts to recall the hidden information or
answer the question, then presses a key to reveal the answer. The
user then rates his or her recall or performance on that
topic. This rating information is used to reschedule the topic
for future review using the `org-learn' library.

Org-drill proceeds by:

- Finding all topics (headings) in SCOPE which have either been
  used and rescheduled by org-learn before (i.e. the LEARN_DATA
  property is set), or which have a tag that matches
  `org-drill-question-tag'.

- All matching topics which are either unscheduled, or are
  scheduled for the current date or a date in the past, are
  considered to be candidates for the drill session.

- If `org-drill-maximum-items-per-session' is set, a random
  subset of these topics is presented. Otherwise, all of the
  eligible topics will be presented.

SCOPE determines the scope in which to search for
questions.  It is passed to `org-map-entries', and can be any of:

nil     The current buffer, respecting the restriction if any.
        This is the default.
tree    The subtree started with the entry at point
file    The current buffer, without restriction
file-with-archives
        The current buffer, and any archives associated with it
agenda  All agenda files
agenda-with-archives
        All agenda files with any archive files associated with them
 (file1 file2 ...)
        If this is a list, all files in the list will be scanned."

  (interactive)
  (let ((end-pos nil)
        (cnt 0))
    (block org-drill
      (setq *org-drill-done-entries* nil
            *org-drill-new-entries* nil
            *org-drill-mature-entries* nil
            *org-drill-failed-entries* nil
            *org-drill-again-entries* nil)
      (setq *org-drill-session-qualities* nil)
      (setq *org-drill-start-time* (float-time (current-time)))
      (unwind-protect
          (save-excursion
            (let ((org-trust-scanner-tags t))
              (org-map-entries
               (lambda ()
                 (when (zerop (% (incf cnt) 50))
                   (message "Processing drill items: %4d%s"
                            (+ (length *org-drill-new-entries*)
                               (length *org-drill-mature-entries*)
                               (length *org-drill-failed-entries*))
                            (make-string (ceiling cnt 50) ?.)))
                 (when (org-drill-entry-due-p)
                   (cond
                    ((org-drill-entry-new-p)
                     (push (point-marker) *org-drill-new-entries*))
                    ((and (org-drill-entry-last-quality)
                          (<= (org-drill-entry-last-quality)
                              org-drill-failure-quality))
                     (push (point-marker) *org-drill-failed-entries*))
                    (t
                     (push (point-marker) *org-drill-mature-entries*)))))
               (concat "+" org-drill-question-tag) scope))
            (cond
             ((and (null *org-drill-new-entries*)
                   (null *org-drill-failed-entries*)
                   (null *org-drill-mature-entries*))
              (message "I did not find any pending drill items."))
             (t
              (org-drill-entries)
              (message "Drill session finished!"))))
        ;; (cond
        ;; ((null entries)
        ;;  (message "I did not find any pending drill items."))
        ;; (t
        ;;  (let ((again t))
        ;;    (while again
        ;;      (when (listp again)
        ;;        (setq entries (shuffle-list again)))
        ;;      (setq again (org-drill-entries entries))
        ;;      (cond
        ;;       ((null again)
        ;;        (return-from org-drill nil))
        ;;       ((eql t again)
        ;;        (setq again nil))))
        ;;    (message "Drill session finished!")
        ;;    ))))
        (progn
          (dolist (m (append *org-drill-new-entries*
                             *org-drill-failed-entries*
                             *org-drill-again-entries*
                             *org-drill-mature-entries*))
            (free-marker m)))))
    (cond
     (end-pos
      (switch-to-buffer (marker-buffer end-pos))
      (goto-char (marker-position end-pos))
      (message "Edit topic."))
     (t
      (org-drill-final-report)))))


(defun org-drill-cram (&optional scope)
  "Run an interactive drill session in 'cram mode'. In cram mode,
all drill items are considered to be due for review, unless they
have been reviewed within the last `org-drill-cram-hours'
hours."
  (interactive)
  (let ((*org-drill-cram-mode* t))
    (org-drill scope)))



(add-hook 'org-mode-hook
          (lambda ()
            (if org-drill-use-visible-cloze-face-p
                (font-lock-add-keywords
                 'org-mode
                 org-drill-cloze-keywords
                 t))))



(provide 'org-drill)
Tip: Filter by directory path e.g. /media app.js to search for public/media/app.js.
Tip: Use camelCasing e.g. ProjME to search for ProjectModifiedEvent.java.
Tip: Filter by extension type e.g. /repo .js to search for all .js files in the /repo directory.
Tip: Separate your search with spaces e.g. /ssh pom.xml to search for src/ssh/pom.xml.
Tip: Use ↑ and ↓ arrow keys to navigate and return to view the file.
Tip: You can also navigate files with Ctrl+j (next) and Ctrl+k (previous) and view the file with Ctrl+o.
Tip: You can also navigate files with Alt+j (next) and Alt+k (previous) and view the file with Alt+o.