summary refs log tree commit diff
path: root/mew.scm
blob: 5828f36b3319686640c099e2e071567c9e1e75fb (plain) (blame)
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
(module mew
  (export
     act accumulate andloc at
     boolean
     comp cross-product
     dec def del-at div
     empty? eof esc
     fail fin final for fun*
     gconcatenate gen generator-xfold generic-for-each genumerate get
     gfix giterate gmatch gpick group-by-accumulator gslice-when
     gsplit gsplit-on gwindow
     imp inc inject into
     juxt
     keys
     len lines loc
     mod
     negate
     odometer one-of op op*
     per prn proj puts
     rand range rep
     sample scan scan-right sing? search seq set set-at
     shuffle shuffle! str slurp
     tally-accumulator tbl time
     while
     uniq-accumulator unlist until
     vals void?
     xcond xfold xfold-right xreduce xreduce-right xscan xscan-right
     -> fun-> fun->> set->
     =? <>?
     ~?
     => =>* and=> fun=> op=> set=>

     generic-make-accumulator)

  (import-for-syntax srfi-1)
  (import-for-syntax matchable)

  (import scheme
          (rename (chicken base)
             (print puts)
             (complement negate)
             (compose comp))
          (chicken condition)
          (chicken module)
          (chicken port)
          (chicken random)
          (chicken repl)
          (chicken syntax)
          srfi-17
          (rename (srfi-69)
             (hash-table-keys keys)
             (hash-table-values vals))
          srfi-158
          err)

  (reexport srfi-69)
  (reexport srfi-158)
  (reexport
    (rename (srfi-158)
      (circular-generator cycle)))
  (reexport matchable)
  (reexport
    (rename (matchable)
      (match-lambda match-fun)
      (match-lambda* match-fun*)))
  (reexport (chicken io))
  (reexport (chicken irregex))
  (reexport (chicken pretty-print))
  (reexport (chicken sort))
  (reexport
    (only (r7rs)
      list->vector
      vector-map))
  (reexport
    (only (chicken format)
      format))
  (reexport utf8-srfi-13)

  (reexport
    (only (chicken base)
      rec
      unless
      void
      when))

  (reexport
    (only (chicken time)
      time))

  (import
    (rename (r7rs)
      (floor-quotient div)
      (floor-remainder mod)))

  (reexport
    (rename (except (scheme)
               assoc
               member)
      (lambda fun)
      (apply app)
      (ceiling ceil)
      (truncate trunc)
      ))

  (reexport srfi-1)

  (reexport err)


  (define (inc i)
    (+ i 1))

  (define (dec i)
    (- i 1))

  (define (boolean x)
    (not (not x)))

  (define (tbl=? a b)
    (and (hash-table? a)
         (hash-table? b)
         (= (hash-table-size a) (hash-table-size b))
         (call-with-current-continuation
          (lambda (ret)
            (hash-table-for-each
             a
             (lambda (k v)
               ;; n.b. nan is never equal to anything
               (unless (=? (hash-table-ref/default b k +nan.0) v)
                 (ret #f))))
            #t))))

  (define =?
    (case-lambda
      (()  #t)
      ((_) #t)
      ((x y) (or (equal? x y)
                 (tbl=? x y)))
      ((x . rest) (every (lambda (y) (=? x y)) rest))))

  (define <>?
    (case-lambda
      ((a b) (not (=? a b)))
      ((a b c) (and (not (=? a b))
                    (not (=? b c))
                    (not (=? c a))))
      ((a b c d) (and (not (=? a b))
                      (not (=? a c))
                      (not (=? a d))
                      (not (=? b c))
                      (not (=? b d))
                      (not (=? c d))))
      ((a b c d . rest)
       (call-with-current-continuation
        (lambda (return)
          (let ((seen (tbl)))
            (for-each (lambda (o)
                        (when (hash-table-update!/default seen o not #t)
                          (return #f)))
                      (apply list a b c d rest)))
          #t)))
      ))

  (define (str . args)
    (with-output-to-string
      (lambda ()
        (for-each display args))))

  (define (prn . args)
    (let loop ((args args)
               (ret (void)))
      (if (null? args)
        (begin
          (newline)
          ret)
        (begin
          (write (car args))
          (unless (null? (cdr args))
            (display " "))
          (loop (cdr args) (car args))))))

  (define-syntax seq
    (syntax-rules ()
      ((_)
       (void))
      ((_ . rest)
       (begin . rest))))

  (define-syntax def
    (syntax-rules ()
      ((_ . rest)
       (define . rest))))

  (define-syntax set
    (syntax-rules ()
      ((_ id expr)
       (let ((val expr))
         (set! id val)
         val))))

  (define-syntax esc
    (syntax-rules ()
      ((_ return body ...)
       (receive vals (call-with-current-continuation
                      (lambda (return)
                        (seq body ...)))
         (if (null? vals)
           (void)
           (car vals))))))

  (define-syntax fin
    (syntax-rules ()
      ((_ form rest ...)
       (dynamic-wind
         (lambda () (begin))
         (lambda () form)
         (lambda () (seq rest ...))))))

  (define-syntax loc
    (syntax-rules ()
      ((_ () rest ...)
       (let () (seq rest ...)))
      ((_ (x y . brest) . rest)
       (match-let ((x y)) (loc brest . rest)))))

  (define-syntax andloc
    (syntax-rules (_)
      ((_ () rest ...)
       (let () (seq rest ...)))
      ((_ (_ y . brest) . rest)
       (let ((unused y)) (and unused (andloc brest . rest))))
      ((_ (x y . brest) . rest)
       (let ((x y)) (and x (andloc brest . rest))))))

  (define-syntax fun*
    (syntax-rules ()
      ((_ args body rest ...)
       (match-lambda* (args body rest ...)))))

  (define-syntax op
    (er-macro-transformer
      (lambda (expr rename compare)
        (match expr
          ((_) (rename 'values))
          ((_ x) `(,(rename 'lambda) ... ,x))
          ((_ . rest) `(,(rename 'lambda) (_) ,rest))))))

  (define-syntax op*
    (er-macro-transformer
     (lambda (expr rename compare)
       (when (= 1 (length expr))
         (syntax-error "op* needs at least one argument"))
       `(,(rename 'lambda) ...
         ,(receive (pre post) (break (lambda (x) (compare '... x)) (cdr expr))
            (match post
              (()      `(,(rename apply) ,@pre ...))
              ((x)     `(,(rename apply) ,@pre ...))
              ((x . y) `(,(rename apply) ,@pre
                         (,(rename append) ... (,(rename list) ,@y))))
              ))))))

  (define-syntax rep-internal
    (syntax-rules ()
      ((_ (bindings ...) name () (body ...))
       (let name (bindings ...) (seq body ...)))
      ((_ (bindings ...) name (x y brest ...) body)
       (rep-internal (bindings ... (x y)) name (brest ...) body))))

  (define-syntax rep
    (syntax-rules ()
      ((_ name (bindings ...) body ...)
       (rep-internal () name (bindings ...) (body ...)))))

  (define-syntax while
    (syntax-rules ()
      ((_ cond body ...)
       (let loop ((c cond))
         (if c
           (let ()
             body ...
             (loop cond)))))))

  (define-syntax until
    (syntax-rules ()
      ((_ cond body ...)
       (while (not cond) body ...))))

  (define-syntax xcond
    (syntax-rules ()
      ((_ rest ...)
       (cond rest ... (else (error "missing case in xcond"))))))

  (define (list-ref-default l i default)
    (if (null? l)
      default
      (if (zero? i)
        (car l)
        (list-ref-default (cdr l) (- i 1) default))))

  (define (vector-ref-default v i default)
    (if (< i (vector-length v))
        (vector-ref v i)
        default))

  (define (string-ref-default s i default)
    (if (< i (string-length s))
        (string-ref s i)
        default))

  (define get
    (case-lambda
      ((o k)
       (cond ((list? o) (list-ref o k))
             ((vector? o) (vector-ref o k))
             ((hash-table? o) (hash-table-ref o k))
             ((string? o) (string-ref o k))
             (#t (error "no at defined"))))
      ((o k default)
       (cond ((list? o) (list-ref-default o k default))
             ((vector? o) (vector-ref-default o k default))
             ((hash-table? o) (hash-table-ref/default o k default))
             ((string? o) (string-ref-default o k default))
             (#t (error "no at defined"))))))

  (define (get-setter o k v)
    (cond ; no list-set!
          ((vector? o) (vector-set! o k v))
          ((hash-table? o) (hash-table-set! o k v))
          ((string? o) (string-set! o k v))
          (#t (error "no set for at defined"))))

  (define at (getter-with-setter get get-setter))

  (define (plist-generator l)
    (lambda ()
      (cond ((null? l)        (eof))
            ((pair? (cdr l))  (let ((p (cons (car l) (cadr l))))
                                (set! l (cddr l))
                                p))
            (else
             (error "odd number of elements in key value list")))))

  (define tbl
    (case-lambda
      (()   (make-hash-table))
      (kvs  (into (tbl) (plist-generator kvs)))))

  (define (set-at o . rest)
    (cond ((hash-table? o) (generator-for-each
                            (lambda (kv) (hash-table-set! o (car kv) (cdr kv)))
                            (plist-generator rest)))
          ((vector? o)     (generator-for-each
                            (lambda (kv) (vector-set! o (car kv) (cdr kv)))
                            (plist-generator rest)))
          ((string? o)     (generator-for-each
                            (lambda (kv) (string-set! o (car kv) (cdr kv)))
                            (plist-generator rest)))
          (else            (error "no set-at defined")))
    o)

  (define (del-at o . rest)
    (cond ((hash-table? o) (for-each (lambda (k)
                                       (hash-table-delete! o k))
                                     rest))
          (else            (error "no del-at defined")))
    o)

  (define (empty? o)
    (or (null? o)
        (equal? o "")
        (equal? o #())
        (and (hash-table? o)
             (zero? (hash-table-size o)))))

  (define (empty o)
    (cond ((list? o) '())
          ((string? o) "")
          ((vector? o) #())
          ((hash-table? o) (tbl))
          (else "no empty defined")))

  (define (len o)
    (cond ((list? o) (length o))
          ((string? o) (string-length o))
          ((vector? o) (vector-length o))
          ((hash-table? o) (hash-table-size o))
          ((procedure? o) (generator-count (op #t) o))
          (#t (error "no len defined"))))

  (define (generic-for-each obj)
    (cond ((list? obj) for-each)
          ((vector? obj) vector-for-each)
          ((hash-table? obj) (lambda (f h)
                               (hash-table-for-each h (lambda (k v)
                                                        (f (cons k v))))))
          ((procedure? obj) generator-for-each)
          (#t (error "no generic-for-each defined"))))

  (define-syntax for
    (syntax-rules ()
      ((_ (i obj) body ...)
       (let ((o obj))
         ((generic-for-each o) (match-lambda (i body ...)) o)))))

  (define (eof) #!eof)

  (define (void? x)
    (eq? x (void)))

  (define rand
    (case-lambda
      (()    (pseudo-random-real))
      ((n)   (pseudo-random-integer n))
      ((n m) (+ n (pseudo-random-integer (- m n))))))

  (define (shuffle! v)
    (let loop ((i (- (vector-length v) 1)))
      (when (positive? i)
        (let* ((j (rand (+ i 1)))
               (vi (vector-ref v i))
               (vj (vector-ref v j)))
          (vector-set! v i vj)
          (vector-set! v j vi)
          (loop (dec i)))))
    v)

  (define (shuffle v)
    (let ((l (vector-length v)))
      (do ((res (make-vector l))
           (i 0 (+ i 1)))
          ((= i l) res)
        (let ((j (rand (+ i 1))))
          (unless (= j i)
            (vector-set! res i (vector-ref res j)))
          (vector-set! res j (vector-ref v i))))))

  (define sample
    (let ((gen-get (lambda (o)
                     (if (hash-table? o)
                       (lambda (n)
                         (esc ret
                           (let ((i 0))
                             (hash-table-for-each o
                                                  (lambda (k v)
                                                    (if (= i n)
                                                      (ret (cons k v))
                                                      (set! i (inc i))))))))
                       (lambda (n)
                         (get o n))))))
      (case-lambda
        ((o)
         ((gen-get o) (rand (len o))))
        ((o k)
         (cond
          ((= k 0)        (empty o))
          ((<= (len o) k) (let ((r (into #() o)))
                            (shuffle! r)
                            (if (vector? o)
                              r
                              (into (empty o) r))))
          (else
           ;; Algorithm L with additional shuffle at the end.
           ;; https://dl.acm.org/doi/pdf/10.1145/198429.198435
           (let ((geto (gen-get o))
                 (r (make-vector k))
                 (w (exp (/ (log (rand)) k)))
                 (n (len o))
                 (i 0))
             (while (< i k)
               (vector-set! r i (geto i))
               (set! i (inc i)))
             (while (< i n)
               (set! i (+ i 1 (inexact->exact (floor (/ (log (rand))
                                                        (log (- 1 w)))))))
               (when (< i n)
                 (vector-set! r (rand k) (geto i))
                 (set! w (* w (exp (/ (log (rand)) k))))))
             (shuffle! r)
             (if (vector? o)
               r
               (into (empty o) r)))))
         ))))

  (define range
    (case-lambda
      (()               (make-range-generator 0 +inf.0 1))
      ((start)          (make-range-generator start +inf.0 1))
      ((start end)      (make-range-generator start end 1))
      ((start end step) (set! start (- (+ start step) step))
                        (let ((cmp (if (>= step 0) < >)))
                          (lambda () (if (cmp start end)
                                       (let ((v start))
                                         (set! start (+ start step))
                                         v)
                                       (eof)))))))

  (define (gconcatenate gen)
    (let ((gen2 #f))
      (lambda ()
        (unless gen2
          (set! gen2 (gen)))
        (let loop ()
          (if (eof-object? gen2)
            gen2
            (let ((v (gen2)))
              (if (eof-object? v)
                (begin
                  (set! gen2 (gen))
                  (loop))
                v)))))))

  (define (gpick f gen)
    (lambda ()
      (let loop ((item (gen)))
        (if (eof-object? item)
          item
          (let ((v (f item)))
            (if (eof-object? v)
              (loop (gen))
              v))))))

  (define (gwindow gen n)
    (let ((window #f))
      (lambda ()
        (if (not window)
          (begin
            (set! window (generator->list gen n))
            (if (= (len window) n)
              window
              (eof)))
          (let ((next (gen)))
            (if (eof-object? next)
              (eof)
              (begin
                (set! window (append (cdr window) (list next)))
                window)))))))

  (define (gsplit-on pred gen)
    (let ((slice '())
          (this #f))
      (lambda ()
        (if (eof-object? this)
          this
          (let loop ()
            (set! this (gen))
            (if (eof-object? this)
              (if (null? slice)
                (eof)
                (reverse slice))
              (if (pred this)
                (let ((finished-slice (reverse slice)))
                  (set! slice '())
                  finished-slice)
                (begin
                  (set! slice (cons this slice))
                  (loop)))))))))

  (define (gslice-when pred gen)
    (let ((slice #f)
          (prev #f)
          (this #f))
      (lambda ()
        (unless slice
          (set! prev (gen))
          (when (eof-object? prev)
            (set! this (eof)))
          (set! slice (list prev)))
        (if (eof-object? this)
          this
          (let loop ()
            (set! this (gen))
            (if (eof-object? this)
              (reverse slice)
              (if (pred prev this)
                (let ((finished-slice (reverse slice)))
                  (set! slice (list this))
                  (set! prev this)
                  finished-slice)
                (begin
                  (set! slice (cons this slice))
                  (set! prev this)
                  (loop)))))))))

  (define (genumerate gen)
    (let ((n -1))
      (lambda ()
        (let ((val (gen)))
          (if (eof-object? val)
            val
            (begin
              (set! n (inc n))
              (cons n val)))))))

  (define (giterate f x)
    (make-unfold-generator (op #f) (op) f x))

  (define (gfix g)
    (let ((prev (void)))
      (gmap (lambda (x)
              (if (equal? prev x)
                (eof)
                (begin
                  (set! prev x)
                  x)))
            g)))

  (define (final g)
    (generator-fold (lambda (x a) x) (void) g))

  (define (odometer . wheels)
    (define (grepeat rep gen)
      (gconcatenate (gmap (lambda (item)
                            (gtake (cycle item) rep))
                          gen)))
    (if (null? wheels)
      (generator)
      (match-let (((total . parts) (scan-right * 1 wheels)))
        (gtake (apply gmap list (map (lambda (r i)
                                       (grepeat r (gmap (op mod _ i) (range 0))))
                                     parts wheels))
               total))))

  (define (cross-product . xs)
    (gmap (op map get xs _) (apply odometer (map len xs))))

  (define-syntax and-apply
    (syntax-rules ()
      ((_ x f args ...)
       (let ((v x))
         (if v
           (f v args ...)
           #f)))))

  (define-syntax and-apply-last
    (syntax-rules ()
      ((_ x f args ...)
       (let ((v x))
         (if v
           (f args ... v)
           #f)))))

  (define-syntax if-apply
    (syntax-rules ()
      ((_ expr bool (then . then-rest) (else . else-rest))
       (let ((val expr))
         (if bool
           (then val . then-rest)
           (else val . else-rest))))
      ((_ expr bool (then . then-rest) else)
       (if-apply expr bool (then . then-rest) (else)))
      ((_ expr bool then (else . else-rest))
       (if-apply expr bool (then) (else . else-rest)))
      ((_ expr bool then else)
       (if-apply expr bool (then) (else)))
      ((_ expr bool then)
       (if-apply expr bool then ((op))))
      ))

  (define-syntax if-apply-last
    (syntax-rules ()
      ((_ expr bool (then then-rest ...) (else else-rest ...))
       (let ((val expr))
         (if bool
           (then then-rest ... val)
           (else else-rest ... val))))
      ((_ expr bool (then . then-rest) else)
       (if-apply-last expr bool (then . then-rest) (else)))
      ((_ expr bool then (else . else-rest))
       (if-apply-last expr bool (then) (else . else-rest)))
      ((_ expr bool then else)
       (if-apply-last expr bool (then) (else)))
      ((_ expr bool then)
       (if-apply-last expr bool then ((op))))
      ))

  (define-syntax ok-apply
    (syntax-rules ()
      ((_ x f args ...)
       (let ((v x))
         (if (ok? v)
           (f v args ...)
           v)))))

  (define-syntax ok-apply-last
    (syntax-rules ()
      ((_ x f args ...)
       (let ((v x))
         (if (ok? v)
           (f args ... v)
           v)))))

  (define-syntax err-apply
    (syntax-rules ()
      ((_ x f args ...)
       (let ((v x))
         (if (err? v)
           (f (unerr v) args ...)
           v)))))

  (define-syntax err-apply-last
    (syntax-rules ()
      ((_ x f args ...)
       (let ((v x))
         (if (err? v)
           (f args ... (unerr v))
           v)))))

  (define-syntax ->
    (syntax-rules ()
      ((_ rest ...)
       (->chunk () () (rest ...)))))

  (define-syntax ->chunk
    (syntax-rules (-> ->> and-> and->> if-> if->> ok-> ok->> err-> err->>)
      ((_ (result ...) (current ...) (-> rest ...))
       (->chunk (result ... (current ...)) (->) (rest ...)))
      ((_ (result ...) (current ...) (->> rest ...))
       (->chunk (result ... (current ...)) (->>) (rest ...)))
      ((_ (result ...) (current ...) (and-> rest ...))
       (->chunk (result ... (current ...)) (-> and-apply) (rest ...)))
      ((_ (result ...) (current ...) (and->> rest ...))
       (->chunk (result ... (current ...)) (-> and-apply-last) (rest ...)))
      ((_ (result ...) (current ...) (if-> rest ...))
       (->chunk (result ... (current ...)) (-> if-apply) (rest ...)))
      ((_ (result ...) (current ...) (if->> rest ...))
       (->chunk (result ... (current ...)) (-> if-apply-last) (rest ...)))
      ((_ (result ...) (current ...) (ok-> rest ...))
       (->chunk (result ... (current ...)) (-> ok-apply) (rest ...)))
      ((_ (result ...) (current ...) (ok->> rest ...))
       (->chunk (result ... (current ...)) (-> ok-apply-last) (rest ...)))
      ((_ (result ...) (current ...) (err-> rest ...))
       (->chunk (result ... (current ...)) (-> err-apply) (rest ...)))
      ((_ (result ...) (current ...) (err->> rest ...))
       (->chunk (result ... (current ...)) (-> err-apply-last) (rest ...)))
      ((_ (result ...) (current ...) (a rest ...))
       (->chunk (result ...) (current ... a) (rest ...)))
      ((_ ((x) result ...) (current ...) ())
       (->thread x (result ... (current ...))))
      ((_ (x result ...) (current ...) ())
       (->thread x (result ... (current ...))))))

  (define-syntax ->thread
    (syntax-rules (-> ->>)
      ((_ result ((-> f args ...) rest ...))
       (->thread (f result args ...) (rest ...)))
      ((_ result ((->> f args ...) rest ...))
       (->thread (f args ... result) (rest ...)))
      ((_ result ())
       result)))

  (define-syntax fun->
    (syntax-rules ()
      ((_ rest ...)
       (lambda (x) (-> x -> rest ...)))))

  (define-syntax fun->>
    (syntax-rules ()
      ((_ rest ...)
       (lambda (x) (-> x ->> rest ...)))))

  (define-syntax set->
    (syntax-rules (-> ->> and-> and->> if-> if->> ok ok->> err-> err->>)
      ((_ location -> rest ...)
       (set! location (-> location -> rest ...)))
      ((_ location ->> rest ...)
       (set! location (-> location ->> rest ...)))
      ((_ location and-> rest ...)
       (set! location (-> location and-> rest ...)))
      ((_ location and->> rest ...)
       (set! location (-> location and->> rest ...)))
      ((_ location if-> rest ...)
       (set! location (-> location if-> rest ...)))
      ((_ location if->> rest ...)
       (set! location (-> location if->> rest ...)))
      ((_ location ok-> rest ...)
       (set! location (-> location ok-> rest ...)))
      ((_ location ok->> rest ...)
       (set! location (-> location ok->> rest ...)))
      ((_ location err-> rest ...)
       (set! location (-> location err-> rest ...)))
      ((_ location err->> rest ...)
       (set! location (-> location err->> rest ...)))
      ((_ location rest ...)            ; default to ->
       (set! location (-> location -> rest ...)))))

  (define (~? str pat)
    (let ((data (irregex-search pat str)))
      (if data
        (list-tabulate (inc (irregex-match-num-submatches data))
                       (op irregex-match-substring data _))
        #f)))

  (define (gmatch pat str)
    (let ((start 0))
      (lambda ()
        (if (<= 0 start (string-length str))
          (let ((data (irregex-search pat str start)))
            (if data
              (begin
                (set! start (irregex-match-end-index data 0))
                (when (= (irregex-match-start-index data 0)
                         (irregex-match-end-index data 0))
                  (set! start (inc start)))
                (if (> (irregex-match-num-submatches data) 0)
                  (list-tabulate (inc (irregex-match-num-submatches data))
                                 (op irregex-match-substring data _))
                  (irregex-match-substring data 0)))
              (begin
                (set! start -1)
                (eof))))
          (eof)))))

  (define (gsplit pat str . max)
    (let ((start 0)
          (n 1)
          (max (optional max -1)))
      (lambda ()
        (cond ((< start 0)   (eof))
              ((<= 0 max n)  (let ((s (substring str start)))
                               (set! start -1)
                               s))
              (else          (let ((data (irregex-search pat str start)))
                               (if data
                                 (let ((s (substring str start (irregex-match-start-index data 0))))
                                   (set! n (inc n))
                                   (if (equal? s "")
                                     (begin
                                       (set! s (substring str start (inc start)))
                                       (set! start (inc start)))
                                     (set! start (irregex-match-end-index data 0)))
                                   (when (= start (len str))
                                     (set! start -1))
                                   s)
                                 (begin
                                   (let ((s (substring str start)))
                                     (set! start -1)
                                     s)))))))))

  (define (slurp io)
    (cond ((not io)          (read-string #f (current-input-port)))
          ((input-port? io)  (read-string #f io))
          ((string? io)      (with-input-from-file io
                               (lambda ()
                                 (read-string #f (current-input-port)))))
          (else              (error "no slurp defined"))))

  (define lines
    (case-lambda
      (() read-line)
      ((x) (cond ((input-port? x)
                  (lambda ()
                    (read-line x)))
                 ((string? x)
                  (let ((file (open-input-file x)))
                    (lambda ()
                      (let ((line (read-line file)))
                        (when (eof-object? line)
                          (close-input-port file))
                        line))))
                 (else
                  (error "can't read lines"))))))

  (define (hash-table->generator h)
    (make-for-each-generator (lambda (f t)
                               (hash-table-for-each t (lambda (k v)
                                                        (f (cons k v)))))
                             h))

  (define (gen o . rest)
    (cond ((list? o)       (apply list->generator o rest))
          ((vector? o)     (apply vector->generator o rest))
          ((string? o)     (apply string->generator o rest))
          ((hash-table? o) (apply hash-table->generator o rest))
          ((procedure? o)  o)
          (else            (error "no gen defined"))))

  (define (generic-make-accumulator a)
    (cond ((procedure? a) a)
          ((list? a)      (make-accumulator cons (reverse a) reverse))
          ((vector? a)    (make-accumulator cons (reverse (vector->list a))
                                            (lambda (x)
                                              (list->vector (reverse x)))))
          ((hash-table? a) (make-accumulator (lambda (kv h)
                                               (hash-table-set! h (car kv) (cdr kv))
                                               h)
                                             a
                                             (op)))
          ((string? a)     (make-accumulator cons (reverse (string->list a))
                                             (lambda (lst) (list->string (reverse lst)))))
          (else            (error "no make-accumulator defined"))))

  (def (into acc . generators)
    (let ((acc (generic-make-accumulator acc))
          (gen (apply gappend (map gen generators))))
      (let loop ((val (gen)))
        (acc val)
        (if (not (eof-object? val))
          (loop (gen))
          (acc val)))))

  (define-syntax accumulate
    (syntax-rules ()
      ((_ (var init) body ...)
       (let ((var (generic-make-accumulator init)))
         body ...
         (var (eof))))))

  (define (tally-accumulator)
    (let ((tally (tbl)))
      (lambda (x)
        (if (eof-object? x)
            tally
            (hash-table-update!/default tally x inc 0)))))

  (define (group-by-accumulator f)
    (let ((groups (tbl)))
      (lambda (x)
        (if (eof-object? x)
            groups
            (hash-table-update!/default groups (f x) (op cons x _) '())))))

  (define uniq-accumulator
    (case-lambda
      (() (uniq-accumulator (op)))
      ((f) (let ((items (tbl)))
             (lambda (x)
               (if (eof-object? x)
                 (hash-table-values items)
                 (hash-table-update!/default items (f x) identity x)))))))

  (define (generator-xfold f seed . gs)
    (define (inner-xfold seed)
      (let ((vs (map (lambda (g) (g)) gs)))
        (if (any eof-object? vs)
          seed
          (inner-xfold (apply f seed vs)))))
    (inner-xfold seed))

  (define-syntax one-of
    (er-macro-transformer
     (lambda (expr rename compare)
       `(,(rename 'lambda) (x)
         (,(rename 'or) ,@(map (lambda (v)
                                 `(,(rename 'equal?) x ,v))
                               (cdr expr)))))))

  (define inject
    (case-lambda
      ((f) (lambda (o)
             (let* ((g (gen o))
                    (v (g)))
               (if (eof-object? v)
                 (f)
                 (generator-xfold f v g)))))
      ((f v) (lambda (o)
               (generator-xfold f v (gen o))))
      ((f v g)
       ((inject f v) (gen g)))))

  (define (sing? l)
    (match l
      ((_) #t)
      (_   #f)))

  (define (unlist args)
    (apply values args))

  (define (juxt . fs)
    (lambda args
      (unlist (map (lambda (f) (apply f args)) fs))))

  (define (per . args)
    (apply comp (reverse args)))

  (define (act x . fs)
    ((apply per fs) x))

  (define => act)

  (define-syntax =>*
    (syntax-rules ()
      ((_ expr . fs)
       (receive args expr
         (apply (per . fs) args)))))

  (define-syntax set=>
    (syntax-rules ()
      ((_ location . fs)
       (set location (=> location . fs)))))

  (define (and=> x . fs)
    (and x
         (if (null? fs)
           x
           (let ((result ((car fs) x)))
             (and result
                  (apply and=> result (cdr fs)))))))

  (define-syntax fun=>-inner
    (syntax-rules ()
      ((_ (acc ...))
       (compose acc ...))
      ((_ (acc ...) ,arg args ...)
       (fun=>-inner (arg acc ...) args ...))
      ((_ (acc ...) (arg ...) args ...)
       (fun=>-inner ((op arg ...) acc ...) args ...))
      ((_ (acc ...) arg args ...)
       (fun=>-inner (arg acc ...) args ...))
      ))

  (define-syntax fun=>
    (syntax-rules ()
      ((fun=> . args)
       (fun=>-inner () . args))))

  (define-syntax op=>
    (syntax-rules (_)
      ((op=> init . args)
       ((fun=> . args) init))))

  (define-syntax proj
    (er-macro-transformer
      (lambda (expr rename compare)
        (let* ((items (cdr expr))
               (max-n (if (null? items) 0 (+ 1 (apply max items))))
               (args (list-tabulate max-n
                                    (lambda (n)
                                      (string->symbol
                                       (string-append "x"
                                                      (number->string n)))))))
          `(,(rename 'lambda) (,@args . rest)
            (,(rename 'values) ,@(map (lambda (n) (list-ref args n)) items)))))))

  (define (fail exn . args)
    (if (list? exn)
      (signal (apply condition
                     (list (car exn) 'message (apply format args))
                     (map list (cdr exn))))
      (apply fail '(exn) exn args)))

  ;; The QuickSearch algorithm, for generic sequences
  ;; http://www-igm.univ-mlv.fr/~lecroq/string/node19.html#SECTION00190
  (define search
    (case-lambda
      ((needle haystack) (search needle haystack 0))
      ((needle haystack start)
       (let* ((lh (len haystack))
              (ln (len needle))
              (t  (into (tbl) (gmap (lambda (c i)
                                      (cons c (- ln i)))
                                    (gen needle)
                                    (range 0)))))
         (def (match? offset)
           (let loop ((i (dec ln)))
             (and (=? (at haystack (+ i offset)) (at needle i))
                  (or (zero? i)
                      (loop (dec i))))))

         (if (zero? ln)
           start
           (let loop ((i start))
             (if (<= i (- lh ln))
               (if (match? i)
                 i
                 (loop (+ i (get t (get haystack (+ i ln) #f) (inc ln)))))
               #f)))))))

  (define-syntax imp
    (syntax-rules ()
      ((_ a b)
       (or (not a) b))
      ((_ a b c ...)
       (or (not a) (imp b c ...)))))

  ;; adapted from https://code.call-cc.org/svn/chicken-eggs/release/5/srfi-1/trunk/srfi-1.scm ------------------------------
  (define (##srfi1#cars+cdrs lists)
    (##sys#call-with-current-continuation
     (lambda (abort)
       (let recur ((lists lists))
         (if (pair? lists)
	   (receive (list other-lists) (car+cdr lists)
	     (if (null-list? list)
               (abort '() '()) ; LIST is empty -- bail out
	       (receive (a d) (car+cdr list)
		 (receive (cars cdrs) (recur other-lists)
		   (values (cons a cars) (cons d cdrs))))))
	   (values '() '()))))))

  (define (##srfi1#cdrs lists)
    (##sys#call-with-current-continuation
     (lambda (abort)
       (let recur ((lists lists))
	 (if (pair? lists)
	   (let ((lis (car lists)))
	     (if (null-list? lis)
               (abort '())
	       (cons (cdr lis) (recur (cdr lists)))))
	   '())))))

  (define (xfold kons knil lis1 . lists)
    (if (pair? lists)
      (let lp ((lists (cons lis1 lists)) (ans knil))	; N-ary case
	(receive (cars cdrs) (##srfi1#cars+cdrs lists)
	  (if (null? cars)
            ans ; Done.
	    (lp cdrs (apply kons ans cars)))))

      (let lp ((lis lis1) (ans knil))			; Fast path
	(if (null-list? lis)
          ans
	  (lp (cdr lis) (kons ans (car lis)))))))

  (define (xfold-right kons knil lis1 . lists)
    (if (pair? lists)
      (let recur ((lists (cons lis1 lists)))		; N-ary case
        (let ((cdrs (##srfi1#cdrs lists)))
	  (if (null? cdrs)
            knil
	    (apply kons (recur cdrs) (map car lists)))))

      (let recur ((lis lis1))				; Fast path
	(if (null-list? lis)
          knil
	  (let ((head (car lis)))
	    (kons (recur (cdr lis)) head))))))

  (define (xreduce f ridentity lis)
    (if (null-list? lis)
      ridentity
      (xfold f (car lis) (cdr lis))))

  (define (xreduce-right f ridentity lis)
    (if (null-list? lis)
      ridentity
      (let recur ((head (car lis)) (lis (cdr lis)))
	(if (pair? lis)
	  (f (recur (car lis) (cdr lis)) head)
	  head))))
  ;; end of code lifted from srfi-1.scm ------------------------------

  (define (scan kons knil . lists)
    (reverse (apply xfold (lambda (acc . elts)
                            (cons (apply kons (append elts (list (car acc)))) acc))
                    (list knil)
                    lists)))

  (define (scan-right kons knil . lists)
    (apply xfold-right (lambda (acc . elts)
                         (cons (apply kons (append elts (list (car acc)))) acc))
           (list knil)
           lists))

  (define (xscan kons knil . lists)
    (reverse (apply xfold (lambda (acc . elts)
                           (cons (apply kons (car acc) elts) acc))
                    (list knil)
                    lists)))

  (define (xscan-right kons knil . lists)
    (apply xfold-right (lambda (acc . elts)
                         (cons (apply kons (car acc) elts) acc))
           (list knil)
           lists))

  (let ((old-repl-prompt (repl-prompt)))
    (repl-prompt (lambda ()
                   (let ((old-prompt (old-repl-prompt)))
                     (str (substring old-prompt 0 2)
                          "^_^;"
                          (substring old-prompt 2))))))

  (set-pseudo-random-seed! (random-bytes))
)