-
Notifications
You must be signed in to change notification settings - Fork 2
/
types.scm
689 lines (541 loc) · 19.9 KB
/
types.scm
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
;;; types
(define-record-type rtd/type-definition
(really-make-type-definition name ancestors defined super priority slots)
ykk-type?
;; definition
(name type-name)
(ancestors defined-ancestors)
(defined defined-slots)
;; computed
(super type-super)
(priority really-type-priority)
(pred type-instance-predicate set-type-instance-predicate!)
(slots type-slots))
(define-record-discloser rtd/type-definition
(lambda (type)
`(type ,(type-name type))))
(define (make-type-definition name ancestors slot-defs)
(initialize!
(let ((super (list (most-specific-common-superior ancestors))))
(really-make-type-definition
name
ancestors
slot-defs
super
(compute-priority super)
(inherit-slots (car super) slot-defs ancestors)))))
(define (initialize! new-type)
(set-type-instance-predicate! new-type (make-type-instance-predicate new-type))
new-type)
(define (make-type-instance-predicate type)
(lambda (foo)
(and (type-instance? foo)
(let ((i-type (instance-type foo)))
(or (identical-type? i-type type)
(strict-subtype? i-type type))))))
(define :ykk (initialize!
(really-make-type-definition
':ykk '() '() '() 0 '())))
(define :ykk-type rtd/type-definition)
;; MAYBE: could each SUPER possibly be an expression in the
;; module-configuration language?
(define-syntax type-definition
(syntax-rules ()
((_ (super ...) rest ...)
(type-definition #f (super ...) rest ...))
((_ name () rest ...)
(type-definition name (:ykk) rest ...))
((_ name (super ...) (slot-def ...) ...)
(make-type-definition
'name
(list super ...)
(make-slot-definitions (slot-def ...) ...)))))
(define-syntax define-type
(syntax-rules ()
((_ name (super ...) (slot-def ...) ...)
(define name (type-definition name (super ...) (slot-def ...) ...)))
((_ name (super ...) pred? (slot-def ...) ...)
(begin
(define-type name (super ...) (slot-def ...) ...)
(define pred? (type-instance-predicate name))))))
(define (inherit-slots super defs ancestors)
(receive (projection rest)
(project-slots-onto (merge-slots-by-name (append (map type-slots ancestors) (list defs)))
super)
(append projection rest)))
;; --------------------
;; from methods.scm
(define *increment* 10)
(define (compute-priority supers)
(if (null? supers)
0
(+ (apply max (map %type-priority supers))
*increment*)))
(define (more-specific-type? t1 t2)
(> (%type-priority t1) (%type-priority t2)))
;; --------------------
;;; predicates on types
(define-syntax define-meta-type-predicate
(syntax-rules ()
((_ name meta-pred?)
(define (name t1 t2)
(and (meta-pred? t1)
(meta-pred? t2))))))
(define-meta-type-predicate simple-types? simple-type?)
(define-meta-type-predicate record-types? record-type?)
(define-meta-type-predicate ykk-types? ykk-type?)
(define identical-type? eq?)
;; --------------------
;; strict subtype
;; Strict subtyping is meant in the "Liskov Substitution Principle"
;; sense. See http://okmij.org/ftp/Computation/Subtyping/
;; Strict subtyping is used to integrate ykk types with generic
;; dispatch.
(define (strict-subtype? t1 t2)
(and (or (%same-type? t1 t2)
(direct-descendant? t1 t2))))
;; --------------------
;; ancestor set predicates
(define (direct-descendant? t1 t2)
(find (cut %same-type? t2 <>) (ancestors t1)))
(define (ancestors<= t1 t2)
(ancestor-set-pred lset<= %same-type? t1 t2))
(define (ancestors-equal? t1 t2)
(ancestor-set-pred lset= %same-type? t1 t2))
(define (ancestor-set-pred lset-op pred? t1 t2)
(lset-op pred?
(ancestors t1)
(ancestors t2)))
;; --------------------
;; similar types
;; Can T1 be substituted for T2 in some form without generating any
;; logical-errors if that form is recompiled?
(define (%similar-type? t1 t2)
(or (identical-type? t1 t2)
;; FIXME: temporary kludge while ykk type top-level remains a simple-type
(and (ykk-type? t1) (identical-type? t2 :ykk))
(cond ((simple-types? t1 t2) (similar:simple? t1 t2))
((record-types? t1 t2) (similar:record? t1 t2))
((ykk-types? t1 t2) (similar:ykk? t1 t2))
(else (similar-type? t1 t2)))))
(define (similar:simple? t1 t2)
;; Trust that simple types do not violate a this assertion:
;;
;; ((type-predicate t2) instance-of-t1) ==> #t
;;
;; And, more generally, that INSTANCE-OF-T1 will not generate a run-time error
;; when it is passed to a procedure that accepts an argument of type T2.
(or (identical-type? t1 t2)
(%same-type? t1 t2)
(find-superior (cut %same-type? t2 <>)
(%type-superiors t1))))
(define (similar:record? t1 t2)
;; punt -- record accessors run through checked-record-ref, which
;; will error on any record instance not eq? in type to the one the
;; accessor is defined over.
(%same-type? t1 t2))
(define (similar:ykk? t1 t2)
;; YKK types have typed slots. Use these, namewise, as the basis of
;; type-equality comparison. Destructuring is based on slot names,
;; so slot order and superiors don't matter.
;;
;; All slot names in T2 must be present in T1. For each pair of
;; matching slots, the slot in T1 must be a similar to the slot in
;; T2.
(or (identical-type? t1 t2)
(identical-type? t2 :ykk)
(recursive-slot-type-assertion? %similar-type? t1 t2)))
(define (find-superior pred? supers)
(breadth-first pred? type-superiors supers))
(define (breadth-first pred? expand set)
(or (any pred? set)
(any (cut breadth-first pred? expand <>)
(map expand set))))
(define-syntax bind-joined
(syntax-rules (<>)
((_ (cut-expr ...) (join-expr ...))
(let ((joined (join-expr ...)))
(and joined
((cut cut-expr ...) joined))))))
(define (recursive-slot-type-assertion? pred? t1 t2)
(bind-joined
(every (joined-pred pred?) <>)
(join-all-slots->types t1 t2)))
(define (join-all-slots->types more-specific less-specific)
(bind-joined
(map-joined slot-type <>)
(join-all slot-name-eq? (type-slots more-specific) (type-slots less-specific))))
(define (join-all pred? larger-set smaller-set)
(call-with-current-continuation
(lambda (return)
(define (match item result)
(define (found-it matched)
(cons (list matched item)
result))
(cond ((find (cut pred? item <>) larger-set) => found-it)
(else (return #f))))
(fold match '() smaller-set))))
(define (joined-pred pred?)
(cut apply pred? <>))
(define (map-joined proc joined)
(map (cut map proc <>) joined))
;;; operations on types
(define (%type-priority t)
(if (ykk-type? t)
(really-type-priority t)
(type-priority t)))
(define (%type-superiors t)
(cond ((ykk-type? t) (type-super t))
(else (type-superiors t))))
(define (%same-type? t1 t2)
(or (identical-type? t1 t2)
(same-type? t1 t2)))
(define (ancestors-and-self t)
(cons t (ancestors t)))
(define (ancestors t)
(delete-duplicates (accumulate-superiors t) %same-type?))
(define (accumulate-superiors t)
(expanding-fold cons %type-superiors '() (%type-superiors t)))
(define (sort-by-specificity unique-types)
(insertion-sort more-specific-type? unique-types))
(define (most-specific-common-superior types)
(cond ((null? types)
'())
((null? (cdr types))
(car types))
(else
(most-specific-type
(apply-intersection %same-type? (map ancestors-and-self types))))))
(define (most-specific-type types)
(car (sort-by-specificity types)))
(define (type-slot-ref type name)
(find (lambda (slot) (eq? name (slot-name slot)))
(type-slots type)))
;; --------------------
;; utility
(define (insertion-sort > lst)
(fold (cut insert > <> <>)
'()
lst))
;; insert ITEM into LST, maintaining the invariant
;;
;; (apply > lst) ==> #t
(define (insert > item lst)
(if (null? lst)
(list item)
(receive (left right)
(partition (cut > <> item) lst)
(append left (cons item right)))))
;; depth-first expansion
(define (expanding-fold kons expand seed lst)
(define (recur item acc)
;; minor optimization: check for a non-null expansion before
;; making the recursive call.
(let ((expanded (expand item)))
(if (null? expanded)
acc
(expanding-fold kons expand acc expanded))))
(fold (lambda (item acc) (kons item (recur item acc)))
seed
lst))
(define (apply-intersection pred? sets)
(apply lset-intersection (cons pred? sets)))
;;; slots
(define-record-type rtd/slot-definition
(really-make-slot-definition name type initform)
slot-definition?
(name slot-name)
(type slot-type)
(initform slot-initform))
(define-record-discloser rtd/slot-definition
(lambda (def)
`(slot-definition ,(slot-name def) ,(slot-type def))))
(define-syntax define-slot
(syntax-rules ()
((_ name)
(define-slot name :value))
((_ name type)
(define-slot name type (undefined)))
((_ name type initform)
(really-make-slot-definition 'name type initform))))
(define-syntax make-slot-definitions
(syntax-rules ()
((_ (def ...) ...)
(slot-definitions->type-definition-slots
(list (define-slot def ...) ...)))))
;;; operations on slots
(define (project-slots-onto slots type)
(project-slots-onto-names slots (map slot-name (type-slots type))))
(define (project-slots-onto-names slots names)
(define (find-name slot)
(memq (slot-name slot) names))
(define (find-slot name slots)
(find (lambda (slot)
(eq? name (slot-name slot)))
slots))
(receive (matched unmatched)
(partition find-name slots)
(values (map (cut find-slot <> matched) names)
unmatched)))
(define (merge-slots-by-name slot-sets)
(map merge-slot-group (group-slots-by-name slot-sets)))
(define (merge-slot-group slot-group)
(define (error slot continue-with-value . error-args)
(nonfatal-continue
continue-with-value
(apply type-error `(,@error-args
(bad-slot: ,slot)
(last-good-value: ,continue-with-value)
(group: ,slot-group)))))
(define (choose-name slot name)
(if (or (not name) (eq? name (slot-name slot)))
(slot-name slot)
(error slot name "merge-slot-group: inconsistent name")))
(define (choose-type slot type)
(cond ((not type) (slot-type slot))
((strict-subtype? type (slot-type slot)) type)
(else
(error slot type "merge-slot-group: not a strict supertype"))))
(define (choose-initform slot form)
(if (undefined? form)
(slot-initform slot)
form))
(apply really-make-slot-definition
(fold (lambda (slot template)
(list (choose-name slot (car template))
(choose-type slot (cadr template))
(choose-initform slot (caddr template))))
(list #f #f (undefined))
slot-group)))
(define (group-slots-by-name slot-sets)
(ordered-groups slot-name-eq?
slot-more-specific?
slot-sets))
(define (slot-name-eq? s1 s2)
(eq? (slot-name s1) (slot-name s2)))
(define (slot-more-specific? s1 s2)
(more-specific-type? (slot-type s1) (slot-type s2)))
;; --------------------
;; utility
(define (ordered-groups = > relations)
(define (insert-one item groups)
(cond ((null? groups)
(cons (list item) groups))
((= item (caar groups))
(cons (insert > item (car groups))
(cdr groups)))
(else
(cons (car groups)
(insert-one item (cdr groups))))))
(define (group-one rel groups)
(fold insert-one groups rel))
(fold group-one '() relations))
;;; type instances
(define-record-type rtd/type-instance
(make-type-instance type values)
type-instance?
(type instance-type)
(values instance-values))
(define-record-discloser rtd/type-instance
(lambda (instance)
`(instance of ,(type-name (instance-type instance)))))
(define-syntax new
(syntax-rules ()
((_ type args ...)
(make-type-instance
type
(fold-slot-values type (list args ...))))))
;; FOLD-SLOT-VALUES -- check the arguments about to be applied to the
;; constructor, interspersing initforms where necessary.
(define (fold-slot-values type arguments)
(let loop ((defs (type-slots type))
(arguments arguments)
(all-arguments '()))
(cond ((and (null? arguments)
(null? defs))
(reverse all-arguments))
((null? defs)
(nonfatal-continue
(loop '() '() all-arguments)
(type-error "fold-slot-values: too many arguments for type"
`(arguments ,arguments)
type)))
((has-init-form? (car defs))
(loop (cdr defs)
arguments
(cons (eval-initform (car defs))
all-arguments)))
((null? arguments)
(nonfatal-continue
(loop '() '() all-arguments)
(type-error "fold-slot-values: missing arguments for type"
`(arguments ,(map slot-name defs))
type)))
(else
(let ((slot (car defs)))
(loop (cdr defs)
(cdr arguments)
(cons (assert-type slot (car arguments))
all-arguments)))))))
(define (eval-initform slot)
;; FIXME: punt for now
(slot-initform slot))
(define (assert-type slot value)
(if ((type-predicate (slot-type slot)) value)
value
(nonfatal-continue
value
(type-error "assert-type failed: value is not an instance of type"
`(value: ,value)
`(type: ,(slot-type slot))
slot))))
(define-syntax define-updater
(syntax-rules (update)
((_ (proc-name formals ...) (instance type) (name value) ...)
(define proc-name
(let ((slot-name-check (delay (remove (cute memq <> (map slot-name (type-slots type))) '(name ...))))
(pred? (type-predicate type)))
(lambda (formals ...)
;; This first check is to make sure that the names from the
;; (NAME VALUE) pairs are all good (i.e. actual slot
;; names). Only do the work once.
(let ((bad (force slot-name-check)))
(if (not (null? bad)) (type-error 'slots-do-not-exist 'proc-name bad)))
;; The next check is to make sure the instance passed in
;; consistent with the type the updater is defined over.
(if (not (pred? instance))
(type-error 'updater-argument-not-proper-type 'proc-name type instance))
;; Finally, do the actual update.
(update-type-instance instance (cons 'name value) ...)))))))
(define (update-type-instance instance . new-slot-values)
(share instance
instance-values
(cut shared-update instance <> new-slot-values)
(cut make-type-instance (instance-type instance) <>)))
(define (shared-update instance values new-values)
(shared:map2 (lambda (value slot)
(cond ((assq (slot-name slot) new-values)
=> (lambda (pair) (assert-type slot (cdr pair))))
(else value)))
values
(type-slots (instance-type instance))))
;;; integration with METHODS
(define simple-type (record-ref :value 0))
(define (simple-type? foo)
(and (record? foo)
(eq? (record-ref foo 0) simple-type)))
(define-method &type-predicate ((type rtd/type-definition))
(type-instance-predicate type))
(define-method &type-superiors ((type rtd/type-definition))
(type-super type))
(define-method &type-priority ((type rtd/type-definition))
(really-type-priority type))
(define-generic similar-type? &similar-type? (t1 t2))
(define-method &similar-type? ((t1 :simple-type) (t2 :simple-type))
(similar:simple? t1 t2))
(define-method &similar-type? ((t1 :record-type) (t2 :simple-type))
(similar:record? t1 t2))
(define-method &similar-type? ((t1 rtd/type-definition) (t2 rtd/type-definition))
(similar:ykk? t1 t2))
;;; operations on type instances and slots
(define (undefined) undefined)
(define (undefined? foo) (eq? foo undefined))
(define (has-init-form? slot-def)
(not (undefined? (slot-initform slot-def))))
(define (slot-definitions->type-definition-slots definitions)
definitions)
(define (slot-names instance)
(map slot-name (type-slots (instance-type instance))))
(define (slot-types instance)
(map (lambda (slot-def)
(slot-type slot-def))
(type-slots (instance-type instance))))
(define (instance-ref instance name)
(instance-lookup-ref (instance-lookup instance) name))
(define-syntax unstructure
(syntax-rules ()
((_ instance name ...)
(really-unstructure instance '(name ...)))))
(define (really-unstructure instance names)
(apply values
(if (null? names)
(instance-values instance)
(unstructure-pattern (instance-lookup instance) '() names))))
(define (unstructure-pattern lookup seed names)
(fold-right (lambda (name acc)
(if (not (pair? name))
(cons (instance-lookup-ref lookup name) acc)
(let ((nested (instance-lookup-ref lookup (car name))))
(unstructure-pattern (instance-lookup nested)
acc
(cdr name)))))
seed
names))
(define (instance-lookup instance)
(zip (slot-names instance) (instance-values instance)))
(define (instance-lookup-ref lookup name)
(cond ((assq name lookup) => cadr)
(else (type-error 'slot-not-found name))))
;;; auxiliary
(define-condition
type-error (syntax-error)
type-error?)
(define-condition
type-warning (warning)
type-warning?)
(define-syntax nonfatal-continue
(syntax-rules ()
((_ continue-form warn-form)
(begin warn-form continue-form))))
;;; tests
;; --------------------
;; instances
(begin
;; --------------------
;; construction
(define-type :foo ()
(a :symbol 'a-value) (b))
(let ((inst (new :foo 'b-value)))
(assert (instance-values inst) => `(a-value b-value))
(assert (instance-ref inst 'a) => 'a-value))
(let ((a b (unstructure (new :foo (new :foo 'b-value)) a (b b))))
(assert a => 'a-value)
(assert b => 'b-value))
;; --------------------
;; updates
(define-updater (update-foo foo new-a-value)
(foo :foo) (a new-a-value))
(assert (instance-values (update-foo (new :foo 'b-value) 'a)) => `(a b-value)))
;; --------------------
;; generics
(begin
(assert (similar:simple? :real :number))
(assert (similar:simple? :number :real) => #f)
(define-type :food ()
(name :string))
(define-type :spice (:food)
(hot? :boolean))
(define-type :fruit (:food)
(tropical? :boolean))
(define-type :cinnamon (:spice)
(hot? :boolean #t))
(define-type :apple (:fruit)
(tropical? :boolean #f))
(define-type :pie (:apple :cinnamon)
(name :string "apple-cinnamon"))
(define-type :pastry (:food)
(hot? :boolean)
(frosting-flavor :symbol))
(assert (similar-type? :pastry :spice))
(assert (not (similar-type? :pie :pastry)))
(assert (direct-descendant? :pie :food))
(assert (not (direct-descendant? :pie :apple)))
(assert (strict-subtype? :pie :food))
(assert (not (strict-subtype? :pastry :cinnamon)))
(assert (not (strict-subtype? :pastry :pie)))
(define-generic cook &cook)
(define-method &cook (v) "I don't know how")
(define-method &cook ((v :apple)) "roast it")
(assert (cook (new :pie)) => "I don't know how")
(assert (cook (new :apple "apple sauce")) => "roast it")
(assert (cook (new :pastry "cinnamon roll" #t 'caramel)) => "I don't know how"))