-
Notifications
You must be signed in to change notification settings - Fork 2
/
match-1-2.sls
590 lines (555 loc) · 24.2 KB
/
match-1-2.sls
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
#!r6rs
;; Copyright 2009 Derick Eddington. My MIT-style license is in the file named
;; LICENSE from the original collection this file is distributed with.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Destructuring binding pattern matcher by Derick Eddington
;;
;; Features:
;; - Regular expression matching against strings, with sub-group matching.
;; (Utilizes Alex Shinn's IrRegex library).
;; - Record matching, with field matching.
;; - Arbitrary predicate matching.
;; - "and", "or", and "not" matching.
;; - quasiquote patterns, with the unquote'd expressions evaluated as
;; normal expressions in the environment of the match expression.
;; - "..." sequence matching, with specifiable minimum and maximum.
;; - Multiple "..." in the same pattern.
;; - "..." works with, and the same for, every compound pattern type, i.e.,
;; regular expression with sub-group patterns, record with field patterns,
;; "and", "or", and "not", nested "..." patterns, and everything else.
;; - "(x ... . r)" pattern matches a possibly empty chain of pairs,
;; like syntax-case.
;; - Clean and tractable design. syntax-case eases implementation.
;; - The executed expanded form uses procedural abstraction instead of
;; generating redundant code.
;; - Efficient execution.
;; - Functional, i.e., no mutation.
;; - match-lambda does the main matching logic and the other forms are defined
;; in terms of it. This allows patterns' internal matchers to be initialized
;; only once per match-lambda expression evaluation, which for some patterns
;; can significantly improve efficiency when repeated calls to a match-lambda
;; procedure are done.
;;
;; Grammar:
;;
;; (match-lambda <clause> <clause> ...)
;; (match-lambda* <clause> <clause> ...)
;; (match <expr> <clause> <clause> ...)
;; (matches? <pat>)
;; (match-let ((<pat> <expr>) ...) <body>)
;; (match-let* ((<pat> <expr>) ...) <body>)
;;
;; <clause> ::= (<pat> <expr>)
;; | (<pat> <fender> <expr>)
;; <fender> ::= <expr>
;; <pat> Matches:
;; ::= _ Anything, does not bind
;; | <pat-var> Anything, bind variable
;; | <constant> Datum, according to equal?
;; | (quote <datum>) Datum, according to equal?
;; | (quasiquote <qq-template>) Datum, according to equal?
;; | () Empty list
;; | (<pat> . <pat>) Pair
;; | (<pat> <ooo> . <pat>) Chain of pairs, possibly empty
;; | #(<vec-pat> ...) Vector
;; | (:and <pat> ...) If all sub-patterns match value
;; | (:or <pat> ...) If any sub-pattern matches value
;; | (:not <pat>) If sub-pattern does not match value
;; | (:regex <irx> <pat> ...) String, if it matches the regular
;; expression and if the captured groups
;; (which are strings) match sub-patterns
;; | (:symbol <irx> <pat> ...) Symbol, if it matches the regular
;; expression and if the captured groups
;; (which are symbols) match sub-patterns
;; | (:record <r-type> <pat> ...) Record of specified type,
;; whose fields' values match sub-patterns
;; | (:predicate <expr>) If result of expression applied to value
;; returns true
;; <pat-var> ::= Any <identifier> except:
;; ... quote quasiquote :and :or :not
;; :regex :symbol :record :predicate
;; <constant> ::= <boolean> | <number> | <character>
;; | <string> | <bytevector>
;; <ooo> ::= ... | (... <integer>) | (... <integer> <integer>)
;; <vec-pat> ::= <pat> | <pat> <ooo>
;; <irx> ::= <expr> which evaluates to a valid irregex for Alex Shinn's
;; IrRegular Expressions library.
;; I.e., a string, SRE, or compiled irregex.
;; <r-type> ::= R6RS <record-name> handle for the record type. This gets
;; wrapped with record-type-descriptor.
;; | (RTD <expr>) where the expression evaluates to a first-class
;; record type descriptor
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(library (xitomatl match (1 2))
(export
match matches?
match-lambda match-lambda*
match-let match-let*)
(import
(rnrs)
(only (xitomatl irregex (or (0 (>= 7)) ((>= 1))))
irregex irregex-match irregex-match-substring irregex-num-submatches)
(only (xitomatl records)
record-type-accessors)
(for (only (xitomatl macro-utils)
identifier?/name=? name=? unique-ids?/raise)
expand)
(for (only (xitomatl indexes)
enumerate)
expand)
(for (only (xitomatl predicates)
exact-non-negative-integer? exact-positive-integer?)
expand))
(define-syntax match-lambda
(lambda (in-stx)
(define (keyword? pat-stx)
(and (identifier? pat-stx)
(exists (lambda (x) (name=? pat-stx x))
'(quote quasiquote :and :or :not
:regex :symbol :record :predicate ...))))
(define (ooo-range-valid? ooo-stx)
(syntax-case ooo-stx ()
((min max)
(let ((min (syntax->datum #'min))
(max (syntax->datum #'max)))
(and (exact-non-negative-integer? min)
(or (not max)
(and (exact-positive-integer? max)
(<= min max))))))))
(define (ooo? ooo-stx)
(syntax-case ooo-stx ()
((ooo min)
(and (identifier?/name=? #'ooo '...)
(ooo-range-valid? #'(min #F))))
((ooo min max)
(and (identifier?/name=? #'ooo '...)
(ooo-range-valid? #'(min max))))
(ooo
(identifier?/name=? #'ooo '...))
(_ #F)))
(define (ooo-range ooo-stx)
(syntax-case ooo-stx ()
((_ min) #'(min #F))
((_ min max) #'(min max))
(_ #'(0 #F))))
;; Used for :regex and :symbol
(define (P-regex M-obj who irx pats make-indexer)
(with-syntax ((num-pats (length pats))
((indexers ...) (map make-indexer (enumerate pats)))
(((M V ...) ...) (map P pats)))
#`((let ((irx-c (irregex #,irx))
(l-idxrs (list indexers ...))
(l-m (list M ...)))
(check-regex-patterns #,who num-pats irx-c)
(make-matcher #,M-obj irx-c l-idxrs l-m))
V ... ...)))
;; P does the core of the syntax logic. It is given a syntax object of
;; a match pattern. It returns a syntax object that is a list whose
;; first element is an expression which evaluates to a matcher procedure
;; and whose, possibly empty, remaining elements are identifiers of
;; pattern variables, in lexical left-to-right order, which are to be
;; bound by the pattern. P is used recursively as a recursive match
;; pattern is parsed.
(define (P pat-stx)
(syntax-case pat-stx ()
;; empty list
(()
#'(M-null))
;; anything, ignore, don't bind
(underscore
(identifier?/name=? #'underscore '_)
#'(M-ignore))
;; prevent misuse of pattern syntax keywords
(invalid
(keyword? #'invalid)
(syntax-violation 'match "misuse of pattern syntax" in-stx pat-stx))
;; anything, do bind
(var
(identifier? #'var)
#'(M-variable
var))
;; quote'd datum
((q datum)
(identifier?/name=? #'q 'quote)
#'((make-matcher M-datum (quote datum))))
;; quasiquote'd datum
((qq datum)
(identifier?/name=? #'qq 'quasiquote)
#'((let ((d (quasiquote datum)))
(make-matcher M-datum d))))
;; and
((:and pat ...)
(identifier?/name=? #':and ':and)
(with-syntax ((((M V ...) ...) (map P #'(pat ...))))
#'((let ((l-m (list M ...)))
(make-matcher M-and l-m))
V ... ...)))
;; or
((:or pat ...)
(identifier?/name=? #':or ':or)
(with-syntax ((((M V ...) ...) (map P #'(pat ...))))
(let ((Vs #'((V ...) ...)))
(when (positive? (length Vs))
(unless (let ((syms (map syntax->datum (car Vs))))
(for-all (lambda (x)
(equal? syms (map syntax->datum x)))
(cdr Vs)))
(syntax-violation 'match ":or pattern variables mismatch"
in-stx pat-stx)))
(with-syntax (((V ...) (if (positive? (length Vs))
(car Vs)
'())))
#'((let ((l-m (list M ...)))
(make-matcher M-or l-m))
V ...)))))
;; not
((:not pat)
(identifier?/name=? #':not ':not)
(with-syntax (((M V ...) (P #'pat)))
(when (positive? (length #'(V ...)))
(syntax-violation 'match ":not pattern contains variables"
in-stx pat-stx))
#'((let ((m M))
(make-matcher M-not m)))))
;; string, according to IrRegex regular expression
((:regex irx pat ...)
(identifier?/name=? #':regex ':regex)
(P-regex #'M-irregex ":regex"
#'irx #'(pat ...)
(lambda (i)
#`(lambda (m) (irregex-match-substring m #,(+ 1 i))))))
;; symbol, according to IrRegex regular expression
((:symbol irx pat ...)
(identifier?/name=? #':symbol ':symbol)
(P-regex #'M-symbol ":symbol"
#'irx #'(pat ...)
(lambda (i)
#`(lambda (m)
(let ((s (irregex-match-substring m #,(+ 1 i))))
(and s (string->symbol s)))))))
;; record
((:record rtype pat ...)
(and (identifier?/name=? #':record ':record)
(or (identifier? #'rtype)
(syntax-case #'rtype ()
((RTD _) (identifier?/name=? #'RTD 'RTD) #T)
(_ #F))))
(with-syntax ((rtd-expr
(syntax-case #'rtype ()
((_ x) #'x)
(x #'(record-type-descriptor x))))
(num-pats (length #'(pat ...)))
(((M V ...) ...) (map P #'(pat ...))))
#'((let ((rtd rtd-expr)
(l-m (list M ...)))
(let ((pred (record-predicate rtd))
(accessors (record-type-accessors rtd)))
(check-record-patterns num-pats accessors)
(make-matcher M-record pred accessors l-m)))
V ... ...)))
;; arbitrary predicate
((:predicate pred)
(identifier?/name=? #':predicate ':predicate)
#'((let ((p pred))
(make-matcher M-predicate p))))
;; multiple elements of, possibly empty, chain of pairs
((pat ooo . pat-rest)
(ooo? #'ooo)
(with-syntax
(((ooo-M ooo-V ...) (P #'pat))
((min max) (ooo-range #'ooo))
((rest-M rest-V ...) (P #'pat-rest)))
#`((let ((m-ooo ooo-M)
(m-rest rest-M))
(make-matcher M-pair-chain
m-ooo min max
(quote #,(map (lambda (_) '()) #'(ooo-V ...)))
m-rest))
ooo-V ... rest-V ...)))
;; prevent misuse of pattern syntax keywords
((invalid . _)
(keyword? #'invalid)
(syntax-violation 'match "misuse of pattern syntax" in-stx pat-stx))
;; pair / list / improper list
((pat-car . pat-cdr)
(with-syntax (((car-M car-V ...) (P #'pat-car))
((cdr-M cdr-V ...) (P #'pat-cdr)))
#'((let ((m-car car-M)
(m-cdr cdr-M))
(make-matcher M-pair m-car m-cdr))
car-V ... cdr-V ...)))
;; multiple elements of vector
(#(pat ...)
(let scan ((pats #'(pat ...)) (preceded #F))
(and (pair? pats)
(if (ooo? (car pats))
preceded
(scan (cdr pats) #T))))
(let-values
(((pats-preceding pat-ooo min max pats-rest)
(let scan ((pats #'(pat ...))
(preceding '()))
(let ((x (car pats)))
(if (ooo? x)
(with-syntax (((min max) (ooo-range x)))
(values (reverse (cdr preceding))
(car preceding) #'min #'max
(cdr pats)))
(scan (cdr pats)
(cons x preceding)))))))
(with-syntax
((p-len (length pats-preceding))
(((preceding-M preceding-V ...) ...) (map P pats-preceding))
((ooo-M ooo-V ...) (P pat-ooo))
((min max) (list min max))
;; NOTE: the rest is matched as a list
((rest-M rest-V ...) (P pats-rest)))
#`((let ((l-m-preceding (list preceding-M ...))
(m-ooo ooo-M)
(m-rest rest-M))
(make-matcher M-vector-ooo
p-len l-m-preceding
m-ooo min max
(quote #,(map (lambda (_) '()) #'(ooo-V ...)))
m-rest))
preceding-V ... ... ooo-V ... rest-V ...))))
;; vector
(#(pat ...)
(with-syntax ((len (length #'(pat ...)))
(((M V ...) ...) (map P #'(pat ...))))
#'((let ((l-m (list M ...)))
(make-matcher M-vector len l-m))
V ... ...)))
;; self-quoting datum
(const
#'((make-matcher M-datum const)))))
;; start transforming
(syntax-case in-stx ()
((_ clause0 clause ...)
(with-syntax
((((matcher fender-proc ... true-expr-proc) ...)
(map (lambda (c)
(syntax-case c ()
((pattern fender ... true-expr)
(<= (length #'(fender ...)) 1)
(with-syntax
(((M V ...) (P #'pattern)))
(unique-ids?/raise #'(V ...) in-stx)
#'(M
(lambda (V ...) fender) ...
(lambda (V ...) true-expr))))
(_ (syntax-violation 'match "invalid clause" in-stx c))))
#'(clause0 clause ...)))
((m ...) (generate-temporaries #'(clause0 clause ...))))
;; macro output
#'(let ((m matcher) ...)
(lambda (obj)
(cond
((do-matching m obj fender-proc ...)
=> (lambda (vars) (apply true-expr-proc vars)))
...
(else (failed-to-match obj))))))))))
(define-syntax do-matching
(syntax-rules ()
((_ matcher obj)
(let ((vars (matcher obj '())))
(and vars
(reverse vars))))
((_ matcher obj fender)
(let ((vars (matcher obj '())))
(and vars
(let ((vars (reverse vars)))
(and (apply fender vars)
vars)))))))
(define (AV msg . irrts)
(apply assertion-violation 'match msg irrts))
(define (check-regex-patterns who num-pats irx-c)
(let ((num-subs (irregex-num-submatches irx-c)))
(unless (= num-pats num-subs)
(AV (string-append who " sub-patterns mismatch sub-matches")
num-pats num-subs))))
(define (check-record-patterns num-pats accessors)
(let ((num-fields (length accessors)))
(unless (= num-pats num-fields)
(AV ":record sub-patterns mismatch fields" num-pats num-fields))))
(define (failed-to-match obj)
(AV "failed to match" obj))
;;------------------------------------------------------------------------
(define-syntax make-matcher
(syntax-rules ()
((_ M args ...)
(lambda (obj vars)
(M obj vars args ...)))))
;; `vars' in the below matchers is a list of the pattern variables' values,
;; in the reverse order the values are extracted when destructuring, i.e.,
;; accumulated in the order the values are extracted by cons'ing onto the
;; head of the list. This is also the reverse order of the variables'
;; identifiers lexical occurance in the entire compound pattern.
(define (M-null obj vars)
(and (null? obj)
vars))
(define (M-ignore obj vars)
vars)
(define (M-variable obj vars)
(cons obj vars))
(define (M-datum obj vars datum)
(and (equal? datum obj)
vars))
(define (M-and obj vars matchers)
(if (null? matchers)
vars
(let ((vars ((car matchers) obj vars)))
(and vars
(M-and obj vars (cdr matchers))))))
(define (M-or obj vars matchers)
(if (null? matchers)
#F
(let ((next-vars ((car matchers) obj vars)))
(or next-vars
(M-or obj vars (cdr matchers))))))
(define (M-not obj vars matcher)
(if (matcher obj '())
#F
vars))
(define (do-sub-matching obj procs matchers vars)
(if (null? matchers)
vars
(let ((vars ((car matchers) ((car procs) obj) vars)))
(and vars
(do-sub-matching obj (cdr procs) (cdr matchers) vars)))))
(define (M-irregex obj vars irx indexers matchers)
(and (string? obj)
(let ((m (irregex-match irx obj)))
(and m
(do-sub-matching m indexers matchers vars)))))
(define (M-symbol obj vars irx indexers matchers)
(and (symbol? obj)
(let ((m (irregex-match irx (symbol->string obj))))
(and m
(do-sub-matching m indexers matchers vars)))))
(define (M-record obj vars pred accessors matchers)
(and (pred obj)
(do-sub-matching obj accessors matchers vars)))
(define (M-predicate obj vars pred)
(and (pred obj)
vars))
(define (M-pair obj vars car-matcher cdr-matcher)
(and (pair? obj)
(let ((vars (car-matcher (car obj) vars)))
(and vars
(cdr-matcher (cdr obj) vars)))))
(define (do-match-vector vec i matchers vars)
(if (null? matchers)
vars
(let ((vars ((car matchers) (vector-ref vec i) vars)))
(and vars
(do-match-vector vec (+ 1 i) (cdr matchers) vars)))))
(define (M-vector obj vars len matchers)
(and (vector? obj)
(= len (vector-length obj))
(do-match-vector obj 0 matchers vars)))
(define (M-pair-chain obj vars
ooo-matcher min max
empty-ooo-vars
rest-matcher)
;; In order to match rest-matcher against the end of the chain, we must
;; work backwards across the chain of pairs (otherwise it might match
;; before the end). So we create a list of the pairs in reverse order
;; and use that. This is more effecient than the non-tail-recursive
;; solution of a function which immediately recurs forwards across the
;; chains and does the backwards work as the recursive calls return. The
;; stack space used by that solution significantly exceeds that of the
;; space used by the reversed chain list, and that solution does not
;; return as a tail-return because it must test each recursive call's
;; return value, which costs significantly more time.
(let match-last ((rev (let reverse-chain ((obj obj) (rev '()))
(if (pair? obj)
(reverse-chain (cdr obj) (cons obj rev))
(cons obj rev)))))
(and (pair? rev)
(let ((rest-vars (rest-matcher (car rev) '())))
(if rest-vars
(let match-ooo ((rev (cdr rev))
(accum-ooo-vars empty-ooo-vars)
(count 0))
(if (pair? rev)
(and (or (not max)
(< count max))
(let ((ooo-vars (ooo-matcher (caar rev) '())))
(and ooo-vars
(match-ooo (cdr rev)
(map cons ooo-vars accum-ooo-vars)
(+ 1 count)))))
(and (>= count min)
(append rest-vars
accum-ooo-vars
vars))))
(match-last (cdr rev)))))))
(define (M-vector-ooo obj vars
p-len preceding-matchers
ooo-matcher min max
empty-ooo-vars
rest-matcher)
(and (vector? obj)
(let ((obj-len (vector-length obj)))
(and (>= obj-len p-len)
(let ((vars (do-match-vector obj 0 preceding-matchers vars)))
(and vars
(let match-last ((last '())
(y (- obj-len 1)))
(let ((rest-vars (rest-matcher last '())))
(if rest-vars
(let match-ooo ((x y)
(accum-ooo-vars empty-ooo-vars)
(count 0))
(if (>= x p-len)
(and (or (not max)
(< count max))
(let ((ooo-vars
(ooo-matcher (vector-ref obj x) '())))
(and ooo-vars
(match-ooo (- x 1)
(map cons ooo-vars accum-ooo-vars)
(+ 1 count)))))
(and (>= count min)
(append rest-vars
accum-ooo-vars
vars))))
(and (>= y p-len)
(match-last (cons (vector-ref obj y) last)
(- y 1))))))))))))
;;------------------------------------------------------------------------
(define-syntax match
(syntax-rules ()
((_ expr clause0 clause ...)
((match-lambda clause0 clause ...) expr))))
(define-syntax matches?
(syntax-rules ()
((_ pattern)
(match-lambda (pattern #T) (_ #F)))))
(define-syntax match-lambda*
(syntax-rules ()
((_ clause ...)
(let ((m (match-lambda clause ...)))
(lambda x (m x))))))
(define-syntax match-let
(syntax-rules ()
((_ () body0 body ...)
(let () body0 body ...))
((_ ((pat expr)) body0 body ...)
(match expr
(pat
(let () body0 body ...))))
((_ ((pat expr) ...) body0 body ...)
(match (vector expr ...)
(#(pat ...)
(let () body0 body ...))))))
(define-syntax match-let*
(syntax-rules ()
((_ () body0 body ...)
(let () body0 body ...))
((_ ((pat0 expr0) (pat expr) ...) body0 body ...)
(match expr0
(pat0
(match-let* ((pat expr) ...) body0 body ...))))))
)