1 ;;; GNU Guix --- Functional package management for GNU
2 ;;; Copyright © 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019 Ludovic Courtès <ludo@gnu.org>
3 ;;; Copyright © 2018 Mark H Weaver <mhw@netris.org>
5 ;;; This file is part of GNU Guix.
7 ;;; GNU Guix is free software; you can redistribute it and/or modify it
8 ;;; under the terms of the GNU General Public License as published by
9 ;;; the Free Software Foundation; either version 3 of the License, or (at
10 ;;; your option) any later version.
12 ;;; GNU Guix is distributed in the hope that it will be useful, but
13 ;;; WITHOUT ANY WARRANTY; without even the implied warranty of
14 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 ;;; GNU General Public License for more details.
17 ;;; You should have received a copy of the GNU General Public License
18 ;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
20 (define-module (guix records)
21 #:use-module (srfi srfi-1)
22 #:use-module (srfi srfi-9)
23 #:use-module (srfi srfi-26)
24 #:use-module (ice-9 match)
25 #:use-module (ice-9 regex)
26 #:use-module (ice-9 rdelim)
27 #:export (define-record-type*
35 ;;; Utilities for dealing with Scheme records.
39 (define-syntax record-error
41 "Report a syntactic error in use of CONSTRUCTOR."
42 ((_ constructor form fmt args ...)
43 (syntax-violation constructor
44 (format #f fmt args ...)
47 (eval-when (expand load eval)
48 ;; The procedures below are needed both at run time and at expansion time.
50 (define (current-abi-identifier type)
51 "Return an identifier unhygienically derived from TYPE for use as its
52 \"current ABI\" variable."
53 (let ((type-name (syntax->datum type)))
57 (string-append "% " (symbol->string type-name)
60 (define (abi-check type cookie)
61 "Return syntax that checks that the current \"application binary
62 interface\" (ABI) for TYPE is equal to COOKIE."
63 (with-syntax ((current-abi (current-abi-identifier type)))
64 #`(unless (eq? current-abi #,cookie)
65 ;; The source file where this exception is thrown must be
67 (throw 'record-abi-mismatch-error 'abi-check
68 "~a: record ABI mismatch; recompilation needed"
71 (define (report-invalid-field-specifier name bindings)
72 "Report the first invalid binding among BINDINGS."
73 (let loop ((bindings bindings))
74 (syntax-case bindings ()
75 (((field value) rest ...) ;good
77 ((weird _ ...) ;weird!
78 (syntax-violation name "invalid field specifier" #'weird)))))
80 (define (report-duplicate-field-specifier name ctor)
81 "Report the first duplicate identifier among the bindings in CTOR."
84 (let loop ((bindings #'(bindings ...))
86 (syntax-case bindings ()
87 (((field value) rest ...)
88 (not (memq (syntax->datum #'field) seen))
89 (loop #'(rest ...) (cons (syntax->datum #'field) seen)))
91 (syntax-violation name "duplicate field initializer"
96 (define-syntax make-syntactic-constructor
98 "Make the syntactic constructor NAME for TYPE, that calls CTOR, and
99 expects all of EXPECTED fields to be initialized. DEFAULTS is the list of
100 FIELD/DEFAULT-VALUE tuples, THUNKED is the list of identifiers of thunked
101 fields, and DELAYED is the list of identifiers of delayed fields.
103 ABI-COOKIE is the cookie (an integer) against which to check the run-time ABI
104 of TYPE matches the expansion-time ABI."
105 ((_ type name ctor (expected ...)
106 #:abi-cookie abi-cookie
113 (define (record-inheritance orig-record field+value)
114 ;; Produce code that returns a record identical to ORIG-RECORD,
115 ;; except that values for the FIELD+VALUE alist prevail.
116 (define (field-inherited-value f)
117 (and=> (find (lambda (x)
118 (eq? f (car (syntax->datum x))))
122 ;; Make sure there are no unknown field names.
123 (let* ((fields (map (compose car syntax->datum) field+value))
124 (unexpected (lset-difference eq? fields '(expected ...))))
125 (when (pair? unexpected)
126 (record-error 'name s "extraneous field initializers ~a"
129 #`(make-struct/no-tail type
130 #,@(map (lambda (field index)
131 (or (field-inherited-value field)
132 (if (innate-field? field)
134 field (field-default-value field))
135 #`(struct-ref #,orig-record
138 (iota (length '(expected ...))))))
140 (define (thunked-field? f)
141 (memq (syntax->datum f) 'thunked))
143 (define (delayed-field? f)
144 (memq (syntax->datum f) 'delayed))
146 (define (innate-field? f)
147 (memq (syntax->datum f) 'innate))
149 (define (wrap-field-value f value)
150 (cond ((thunked-field? f)
151 #`(lambda () #,value))
156 (define default-values
157 ;; List of symbol/value tuples.
160 (list (syntax->datum f) v)))
163 (define (field-default-value f)
164 (car (assoc-ref default-values (syntax->datum f))))
166 (define (field-bindings field+value)
167 ;; Return field to value bindings, for use in 'let*' below.
168 (map (lambda (field+value)
169 (syntax-case field+value ()
172 #,(wrap-field-value #'field #'value)))))
175 (syntax-case s (inherit expected ...)
176 ((_ (inherit orig-record) (field value) (... ...))
177 #`(let* #,(field-bindings #'((field value) (... ...)))
178 #,(abi-check #'type abi-cookie)
179 #,(record-inheritance #'orig-record
180 #'((field value) (... ...)))))
181 ((_ (field value) (... ...))
182 (let ((fields (map syntax->datum #'(field (... ...)))))
183 (define (field-value f)
184 (or (find (lambda (x)
185 (eq? f (syntax->datum x)))
187 (wrap-field-value f (field-default-value f))))
189 ;; Pass S to make sure source location info is preserved.
190 (report-duplicate-field-specifier 'name s)
192 (let ((fields (append fields (map car default-values))))
193 (cond ((lset= eq? fields '(expected ...))
194 #`(let* #,(field-bindings
195 #'((field value) (... ...)))
196 #,(abi-check #'type abi-cookie)
197 (ctor #,@(map field-value '(expected ...)))))
198 ((pair? (lset-difference eq? fields
200 (record-error 'name s
201 "extraneous field initializers ~a"
202 (lset-difference eq? fields
205 (record-error 'name s
206 "missing field initializers ~a"
210 ((_ bindings (... ...))
211 ;; One of BINDINGS doesn't match the (field value) pattern.
212 ;; Report precisely which one is faulty, instead of letting the
213 ;; "source expression failed to match any pattern" error.
214 (report-invalid-field-specifier 'name
215 #'(bindings (... ...))))))))))
217 (define-syntax-rule (define-field-property-predicate predicate property)
218 "Define PREDICATE as a procedure that takes a syntax object and, when passed
219 a field specification, returns the field name if it has the given PROPERTY."
220 (define (predicate s)
221 (syntax-case s (property)
222 ((field (property values (... ...)) _ (... ...))
224 ((field _ properties (... ...))
225 (predicate #'(field properties (... ...))))
228 (define-syntax define-record-type*
230 "Define the given record type such that an additional \"syntactic
231 constructor\" is defined, which allows instances to be constructed with named
232 field initializers, à la SRFI-35, as well as default values. An example use
235 (define-record-type* <thing> thing make-thing
237 (name thing-name (default \"chbouib\"))
239 (default (current-output-port)) (thunked))
240 (loc thing-location (innate) (default (current-source-location))))
242 This example defines a macro 'thing' that can be used to instantiate records
247 (port (current-error-port)))
249 The value of 'name' or 'port' could as well be omitted, in which case the
250 default value specified in the 'define-record-type*' form is used:
254 The 'port' field is \"thunked\", meaning that calls like '(thing-port x)' will
255 actually compute the field's value in the current dynamic extent, which is
256 useful when referring to fluids in a field's value.
258 A field can also be marked as \"delayed\" instead of \"thunked\", in which
259 case its value is effectively wrapped in a (delay …) form.
261 It is possible to copy an object 'x' created with 'thing' like this:
263 (thing (inherit x) (name \"bar\"))
265 This expression returns a new object equal to 'x' except for its 'name'
266 field and its 'loc' field---the latter is marked as \"innate\", so it is not
269 (define (field-default-value s)
270 (syntax-case s (default)
271 ((field (default val) _ ...)
272 (list #'field #'val))
273 ((field _ properties ...)
274 (field-default-value #'(field properties ...)))
277 (define-field-property-predicate delayed-field? delayed)
278 (define-field-property-predicate thunked-field? thunked)
279 (define-field-property-predicate innate-field? innate)
281 (define (wrapped-field? s)
282 (or (thunked-field? s) (delayed-field? s)))
284 (define (wrapped-field-accessor-name field)
285 ;; Return the name (an unhygienic syntax object) of the "real"
286 ;; getter for field, which is assumed to be a wrapped field.
287 (syntax-case field ()
288 ((field get properties ...)
289 (let* ((getter (syntax->datum #'get))
290 (real-getter (symbol-append '% getter '-real)))
291 (datum->syntax #'get real-getter)))))
293 (define (field-spec->srfi-9 field)
294 ;; Convert a field spec of our style to a SRFI-9 field spec of the
296 (syntax-case field ()
297 ((name get properties ...)
299 #,(if (wrapped-field? field)
300 (wrapped-field-accessor-name field)
303 (define (thunked-field-accessor-definition field)
304 ;; Return the real accessor for FIELD, which is assumed to be a
306 (syntax-case field ()
308 (with-syntax ((real-get (wrapped-field-accessor-name field)))
309 #'(define-inlinable (get x)
310 ;; The real value of that field is a thunk, so call it.
313 (define (delayed-field-accessor-definition field)
314 ;; Return the real accessor for FIELD, which is assumed to be a
316 (syntax-case field ()
318 (with-syntax ((real-get (wrapped-field-accessor-name field)))
319 #'(define-inlinable (get x)
320 ;; The real value of that field is a promise, so force it.
321 (force (real-get x)))))))
323 (define (compute-abi-cookie field-specs)
324 ;; Compute an "ABI cookie" for the given FIELD-SPECS. We use
325 ;; 'string-hash' because that's a better hash function that 'hash' on a
327 (syntax-case field-specs ()
328 (((field get properties ...) ...)
329 (string-hash (object->string
330 (syntax->datum #'((field properties ...) ...)))
331 most-positive-fixnum))))
334 ((_ type syntactic-ctor ctor pred
335 (field get properties ...) ...)
336 (let* ((field-spec #'((field get properties ...) ...))
337 (thunked (filter-map thunked-field? field-spec))
338 (delayed (filter-map delayed-field? field-spec))
339 (innate (filter-map innate-field? field-spec))
340 (defaults (filter-map field-default-value
341 #'((field properties ...) ...)))
342 (cookie (compute-abi-cookie field-spec)))
343 (with-syntax (((field-spec* ...)
344 (map field-spec->srfi-9 field-spec))
345 ((thunked-field-accessor ...)
346 (filter-map (lambda (field)
347 (and (thunked-field? field)
348 (thunked-field-accessor-definition
351 ((delayed-field-accessor ...)
352 (filter-map (lambda (field)
353 (and (delayed-field? field)
354 (delayed-field-accessor-definition
358 (define-record-type type
362 (define #,(current-abi-identifier #'type)
364 thunked-field-accessor ...
365 delayed-field-accessor ...
366 (make-syntactic-constructor type syntactic-ctor ctor
368 #:abi-cookie #,cookie
372 #:defaults #,defaults))))))))
374 (define* (alist->record alist make keys
375 #:optional (multiple-value-keys '()))
376 "Apply MAKE to the values associated with KEYS in ALIST. Items in KEYS that
377 are also in MULTIPLE-VALUE-KEYS are considered to occur possibly multiple
378 times in ALIST, and thus their value is a list."
379 (let ((args (map (lambda (key)
380 (if (member key multiple-value-keys)
381 (filter-map (match-lambda
383 (and (equal? k key) v)))
385 (assoc-ref alist key)))
389 (define (object->fields object fields port)
390 "Write OBJECT (typically a record) as a series of recutils-style fields to
391 PORT, according to FIELDS. FIELDS must be a list of field name/getter pairs."
392 (let loop ((fields fields))
396 (((field . get) rest ...)
397 (format port "~a: ~a~%" field (get object))
400 (define %recutils-field-charset
401 ;; Valid characters starting a recutils field.
402 ;; info "(recutils) Fields"
403 (char-set-union char-set:upper-case
407 (define (recutils->alist port)
408 "Read a recutils-style record from PORT and return it as a list of key/value
409 pairs. Stop upon an empty line (after consuming it) or EOF."
410 (let loop ((line (read-line port))
412 (cond ((eof-object? line)
416 (loop (read-line port) result) ; leading space: ignore it
417 (reverse result))) ; end-of-record marker
419 ;; Now check the first character of LINE, since that's what the
420 ;; recutils manual says is enough.
421 (let ((first (string-ref line 0)))
423 ((char-set-contains? %recutils-field-charset first)
424 (let* ((colon (string-index line #\:))
425 (field (string-take line colon))
426 (value (string-trim (string-drop line (+ 1 colon)))))
427 (loop (read-line port)
428 (alist-cons field value result))))
429 ((eqv? first #\#) ;info "(recutils) Comments"
430 (loop (read-line port) result))
431 ((eqv? first #\+) ;info "(recutils) Fields"
432 (let ((new-line (if (string-prefix? "+ " line)
434 (string-drop line 1))))
436 (((field . value) rest ...)
437 (loop (read-line port)
438 `((,field . ,(string-append value "\n" new-line))
441 (error "unmatched line" line))))))))
443 (define-syntax match-record
445 "Bind each FIELD of a RECORD of the given TYPE to it's FIELD name.
446 The current implementation does not support thunked and delayed fields."
447 ((_ record type (field fields ...) body ...)
448 (if (eq? (struct-vtable record) type)
449 ;; TODO compute indices and report wrong-field-name errors at
451 ;; TODO support thunked and delayed fields
452 (let ((field ((record-accessor type 'field) record)))
453 (match-record record type (fields ...) body ...))
454 (throw 'wrong-type-arg record)))
455 ((_ record type () body ...)
458 ;;; records.scm ends here