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
|
#| records.jl -- record types
$Id: records.jl,v 1.9 2000/09/10 20:03:17 john Exp $
Copyright (C) 2000 John Harper <john@dcs.warwick.ac.uk>
This file is part of librep.
librep is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
librep is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with Jade; see the file COPYING. If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
|#
;; Commentary:
;; This was inspired by the Scheme48 record interface (surprise,
;; surprise!). You do something like:
;; (define-record-type :pare
;; (kons x y) ; constructor
;; pare? ; predicate
;; (x kar set-kar!) ; fields w/ optional accessors
;; (y kdr)) ;and modifiers
;; the variable `:pare' is bound to the record type. This can be used
;; to redefine the printed representation of the record type (e.g. by
;; default `#<:pare>') using define-record-discloser:
;; (define-record-discloser :pare
;; (lambda (x) `(pare ,(kar x) ,(kdr x))))
;; General syntax of define-record-type is:
;; (define-record-type <type-name>
;; (<constructor-name> <field-param>*)
;; [<predicate-name>]
;; (<field-tag> [<accessor-name> [<modifier-name>]])*)
;; <field-param>* is a standard lambda list, the parameters should
;; match the <field-tag>'s to be initialized
(define-structure rep.data.records
(export make-record-type
make-record-datum
record-constructor
record-accessor
record-modifier
record-predicate
record-printer
define-record-type
define-record-discloser)
(open rep
rep.data.datums)
(define-structure-alias records rep.data.records)
;;; record type structures
(define (make-record-type name fields)
(let ((rt (vector name fields nil)))
(define-datum-printer rt (record-printer rt))
rt))
(define (record-type-name rt) (aref rt 0))
(define (record-type-fields rt) (aref rt 1))
(define (record-type-discloser rt) (aref rt 2))
(define (define-record-discloser rt x) (aset rt 2 x))
;;; record mechanics
(define (make-record rt)
(make-datum (make-vector (length (record-type-fields rt))) rt))
(define make-record-datum make-datum)
(define (field-index rt field)
(do ((i 0 (1+ i))
(fields (record-type-fields rt) (cdr fields)))
((eq (car fields) field) i)
(and (null fields) (error "No such field: %s, %s"
(record-type-name rt) field))))
(define (field-ref rt record index)
(aref (datum-ref record rt) index))
(define (field-set rt record index value)
(aset (datum-ref record rt) index value))
;;; interface implementations
(define (record-constructor rt fields)
(let ((indices (mapcar (lambda (field)
(field-index rt field)) fields)))
(lambda args
(let ((record (make-record rt)))
(let loop ((rest args)
(ids indices))
(if (and rest ids)
(progn
(field-set rt record (car ids) (car rest))
(loop (cdr rest) (cdr ids)))
record))))))
(define (make-record-constructor rt args field-names)
(define (has-field-p field)
(let loop ((rest args))
(cond ((null rest) nil)
((eq (or (caar rest) (car rest) rest) field) t)
(t (loop (cdr rest))))))
(let loop ((rest field-names)
(out '()))
(if (null rest)
`(lambda ,args
(make-record-datum (vector ,@(nreverse out)) ,rt))
(loop (cdr rest)
(cons (and (has-field-p (car rest)) (car rest)) out)))))
(define (record-accessor rt field)
(let ((index (field-index rt field)))
(lambda (record)
(field-ref rt record index))))
(define (record-modifier rt field)
(let ((index (field-index rt field)))
(lambda (record value)
(field-set rt record index value))))
(define (record-predicate rt)
(lambda (arg)
(has-type-p arg rt)))
(define (record-printer rt)
(lambda (record stream)
(if (record-type-discloser rt)
(let ((out ((record-type-discloser rt) record)))
(if (stringp out)
(write stream out)
(prin1 out stream)))
(format stream "#<%s>" (record-type-name rt)))))
;;; syntax
(defmacro define-record-type (rt constructor . fields)
(let (names predicate-defs accessor-defs modifier-defs)
(when (and fields (symbolp (car fields)))
(setq predicate-defs `((define ,(car fields) (record-predicate ,rt))))
(setq fields (cdr fields)))
(setq names (mapcar car fields))
(mapc (lambda (field)
(when (cadr field)
(setq accessor-defs
(cons `(define ,(cadr field)
(record-accessor ,rt ',(car field)))
accessor-defs)))
(when (caddr field)
(setq modifier-defs
(cons `(define ,(caddr field)
(record-modifier ,rt ',(car field)))
modifier-defs))))
fields)
`(progn
(define ,rt (make-record-type ',rt ',names))
(define ,(car constructor)
,(make-record-constructor rt (cdr constructor) names))
,@predicate-defs
,@accessor-defs
,@modifier-defs))))
|
