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+#| -*-Scheme-*-
+
+$Header: /Users/cph/tmp/foo/mit-scheme/mit-scheme/v7/src/runtime/record.scm,v 1.1 1989/02/28 18:34:09 cph Exp $
+
+Copyright (c) 1989 Massachusetts Institute of Technology
+
+This material was developed by the Scheme project at the Massachusetts
+Institute of Technology, Department of Electrical Engineering and
+Computer Science.  Permission to copy this software, to redistribute
+it, and to use it for any purpose is granted, subject to the following
+restrictions and understandings.
+
+1. Any copy made of this software must include this copyright notice
+in full.
+
+2. Users of this software agree to make their best efforts (a) to
+return to the MIT Scheme project any improvements or extensions that
+they make, so that these may be included in future releases; and (b)
+to inform MIT of noteworthy uses of this software.
+
+3. All materials developed as a consequence of the use of this
+software shall duly acknowledge such use, in accordance with the usual
+standards of acknowledging credit in academic research.
+
+4. MIT has made no warrantee or representation that the operation of
+this software will be error-free, and MIT is under no obligation to
+provide any services, by way of maintenance, update, or otherwise.
+
+5. In conjunction with products arising from the use of this material,
+there shall be no use of the name of the Massachusetts Institute of
+Technology nor of any adaptation thereof in any advertising,
+promotional, or sales literature without prior written consent from
+MIT in each case. |#
+
+;;;; Records
+;;; written by Jonathan Rees
+
+(declare (usual-integrations))
+\f
+(define (make-record-type type-id field-names)
+  (let ((size (+ (length field-names) 1)))
+
+    (define (constructor names)
+      (let ((number-of-inits (length names))
+           (indexes (map field-index names)))
+       (lambda field-values
+         (if (not (= (length field-values) number-of-inits))
+             (error "wrong number of arguments to record constructor"
+                    field-values type-id names))
+         (let ((record (make-vector size)))
+           (vector-set! record 0 the-descriptor)
+           (for-each (lambda (index value) (vector-set! record index value))
+                     indexes
+                     field-values)
+           record))))
+
+    (define (predicate obj)
+      (and (vector? obj)
+          (= (vector-length obj) size)
+          (eq? (vector-ref obj 0) the-descriptor)))
+
+    (define (guarantee record)
+      (if (not (predicate record))
+         (error "invalid argument to record accessor" record type-id)))
+
+    (define (accessor name)
+      (let ((index (field-index name)))
+       (lambda (record)
+         (guarantee record)
+         (vector-ref record index))))
+
+    (define (updater name)
+      (let ((index (field-index name)))
+       (lambda (record new-value)
+         (guarantee record)
+         (vector-set! record index new-value))))
+
+    (define (describe record)
+      (guarantee record)
+      (map (lambda (name index)
+            (list name (vector-ref record (field-index name))))
+          field-names))
+
+    (define (field-index name)
+      (let loop ((names field-names) (index 1))
+       (cond ((null? names) (error "bad field name" name))
+             ((eq? name (car names)) index)
+             (else (loop (cdr names) (+ index 1))))))
+
+    (define (the-descriptor request)
+      (case request
+       ((CONSTRUCTOR) constructor)
+       ((PREDICATE) predicate)
+       ((ACCESSOR) accessor)
+       ((UPDATER) updater)
+       (else (error "invalid request to record type" type-id request))))
+
+    (unparser/set-tagged-vector-method! the-descriptor
+                                       (unparser/standard-method type-id))
+    (named-structure/set-tag-description! the-descriptor describe)
+    the-descriptor))
+
+(define (record-constructor record-type names)
+  ((record-type 'CONSTRUCTOR) names))
+
+(define (record-predicate record-type)
+  (record-type 'PREDICATE))
+
+(define (record-accessor record-type field-name)
+  ((record-type 'ACCESSOR) field-name))
+
+(define (record-updater record-type field-name)
+  ((record-type 'UPDATER) field-name))
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