@@ 42,6 42,95 @@
(format #f fmt args ...)
form))))
+(define* (make-syntactic-constructor type name ctor fields
+ #:key thunked defaults)
+ "Make the syntactic constructor NAME for TYPE, that calls CTOR, and expects
+all of FIELDS to be initialized. DEFAULTS is the list of FIELD/DEFAULT-VALUE
+tuples, and THUNKED is the list of identifiers of thunked fields."
+ (with-syntax ((type type)
+ (name name)
+ (ctor ctor)
+ (expected fields)
+ (defaults defaults))
+ #`(define-syntax name
+ (lambda (s)
+ (define (record-inheritance orig-record field+value)
+ ;; Produce code that returns a record identical to ORIG-RECORD,
+ ;; except that values for the FIELD+VALUE alist prevail.
+ (define (field-inherited-value f)
+ (and=> (find (lambda (x)
+ (eq? f (car (syntax->datum x))))
+ field+value)
+ car))
+
+ ;; Make sure there are no unknown field names.
+ (let* ((fields (map (compose car syntax->datum) field+value))
+ (unexpected (lset-difference eq? fields 'expected)))
+ (when (pair? unexpected)
+ (record-error 'name s "extraneous field initializers ~a"
+ unexpected)))
+
+ #`(make-struct type 0
+ #,@(map (lambda (field index)
+ (or (field-inherited-value field)
+ #`(struct-ref #,orig-record
+ #,index)))
+ 'expected
+ (iota (length 'expected)))))
+
+ (define (thunked-field? f)
+ (memq (syntax->datum f) '#,thunked))
+
+ (define (field-bindings field+value)
+ ;; Return field to value bindings, for use in 'let*' below.
+ (map (lambda (field+value)
+ (syntax-case field+value ()
+ ((field value)
+ #`(field
+ #,(if (thunked-field? #'field)
+ #'(lambda () value)
+ #'value)))))
+ field+value))
+
+ (syntax-case s (inherit #,@fields)
+ ((_ (inherit orig-record) (field value) (... ...))
+ #`(let* #,(field-bindings #'((field value) (... ...)))
+ #,(record-inheritance #'orig-record
+ #'((field value) (... ...)))))
+ ((_ (field value) (... ...))
+ (let ((fields (map syntax->datum #'(field (... ...))))
+ (dflt (map (match-lambda
+ ((f v)
+ (list (syntax->datum f) v)))
+ #'defaults)))
+
+ (define (field-value f)
+ (or (and=> (find (lambda (x)
+ (eq? f (car (syntax->datum x))))
+ #'((field value) (... ...)))
+ car)
+ (let ((value
+ (car (assoc-ref dflt (syntax->datum f)))))
+ (if (thunked-field? f)
+ #`(lambda () #,value)
+ value))))
+
+ (let ((fields (append fields (map car dflt))))
+ (cond ((lset= eq? fields 'expected)
+ #`(let* #,(field-bindings
+ #'((field value) (... ...)))
+ (ctor #,@(map field-value 'expected))))
+ ((pair? (lset-difference eq? fields 'expected))
+ (record-error 'name s
+ "extraneous field initializers ~a"
+ (lset-difference eq? fields
+ 'expected)))
+ (else
+ (record-error 'name s
+ "missing field initializers ~a"
+ (lset-difference eq? 'expected
+ fields))))))))))))
+
(define-syntax define-record-type*
(lambda (s)
"Define the given record type such that an additional \"syntactic
@@ 78,99 167,6 @@ It is possible to copy an object 'x' created with 'thing' like this:
This expression returns a new object equal to 'x' except for its 'name'
field."
- (define* (make-syntactic-constructor type name ctor fields
- #:key thunked defaults)
- "Make the syntactic constructor NAME for TYPE, that calls CTOR, and
-expects all of FIELDS to be initialized. DEFAULTS is the list of
-FIELD/DEFAULT-VALUE tuples, and THUNKED is the list of identifiers of
-thunked fields."
- (with-syntax ((type type)
- (name name)
- (ctor ctor)
- (expected fields)
- (defaults defaults))
- #`(define-syntax name
- (lambda (s)
- (define (record-inheritance orig-record field+value)
- ;; Produce code that returns a record identical to
- ;; ORIG-RECORD, except that values for the FIELD+VALUE alist
- ;; prevail.
- (define (field-inherited-value f)
- (and=> (find (lambda (x)
- (eq? f (car (syntax->datum x))))
- field+value)
- car))
-
- ;; Make sure there are no unknown field names.
- (let* ((fields (map (compose car syntax->datum)
- field+value))
- (unexpected (lset-difference eq? fields 'expected)))
- (when (pair? unexpected)
- (record-error 'name s "extraneous field initializers ~a"
- unexpected)))
-
- #`(make-struct type 0
- #,@(map (lambda (field index)
- (or (field-inherited-value field)
- #`(struct-ref #,orig-record
- #,index)))
- 'expected
- (iota (length 'expected)))))
-
- (define (thunked-field? f)
- (memq (syntax->datum f) '#,thunked))
-
- (define (field-bindings field+value)
- ;; Return field to value bindings, for use in 'let*' below.
- (map (lambda (field+value)
- (syntax-case field+value ()
- ((field value)
- #`(field
- #,(if (thunked-field? #'field)
- #'(lambda () value)
- #'value)))))
- field+value))
-
- (syntax-case s (inherit #,@fields)
- ((_ (inherit orig-record) (field value) (... ...))
- #`(let* #,(field-bindings #'((field value) (... ...)))
- #,(record-inheritance #'orig-record
- #'((field value) (... ...)))))
- ((_ (field value) (... ...))
- (let ((fields (map syntax->datum #'(field (... ...))))
- (dflt (map (match-lambda
- ((f v)
- (list (syntax->datum f) v)))
- #'defaults)))
-
- (define (field-value f)
- (or (and=> (find (lambda (x)
- (eq? f (car (syntax->datum x))))
- #'((field value) (... ...)))
- car)
- (let ((value
- (car (assoc-ref dflt
- (syntax->datum f)))))
- (if (thunked-field? f)
- #`(lambda () #,value)
- value))))
-
- (let ((fields (append fields (map car dflt))))
- (cond ((lset= eq? fields 'expected)
- #`(let* #,(field-bindings
- #'((field value) (... ...)))
- (ctor #,@(map field-value 'expected))))
- ((pair? (lset-difference eq? fields 'expected))
- (record-error 'name s
- "extraneous field initializers ~a"
- (lset-difference eq? fields
- 'expected)))
- (else
- (record-error 'name s
- "missing field initializers ~a"
- (lset-difference eq? 'expected
- fields))))))))))))
-
(define (field-default-value s)
(syntax-case s (default)
((field (default val) _ ...)