bug#11196: missing constructor procedure in new srfi-9 records

bug#11196: missing constructor procedure in new srfi-9 records

[Klaus Stehle]

Hi,

;;;; A short example script to describe the problem:

(use-modules (srfi srfi-9))

;; A simple record definition for example
(define-record-type my-record
  (make-my-record one two)
  my-record?
  (one my-one)
  (two my-two))

;; "Normal" construction is working well
(define r1 (make-my-record "1" "2"))

;; This should also work, but it doesn't!
(define r2 ((record-constructor my-record) "1" "2"))
=> ERROR

;; Where's the constructor procedure?
(display (record-constructor my-record)) (newline)

=> #f


The bug is located in the new srfi-9.scm which forgets to set the
record's constructor procedure.
The following patch may help (hoping not to introduce new problems):



--- srfi-9.scm  2012-04-06 16:52:02.000000000 +0200
+++ srfi-9.scm  2012-04-06 17:14:36.000000000 +0200
@@ -188,7 +188,9 @@
        (let* ((fields      (field-identifiers #'(field-spec ...)))
               (field-count (length fields))
               (layout      (string-concatenate (make-list field-count 
"pw")))
-              (indices     (field-indices (map syntax->datum fields))))
+              (indices     (field-indices (map syntax->datum fields)))
+              (ctor-proc   (syntax-case #'constructor-spec ()
+                             ((func args ...) (syntax func)))))
          #`(begin
              (define type-name
                (let ((rtd (make-struct/no-tail
@@ -204,7 +206,7 @@
                     (eq? (struct-vtable obj) type-name)))

              #,(constructor #'type-name #'constructor-spec indices)
-
+             (struct-set! type-name (+ 2 vtable-offset-user) #,ctor-proc)
              #,@(accessors #'type-name #'(field-spec ...) indices)))))))

 ;;; srfi-9.scm ends here




Cheers,
Klaus Stehle


----------------------------
guile --version
guile (GNU Guile) 2.0.5

uname -srm
Linux 2.6.32-5-amd64 x86_64

bug#11196: missing constructor procedure in new srfi-9 records

[Ludovic Courtès]

Hi Klaus,

Klaus Stehle <klaus.stehle@uni-tuebingen.de> skribis:

> (use-modules (srfi srfi-9))
>
> ;; A simple record definition for example
> (define-record-type my-record
>   (make-my-record one two)
>   my-record?
>   (one my-one)
>   (two my-two))
>
> ;; "Normal" construction is working well
> (define r1 (make-my-record "1" "2"))
>
> ;; This should also work, but it doesn't!
> (define r2 ((record-constructor my-record) "1" "2"))
> => ERROR

The use of ‘record-constructor’ above relies on a implementation detail
of the SRFI-9 implementation in Guile 1.8–namely, that SRFI-9 records
were implemented in terms of “Guile records” (info "(guile) Records").

In Guile 2.0, SRFI-9 records are no longer “Guile records”, so they no
longer have a “record-type descriptor” attached.  Thus,
‘record-constructor’ cannot be used with them.

Since you are using SRFI-9 anyway, I would recommend sticking to the
mechanisms specified by SRFI-9, thus avoiding ‘record-constructor’.

How would it work for you?

Thanks,
Ludo’.

bug#11196: missing constructor procedure in new srfi-9 records

[Ludovic Courtès]

Hi Klaus,

Please forget my previous message.  SRFI-9 in Guile 2.0 _is_ actually
implemented in terms of “Guile records”.  So I applied a patch similar
to yours as commit 5ef102cc93a4f2eba0f5dad94a7306085b353000.

Thanks!

Ludo’.