GNU bug report logs - #11198
serializing structs (prefabs)

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From: ludo <at> gnu.org (Ludovic Courtès)
To: Mark H Weaver <mhw <at> netris.org>
Cc: Andy Wingo <wingo <at> pobox.com>, 11198 <at> debbugs.gnu.org, Klaus Stehle <klaus.stehle <at> uni-tuebingen.de>
Subject: bug#11198: problems reading data with a "read-hash-extend" registered reader
Date: Sun, 22 Apr 2012 20:01:37 +0200

Hello!

I think the reader should only return valid Scheme objects that have a
read syntax (info "(r5rs) Lexical Structure"), and records are not among
them.

So a short-term solution would be to change ‘read-R’ to return the
expressions that builds the record, instead of the record itself–just
like macros return syntax objects, not arbitrary Scheme objects.

  (define (read-R chr port)
    (let ((rlst (read port)))
      (if (not (pair? rlst))
          #f
          (let* ((name (car rlst))
                 (lst (cdr rlst))
                 (rtd (primitive-eval name))
                 (fields (record-type-fields rtd)))
            `(apply (record-constructor name)
                    ,@(map (lambda (f)
                            ...)
                           fields))))))

We could imagine changing the compiler to be able to serialize records
in the future, but I think that’s a longer-term approach, and not
directly relevant to this report.

WDYT?

Ludo’.

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