GNU bug report logs - #6017
23.1.96; savehist-printable for hash tables

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: "Drew Adams" <drew.adams <at> oracle.com>
To: <bug-gnu-emacs <at> gnu.org>
Subject: 23.1.96; savehist-printable for hash tables
Date: Fri, 23 Apr 2010 10:49:22 -0700

IIUC, starting with Emacs 23.2, we can prin1 and read hash tables. If
that's correct, then `savehist-printable' could presumably be updated to
add this sexp to the cond: (hash-table-p value). IOW:
 
(defun savehist-printable (value)
  "Return non-nil if VALUE is printable."
  (cond
   ((stringp value))
   ((numberp value))
   ((symbolp value))
   ((hash-table-p value))
   (t
    (with-temp-buffer
      (condition-case nil
   (let ((print-readably t) (print-level nil))
   (prin1 value (current-buffer))
   (read (point-min-marker))
   t)
 (error nil))))))

In GNU Emacs 23.1.96.1 (i386-mingw-nt5.1.2600)
 of 2010-04-20 on G41R2F1
Windowing system distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --no-opt --cflags -Ic:/xpm/include'
 

Message #8 received at 6017 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
To: "Drew Adams" <drew.adams <at> oracle.com>
Cc: 6017 <at> debbugs.gnu.org
Subject: Re: bug#6017: 23.1.96; savehist-printable for hash tables
Date: Fri, 23 Apr 2010 14:15:45 -0400

> IIUC, starting with Emacs 23.2, we can prin1 and read hash tables. If
> that's correct, then `savehist-printable' could presumably be updated to
> add this sexp to the cond: (hash-table-p value). IOW:
 
> (defun savehist-printable (value)
>   "Return non-nil if VALUE is printable."
>   (cond
>    ((stringp value))
>    ((numberp value))
>    ((symbolp value))
>    ((hash-table-p value))
>    (t
>     (with-temp-buffer
>       (condition-case nil
>    (let ((print-readably t) (print-level nil))
>    (prin1 value (current-buffer))
>    (read (point-min-marker))
>    t)
>  (error nil))))))

That won't check whether the contents of the has-table are
themsevles printable.


        Stefan

Message #11 received at 6017 <at> debbugs.gnu.org (full text, mbox):

From: "Drew Adams" <drew.adams <at> oracle.com>
To: "'Stefan Monnier'" <monnier <at> IRO.UMontreal.CA>
Cc: 6017 <at> debbugs.gnu.org
Subject: RE: bug#6017: 23.1.96; savehist-printable for hash tables
Date: Fri, 23 Apr 2010 11:34:55 -0700

> That won't check whether the contents of the has-table are
> themsevles printable.

Good point. I don't know how the support for printing & reading hash tables
works. If it just ensures that the top level is readable (the hash table
itself), then yes, there is no guarantee that its content is really readable.

Is this feature of hash-table print+read support specified anywhere, so we know
what the support really is? If not, could you please document it? 

It sounds like it is similar to printing a list - no guarantees about
readability of list members etc. If so, we should at least say that somewhere.

Message #16 received at 6017-done <at> debbugs.gnu.org (full text, mbox):

From: Chong Yidong <cyd <at> stupidchicken.com>
To: "Drew Adams" <drew.adams <at> oracle.com>
Cc: 6017-done <at> debbugs.gnu.org, 'Stefan Monnier' <monnier <at> IRO.UMontreal.CA>
Subject: Re: bug#6017: 23.1.96; savehist-printable for hash tables
Date: Sun, 25 Apr 2010 14:30:35 -0400

"Drew Adams" <drew.adams <at> oracle.com> writes:

> Is this feature of hash-table print+read support specified anywhere,
> so we know what the support really is? If not, could you please
> document it?

See `Creating Hash Tables' in the Lisp manual.

Message #17 received at 6017-done <at> debbugs.gnu.org (full text, mbox):

From: "Drew Adams" <drew.adams <at> oracle.com>
To: "'Chong Yidong'" <cyd <at> stupidchicken.com>
Cc: 6017-done <at> debbugs.gnu.org, 'Stefan Monnier' <monnier <at> IRO.UMontreal.CA>
Subject: RE: bug#6017: 23.1.96; savehist-printable for hash tables
Date: Sun, 25 Apr 2010 11:59:45 -0700

> > Is this feature of hash-table print+read support specified anywhere,
> > so we know what the support really is? If not, could you please
> > document it?
> 
> See `Creating Hash Tables' in the Lisp manual.

That explanation seems clear and complete. Thx. 

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