From mboxrd@z Thu Jan  1 00:00:00 1970
From: Daimrod <daimrod@gmail.com>
Subject: Re: Circular lists/shared structures in org-element parse-tree
Date: Fri, 28 Jun 2013 22:43:34 +0200
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In-Reply-To: <87a9ma9fra.fsf@gmail.com> (Thorsten Jolitz's message of "Fri, 28
	Jun 2013 21:50:17 +0200")
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To: Thorsten Jolitz <tjolitz@gmail.com>
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Thorsten Jolitz <tjolitz@gmail.com> writes:

> Hi List,=20
>
> I wonder how I can find out in a (elisp) program the points in the parse
> tree (returned by org-element-parse-buffer) where shared structures are
> used.=20
>
> In the read-syntax, its easy to see (especially with `print-circle' set
> to non-nil):
>
> #+begin_src emacs-lisp
>   #2=3D(org-data nil #1=3D(headline (:raw-value "header 1"
>    [...] :parent #2#) [...]=20=20
> #+end_src
>
> but when processing the parse tree as a list in elisp, how can I detect t=
he
> fact that=20
>
> ,------------
> | :parent #2#
> `------------
>
> refers to=20
>
> ,-----------------
> | #2=3D(org-data nil
> `-----------------
>
> i.e. points back to an already existing structure?

AFAIK you have to track all pointers inspected to see if one has already
be seen.

For example, I've implemented a version of equal[1] to compare this kind
of lists (to add tests to org-sync).

[1] https://github.com/daimrod/Emacs-config/blob/master/elisp/dmd-utils.el#=
L25

=2D-=20
Daimrod/Greg

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