From: tomas@tuxteam.de
To: Nordlöw <per.nordlow@gmail.com>
Cc: help-gnu-emacs@gnu.org
Subject: Re: Hash-tables containing references to hash-tables
Date: Mon, 23 Nov 2009 13:41:00 +0100 [thread overview]
Message-ID: <20091123124100.GA10283@tomas> (raw)
In-Reply-To: <7a116be4-52cb-482d-b555-09bc4950d5f7@31g2000vbf.googlegroups.com>
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On Mon, Nov 23, 2009 at 03:12:22AM -0800, Nordlöw wrote:
> Is it possible for a hash-table to contain a *reference* to another
> hash-table, similar to how we can build arbitrary graphs using conses/
> lists and setf?
Yes, it is -- in a way.
> If so how? If not, is there reason for being so or is it just an emacs
> todo?
>
> If we have
> (puthash parent-key (make-hash-table : size CHILD-SIZE) parent-hash)
> then I want
> (gethash parent-key parent-hash)
> to return a *reference* to hash-table contained in parent-hash.
It already does. In Lisp, you _always_ get a reference for anything
beyond simple data types (as integers and friends).
> I already have a working code for this but I am uncertain how this
> will perform when CHILD-SIZE is really large.
Ah, it's performance you are worried about. No -- gethash isn't
returning a copy of the child table, but "the child table itself".
Change it and you'll see...
Regards
- -- tomás
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next prev parent reply other threads:[~2009-11-23 12:41 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-23 11:12 Hash-tables containing references to hash-tables Nordlöw
2009-11-23 12:41 ` tomas [this message]
2009-11-23 14:10 ` Pascal J. Bourguignon
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