From: Stefan Monnier <monnier@iro.umontreal.ca>
Subject: Re: Object identity
Date: Tue, 21 Oct 2003 16:09:43 GMT [thread overview]
Message-ID: <jwvekx67ex4.fsf-monnier+gnu.emacs.help@vor.iro.umontreal.ca> (raw)
In-Reply-To: yvclb.124$lK3.43@news.level3.com
> So let's try augmenting it with additional information, like a timestamp.
> This obviously can't be the time that object-identity was called, because
> then it will be different every time. It needs to be something associated
> with the object itself, like the time it was created or the time that
> object-identity was first invoked on it. This implies that every object
> needs to have a slot to store its creation time. As a result, the size of
> every object will have to grow by at least 4 bytes. Assuming cons cells
> are 8 bytes, this means increasing the space they use by 50%. Since most
> objects in memory will never have object-identity called on them, this
> space is mostly wasted.
But since Java has such a function and Java is an attention-grabber, people
have been working on clever ways to implement this efficiently.
I still have no clue what it's useful for, so I tend to find such research
rather pointless. But I'm probably just missing the point.
Stefan
next prev parent reply other threads:[~2003-10-21 16:09 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <mailman.2049.1066716515.21628.help-gnu-emacs@gnu.org>
2003-10-21 15:09 ` Object identity Stefan Monnier
2003-10-21 16:55 ` Stefan Monnier
2003-10-21 19:00 ` Lars Brinkhoff
[not found] ` <mailman.2095.1066762882.21628.help-gnu-emacs@gnu.org>
2003-10-21 19:27 ` Barry Margolin
2003-10-21 19:49 ` Lars Brinkhoff
[not found] ` <mailman.2101.1066765792.21628.help-gnu-emacs@gnu.org>
2003-10-21 19:56 ` Barry Margolin
2003-10-22 7:35 ` Lars Brinkhoff
2003-10-21 15:44 ` Barry Margolin
2003-10-21 16:09 ` Stefan Monnier [this message]
2003-10-21 16:19 ` Barry Margolin
2003-10-21 16:50 ` Stefan Monnier
2003-10-21 17:19 ` Barry Margolin
2003-10-21 17:42 ` Lars Brinkhoff
[not found] ` <mailman.2089.1066758667.21628.help-gnu-emacs@gnu.org>
2003-10-21 19:59 ` Stefan Monnier
2003-10-21 20:13 ` Lars Brinkhoff
[not found] ` <mailman.2104.1066767237.21628.help-gnu-emacs@gnu.org>
2003-10-21 21:22 ` Stefan Monnier
2003-10-21 21:39 ` Barry Margolin
2003-10-21 6:07 Lars Brinkhoff
2003-10-26 17:30 ` jan
2003-10-26 22:45 ` jan
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