From: Nicolas Cannasse <ncannasse@motion-twin.com>
To: Tom Hawkins <tom@confluent.org>
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] Physical compare
Date: Wed, 23 Nov 2005 20:49:20 +0100 [thread overview]
Message-ID: <4384C7C0.6070503@motion-twin.com> (raw)
In-Reply-To: <4384C0E3.5030300@confluent.org>
Tom Hawkins wrote:
> Is their a version of "compare" that is based on physical equality? If
> not, how can I define one? I tried:
>
> let compareq a b = if a == b then 0 else if a > b then 1 else (-1)
>
> But unfortunately, (>) is a structural comparison.
>
> I need to make a Map where the keys are distinguished by the physical
> instance.
>
> Thanks!
>
> -Tom
It's not possible.
One of the reason is that the GC might move your memory addresses around
and then break your Map constitency. You need to attribute an unique id
to each of your items and use it for comparison.
Nicolas
next prev parent reply other threads:[~2005-11-23 19:40 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-11-23 19:20 Tom Hawkins
2005-11-23 19:38 ` [Caml-list] " Jon Harrop
2005-11-23 19:49 ` Nicolas Cannasse [this message]
2005-11-24 15:33 ` Jean-Christophe Filliatre
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