From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <6b02a9a02907b3d6abd735ed6abe8600@terzarima.net>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] ls, rc question
From: Charles Forsyth <forsyth@terzarima.net>
In-Reply-To: <d6c7d8de9892932bdad0988da6bc3a7e@hamnavoe.com>
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Date: Fri, 19 Mar 2004 10:42:35 +0000
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>>By "this point", I meant the observation that bind(..MAFTER|MBEFORE)
>>doesn't produce a union in the mathematical sense, but a list.  If
>>someone finds a reference anywhere in the mathematical literature to a
>>union operator which is non-commutative, I will happily retract my claim.

a non-commutative union does occur when working with certain constructions
on trees (funnily enough) [for much the same reason that addition and
multiplication aren't always commutative] but i haven't got a good reference.