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Re: How is this collection called?

From: Mikito Harakiri <mikharakiri_at_iahu.com>
Date: Tue, 30 Mar 2004 08:27:46 -0800
Message-ID: <Knhac.12$mR.34@news.oracle.com>

"Paul" <pbrazier_at_cosmos-uk.co.uk> wrote in message news:51d64140.0403300727.2ef94b6_at_posting.google.com...
> Define a*b as "a U {b}" (where U is set union)
> Then a*(b*c) = aU{bU{c}} != (a*b)*c = aU{b}U{c}.

I wonder how your example works. It reminds me Kuratowski's definition of ordered pair

(a,b) = {{a}, {a,b}}

Formally,

((a,b),c)={ {{a}, {a,b}}, {{{a}, {a,b}} ,{c}} } (a,(b,c))={ {{b}, {b,c}}, {{{b}, {b,c}} ,{a}} }

are different sets, but we still consider them isomorphic. There was a recent thread on sci.math "Question about associativity of cartesian product". Received on Tue Mar 30 2004 - 10:27:46 CST

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