Re: How is this collection called?

From: Paul <>
Date: 30 Mar 2004 07:27:04 -0800
Message-ID: <>

"Mikito Harakiri" <> wrote in message news:<qA2ac.38$>...
> Let '*' be binary aggregation operator.
> What collection type meets
> a*a!=a
> a*b!=b*a
> a*(b*c)!=(a*b)*c

not sure if this is exactly what you mean but as an example:

Let a,b be sets.

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}.

Maybe you could call these things with the * operation "boxes". And the binary aggregation operator (I guess you're thinking of operators that are analogous to the union operator for sets?) is kind of like the act of putting the second "box" inside the first.

Perhaps "objects" could be thought of like this. To "union" two objects you could put the second inside the first. (As opposed to creating a new third object that contained the first two).

Paul. Received on Tue Mar 30 2004 - 17:27:04 CEST

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