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Re: How is this collection called?

From: Michael Mendelsohn <keine.Werbung.1300_at_michael.mendelsohn.de>
Date: Tue, 30 Mar 2004 11:40:59 +0200
Message-ID: <406940AB.883662FF@michael.mendelsohn.de>


Mikito Harakiri schrieb:
> Let '*' be binary aggregation operator.
 

> Then, sets obey the following laws:
> a*a=a
> a*b=b*a
> a*(b*c)=(a*b)*c

> Lists:
> a*a!=a
> a*b!=b*a
> a*(b*c)=(a*b)*c

> What collection type meets
> a*a!=a
> a*b!=b*a
> a*(b*c)!=(a*b)*c
>
> ?

Stack?
x * y := pop elements off stack x and push them on y

Example:

a=(1,2), b=(3,4), c=(5,6)
 a*b  = (1,2)*(3,4) = (2)*(1,3,4) = (2,1,3,4)
 b*c  = (3,4)*(5,6) = (4,3,5,6)

(a*b)*c = (2,1,3,4) * (5,6) = (4,3,1,2,5,6) a*(b*c) = (1,2) * (4,3,5,6) = (2,1,4,3,5,6)

Michael

-- 
Feel the stare of my burning hamster and stop smoking!
Received on Tue Mar 30 2004 - 03:40:59 CST

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