# 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_at_michael.mendelsohn.de>

Date: Tue, 30 Mar 2004 11:40:59 +0200

Message-ID: <406940AB.883662FF_at_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

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 - 11:40:59 CEST