Oracle FAQ | Your Portal to the Oracle Knowledge Grid |
Home -> Community -> Usenet -> comp.databases.theory -> Re: How is this collection called?
PLEASE don't do homework for someone...
"Michael Mendelsohn" <keine.Werbung.1300_at_michael.mendelsohn.de> wrote in
message news: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
>
> 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 - 09:14:40 CST