Re: How is this collection called?

"Michael Mendelsohn" <keine.Werbung.1300_at_michael.mendelsohn.de> wrote in message news:406940AB.883662FF_at_michael.mendelsohn.de...
> 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)

Let
a*b=a^(-1).b

where "^(-1)" is list inversion:

(1,2,3)^(-1)=(3,2,1)

and "." is list concatenation:

(1,2,3).(4,5)=(1,2,3,4,5)

Then:

a*a=a^(-1).a != a

a*b=a^(-1).b != b^(-1).a=b*a

and, finally,

(a*b)*c=(a^(-1).b)^(-1).c=b^(-1).a.c

a*(b*c)=a^(-1).b^(-1).c Received on Tue Mar 30 2004 - 19:22:35 CEST