Re: More on lists and sets

vc wrote:
> Mikito Harakiri wrote:
> > vc wrote:
> > > Mikito Harakiri wrote:
> > > > It is remarkable that list intersection laws mimic the ones for the
> > > > union:
> > > > A /\ A != A
> > >
> > > This is not correct.
> >
> > Let A = 1->1. Then A /\ A = 1->1->1->1.
>
> According to your unknown private definition, maybe, but that's not
> how list intersection is usually defined.

Let's focus on bags, first. Do you agree that

{1,1} /\ {1,1,1} = {1,1,1,1,1,1}

? (Intersection is join. Join is cartesian product followed by selection).

As we descend down the chain lists-bags-sets, the list intersection operation has to be compatible with the bags one. The standard list intersection does not. Besides, the second argument in the standard list intersection behaves like a set, not list. Received on Wed Mar 22 2006 - 12:02:42 CST