# Re: [gentoo-user] Portage 2.2

On Wed, 24 Jul 2013 12:46:59 +0200, Alan McKinnon wrote:

> > What does that mean? set1 and one of set2 or set 3? Or both set1 and
> > set2 or set3 only? I'm not sure how this would be useful but I can
> > certainly see how it would cause confusion and problems, but I hadn't
> > heard if it before.
> >
> >
>
> It's standard mathematical set operators. In maths, a set is defined as
> "a collection of well-defined objects". Sets have no dupes.
>
> http://en.wikipedia.org/wiki/Set_%28mathematics%29
> http://en.wikipedia.org/wiki/Set_theory
>
> Sets have several well-defined operations that can be done on them:
> union, intersection, difference plus a few others.
>
> @set1+@set2/@set3 reduces to:
>
> all the elements of set1 and set2 without the elements that are in set3
> (/ is difference).
>
> As an example, assume portage ships two sets @kde and @kdedev:
>
> @kde
>   kdebase-meta
>   kdemultimedia-meta
>   kdepim-meta
>   ...
>
> @kdedev
>   kdewebdev-meta
>   kdebindings-meta
>   kdesdk-meta
>
>
> However, kmail sucks and akonadi sucks moar, so define for yourself
>
> @suckykde
>   kdepim-meta
>
>
> @kde+@kdedev/@suckykde
>

I see, what about operator precedence, is that equivalent to

(@kde+@kdedev)/@kdesuckykde or @kde+(@kdedev/@kdesuckykde)

It's been a long time since I studied set operators at Uni :(

--
Neil Bothwick

I cna ytpe 300 wrods pre mniuet!!!

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