Re: A different definition of MINUS, Part 3
From: Cimode <cimode_at_hotmail.com>
Date: Thu, 18 Dec 2008 12:36:38 -0800 (PST)
Message-ID: <9a8f98d7-fa06-45b8-8256-dc13101b32a5_at_k36g2000pri.googlegroups.com>
Date: Thu, 18 Dec 2008 12:36:38 -0800 (PST)
Message-ID: <9a8f98d7-fa06-45b8-8256-dc13101b32a5_at_k36g2000pri.googlegroups.com>
On 18 déc, 20:31, Cimode <cim..._at_hotmail.com> wrote:
> Hope this will publish adequately...
>
> R-D= R - (R ∩ D) = R-[(RXD) - (R ∆ D)] = R U R∆D - RXD
>
> R=[{1},{2},{4}]
> D= [{1},{3}]
>
> R-D = [{1},{2},{4}] U [{2}, {3}] - [{1, 1}{1, 2}{1, 4} {3, 1} {3, 2}
> {3, 4}]
> =[{1}{2}{3}{4}] - [{1, 1}{1, 2}{1, 4} {3, 1} {3, 2}{3, 4}]
> =[{1}{2}{3}{4}] - [{1}, {3}]
> =[{2}{4}]
To be more precise, I should have written
R-D= R - (R ∩ D) = R-[(RXD) - (R ∆ D)] = R U R∆D - DXR --> Does make a difference when headers are brought into the equation...
Apologies.. Received on Thu Dec 18 2008 - 21:36:38 CET