Re: Cases
- To: mathgroup at smc.vnet.net
- Subject: [mg50439] Re: [mg50423] Cases
- From: "Ingolf Dahl" <ingolf.dahl at telia.com>
- Date: Sat, 4 Sep 2004 01:43:14 -0400 (EDT)
- Reply-to: <ingolf.dahl at telia.com>
- Sender: owner-wri-mathgroup at wolfram.com
Jerry,
I think Not[d] is only defined if d is True or False, and it is not a
pattern. Moreover, if a, b, c and d are undefined, Mathematica does not know
if they are equal or not. You might test if these symbols are identical:
Cases[x, y_ /; UnsameQ[y, d]]
gives you
{a, b, c}
Ingolf Dahl
Sweden
-----Original Message-----
From: Blimbaum, Jerry AA R22 [mailto:jerry.blimbaum at navy.mil]
To: mathgroup at smc.vnet.net
Subject: [mg50439] [mg50423] Cases
Given: x = {a,b,c,d,d};
Applying Cases[x,d] gives an output of {a,b,c}......
However, Cases[x,Not[d]] gives as output an empty list { }... I
expected {a,b,c}.....
Why didnt I get that?
This issue came up when using Thread on vectors...and in some cases the
Thread resulted in 0 == 0 so it's output in the list was
True....and I
wanted to remove them....
thanks.....jerry blimbaum