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MathGroup Archive 2004

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Re: Cases

  • To: mathgroup at smc.vnet.net
  • Subject: [mg50447] Re: [mg50423] Cases
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Sat, 4 Sep 2004 01:43:23 -0400 (EDT)
  • Reply-to: hanlonr at cox.net
  • Sender: owner-wri-mathgroup at wolfram.com

If d is a Symbol, Not[d] is not a boolean

Not[d]

¬d

x={a,b,c,d,d};

Cases[x,_?(!(#===d)&)]

{a, b, c}

Select[x,!(#===d)&]

{a, b, c}


Bob Hanlon

> 
> From: "Blimbaum, Jerry AA R22" <jerry.blimbaum at navy.mil>
To: mathgroup at smc.vnet.net
> Date: 2004/09/03 Fri AM 03:35:08 EDT
> To: mathgroup at smc.vnet.net
> Subject: [mg50447] [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
> 
> 


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