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MathGroup Archive 2005

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Re: Need a functional process for this.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg55602] Re: [mg55589] Need a functional process for this.
  • From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
  • Date: Thu, 31 Mar 2005 01:23:53 -0500 (EST)
  • References: <200503300822.DAA21909@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

On 30 Mar 2005, at 10:22, Steve Gray wrote:

> 	I have two lists, aa and bb. aa has the general form {2,5,7,9,11,...}
> (or{{2},{5},{7},{9},{11},
> }}), and bb has the general form {{6,4},{9,2},{5,6},{3,8},
> }. If either
> the first or second element in any sublist (pair of integers) of bb 
> matches any element in aa, I
> want to delete that sublist from bb. In the above example, neither 
> member of {6,4} or {3,8} belongs
> to aa, while at least one element of {9,2} and {5,6} belongs to aa, so 
> bb becomes {{6,4},{3,8}}. If
> aa had only one element, for example 7, I could do 
> bb=Delete[bb,Position[bb,{x_,7}|{7,y_}]], but I
> don't know how to do it for several values instead of just "7" without 
> using a procedural loop.
> 	What is a good functional way to do this?
> 	Thank you for any tips.
>
> Steve Gray
>
>
>

For example

ls={2,5,7,9,11};


DeleteCases[{{6,4},{9,2},{5,6},{3,8}},_?(Intersection[#,ls]!={}&)]

{{6,4},{3,8}}

Strictly speaking you can't call this "functional" since it principally 
uses pattern matching but it seems that you are using this term in a 
very broad sense.

Andrzej Kozlowski


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