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Re: Need a functional process for this.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg55633] Re: Need a functional process for this.
  • From: Bill Rowe <readnewsciv at earthlink.net>
  • Date: Thu, 31 Mar 2005 01:25:43 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

On 3/30/05 at 3:22 AM, stevebg at adelphia.net (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},Ã?}}), and bb has the
>general form {{6,4},{9,2},{5,6},{3,8},Ã?}. 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.

aa = {2, 5, 7, 9, 11}; 
bb = {{6, 4}, {9, 2}, {5, 6}, {3, 8}}; 
Select[bb, FreeQ[aa, First@#] && FreeQ[aa, Last@#1]&]

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