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Re: Generalizing Complement to handle multiple occurrences of elements

  • To: mathgroup at smc.vnet.net
  • Subject: [mg112443] Re: Generalizing Complement to handle multiple occurrences of elements
  • From: Yves Klett <yves.klett at googlemail.com>
  • Date: Wed, 15 Sep 2010 20:02:57 -0400 (EDT)
  • References: <i6q0ml$l7c$1@smc.vnet.net>

Hi,

what about:

a = {1, 2, 2, 3, 4, 4, 4, 4};
b = {3, 5, 7};

Cases[a, Alternatives @@ Complement[a, b]]

{1, 2, 2, 4, 4, 4, 4}

Predictably, there will be faster solutions than using Cases though.

Regards,
Yves

Am 15.09.2010 10:38, schrieb Mark Coleman:
> Greetings,
> 
> I'm wondering how one can efficiently generalize the built-in
> Complement function to return multiple occurrences of elements. For
> instance, the current version generates
> 
> a={1,2,2,3,4,4,4,4}
> b={3,5,7}
> 
> Complement[a,b]={1,2,4}
> 
> I'm looking for a way to define
> 
> myComplement[a,b]={1,2,2,4,4,4,4}
> 
> My current code is very inefficient!
> 
> Thanks,
> 
> Mark
> 


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