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Re: How to select unique elements in a list?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg8348] Re: How to select unique elements in a list?
  • From: "Nigel King" <nigelk at nortel.ca>
  • Date: Tue, 26 Aug 1997 02:22:42 -0400
  • Organization: Nortel
  • Sender: owner-wri-mathgroup at wolfram.com

In article <5rmq5u$po1 at smc.vnet.net>,
crose at c2.telstra-mm.net.au (Colin Rose) wrote:

>"Carl Woll" <carlw at u.washington.edu> wrote:
>
> First, let me say that Union does not do what I'm looking for! I am
> interested in a function which returns the unique elements from a list.
> Let's call the function Distinct. Then, I want
>
> Distinct[{i1,i2,i3,i2}]        to return        {i1,i3}
>  
>  RemoveDuplicates[a___,i_,i_,b___]:=RemoveDuplicates[a,b]
>  Distinct[a_List]:=List@@RemoveDuplicates@@Sort[a]

I am not sure that people have noticed in this that the removal above does
not remove odd numbers of duplicates

In[19]:=Distinct[{1,2,2,2,3}]
Out[19]={1,2,3}

any solutions? As noticed pattern matching is not easy!

Nigel King
Northern Telecom




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