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MathGroup Archive 2000

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Sorting with Infinity

  • To: mathgroup at smc.vnet.net
  • Subject: [mg23513] Sorting with Infinity
  • From: Jack Goldberg <jackgold at math.lsa.umich.edu>
  • Date: Tue, 16 May 2000 02:44:59 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hi group;

I construct lists which may look like this

	{7,-2,-Infinity,Infinity,1}

When this list is sorted by using Sort, I get

	{-2,1,7,-Infinity,Infinity}

I would prefer, naturally, 

	{-Infinity,-2,1,7,Infinity}

This is easy to do if one doesn't care about elegance.  Without 
spelling out the obvious details, here are a few kludges:

(1) Replace Infinity by 10^15, Sort  then switch back to Infinity.
(2) Use Append and Prepend after Sort and  deleting infinities.
(3) RotateRight after Sort and switch signs on infinities

Anyone got a "cute" solution say by using a sorting function or 
perhaps some arcane command unknown to mere mortals? 

Jack

 



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