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Re: Sorting with Infinity

  • To: mathgroup at smc.vnet.net
  • Subject: [mg23520] Re: Sorting with Infinity
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Tue, 16 May 2000 22:29:52 -0400 (EDT)
  • Organization: Universitaet Leipzig
  • References: <8fqrpb$h5g@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

Sort[{-2, 1, 7, -Infinity, Infinity}, N[#1] < N[#2] &]

gives

{-\[Infinity], -2, 1, 7, \[Infinity]}

Regards
  Jens

Jack Goldberg wrote:
> 
> 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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