Re: Sorting with Infinity

• To: mathgroup at smc.vnet.net
• Subject: [mg23517] Re: Sorting with Infinity
• From: Daniel Reeves <dreeves at eecs.umich.edu>
• Date: Tue, 16 May 2000 22:29:50 -0400 (EDT)
• References: <8fqrpb\$h5g@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```The problem is that Sort uses OrderedQ and
OrderedQ[{-Infinity, 123}] == False

But you can use Less instead, as in
Sort[list, Less]

--    --    --    --    --    --    --    --    --    --    --    --
Daniel Reeves               http://ai.eecs.umich.edu/people/dreeves/

Build a man a fire, and he's warm for the
rest of the evening. Set a man on fire and
he's warm for the rest of his life.

---\/   FROM Jack Goldberg ON 00.05.16 03:02 (Today)   \/---

> 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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