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Re: More /.{I->-1} craziness

  • To: mathgroup at smc.vnet.net
  • Subject: [mg106051] Re: [mg106017] More /.{I->-1} craziness
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Thu, 31 Dec 2009 03:16:47 -0500 (EST)
  • Organization: Mathematics & Statistics, Univ. of Mass./Amherst
  • References: <200912300915.EAA17299@smc.vnet.net>
  • Reply-to: murray at math.umass.edu

These "seemingly wildly inconsistent" results are explained, in large 
part, by what has been posted in this thread earlier, and in particular 
by [mg106003] from Daniel Lichtblau.  Perhaps "at first surprising" 
would be a much better description tan "seemingly wildly inconsistent".

Try these:

   FullForm /@ {-I, -E, -Pi, -Infinity}
   AtomQ /@ {-I, -E, -Pi, -Infinity}

To my mind, the only possible surprise here -- simply because I never 
looked at it before, concerns -Infinity.  But anything concerning 
infinite quantities is bound to be so special that nothing about 
handling of Infinity would really surprise me.

AES wrote:
> The more I play with these I->-I substitution rules, the more seemingly 
> wildly inconsistent results emerge.  For example:  
> 
>    In[1]:= -I/.I->-I
> 
>    Out[1]= -I
> 
>    In[3]:= -E/.E->-E
> 
>    Out[3]= << The Esc e e Esc symbol >>
> 
>    In[4]:= -Pi/.Pi->-Pi
> 
>    Out[4]= \[Pi]
> 
>    In[5]:= -Infinity/.Infinity->-Infinity
> 
>    Out[5]= -\[Infinity]
> 
> (In/Out[2] is removed because it was an irrelevant cell.)
> 

-- 
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305


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