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
- References:
- More /.{I->-1} craziness
- From: AES <siegman@stanford.edu>
- More /.{I->-1} craziness