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MathGroup Archive 1992

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Re: A Simplify that really simplifies? Summary

  • To: mathgroup at
  • Subject: Re: A Simplify that really simplifies? Summary
  • From: alex at (Alex Dommasch)
  • Date: Thu, 8 Oct 92 10:36:22 MDT

>	 It is not possible to incorporate all of these operations into a
>	 single function like Simplify.  Some of the heuristics are
>	 incompatible with each other, and even if they weren't, the resulting
>	 function would be prohibitively slow.

>If it can't be done automatically, can we get some support for doing it
>manually?  I'd like to be able to extract a subexpression, perform some
>operations on it, and replace it in the original expression.  All this
>is possible with ordinary Mma of course, but I want some help to ensure
>that because of a typo (for example) I don't inadvertently change the value 

>of the subexpression.  I should be able to type Factor[%], but not %^2.
>Perhaps Mma could be persuaded to evaluate Simplify[%==%%] in the background,
>and notify me if it's untrue.  Mma should also remember what the original
>expression was, so I don't have to look it up to perform the replacement.

I wholeheartedly agree.  It is so frustrating to see how a subexpression could  
be simplified, and yet have no way of directing Mma to do it (aside from  
manually picking apart the expression and then reassembling it).  I suppose  
this is related to my earlier message about improved Mma front ends.  (By the  
way, I got quite a few messages back about that, all in agreement, and a few  
even encouraging me to do it myself - which I would love to do if I didn't have 
a full time job).  What would be ideal is if you could select part of an  
expression, and press a "Factor" button, or "Group" button, or something like  
that, and be assured that Mma will only change the form, not the value, of the  
D. A. (Alex) Dommasch, Programmer
Field-Flow Fractionation Research Center
Department of Chemistry, University of Utah
Salt Lake City, Utah 84112
(801)581-7168           FAX: (801)581-4353
alex at (NeXT Mail)

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