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Re: Replacement Rule with Sqrt in denominator

  • To: mathgroup at smc.vnet.net
  • Subject: [mg114434] Re: Replacement Rule with Sqrt in denominator
  • From: Bill Rowe <readnews at sbcglobal.net>
  • Date: Sat, 4 Dec 2010 06:14:11 -0500 (EST)

On 12/3/10 at 5:19 AM, fateman at cs.berkeley.edu (Richard Fateman)
wrote:

>Anyway, I would rather have the CAS do some simple guessing of what
>I mean, as at least a fair trade for me having to guess what secret
>things will happen in FullSimplify or Integrate or Solve,  or ...
>especially as versions change.

I definitely do not want Mathematica to do any guessing as to
what I mean. I very strongly dislike software that behaves in
that manner. This leads to unpredictability and often
significant difficulty in stopping the "guessing" to have
exactly what I inputed executed as I want. Word is a good
example of software that implements this "guessing" which is one
reason I very much dislike Word.

I also see a very significant difference between how replacement
rules operate and changes in things like FullSimplify,
Integrate, Solve ... These functions are not "guessing" as to
what I want. Yes, they involve complex algorithms that may
change from version to version and may mean results change from
version to version. Unlike these functions, operation of
replacement rules is truly easy to predict once you realize the
operate on the FullForm of an expression. There is no ambiguity.
And since replacement is a literal replacement, the behavior is
consistent from version to version.

>Basically, explaining a bug does not make it into a feature,

When an aspect of software works as designed it is inappropriate
to refer to that aspect as a bug. The fact replacement rules
operate on the FullForm of an expression but what is displayed
is not the FullForm does mean inexperienced users of Mathematica
will encounter some difficulties with replacement rules. But,
that simply doesn't equate to being a bug.



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