MathGroup Archive 2010

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Replace and ReplaceAll -- simple application

  • To: mathgroup at
  • Subject: [mg106171] Re: Replace and ReplaceAll -- simple application
  • From: Bill Rowe <readnews at>
  • Date: Sun, 3 Jan 2010 03:44:16 -0500 (EST)

On 1/1/10 at 9:16 AM, fateman at (Richard Fateman)

>Bill Rowe wrote: ...

>>That is, failure of any software to do what a user expects is
>>certainly not a bug if that is what the software is documented to


>Here's why.  By your definition, no program has a bug if the
>programmer asserts that the program, by virtue of being written in a
>high-level language, is its own readable documentation. Therefore
>anything that the program does is documented by its own code and
>therefore is not a bug.

I agree there are those who lack sufficient integrity/honesty to
admit error claiming whatever result is obtained is what was
intended in the first place. But, I don't agree the existence of
such people shows my definition above is equivalent to saying
"no program has a bug". In short, your hypothetical is rather inane.

>>The key problem here is a novice user of Mathematica might think of
>>using replacement rules as doing mathematics.

>Maybe he was confused by the title "Mathematica -- A System for
>Doing Mathematics",  and thought that Mathematica was a system for
>doing mathematics.

>>That simply isn't the case.

>Apparently you thought that Mathematica was "A system for doing
>rule-based syntactic transformations on FullForm expressions which
>may or may not correspond to what is displayed"

I am very much aware something as complex as Mathematica is not
adequately defined by a simple one line statement. That is
Mathematica is more than simply a system for doing mathematics
or a system for doing rule-based syntactic transformations. If I
was forced to define Mathematica is a simple one line statement
it would be something along the lines of "Mathematica is a
general purpose programming language with an emphasis on doing mathematics.  "

If Mathematica was limited to doing just valid mathematics, it
would be significantly less powerful and useful than it is currently.

>>And since replacing one thing with another is not mathematics,
>>insisting the result makes sense mathematically simply isn't a
>>realistic expectation.

>TaDa.  I couldn't have expressed it better myself.  Insisting that
>the results of a transformation is mathematically consistent, "isn't
>a realistic expectation."

>Which, in my view, demonstrates the existence of a bug.

This would be a logical conclusion *if* the only allowed
transformations where mathematical transformations. But since
Mathematica provides the capability of doing far more than just
mathematical transformations, it is very much unrealistic to
expect a non-mathematical transformatino to be mathematically
valid. And the fact such non-mathematical transformations exist
certainly is a design feature not a bug.

>I suppose one could try to determine who is right by a survey,  or ask
>people in the street what they think.

And what would this accomplish? If I walk out to the street and
ask those I encounter, my expectation is the overwhelming
response would be "What is Mathematica?".

Your entire point seems to be Mathematica should only return
mathematically valid results and anything else is a "bug". This
point ignores the fact that Mathematica is far more than a
system for doing mathematics and consequently isn't a valid point.

  • Prev by Date: Re: More /.{I->-1} craziness
  • Next by Date: Re: algebraic numbers
  • Previous by thread: Re: Replace and ReplaceAll -- simple application
  • Next by thread: Re: Replace and ReplaceAll -- simple application