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Re: Solve never calls Equal?

  • To: mathgroup at
  • Subject: [mg120307] Re: Solve never calls Equal?
  • From: Andrzej Kozlowski <akoz at>
  • Date: Mon, 18 Jul 2011 06:13:44 -0400 (EDT)
  • References: <> <ivovvt$qpa$> <> <> <ivuc93$gth$> <>

> I think it is hard to claim that these test could be done only with 
Significance arithmetic.  However, DanL has indicated that tracing Equal 
may not be effective if the system programs utilize some internal call 
to a system entry into PossibleZeroQ.  The point remains that
> redefining Equal as done here does not seem to adversely affect 
NSolve, Reduce, NIntegrate. Nor does it seem to take much time.

As usual, your reply avoids the only important thing, which is the 
example that I posted.

Reduce[Exp[x] - x == 1/2&&  Abs[x]<  1, x]

Try it again yourself, with Equal replaced by SameQ and without. What do 
you see?

It's amazing that you can deny what you can and everyone can see and 
still claim that "Reduce has not been effected". It is also clear that 
you do not understand why I chose this particular example and why your 
improvement broke it.

Hint: this equation is being solved *exactly* and yet your "improvement" 
breaks it. 

The main problem is that you don't understand the mathematics involved 
here.   The fact that you than produces a lot of examples that have 
obviously no relevance to this issue confirms this.

This sort of thing is not new Richard. I have already offered, to 
re-post some of your past posts which show you lack of understanding of 
the basics of Mathematica. But I can also post some examples, like this 
one, that show that you do not understand the mathematics behind it, and 
yet arrogantly presume to be instructing those who do (at least better 
than you).

Andrzej Kozlowski

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