Re: Solve never calls Equal?

*To*: mathgroup at smc.vnet.net*Subject*: [mg120307] Re: Solve never calls Equal?*From*: Andrzej Kozlowski <akoz at mimuw.edu.pl>*Date*: Mon, 18 Jul 2011 06:13:44 -0400 (EDT)*References*: <201107150118.VAA23606@smc.vnet.net> <ivovvt$qpa$1@smc.vnet.net> <201107160941.FAA08237@smc.vnet.net> <7BBB2BCC-0234-4BDA-A129-3270EBA623CE@mimuw.edu.pl> <ivuc93$gth$1@smc.vnet.net> <4E2377E3.2010606@cs.berkeley.edu>

> > > 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. > > RJF 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

**Follow-Ups**:**Re: Solve never calls Equal?***From:*Daniel Lichtblau <danl@wolfram.com>

**References**:**Re: Numerical accuracy/precision - this is a bug or a feature?***From:*"Christoph Lhotka" <christoph.lhotka@univie.ac.at>

**Solve never calls Equal?***From:*Richard Fateman <fateman@cs.berkeley.edu>