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Re: Solve never calls Equal?

• To: mathgroup at smc.vnet.net
• Subject: [mg120300] Re: Solve never calls Equal?
• From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
• Date: Sun, 17 Jul 2011 06:04:20 -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> <4E2285B3.9040104@eecs.berkeley.edu> <B41B6049-875E-418A-8B6F-921C87D04326@mimuw.edu.pl>

Maybe the "joke" should be more clearer for the benefit of the more 
naive users (and I include Richard in this category) for reasons that 
will soon become obvious (though they already are to many).

Firstly, Solve does not hold its arguments as everyone except the most 
naive users will know, so the fact that Solve[eqns,x] will first 
evaluate eqns and then will attempt to compare (using Equal) a symbolic 
expression to a number is also news to someone like Richard. (In fact I 
pointed out similar things to him in the past and if he really wants to 
be reminded of that I can post these messages).
So, of course, once Equal has been replaced by SameQ, you wil end up 
with Solve[False,x] etc.

Only someone like Richard will find this so exciting that it needs to be 
explained. I am sorry, but the only reason why I omitted doing so myself 
was that it seemed to me too patronising to other users to explain such 
obvious stuff.

On the other hand, the fact that having modified Equal in this way, 
Richard tested functions which do not normally use significance 
arithmetic instead of choosing an example that actually needs it, does 
show something about Richard's understanding of Mathematica.

So that is what makes his joke so funny, eve if he did not necessarily 
intend it to be so.

Andrzej Kozlowski


On 17 Jul 2011, at 09:30, Andrzej Kozlowski wrote:

>
> On 17 Jul 2011, at 08:48, Richard Fateman wrote:
>
>> The point of this predecessor note was to explain to Andrzej why 
Solve appeared to him to be broken.
>> In fact, Solve does not use Equal in this example.
>
> That's, of course, one of Richard's funnier jokes (as may people here 
I am sure will notice by themselves).
>
> Andrzej Kozlowski

• 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>