Re: Symbolic complex conjugation?

• To: mathgroup at smc.vnet.net
• Subject: [mg89944] Re: [mg89919] Symbolic complex conjugation?
• From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
• Date: Wed, 25 Jun 2008 06:24:21 -0400 (EDT)
• References: <200806240731.DAA11098@smc.vnet.net>

```On 24 Jun 2008, at 16:31, AES wrote:

> I'm sorry, but I just don't understand why the following test case
> works
> just fine:
>
> [In copying it, I've substituted "Isymbol" for the \[ImaginaryI] that
> actually appears in the Out[] cells.]
>
>   In[202]:= eqna={a+I b==0};
>   solna=Solve[eqna,b];
>   b=b/.solna[[1]];
>   bStar=b/.{I->-I};
>   {b, Star}
>
>   Out[205]={ -Isymbol a, Isymbol a }
>
> but the actual calculation that prompted the test case doesn't:
>
>   In[206]:= eqnp={((dwa/2)+I(w-wa))p-I (kappa/(2 w))dN e==0};
>   solnp=Solve[eqnp,p];
>   p=p/.solnp[[1]];
>   pStar=p/.{I->-I}
>
>   Out[208]= { (dN e kappa)/(w (-Isymbol dwa+2 w-2 wa)),
>                        (dN e kappa)/(w (-Isymbol dwa+2 w-2 wa)) }
>
> And actually, I guess my real concern is not understanding "how it
> happens" -- but more "how it can happen" that Mathematica can do
> something this potentially damaging to some innocent user.
>

Because Mathematica is not meant and has never been meant as a tool
for "innocent users" who try to use pattern matching without learning
about FullForm of expressions. Such users would be well advised to use
instead a graphic calculator  or its software equivalent.

For those who are not entirely innocent the following solution is
obvious:

pStar = p/.Complex[a_,b_]:>Complex[a,-b]

Andrzej Kozlowski

```

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