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Re: global real variables
*To*: mathgroup at smc.vnet.net
*Subject*: [mg22046] Re: global real variables
*From*: "Kevin J. McCann" <kevin.mccann at jhuapl.edu>
*Date*: Fri, 11 Feb 2000 02:38:26 -0500 (EST)
*Organization*: Johns Hopkins University Applied Physics Lab, Laurel, MD, USA
*References*: <87trds$5o3@smc.vnet.net>
*Sender*: owner-wri-mathgroup at wolfram.com
There are other ways, but here is one that I use. It employs the
Algebra`ReIm` Package and uses Upsets to tell Mathematica that x and p are reals:
<< Algebra`ReIm`
Re[x] ^= x;
Im[x] ^= 0;
Re[p] ^= p;
Im[p] ^= 0;
Now you can do this:
Conjugate[x]
x
Conjugate[ x + x * p^-1 ]
x + x/p
Note, however
Conjugate[y]
just gives
Conjugate[y]
because Mathematica doesn't know enough about y to do any more.
Hope this helps,
Kevin
--
Kevin J. McCann
Johns Hopkins University APL
Naum Phleger <naum at cava.physics.ucsb.edu> wrote in message
news:87trds$5o3 at smc.vnet.net...
> I asked a dumb question a few weeks ago about making variables real
and
> found that Mathematica 4 took care of this better. I have been using it
> since. I still have a couple of problems with it though. First, I can
have
> variables be treated as real by using the assumption Element[x,Reals] in a
> simplify command, but I want x to be real in all commands so I don't have
to
> keep using Simplify each time I want x to be recognized as real. Second,
> even this doesn't seem to work quite right. Here is what I mean.
>
>
> Say I have tow var.s, x and p. Both are real so I can do this.
>
> Simplify[ Conjugate[ x ] , Element[ x , Reals ] ] ----> x
>
> amd I get the same thing for p, but it stops working if I have functions
of
> x and p, for instance I get
>
>
> Simplify[ Conjugate[ x + x * p^-1 ] , Element[ {x,p} , Reals ] ] ---->
>
> Conjugate[ x + x * p^-1 ]
>
>
> It works if I use FullSimplify AND put p^-1 into the list of variables
> that I want to have real. How can I get around this without listing every
> negative power of every variable and wasting time with FullSimplify.
Thanks
> for any help. Thanks.
>
>
> -NAUM
>
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