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Re: Real variables (i.e. non-complex)

  • To: mathgroup at smc.vnet.net
  • Subject: [mg16565] Re: Real variables (i.e. non-complex)
  • From: "Kevin J. McCann" <kevinmccann at Home.com>
  • Date: Wed, 17 Mar 1999 23:54:50 -0500
  • Organization: @Home Network
  • References: <7cl7ff$9d1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Christian,

It is a bit awkward:

<< Algebra`ReIm`

Re[a] ^= a;
Im[a] ^= 0;

I usually use the following:

<< Algebra`ReIm`

ri[x_]:=Module[{},
  Re[x]^=x;
  Im[x]^=0;
  Conjugate[x]^=x;
  ]

then

ri[a]

The "^=" is called an Upset and essentially associates the rule with the
variable, i.e. whenever Mathematica sees Re[a] it returns a, but only for the
variable a.


Cheers,
Kevin


Christian wrote in message <7cl7ff$9d1 at smc.vnet.net>...
>Hello!
>
>How do I tell Mathematica to assume that one variable is real (i.e.
Im[x]=0)
>or positive? I hoped to achieve that by setting appropriate attributes
(like
>constant) but there are none...
>
>Christian
>
>
>




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