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Re: What is happening here? (TagSet)

  • To: mathgroup at smc.vnet.net
  • Subject: [mg28074] Re: What is happening here? (TagSet)
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Fri, 30 Mar 2001 04:12:25 -0500 (EST)
  • Organization: Universitaet Leipzig
  • References: <99chu9$8eq@smc.vnet.net> <99f5b2$bf8@smc.vnet.net> <99ut4h$62s@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

 just try it. Since Re[] and Im[] are different functions
there is no build in rule that say 

Re[z_]/; Im[z]==0 :=z

and so you should define Re[] and Im[].

Regards
  Jens

John Todd wrote:
> 
> On 23 Mar 2001 04:34:26 -0500, Jens-Peer Kuska
> <kuska at informatik.uni-leipzig.de> wrote:
> 
> One other quick related question:
> 
> if I do the following:
> 
> x/:Im[x]=0;
> y/:Im[y]=0;
> 
> all of the equations and problems work just as well as if I had done
> this:
> 
> x/:Im[x]=0;
> y/:Im[y]=0;
> x/:Re[x]=x;
> y/:Re[y]=y;
> 
> which makes sense to me, because the last two 'upvalues' for x seem
> redundant in my mind, at least from a mathematical viewpoint.  Is
> there some reason that I should go with the latter form as opposed to
> the former, or will the former suffice?
> 
> Thanks,
> 
> JT


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