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Re: complex coefficients and rules...

• To: mathgroup at smc.vnet.net
• Subject: [mg28215] Re: [mg28203] complex coefficients and rules...
• From: BobHanlon at aol.com
• Date: Thu, 5 Apr 2001 03:00:29 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

y /: Conjugate[y] = y;

Conjugate[Exp[-4*I*y]]

E^(4*I*y)

Bob Hanlon

In a message dated 2001/4/4 4:33:54 AM, easther at physics.columbia.edu writes:

>I am having some trouble applying some simple rules to complex
>expressions. 
>
>For instance,
>
> Exp[-4 I y] /. I-> -I
>
>yields
>
> Exp[-4 I y]
>
>This seemed a bit odd, so I looked at the "full form" and found,
>
>Power[E, Times[Complex[0, -4], y]]
>
>However, trying the match 
>
> Exp[-4 I y] /. a_ I -> -a I
>
>doesn't work either, since FullForm[a I ]  is Times[Complex[0, -1], a]
>and so the patterns do not match.  
>
>All I want is a simple complex conjugate (the Conjugate function does
>not assume that y is real), that maps I->-I. The more tricky 
>
> Exp[-4 I y] /. Complex[a_ ,b_] -> Complex[a,-b] 
>
>does work, but it is seems a little cumbersome.
>
>In any case my question is: is there a general way to avoid having to do
>this, or is Mathematica always going to assume that any algebraic
>constant is potentially complex?
>