       Re: complex coefficients and rules...

• To: mathgroup at smc.vnet.net
• Subject: [mg28261] Re: [mg28203] complex coefficients and rules...
• From: "Mark Harder" <harderm at ucs.orst.edu>
• Date: Fri, 6 Apr 2001 01:53:09 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

Richard,
In:= FullForm[Exp[-4 I y] /. I -> -I ]
Out//FullForm=  Power[E, Times[Complex[0, -4], y]]

In:=conj = Exp[-4 I y] /. Complex[a_, b_] -> Complex[a, -b]
4 I y
Out=   E

In:= FullForm[conj]
Out//FullForm= Power[E, Times[Complex[0, 4], y]]

-mark harder

-----Original Message-----
From: Richard Easther <easther at physics.columbia.edu>
To: mathgroup at smc.vnet.net
Subject: [mg28261] [mg28203] complex coefficients and rules...

>
>Hi,
>
>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?
>
>Richard
>

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