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MathGroup Archive 2001

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Re: complex coefficients and rules...

  • To: mathgroup at
  • Subject: [mg28211] Re: complex coefficients and rules...
  • From: Jens-Peer Kuska <kuska at>
  • Date: Thu, 5 Apr 2001 03:00:26 -0400 (EDT)
  • Organization: Universitaet Leipzig
  • References: <9aelr6$>
  • Sender: owner-wri-mathgroup at


the online help (Conjugate|Further Examples) say:

Exp[-4 I y] /. Complex[0, a_] :> Complex[0, -a]

And it *is* the "official" way, even if you don't like it.
The reason is that Complex[1,2] is a numerical data type


with symbolic a and b is *not* Complex[a,b] it is



Richard Easther wrote:
> 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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