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MathGroup Archive 1998

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Re: Complex -> List does not work

It  probably does not answer the question "why" but the following might
throw some light it:



ReleaseHold[Hold[2+3 I]/.Complex->List]

2+3 I

So 2+3 I is not "really" the same as Complex[2,3]. After evaluating
Complex[2,3] its head Complex  behaves like the head "Integer" that
(for example) the integer 2 has rather than like the head List in

At 2:22 AM -0500 1/20/98, Gianluca Gorni wrote:
>I naively tried the following way of turning a complex number into a
>couple of real numbers:
>         2 + 3 I /. Complex -> List
>but it gives me back
>                2 + 3 I
>even though the full form of 2+3I is Complex[2,3]. The reverse however
>is possible:
>   {2,3}/.List->Complex  gives  2+3I
>The help browser says that "you have to use Re and Im to extract parts
>of Complex numbers".
>Why this exception to the basic principles of replacement rules?
>                 Gianluca Gorni
>Gianluca Gorni
>Universita` di Udine
>Dipartimento di Matematica e Informatica via delle Scienze 208
>I-33100 Udine UD
>Ph.:(39) (432) 558422    Fax:(39) (432) 558499

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