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re: Specifying rules

• To: mathgroup at yoda.physics.unc.edu
• Subject: re: Specifying rules
• From: rubin at msu.edu (Paul A. Rubin)
• Date: Wed, 15 Jun 94 16:01:33 EDT

>Hello, I have a problem with complex numbers !
>
>I want to tell Mma that a is real, such that
>Im[a+I] will give 1,
>but I do not get this result.
>
>I have tried
>
>a /: Im[a]=0
>
>
>Can anyone help me ?
>
>==============================================================================
>Marnix Van Daele
>Universiteit Gent
>Vakgroep Toegepaste Wiskunde en Informatica
>Krijgslaan 281 - Gebouw S9
>B9000 Gent (Belgium)
>
>tel. 32-(0)9-264.48.09
>fax. 32-(0)9-264.49.95
>==============================================================================
>
The standard package Algebra`ReIm` should do it:

In[]:=  <<Algebra`ReIm`
In[]:=  a /: Im[a] = 0
Out[]=  0
In[]:=  Im[a + I]
Out[]=  1

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