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MathGroup Archive 1998

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Re: how to pull real numbers out of a linear funktion ?



Roland Bollmann wrote:
> 
> I want to define a function f[x_] with the property, that
> 
> f[c_ x_] := c f[x] whenever c is a real number
> 
> and
> 
> f[c_ x_] := -c f[x] whenever c is a komplex number.
> 

Rolland,
What can x be?
If x is a symbol we can use
In[1]:=
f[c_Complex x_]:= c f[x];

In[2]:=
f[c_Real x_] := -c f[x];

You might also want

In[262]:=
f[c_Integer x_] := -c f[x];

In[263]:=
f[c_Rational x_] := -c f[x];

Other possibilities may be more complicated.

-- 
Allan Hayes
Training and Consulting
Leicester, UK
hay@haystack.demon.co.uk
http://www.haystack.demon.co.uk
voice: +44 (0)116 271 4198
fax: +44 (0)116 271 8642




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