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Re: [Help-gsl] Complex numbers - how?

From: Federico Zenith
Subject: Re: [Help-gsl] Complex numbers - how?
Date: Tue, 1 Mar 2005 15:37:13 +0100
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Alle 15:12, martedì 01 marzo 2005, Anders Misfeldt ha scritto:
> Hi,
> I have a program where I calculate an ugle integral. In the integral I'm
> having
> (1/(x^2-1))^{3/2}
> and my x is lower than 1! But since it's taking to the power of 3/2 I
> should still get a real number. 

Hm, last time I checked i³ = -i. So you should indeed get an imaginary number 
as long as x² < 1. Unless I'm missing something or my coffee was not strong 

> GSL_SET_COMPLEX(&ztest, 3, 4);
> GSL_REAL(ztest);
> printf("%g",ztest);
> but I get the following error:
> error: request for member `dat' in something not a structure or union
> What am I doing wrong?

Well, I suppose you did:

        gsl_complex ztest ;

Other than that, you must consider that GSL_REAL (and GSL_IMAG too) is a macro 
that _returns_ a value, not one that messes up its argument. So, to sum it 

        gsl_complex ztest ;
        GSL_SET_COMPLEX( &ztest, 3, 4 ) ;
        printf( "%g", GSL_REAL(ztest) ) ;


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