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From: Warren <ve3wwg@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Inferring array index type from array object
Date: Tue, 29 Jun 2010 20:55:28 +0000 (UTC)
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Adam Beneschan expounded in news:73a0af1d-7213-44af-90fa-ed6de4c64ce8
@b4g2000pra.googlegroups.com:

> On Jun 29, 12:31�pm, Warren <ve3...@gmail.com> wrote:
>>
>> > So, what is the "missing" function?
>>
>> > <http://www.adaic.com/standards/05rm/html/RM-G-1-2.html>
>>
>> 1) The "inverse" of a complex number.
> 
> Isn't that just 1.0 / X?  

Ok, it seems to be, as the GSL (Gnu Scientific Library)
defines it as:

gsl_complex
gsl_complex_inverse (gsl_complex a)
{                               /* z=1/a */
  double s = 1.0 / gsl_complex_abs (a);

  gsl_complex z;
  GSL_SET_COMPLEX (&z, (GSL_REAL (a) * s) * s, -(GSL_IMAG (a) * s) * s);
  return z;
}

But is this (GSL code) computationally more accurate 
than a simple 1/Z? Faster? I don't know, as I am currently
porting to Ada and avoiding analysis at this point (a huge 
task). But I do know that accuracy can be a good reason to 
implement something as a specialized function (like ATAN2
for example).

Warren