From: "John B. Matthews" <nospam@nospam.invalid>
Subject: Re: Inferring array index type from array object
Date: Tue, 29 Jun 2010 17:47:58 -0400
Date: 2010-06-29T17:47:58-04:00 [thread overview]
Message-ID: <nospam-807C34.17475829062010@news.aioe.org> (raw)
In-Reply-To: Xns9DA6ACEFDCF8BWarrensBlatherings@81.169.183.62
In article <Xns9DA6ACEFDCF8BWarrensBlatherings@81.169.183.62>,
Warren <ve3wwg@gmail.com> wrote:
> Warren expounded in news:Xns9DA6AC2A2C8BWarrensBlatherings@81.169.183.62:
>
> > 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;
> > }
>
> Apologies for following up my own post, but
> looking at the GSL implementation of complex
> division:
> [...]
> Given a=1.0, the inverse function is definitely
> higher performance. It's simpler calculation
> probably implies more accuracy as well.
The more comparable Ada implementation (from GNAT) would be
function "/" (Left : Real'Base; Right : Complex) return Complex is
a : constant R := Left;
c : constant R := Right.Re;
d : constant R := Right.Im;
begin
return Complex'(Re => (a * c) / (c ** 2 + d ** 2),
Im => -((a * d) / (c ** 2 + d ** 2)));
end "/";
--
John B. Matthews
trashgod at gmail dot com
<http://sites.google.com/site/drjohnbmatthews>
next prev parent reply other threads:[~2010-06-29 21:47 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-23 7:30 Inferring array index type from array object Maciej Sobczak
2010-06-23 8:01 ` Dmitry A. Kazakov
2010-06-23 9:03 ` J-P. Rosen
2010-06-23 12:24 ` Georg Bauhaus
2010-06-23 12:52 ` J-P. Rosen
2010-06-23 19:09 ` Simon Wright
2010-06-24 7:25 ` Georg Bauhaus
2010-06-23 14:38 ` Robert A Duff
2010-06-23 15:17 ` J-P. Rosen
2010-06-23 17:17 ` Robert A Duff
2010-06-24 6:16 ` J-P. Rosen
2010-06-23 12:13 ` Niklas Holsti
2010-06-23 14:27 ` Peter C. Chapin
2010-06-23 20:24 ` Niklas Holsti
2010-06-23 16:33 ` Warren
2010-06-23 17:49 ` Dmitry A. Kazakov
2010-06-23 18:45 ` Warren
2010-06-23 20:39 ` Niklas Holsti
2010-06-28 13:44 ` Warren
2010-06-28 22:18 ` Niklas Holsti
2010-06-29 1:49 ` Adam Beneschan
2010-06-29 2:10 ` (see below)
2010-06-29 16:56 ` Warren
2010-06-29 17:50 ` John B. Matthews
2010-06-29 19:31 ` Warren
2010-06-29 20:06 ` Jeffrey R. Carter
2010-06-29 20:16 ` Warren
2010-06-29 20:22 ` Adam Beneschan
2010-06-29 20:39 ` Dmitry A. Kazakov
2010-06-29 20:55 ` Warren
2010-06-29 21:00 ` Warren
2010-06-29 21:47 ` John B. Matthews [this message]
2010-06-29 21:52 ` Damien Carbonne
2010-06-29 22:22 ` Adam Beneschan
2010-06-30 16:43 ` Warren
2010-06-29 21:18 ` Jeffrey R. Carter
2010-06-30 5:01 ` Simon Wright
2010-06-30 14:29 ` Adam Beneschan
2010-06-29 20:28 ` Damien Carbonne
2010-06-29 21:20 ` John B. Matthews
2010-06-23 13:12 ` Gautier write-only
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