dear Prof. Bartholdi,
many thanks for your hint to package 'float' and the examples
of correct use, which should suffice to get approx. roots of complex poly's.
You know, I could calculate symbolic with complex numbers in CAS like
Maxima,
but I wanted to do the work 'inside' GAP.
So 'float' is exactly, what I was looking for.
beste Gruesse
Wolfgang Lindner
-----Ursprüngliche Nachricht-----
Von: Laurent Bartholdi <laurent.bartho...@gmail.com>
An: kroeker <kroe...@uni-math.gwdg.de>; GAP Forum <fo...@gap-system.org>;
Wolfgang Lindner <lindn...@t-online.de>
Datum: Dienstag, 20. März 2012 11:40
Betreff: Re: [GAP Forum] arithmetic in C
Dear Wolfgang,
I reply only now to your question because I'm not on the "forum" mailing
list; it was kindly forwarded by Jakob.
It's very tricky to work with complex numbers in pure algebra; GAP
contains, since its latest release (4.5.2), support for floating-point
approximations of complex numbers, which I assume is what you want.
You'll have to compile the package "float", whose source is part of the
distribution but requires its own configuration (the usual ./configure &&
make in .../pkg/float; hopefully the process works smoothly, but if
something goes wrong please tell me).
Then you can access floating-point complex numbers within GAP; a sample
session is:
gap> LoadPackage("float");
true
gap> SetFloats(MPC,1000); # 1000 bits of precision
gap> r := PolynomialRing(MPC_PSEUDOFIELD,1); # 1 indeterminate
â„‚[z]
gap> r.1^5-1;
z^5-.1e1+.0e0i
gap> RootsFloat(last);
[ .309017e0+.951057e0â…ˆ, -.809017e0+.587785e0â…ˆ, -.809017e0-.587785e0â…ˆ,
.1e1-.989853e-301â…ˆ,
.309017e0-.951057e0â…ˆ ]
gap> last2^2;
z^10+(-.2e1+.0e0i)*z^5+.1e1+.0e0i
gap>
On Tue, Mar 20, 2012 at 10:28 AM, kroeker <kroe...@uni-math.gwdg.de> wrote:
> **
>
>
> -------- Original-Nachricht -------- Betreff: [GAP Forum] arithmetic in C
Datum:
> Wed, 14 Mar 2012 09:05:05 +0100 Von: Wolfgang Lindner
> <lindn...@t-online.de> <lindn...@t-online.de> An:
<fo...@gap-system.org><fo...@gap-system.org> CC:
> forum-requ...@gap-system.org
>
> dear group,
>
> I know how to calculate with Rationals, ZmodnZ, Integers etc.
> But I could not find infos in the help-index of GAP
> how to do calculations in the complex field C
> (I know about gaussionInteger).
>
> I would like to work in C[X] etc.
>
> regards
> Wolfgang
>
>
> _______________________________________________
> Forum mailing
listfo...@mail.gap-system.orghttp://mail.gap-system.org/mailman/listinfo/for
um
>
>
--
Prof. Dr. Laurent Bartholdi \ laurent.bartholdi<at>gmail<dot>com
G.-A. Universität zu Göttingen \ Phone: +49 551 39 7826
Bunsenstraße 3-5 \ Secr: +49 551 39 7752
D-37073 Göttingen, Germany \ Fax: +49 551 39 22674
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