Frank Luebeck has written some utilities for doing just this type of thing:
http://www.math.rwth-aachen.de/~Frank.Luebeck/gap/FUtil/index.html Perhaps they will help. ++++++++++++++++++++++++++++++++++++++++++++++++ On 8/7/07, Mathieu Dutour <[EMAIL PROTECTED]> wrote: > Thank you for this reference I will look at it. > > But the main problem is not there. I have my existing > software for polyhedral computations of polytope defined over > the rational numbers. I want to work with 600-cell, 120-cell > whose vertices are defined over Q(Sqrt(5)) preferably without > having to modify the code. > > The question is on the structure of GAP itself. Is it possible > to redefine the ">" test so that it is the natural order > of the real field, which is used, when comparing two elements > of Q(Sqrt(5)) ? > > Mathieu > > On Tue, Aug 07, 2007 at 12:19:20PM +0300, [EMAIL PROTECTED] wrote: > >> One can implement in GAP exact algorithms for real algebraic numbers, as > >> described e.g. in the recent monograph Algorithms in Real Algebraic > >> Geometry by Basu, Pollack, and Roy (there is also an online version of it > >> on the net). > >> But this is quite a bit of work. > >> HTH, > >> Dima > >> > >> -original message- > >> Subject: [GAP Forum] Real field > >> From: "Mathieu Dutour" <[EMAIL PROTECTED]> > >> Date: 06/08/2007 13:37 > >> > >> Dear all, > >> > >> I would like to work with numbers of the form (1+Sqrt(5))/2 > >> in order to work with 600-cell, 120-cell and such kind of > >> polytopes. > >> > >> Currently such numbers are coded in GAP with cyclotomic > >> extensions, which means that we have no comparison and functions > >> like (1+Sqrt(5))/2 > 30 does not return what I would like. > >> > >> Is there a way to code a real field like Q(Sqrt(5)) in GAP > >> so as to have reliable comparison operator? > >> > >> -- > >> Mathieu Dutour Sikiric Researcher in Mathematics > >> Telephone:.(+385)1 4571 237 and Computer Science > >> Cell Phone: (+385)9 19 36 30 80 Laboratory of satellite oceanography > >> E-mail: [EMAIL PROTECTED] Rudjer Boskovic Institute > >> http://www.liga.ens.fr/~dutour Zagreb Croatia > >> skype name: mathieudutour > >> > >> _______________________________________________ > >> Forum mailing list > >> [email protected] > >> http://mail.gap-system.org/mailman/listinfo/forum > > -- > Mathieu Dutour Sikiric Researcher in Mathematics > Telephone:.(+385)1 4571 237 and Computer Science > Cell Phone: (+385)9 19 36 30 80 Laboratory of satellite oceanography > E-mail: [EMAIL PROTECTED] Rudjer Boskovic Institute > http://www.liga.ens.fr/~dutour Zagreb Croatia > skype name: mathieudutour > > _______________________________________________ > Forum mailing list > [email protected] > http://mail.gap-system.org/mailman/listinfo/forum > _______________________________________________ Forum mailing list [email protected] http://mail.gap-system.org/mailman/listinfo/forum
