Karim Belabas on Fri, 12 Sep 2008 09:56:43 +0200 |
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Re: qfrep of binary forms |
* Ariel Pacetti [2008-09-11 18:46]: > Is there an easy way to compute the numbers represented by a binary > quadratic form? There is no built-in solution. > qfrem and qfminim do not accept a binary quadratic form (as output from > Qfb) as input and there is no implemented routine to transform a binary > quadratic form into a 2 by 2 matrix (the only solution I found is to > compute Vec() and construct the matrix from this, although there might be > a better one). Even though none of these two function really answer your question, it would make sense for the Mat(t_QFB) conversion to return the associated 2 x 2 matrix, instead of the 1 x 1 matrix containing the qfb. E.g. (09:49) gp > Mat( Qfb(1,2,3) ) %1 = [1 1] [1 3] instead of the current (09:49) gp > Mat( Qfb(1,2,3) ) %2 = [Qfb(1, 2, 3)] which is essentielly useless since addition is not defined for t_QFB (so that no matrix operation will succeed). Cheers, K.B. -- Karim Belabas, IMB (UMR 5251) Tel: (+33) (0)5 40 00 26 17 Universite Bordeaux 1 Fax: (+33) (0)5 40 00 69 50 351, cours de la Liberation http://www.math.u-bordeaux.fr/~belabas/ F-33405 Talence (France) http://pari.math.u-bordeaux.fr/ [PARI/GP] `