Re: qfrep of binary forms

["Karim Belabas" <Karim.Belabas@math.u-bordeaux1.fr>]

* 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
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