Karim BELABAS on Sat, 15 Mar 2003 15:29:46 +0100 (MET)

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Re: QX_caract

On Wed, 5 Mar 2003, Bill Allombert wrote:
> Why not use the modular algorithm of ZX_caract directly in QX_caract
> instead of removing the content and calling ZX_caract ?
> Of course I have not addressed how to implement this, in particular
> how to know we have a sufficiently large modulus.

For this to work, the result needs to be in Z[X], wich is not the current
specification of QX_caract.

Hum. Well, there's no documented specification, and the current behaviour is
already incoherent (one argument is assumed to be integral). So I might as
well assume the result is integral, since it's the only situation
which is of interest here.


OK, this is implemented in CVS. The modulus bound is rigorous (~ Hadamard
bound + floating point computation if bound is huge).

I have removed QX_caract: simply some of the ZX_* functions tolerate a
non-integral argument _provided_ the result is integral. As they already did
in fact [ replacing the QX_caract call by ZX_caract would have worked ! ]

I know, all of this needs to be documented ...


Karim Belabas                     Tel: (+33) (0)1 69 15 57 48
Dép. de Mathématiques, Bât. 425   Fax: (+33) (0)1 69 15 60 19
Université Paris-Sud              http://www.math.u-psud.fr/~belabas/
F-91405 Orsay (France)            http://www.parigp-home.de/  [PARI/GP]