Re: factor() boob

[Karim BELABAS <Karim.Belabas@math.u-psud.fr>]

On Wed, 13 Aug 2003, Phil Carmody wrote:
> The following version of GP:
>
> GP/PARI CALCULATOR Version 2.2.5 (alpha)
> i686 running linux (ix86/GMP-4.1.2 kernel) 32-bit version
> (readline v4.1 enabled, extended help available)
>
>
> does naughty things when asked to factor simple difference of squares
> quadratics:
>
>
> gp > for(i=1,908,if(length(factor(x^2-i*i)~)==1,print(i"\t("x^2-i*i")\t"factor(x^2-i*i))))
> 58      (x^2 - 3364)    Mat([x^2 - 3364, 1])
[...]
> Has this been noticed before or even already fixed?

Yes and yes [ introduced in 2.2.5, fixed in 2.2.6 ( missing factor 2 in
root_bound(), when bounding the root of largest modulus ). ].

When using the unstable version, you should try and upgrade once in a while
( 2.2.5 is 6 months old already!. As usual, CVS is the preferred way to keep
up. )

Cheers,

    Karim.
-- 
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]