Re: GP: issquare() bug

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

On Mon, 29 Apr 2002, Michael Somos wrote:
> ? issquare(I)
> %1 = 1
> ? issquare(I,&x)
>   ***   not an integer argument in an arithmetic function
>
> which seems inconsistent to me. Shalom, Michael

Well, the manual says:

issquare(x,{&n}):

[...] If n is given and an exact square root had to be computed in the
checking process, puts that square root in n. This is in particular the case
when x is an integer or a polynomial.


This means that the issquare(x,&n) form is (a priori) only accepted when x is
a t_INT or a t_POL. The point is that, for some types, we can't prove x is a
square without actually computing a square root. In that case, it is nicer to
make that square root available to the user instead of forcing him to
recompute it.


Another potential problem in your example:  a t_COMPLEX is understood as a
general complex number, which admits a square root by definition.
( issquare(I) doesn't assert anything about Gauss integers. )


If you find the documentation for that routine misleading, please rewrite it
in a less confusing way.

Thanks,

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