Bill Allombert on Tue, 29 Jan 2013 15:55:07 +0100


[Date Prev] [Date Next] [Thread Prev] [Thread Next] [Date Index] [Thread Index]

Re: Is this a bug ? 

On Tue, Jan 29, 2013 at 03:33:15PM +0100, Karim Belabas wrote:
> * Ewan Delanoy [2013-01-29 15:14]:
> >  ? polcoeff(8*a+9*b,1,b)
> >  %2 = 9
> >  ? (polcoeff(8*a+9*b,1,b))%4
> >  %3 = 0
> 
> The last division takes place in Q[a], in which 4 is invertible. You
> probably want to do something like
>   n = simplify( polcoeff(8*a+9*b,1,b) );
>   n % 9

It is usually better do to 
polcoeff(polcoeff(8*a+9*b,1,b),0,a)

Cheers,
Bill.