Re: bb_field.{sub,div}

[Bill Allombert <allomber@math.u-bordeaux.fr>]

On Sat, Feb 01, 2014 at 09:17:37PM +0000, Peter Bruin wrote:
> Hi Bill,
> 
> Just out of curiosity, are you actually expecting new bb_field instances
> (using Zech logarithms, maybe)?

Yes, for some infinite fields.

> > I am not in favor of adding methods before there are a practical use
> > for them.
> 
> At least for subtraction there is one (and at the moment admittedly only
> one).  Also, I did not make the patch for abstract reasons, but because
> I was writing a function gen_matinvimage() (doing as the name suggests)
> that would profit from both sub() and div().

What will be the difference with gen_Gauss ?

> Last week I also wrote a bb_field implementation of Strassen's matrix
> multiplication algorithm (for personal use; as far as I understand it is
> considered to be outside the scope of PARI).

I do not think it is outside the scope of PARI. Rather so far
we did not have any application for it.

> Subtraction (not division, though) is also quite helpful for that.  
> So at least from my experience
> it would be user-friendly to provide sub() and div() even if there are
> currently no direct uses inside the PARI library.

...assuming the user does not want to implement a bb_field.

Cheers,
Bill.