Bill Allombert on Sun, 09 Dec 2007 20:53:59 +0100 |
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Re: FFELT: how to recover the field? |
On Sun, Dec 09, 2007 at 07:46:30PM +0100, Jeroen Demeyer wrote: > Bill Allombert wrote: > >Why are sqrtn(x,p) and x^(1/p) less obvious ? > > Karim Belabas wrote: > >What's wrong with sqrtn(x,p) ? > > Okay, true. I guess I was thinking too much as a programmer instead of > a mathematician. By the way, these functions don't work for finite > field POLMODs, so it's not *that* obvious :-) Fixing this limitation was one of the motivation of adding FFELT. > Karim Belabas wrote: > >It doesn't seem to be possible currently (only x.p and x.pol work). > >I'll add x.mod to the allowed member functions > > Maybe you could also add lift(x) to make things more analogous to POLMODs. What should lift return ? a POLMOD by analogy to INTMOD ? FFELTs are not supposed to be analogous to POLMODs, but rather to INTMODs. Also there is a technical limitation: FFELTs do not respect variables priorities (which make them much less troublesome to use than POLMODs) so if you allow to lift the FFELT coefficients of a polynomial, you might end up with a invalid polynomial. Cheers, Bill.