Re: ell from j

[Bill Allombert <Bill.Allombert@math.u-bordeaux1.fr>]

On Mon, Jun 11, 2012 at 07:56:48AM -0700, William Stein wrote:
> Just a note -- that's what I did with Sage for a while, e.g.,
> 
>    EllipticCurve(j)
> 
> produced a curve with j-invariant j.  This caused no end of confusion
> and bugs in user code, since it is so similar to
> 
>    EllipticCurve(v)
> 
> where v is a list of invariants or
> 
>    EllipticCurve(a4,a6).
> 
> People were so annoyed by my choice, they deprecated it.

Well, so I have just called the function ellfromj() and it returns an ell5:

? ellfromj(-3375)
%1 = [0,0,0,-51667875,-175774110750]
? E=ellinit(%1);
? algdep(E.omega[1]/E.omega[2],2)
%3 = 2*x^2-x+1

We can still change the interface though.

Cheers,
Bill.