| William Stein on Mon, 11 Jun 2012 16:57:36 +0200 |
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| Re: ell from j |
On Mon, Jun 11, 2012 at 7:38 AM, Andreas Enge <andreas.enge@inria.fr> wrote: > On Fri, Jun 08, 2012 at 09:37:39PM +0200, Bill Allombert wrote: >> It has been suggested to add a function to PARI which return an elliptic curve with >> a prescribed j-invariant. >> >> An example of such function is >> >> ellfromj(j)=if(j==0,[0,0,0,0,1],if(j==1728,[0,0,0,1,0],[0,0,0,3,2]*(j/(1728-j)))); >> >> How should we call it ? What should it return ? (an ell2,an ell5, a smallell, etc ?) > > How about calling it "ellinit", using just a scalar parameter? 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. > > Andreas > -- William Stein Professor of Mathematics University of Washington http://wstein.org