How to use a named elliptic curve?

[Jeffrey Walton <noloader@gmail.com>]

Hi Everyone,

I'm working through the elliptic curve tutorial at
https://pari.math.u-bordeaux.fr/Events/PARI2017c/talks/ecc_en.pdf. I
want to use a named curve, like secp256k1 or secp256r1. It does not
appear to be covered in the tutorial.

Here are a couple attempts that don't work:

? E=ellinit(secp256k1)
  ***   at top-level: E=ellinit(secp256k1)
  ***                   ^------------------
  *** ellinit: incorrect type in ellxxx [not an elliptic curve (ell5)] (t_POL).
  ***   Break loop: type 'break' to go back to GP prompt

? E=ellinit("secp256k1")
  ***   at top-level: E=ellinit("secp256k1")
  ***                   ^--------------------
  *** ellinit: incorrect type in ellsearch (t_STR).
  ***   Break loop: type 'break' to go back to GP prompt

How do I create a named curve?

Thanks in advance,

Jeff