Point.double: def of bend-collections@1.0.0.0
Import: import bend-collections@1.0.0.0/src/crypto/ed25519/point.bend as Point
Lines 80-92 of bend-collections@1.0.0.0/src/crypto/ed25519/point.bend: https://jend.leeeet.dev/read.txt?path=bend-collections@1.0.0.0/src/crypto/ed25519/point.bend&start_line=80&end_line=92

import Base
import bend-collections@1.0.0.0/src/crypto/curve25519/field.bend as F

# RFC 8032 5.1.4, doubling
def double(p: Pt) -> Pt:
  match p:
    case Pt{+x1, +y1, +z1, t1}:
      +a = F.sq(x1)
      +b = F.sq(y1)
      +zz = F.sq(z1)
      +cc = F.add(zz, zz)
      +h = F.add(a, b)
      +e = F.sub(h, F.sq(F.add(x1, y1)))
      +g = F.sub(a, b)
      +f = F.add(cc, g)
      Pt{F.mul(e, f), F.mul(g, h), F.mul(f, g), F.mul(e, h)}

Uses (5):
  https://jend.leeeet.dev/definition.txt?path=bend-collections@1.0.0.0/src/crypto/curve25519/field.bend&name=add
  https://jend.leeeet.dev/definition.txt?path=bend-collections@1.0.0.0/src/crypto/curve25519/field.bend&name=mul
  https://jend.leeeet.dev/definition.txt?path=bend-collections@1.0.0.0/src/crypto/curve25519/field.bend&name=sq
  https://jend.leeeet.dev/definition.txt?path=bend-collections@1.0.0.0/src/crypto/curve25519/field.bend&name=sub
  https://jend.leeeet.dev/definition.txt?path=bend-collections@1.0.0.0/src/crypto/ed25519/point.bend&name=Pt