Point.add: def of bend-collections@1.0.0.0
Import: import bend-collections@1.0.0.0/src/crypto/ed25519/point.bend as Point
Lines 66-78 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=66&end_line=78

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

# RFC 8032 5.1.4, addition
def add(+c: Cs, p: Pt, q: Pt) -> Pt:
  match p q:
    case Pt{+x1, +y1, +z1, +t1} Pt{+x2, +y2, +z2, +t2}:
      +a = F.mul(F.sub(y1, x1), F.sub(y2, x2))
      +b = F.mul(F.add(y1, x1), F.add(y2, x2))
      +cc = F.mul(F.mul(t1, cs_d2(c)), t2)
      +dd = F.mul(F.add(z1, z1), z2)
      +e = F.sub(b, a)
      +f = F.sub(dd, cc)
      +g = F.add(dd, cc)
      +h = F.add(b, a)
      Pt{F.mul(e, f), F.mul(g, h), F.mul(f, g), F.mul(e, h)}

Uses (6):
  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=sub
  https://jend.leeeet.dev/definition.txt?path=bend-collections@1.0.0.0/src/crypto/ed25519/point.bend&name=Cs
  https://jend.leeeet.dev/definition.txt?path=bend-collections@1.0.0.0/src/crypto/ed25519/point.bend&name=Pt
  https://jend.leeeet.dev/definition.txt?path=bend-collections@1.0.0.0/src/crypto/ed25519/point.bend&name=cs_d2