Point.dec_fin: def of bend-collections@1.0.0.0
Import: import bend-collections@1.0.0.0/src/crypto/ed25519/point.bend as Point
Lines 136-142 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=136&end_line=142

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

def dec_fin(+x: List<&2, U32>, +y: List<&2, U32>, +x0: U32, fail: Bool) -> Maybe<&2, Pt>:
  match fail:
    case True{}:
      None{}
    case False{}:
      +x2 = F.select(U32.xor(F.parity(x), x0), x, F.neg(x))
      Some{Pt{x2, y, F.one(), F.mul(x2, y)}}

Uses (11):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Maybe
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.xor
  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=neg
  https://jend.leeeet.dev/definition.txt?path=bend-collections@1.0.0.0/src/crypto/curve25519/field.bend&name=one
  https://jend.leeeet.dev/definition.txt?path=bend-collections@1.0.0.0/src/crypto/curve25519/field.bend&name=parity
  https://jend.leeeet.dev/definition.txt?path=bend-collections@1.0.0.0/src/crypto/curve25519/field.bend&name=select
  https://jend.leeeet.dev/definition.txt?path=bend-collections@1.0.0.0/src/crypto/ed25519/point.bend&name=Pt