Field.select: def of bend-collections@1.0.0.0
Import: import bend-collections@1.0.0.0/src/crypto/curve25519/field.bend as Field
Lines 197-207 of bend-collections@1.0.0.0/src/crypto/curve25519/field.bend: https://jend.leeeet.dev/read.txt?path=bend-collections@1.0.0.0/src/crypto/curve25519/field.bend&start_line=197&end_line=207

import Base

# s == 0: a; s == 1: b; limbwise a * (1 - s) + b * s
def select(+s: U32, xs: List<&2, U32>, ys: List<&2, U32>) -> List<&2, U32>:
  match xs:
    case Nil{}:
      Nil{}
    case Con{x, xt}:
      match ys:
        case Nil{}:
          Nil{}
        case Con{y, yt}:
          Con{U32.add(U32.mul(x, U32.sub(1, s)), U32.mul(y, s)), select(s, xt, yt)}

Uses (5):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.add
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.mul
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32.sub