Field.subl: def of bend-collections@1.0.0.0
Import: import bend-collections@1.0.0.0/src/crypto/curve25519/field.bend as Field
Lines 156-170 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=156&end_line=170

import Base

# a + k - b limbwise
def subl(xs: List<&2, U32>, ys: List<&2, U32>, ks: List<&2, U32>) -> List<&2, U32>:
  match xs:
    case Nil{}:
      Nil{}
    case Con{x, xt}:
      match ys:
        case Nil{}:
          Nil{}
        case Con{y, yt}:
          match ks:
            case Nil{}:
              Nil{}
            case Con{k, kt}:
              Con{U32.sub(U32.add(x, k), y), subl(xt, yt, kt)}

Uses (4):
  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.sub