Limbs.add: def of bend-collections@1.0.0.0
Import: import bend-collections@1.0.0.0/src/crypto/secp256k1/limbs.bend as Limbs
Lines 59-64 of bend-collections@1.0.0.0/src/crypto/secp256k1/limbs.bend: https://jend.leeeet.dev/read.txt?path=bend-collections@1.0.0.0/src/crypto/secp256k1/limbs.bend&start_line=59&end_line=64

import Base

# limb-wise sum; the longer tail is kept
def add(xs: List<&2, Nat>, ys: List<&2, Nat>) -> List<&2, Nat>:
  match xs ys:
    case Nil{} _: ys
    case x <> xt Nil{}: x <> xt
    case x <> xt y <> yt: Nat.add(x, y) <> add(xt, yt)

Uses (3):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat.add