Field.sub: def of bend-collections@1.0.0.0
Import: import bend-collections@1.0.0.0/src/crypto/secp256k1/field.bend as Field
Lines 48-53 of bend-collections@1.0.0.0/src/crypto/secp256k1/field.bend: https://jend.leeeet.dev/read.txt?path=bend-collections@1.0.0.0/src/crypto/secp256k1/field.bend&start_line=48&end_line=53

import Base
import bend-collections@1.0.0.0/src/crypto/secp256k1/limbs.bend as L

# a - b = a + (p - b); the first argument is looked at first, so that a
# constant b is never unfolded while a is unknown
def sub(a: List<&2, Nat>, +b: List<&2, Nat>) -> List<&2, Nat>:
  match a:
    case Nil{}: reduce(L.neg_raw(c(), b))
    case x <> t: reduce(L.add(x <> t, L.neg_raw(c(), b)))

Uses (6):
  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=bend-collections@1.0.0.0/src/crypto/secp256k1/field.bend&name=c
  https://jend.leeeet.dev/definition.txt?path=bend-collections@1.0.0.0/src/crypto/secp256k1/field.bend&name=reduce
  https://jend.leeeet.dev/definition.txt?path=bend-collections@1.0.0.0/src/crypto/secp256k1/limbs.bend&name=add
  https://jend.leeeet.dev/definition.txt?path=bend-collections@1.0.0.0/src/crypto/secp256k1/limbs.bend&name=neg_raw