Chacha.prefix: def of bend-collections-laws-crypto@1.0.0.0
Import: import bend-collections-laws-crypto@1.0.0.0/spec/crypto/chacha.bend as Chacha
Lines 130-135 of bend-collections-laws-crypto@1.0.0.0/spec/crypto/chacha.bend: https://jend.leeeet.dev/read.txt?path=bend-collections-laws-crypto@1.0.0.0/spec/crypto/chacha.bend&start_line=130&end_line=135

import Base

# The first n bytes of a list, and the rest.
def prefix(n: Nat, xs: List<&2, U32>) -> List<&2, U32>:
  match n xs:
    case 0n _: Nil{}
    case 1n+p Nil{}: Nil{}
    case 1n+p x <> rest: x <> prefix(p, rest)

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=U32