Chacha.put: 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 25-30 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=25&end_line=30

import Base

# The list with element i replaced (unchanged past its end).
def put(xs: List<&2, U32>, i: Nat, y: U32) -> List<&2, U32>:
  match xs i:
    case Nil{} _: Nil{}
    case x <> rest 0n: y <> rest
    case x <> rest 1n+p: x <> put(rest, p, y)

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