def app_nilu
import bend-osdev-bytes@0.1.1.0/PROOF.bend as PROOFimport Base
248def app_nilu(+xs: List<&2, U32>) -> {List.append(&2, U32, xs, Nil{}) == xs : List<&2, U32>}:
249 match xs:
250 case Nil{}:
251 {==}
252 case Con{h, t}:
253 Equal.cong(List<&2, U32>, List<&2, U32>, l => Con{h, l}, List.append(&2, U32, t, Nil{}), t, app_nilu(t))