def p_drop_append_add

bend-osdev-bytes@0.1.1.0 · PROOF.bend:1205

import Base
import bend-osdev-bytes@0.1.1.0/bytes.bend as B

1205def p_drop_append_add(+a: B.Octets, +n: Nat, +b: B.Octets) -> {B.Octets.drop(Nat.add(B.Octets.len(a), n), B.Octets.append(a, b)) == B.Octets.drop(n, b) : B.Octets}:
1206  match a b:
1207    case B.Octets{+xs} B.Octets{+ys}:
1208      %F_app(xs, ys) : {B.Octets{B.w8s.drop(Nat.add(B.w8s.len.fast(xs), n), _)} == B.Octets{B.w8s.drop(n, ys)} : B.Octets}
1209      %F_len(xs) : {B.Octets{B.w8s.drop(Nat.add(_, n), List.append(&2, B.OctByte, xs, ys))} == B.Octets{B.w8s.drop(n, ys)} : B.Octets}
1210      Equal.cong(List<&2, B.OctByte>, B.Octets, l => B.Octets{l}, B.w8s.drop(Nat.add(List.length(&2, B.OctByte, xs), n), List.append(&2, B.OctByte, xs, ys)), B.w8s.drop(n, ys), off.drop_app_add(xs, n, ys))