law xl

lawful-bytes@0.1.1.0 · proof_shift.bend:317

import Base
import lawful-bytes@0.1.1.0/defs.bend as D
import lawful-bytes@0.1.1.0/proof_core.bend as C
import lawful-arrays@0.1.0.0/proof_tree.bend as P

317# drop(xs, k) has L - k elements.
318law xl:
319  for +len: U32
320  for +t: P.Tree<U32>
321  for +d: Nat
322  for +kk: Nat
323  for +h0: {D.ok(C.BT(len, t), d) == True{} : Bool}
324  {List.length(&2, U32, List.drop(&2, U32, D.view(C.BT(len, t)), kk)) == Nat.sub(U32.to_nat(len), kk) : Nat}