def Deque.pop_back.refill
import bend-kit-collections@0.1.4.1/deque.bend as Dequeimport Base
126def Deque.pop_back.refill(
127 a, -A: Kind(a), fn: List<a, A> & Nat
128) -> Maybe<&1, A & Deque<a, A>>:
129 (f, n) = fn
130 Deque.pop_back.halves(a, A, Deque.split(a, A, Deque.half(n), f))