def peek_back_ready

bend-collections@1.0.0.0 · src/containers/deque.bend:89

import Base
import bend-collections@1.0.0.0/src/containers/types/deque.bend as E

89def peek_back_ready(~T: Data, d: Deque<T>) -> Deque<T> & Result<&2, &2, E.Error, T>:
90  match d:
91    case DE{f, Nil{}, nf, nb}:
92      (DE{f, Nil{}, nf, nb}, Fail{E.EmptyDeque{}})
93    case DE{f, Con{+x, b}, nf, nb}:
94      (DE{f, Con{x, b}, nf, nb}, Done{x})