def List.filter

Base · base.bend:1063

1063def List.filter(~A: Data, ~f: A -> Bool, xs: List<&2, A>) -> List<&2, A>:
1064  match xs:
1065    case Nil{}:
1066      Nil{}
1067    case +h <> t:
1068      List.filter.put(A, h, List.filter(~A, ~f, t), f(h))