fact: Fixpoint pmap_union (f m : pmap) : pmap := match f with | Empty => m | Branch d l r => Branch (match d with | Some x => Some x | None => pmap_here m end) (pmap_union l (pmap_left m)) (pmap_union r (pmap_right m)) end.
imports: ExtLib.Structures.Maps ExtLib.Structures.Functor ExtLib.Data.Option ExtLib.Data.Positive ExtLib.Tactics.Cases