fact: Fixpoint pmap_remove (p : positive) (m : pmap) {struct p} : pmap := match m with | Empty => Empty | Branch d l r => match p with | xH => branch None l r | xO p => branch d (pmap_remove p l) r | xI p => branch d l (pmap_remove p r) end end.
imports: ExtLib.Structures.Maps ExtLib.Structures.Functor ExtLib.Data.Option ExtLib.Data.Positive ExtLib.Tactics.Cases