fact: Fixpoint Tget (p:positive) (T:Tree) {struct p} : Poption := match T with Tempty => PNone | Branch0 T1 T2 => match p with xI pp => Tget pp T2 | xO pp => Tget pp T1 | xH => PNone end | Branch1 a T1 T2 => match p with xI pp => Tget pp T2 | xO pp => Tget pp T1 | xH => PSome a end end.
imports: List BinPos