fact: Fixpoint find_aux n x t := match n with | (S n) => match t [x] with | None => (x, t) | (Some y) => let (ry, t) := find_aux n y t in (ry, t [x>- ry] ) end | O => (x,t) end.
imports: ATBR(Common) ATBR(MyFSets) ATBR(BoolView) ATBR(Numbers)