Definition t_struct_btree := Tstruct _btreeNode noattr.

Lemma In_sorted_lt : forall x i n l lo hi (Hsort : sorted l) (Hlo : lo >= 0) (Hhi : hi <= Zlength l) (Hin : In x (sublist lo hi l)) (Hi : lo <= i < hi) (Hn : Znth i l 0 = n) (Hgt : x < n), In x (sublist lo i l).