Section MoveToSymbol_Sem.
Local Arguments skipn { A } !n !l.
Local Arguments plus : simpl never.
Local Arguments mult : simpl never.
Variable sig : finType.
(* Halt function *)
Variable stop : sig -> bool.
(* Rewrite function *)
Variable f : sig -> sig.

Corollary MoveToSymbol_L_correct_moveleft ls x ls' m rs :
(forall x, List.In x ls -> stop x = false) ->
stop x = true ->
MoveToSymbol_L_Fun stop f (tape_move_left' (ls ++ x :: ls') m rs) =
midtape ls' (f x) (rev (map f ls) ++ m :: rs).