Definition bneq_empty_string(s:string):bool :=
match (string_dec s ""%string) with
| left _ => false
| right _ => true
end.(** ** Lemmas for list *)

Definition concat_list_string(xs:list string) := 
  fold_right (fun s s' : string => (s ++ s')%string) ""%string xs.

Lemma forallb_divide_left : forall (A:Type)(f:A -> bool) (l l':list A), forallb f (l ++ l') = true -> forallb f l = true.