Definition compare (a b : ascii) : Compare lt eq a b :=
    match cmp a b as z return _ = z -> _ with
    | Lt => fun E => LT E
    | Gt => fun E => GT (compare_helper_gt E)
    | Eq => fun E => EQ (compare_helper_eq E)
    end Logic.eq_refl.Definition eq_dec (x y : ascii): {x = y} + { ~ (x = y)} := ascii_dec x y.Definition t := string.Definition eq := @eq string.Definition eq_refl := @eq_refl t.Definition eq_sym := @eq_sym t.Definition eq_trans := @eq_trans t.Inductive lts : string -> string -> Prop :=
    | lts_empty : forall a s, lts EmptyString (String a s)
    | lts_tail : forall a s1 s2, lts s1 s2 -> lts (String a s1) (String a s2)
    | lts_head : forall (a b : ascii) s1 s2,
        lt (nat_of_ascii a) (nat_of_ascii b) ->
        lts (String a s1) (String b s2).Inductive lts : string -> string -> Prop :=
    | lts_empty : forall a s, lts EmptyString (String a s)
    | lts_tail : forall a s1 s2, lts s1 s2 -> lts (String a s1) (String a s2)
    | lts_head : forall (a b : ascii) s1 s2,
        lt (nat_of_ascii a) (nat_of_ascii b) ->
        lts (String a s1) (String b s2).Inductive lts : string -> string -> Prop :=
    | lts_empty : forall a s, lts EmptyString (String a s)
    | lts_tail : forall a s1 s2, lts s1 s2 -> lts (String a s1) (String a s2)
    | lts_head : forall (a b : ascii) s1 s2,
        lt (nat_of_ascii a) (nat_of_ascii b) ->
        lts (String a s1) (String b s2).Inductive lts : string -> string -> Prop :=
    | lts_empty : forall a s, lts EmptyString (String a s)
    | lts_tail : forall a s1 s2, lts s1 s2 -> lts (String a s1) (String a s2)
    | lts_head : forall (a b : ascii) s1 s2,
        lt (nat_of_ascii a) (nat_of_ascii b) ->
        lts (String a s1) (String b s2).Definition lt := lts.

Lemma lts_tail_unique a s1 s2 : lt (String a s1) (String a s2) -> lt s1 s2.