Section MAIN.
(* conseq adjoins an element x of X to finite functions f:(fin N)->X *)
(* This is done by {0->x; m+1->f(m)} : (fin N+1)->X, ie. the new element *)
(* is inserted at the front. That's why it's called conseq: it's the seq *)
(* variant of the cons operator as seen in lists *)
(** %\label{conseq}% *)
Definition conseq :
forall (A : Setoid) (n : Nat) (a : A) (v : seq n A), seq (S n) A.
intros.
apply
(Build_Map
(Ap:=fun m : fin (S n) =>
match m return (A:Type) with
| Build_finiteT x0 x1 =>
match x0 as x2 return (x2 < S n -> (A:Type)) with
| O => fun _ : 0 < S n => a
| S m' =>
fun HSm' : S m' < S n =>
Ap v (Build_finiteT (lt_S_n m' n HSm'))
end x1
end)).
red in |- *.
simpl in |- *.
intros x0 y.
case x0.
case y.
simpl in |- *.
intros x2 y1.
induction x2.
intros x2 y2.
induction x2.
intro; apply Refl.
intro H.
inversion H.
clear IHx2.
simple induction index.
intros h H.
inversion H.
intros.
clear H.
apply Ap_comp; auto with algebra.
Defined.
Notation "a ;; b" := (conseq a b) (at level 60, right associativity).
Variables (A : Setoid) (n : Nat) (a : A).
intros.
simpl in |- *.
red in |- *.
intro i'.
elim i'.
intro i.
simpl in |- *.
case i.
auto.
intros.
apply Ap_comp; auto with algebra.
Qed.
Hint Resolve cons_comp: algebra.
auto with algebra.
Qed.
(** %\label{head}% *)
Definition head (A : Setoid) (n : Nat) (v : seq (S n) A) :=
v (Build_finiteT (lt_O_Sn n)).
unfold head in |- *.
auto with algebra.
Qed.
Hint Resolve head_comp cons_first_element: algebra.
auto with algebra.
Qed.
auto with algebra.
Qed.
Hint Resolve head_unfolding1 head_unfolding2: algebra.
Hint Extern 0 (head _ =' _ in _) => unfold head in |- *: algebra.
Hint Extern 0 (_ =' head _ in _) => unfold head in |- *: algebra.
auto with algebra.
Qed.
Hint Resolve head_cons_inv: algebra.
intros.
unfold head in |- *.
apply Ap_comp; auto with algebra.
Qed.
Hint Resolve seq_S_O_contains_single_elt: algebra.
intros.
simpl in |- *.
red in |- *.
intro.
apply Trans with (head v).
apply seq_S_O_contains_single_elt; auto with algebra.
apply Trans with (head v'); auto with algebra.
Qed.
Hint Resolve seq_S_O_head_fixes_everything: algebra.
intros.
simpl in |- *.
apply Ap_comp; auto with algebra.
Qed.
Hint Resolve cons_later_elements: algebra.
(* Taking the "tl" of a sequence *)
(** %\label{Seqtl}% *)
Definition Seqtl : forall n : Nat, seq n A -> seq (pred n) A.
clear n.
intro n.
case n.
intro f.
exact f.
intros m f.
apply
(Build_Map
(Ap:=fun i' : fin m =>
match i' with
| Build_finiteT i Hi => f (Build_finiteT (lt_n_S _ _ (Hi:i < m)))
end)).
red in |- *.
intros x y.
case x.
case y.
simpl in |- *.
intros.
apply Ap_comp; auto with algebra.
Defined.
induction n.
intros.
simpl in |- *.
auto.
intros.
simpl in |- *.
red in |- *.
simpl in |- *.
intro.
elim x.
intros.
apply Ap_comp; auto with algebra.
Qed.
Hint Resolve Seqtl_comp: algebra.
(** - "hdtl" is a 'tool' for writing a sequence as the cons of its head and its tail %\label{hdtl}% *)
Definition hdtl (v : seq (S n) A) := head v;; Seqtl v:seq (S n) A.

Lemma conseq_hdtl :
forall (v : seq (S n) A) (H : 0 < S n),
v =' v (Build_finiteT H);; Seqtl v in _.