Library Coq.rtauto.Bintree

Require Export List.
Require Export BinPos.
Require Arith.EqNat.

Open Scope positive_scope.

Ltac clean := try (simpl; congruence).

Lemma Gt_Psucc: forall p q,
       (p ?= Pos.succ q) = Gt -> (p ?= q) = Gt.

Lemma Psucc_Gt : forall p,
       (Pos.succ p ?= p) = Gt.

Fixpoint Lget (A:Set) (n:nat) (l:list A) {struct l}:option A :=
match l with nil => None
| x::q =>
match n with O => Some x
| S m => Lget A m q
end end .


Lemma map_app : forall (A B:Set) (f:A -> B) l m,
List.map f (l ++ m) = List.map f l ++ List.map f m.

Lemma length_map : forall (A B:Set) (f:A -> B) l,
length (List.map f l) = length l.

Lemma Lget_map : forall (A B:Set) (f:A -> B) i l,
Lget i (List.map f l) =
match Lget i l with Some a =>
Some (f a) | None => None end.

Lemma Lget_app : forall (A:Set) (a:A) l i,
Lget i (l ++ a :: nil) = if Arith.EqNat.beq_nat i (length l) then Some a else Lget i l.

Lemma Lget_app_Some : forall (A:Set) l delta i (a: A),
Lget i l = Some a ->
Lget i (l ++ delta) = Some a.

Section Store.

Variable A:Type.

Inductive Poption : Type:=
  PSome : A -> Poption
| PNone : Poption.

Inductive Tree : Type :=
   Tempty : Tree
 | Branch0 : Tree -> Tree -> Tree
 | Branch1 : A -> Tree -> Tree -> Tree.

Fixpoint Tget (p:positive) (T:Tree) {struct p} : Poption :=
  match T with
    Tempty => PNone
  | Branch0 T1 T2 =>
    match p with
      xI pp => Tget pp T2
    | xO pp => Tget pp T1
    | xH => PNone
    end
  | Branch1 a T1 T2 =>
    match p with
      xI pp => Tget pp T2
    | xO pp => Tget pp T1
    | xH => PSome a
    end
end.

Fixpoint Tadd (p:positive) (a:A) (T:Tree) {struct p}: Tree :=
 match T with
   | Tempty =>
       match p with
       | xI pp => Branch0 Tempty (Tadd pp a Tempty)
       | xO pp => Branch0 (Tadd pp a Tempty) Tempty
       | xH => Branch1 a Tempty Tempty
       end
   | Branch0 T1 T2 =>
       match p with
       | xI pp => Branch0 T1 (Tadd pp a T2)
       | xO pp => Branch0 (Tadd pp a T1) T2
       | xH => Branch1 a T1 T2
       end
   | Branch1 b T1 T2 =>
       match p with
       | xI pp => Branch1 b T1 (Tadd pp a T2)
       | xO pp => Branch1 b (Tadd pp a T1) T2
       | xH => Branch1 a T1 T2
       end
   end.

Definition mkBranch0 (T1 T2:Tree) :=
  match T1,T2 with
    Tempty ,Tempty => Tempty
  | _,_ => Branch0 T1 T2
  end.

Fixpoint Tremove (p:positive) (T:Tree) {struct p}: Tree :=
   match T with
      | Tempty => Tempty
      | Branch0 T1 T2 =>
        match p with
        | xI pp => mkBranch0 T1 (Tremove pp T2)
        | xO pp => mkBranch0 (Tremove pp T1) T2
        | xH => T
        end
      | Branch1 b T1 T2 =>
        match p with
        | xI pp => Branch1 b T1 (Tremove pp T2)
        | xO pp => Branch1 b (Tremove pp T1) T2
        | xH => mkBranch0 T1 T2
        end
      end.

Theorem Tget_Tempty: forall (p : positive), Tget p (Tempty) = PNone.

Theorem Tget_Tadd: forall i j a T,
       Tget i (Tadd j a T) =
       match (i ?= j) with
         Eq => PSome a
       | Lt => Tget i T
       | Gt => Tget i T
       end.

Record Store : Type :=
mkStore {index:positive;contents:Tree}.

Definition empty := mkStore xH Tempty.

Definition push a S :=
mkStore (Pos.succ (index S)) (Tadd (index S) a (contents S)).

Definition get i S := Tget i (contents S).

Lemma get_empty : forall i, get i empty = PNone.

Inductive Full : Store -> Type:=
    F_empty : Full empty
  | F_push : forall a S, Full S -> Full (push a S).

Theorem get_Full_Gt : forall S, Full S ->
       forall i, (i ?= index S) = Gt -> get i S = PNone.

Theorem get_Full_Eq : forall S, Full S -> get (index S) S = PNone.

Theorem get_push_Full :
  forall i a S, Full S ->
  get i (push a S) =
  match (i ?= index S) with
    Eq => PSome a
  | Lt => get i S
  | Gt => PNone
end.

Lemma Full_push_compat : forall i a S, Full S ->
forall x, get i S = PSome x ->
 get i (push a S) = PSome x.

Lemma Full_index_one_empty : forall S, Full S -> index S = 1 -> S=empty.

Lemma push_not_empty: forall a S, (push a S) <> empty.

Fixpoint In (x:A) (S:Store) (F:Full S) {struct F}: Prop :=
match F with
F_empty => False
| F_push a SS FF => x=a \/ In x SS FF
end.

Lemma get_In : forall (x:A) (S:Store) (F:Full S) i ,
get i S = PSome x -> In x S F.

End Store.









Section Map.

Variables A B:Set.

Variable f: A -> B.

Fixpoint Tmap (T: Tree A) : Tree B :=
match T with
Tempty => Tempty
| Branch0 t1 t2 => Branch0 (Tmap t1) (Tmap t2)
| Branch1 a t1 t2 => Branch1 (f a) (Tmap t1) (Tmap t2)
end.

Lemma Tget_Tmap: forall T i,
Tget i (Tmap T)= match Tget i T with PNone => PNone
| PSome a => PSome (f a) end.

Lemma Tmap_Tadd: forall i a T,
Tmap (Tadd i a T) = Tadd i (f a) (Tmap T).

Definition map (S:Store A) : Store B :=
mkStore (index S) (Tmap (contents S)).

Lemma get_map: forall i S,
get i (map S)= match get i S with PNone => PNone
| PSome a => PSome (f a) end.

Lemma map_push: forall a S,
map (push a S) = push (f a) (map S).

Theorem Full_map : forall S, Full S -> Full (map S).

End Map.


Notation "hyps \ A" := (push A hyps) (at level 72,left associativity).