(**************************************************************)
(*   Copyright Dominique Larchey-Wendling *                 *)
(*                                                            *)
(*                             * Affiliation LORIA -- CNRS  *)
(**************************************************************)
(*      This file is distributed under the terms of the       *)
(*         CeCILL v2 FREE SOFTWARE LICENSE AGREEMENT          *)
(**************************************************************)

Require Import List.

From Undecidability.Shared.Libs.DLW.Vec
  Require Import pos vec.

Set Implicit Arguments.

(* Standard De Bruijn extension and De Bruijn projection *)

(* Fixpoint instead of Definition because of better unfolding properties *)

Fixpoint de_bruijn_ext {X} (ν : nat -> X) x n { struct n } :=
  match n with
    | 0 => x
    | S n => ν n
  end.

Notation "x · ν" := (de_bruijn_ext ν x) (at level 2, format "x · ν", right associativity).
Notation "ν ⭳" := (fun n => ν (S n)) (at level 2, format "ν ⭳", no associativity).

Fact de_bruijn_ext_proj X (ν : nat -> X) x n : (x·ν)⭳ n = ν n.
Proof. reflexivity. Qed.

Fact de_bruijn_proj_ext X (ν : nat -> X) n : (ν 0)·(ν⭳) n = ν n.
Proof. destruct n; reflexivity. Qed.

(* Friendly notations for binders *)

Notation "x '≋' y" := (prod (x->y) (y->x))
   (at level 95, no associativity,
    format "x '≋' y") : type_scope.

Notation "'∀' x .. y , p" := (forall x , .. (forall y , p) ..)
  (at level 200, x binder, y binder, right associativity,
   format "'[' '∀' x .. y , '/ ' p ']'", only printing)
  : type_scope.

Notation "'∃' x .. y , p" := (ex (fun x => .. (ex (fun y => p)) ..))
  (at level 200, x binder, y binder, right associativity,
   format "'[' '∃' x .. y , '/ ' p ']'", only printing)
  : type_scope.

Notation "'∑' x .. y , p" := (sigT (fun x => .. (sigT (fun y => p)) ..))
  (at level 200, x binder, y binder, right associativity,
   format "'[' '∑' x .. y , '/ ' p ']'", only printing)
  : type_scope.

Notation "'∑' x .. y ( z : T ) , p" := (sigT (fun x => .. (sigT (fun y => sig (fun z : T => p))) ..))
  (at level 200, x binder, y binder, right associativity,
   format "'[' '∑' x .. y ( z : T ) , '/ ' p ']'", only printing)
  : type_scope.

Notation "'∑' z : T , p" := (sig (fun z : T => p))
  (at level 200, right associativity,
   format "'[' '∑' z : T , '/ ' p ']'", only printing)
  : type_scope.

(* Various reserved notations *)

Reserved Notation "⇡ sig" (at level 1, format "⇡ sig").

Reserved Notation "t '⟬' σ '⟭'" (at level 1, format "t ⟬ σ ⟭").
Reserved Notation "'⟦' t '⟧'" (at level 1, format "⟦ t ⟧").

Reserved Notation "f '⦃' σ '⦄'" (at level 1, format "f ⦃ σ ⦄").
Reserved Notation "'⟪' f '⟫'" (at level 1, format "⟪ f ⟫").

(* Unary ops *)

Reserved Notation "⌞ x ⌟" (at level 1, format "⌞ x ⌟").
Reserved Notation "↓ x" (at level 1, format "↓ x").
Reserved Notation "x †" (at level 1, format "x †").

(* Infix Binary ops *)

Reserved Notation "x ∙ y" (at level 2, right associativity, format "x ∙ y").
Reserved Notation "x ⪧ y" (at level 2, right associativity, format "x ⪧ y").
Reserved Notation "x → y" (at level 2, right associativity, format "x → y").

Reserved Notation "⟬ s , t ⟭" (at level 1, format "⟬ s , t ⟭").
Reserved Notation "x ∪ y" (at level 52, left associativity).

(* Infix Binary rels *)

Reserved Notation "x ∈ y" (at level 59, no associativity).
Reserved Notation "x ∉ y" (at level 70, no associativity).
Reserved Notation "x ≈ y" (at level 59, no associativity).
Reserved Notation "x ≉ y" (at level 59, no associativity).
Reserved Notation "x ⊆ y" (at level 59, no associativity).

Reserved Notation "x ≾ y" (at level 70, no associativity).

(* Reserved Notation "x ≺ y" (at level 70, no associativity). *)
(* Reserved Notation "x ⊆ y" (at level 70, no associativity). *)