Set Implicit Arguments.
Require Import List Arith Lia.
From Undecidability.HOU Require Import std.std.
From Undecidability.HOU.calculus Require Import
prelim terms syntax semantics typing.
Set Default Proof Using "Type".
(* * Order Typing *)
Section OrderTyping.
Context {X: Const}.
Definition ctx := list type.
Implicit Types (s t: exp X) (n m: nat) (Gamma Delta Sigma: ctx)
(x y: fin) (c d: X) (A B: type)
(sigma tau: fin -> exp X) (delta xi: fin -> fin).
(* ** Order of Types *)
Section Order.
Fixpoint ord A :=
match A with
| typevar beta => 1
| A → B => max (S (ord A)) (ord B)
end.
Lemma ord_1 A: 1 <= ord A.
Proof.
induction A; cbn [ord]; eauto.
transitivity (S (ord A1)); eauto using Nat.max_lub_l.
Qed.
Lemma ord_arr A B: ord (A → B) = max (S (ord A)) (ord B).
Proof. reflexivity. Qed.
Lemma ord_arr_one A B: ~ ord (A → B) <= 1.
Proof.
intros H; rewrite ord_arr in H; eapply Nat.max_lub_l in H.
rewrite ord_1 with (A := A) in H; lia.
Qed.
Fixpoint ord' Gamma :=
match Gamma with
| nil => 0
| A :: Gamma => max (ord A) (ord' Gamma)
end.
Lemma ord'_app Gamma Gamma': ord' (Gamma ++ Gamma') = max (ord' Gamma) (ord' Gamma').
Proof.
induction Gamma; cbn; eauto.
now rewrite IHGamma, Nat.max_assoc.
Qed.
Lemma ord'_rev L:
ord' (rev L) = ord' L.
Proof.
induction L; cbn; rewrite ?ord'_app; eauto.
simplify; cbn; eauto.
rewrite IHL.
simplify. eapply Nat.max_comm.
Qed.
Lemma ord'_in A Gamma: A ∈ Gamma -> ord A <= ord' Gamma.
Proof.
induction Gamma; cbn in *; intuition; subst; eauto; lia.
Qed.
Lemma ord'_elements n Gamma: (forall A, A ∈ Gamma -> ord A <= n) <-> ord' Gamma <= n.
Proof.
induction Gamma; cbn; intuition; subst; eauto.
all: simplify in *; intuition.
Qed.
Lemma ord'_cons n Gamma A:
ord A < n -> ord' Gamma <= n -> ord' (A :: Gamma) <= n.
Proof.
intros; cbn; eapply Max.max_lub; lia.
Qed.
Lemma order_head Gamma s A B:
Gamma ⊢ s : A -> Gamma ⊢ (head s) : B -> isAtom (head s) -> ord A <= ord B.
Proof.
induction 1; eauto; cbn.
- intros H1 _; inv H1. rewrite H in H2; injection H2 as ->; eauto.
- intros H1; inv H1; eauto.
- cbn in *; intuition.
- intros; rewrite <-IHtyping1; eauto.
rewrite ord_arr; eauto.
Qed.
Lemma ord_target A: ord (target A) <= 1.
Proof. induction A; eauto. Qed.
Lemma ord_target' Gamma: ord' (target' Gamma) <= 1.
Proof.
eapply ord'_elements; unfold target'; intros; mapinj; eauto using ord_target.
Qed.
End Order.
Hint Resolve ord'_cons : core.
(* ** Order Typing *)
Reserved Notation "Gamma '⊢(' n ')' s ':' A" (at level 80, s at level 99).
Inductive ordertyping n Gamma: exp X -> type -> Prop :=
| ordertypingVar x A:
ord A <= n -> nth Gamma x = Some A -> Gamma ⊢(n) (var x) : A
| ordertypingConst c:
ord (ctype X c) <= S n -> Gamma ⊢(n) (const c) : ctype X c
| ordertypingLam s A B:
A :: Gamma ⊢(n) s : B -> Gamma ⊢(n) lambda s : A → B
| ordertypingApp s t A B:
Gamma ⊢(n) s : A → B -> Gamma ⊢(n) t : A -> Gamma ⊢(n) s t : B
where "Gamma '⊢(' n ')' s ':' A" := (ordertyping n Gamma s A).
Hint Constructors ordertyping : core.
Lemma ordertyping_step n Gamma s A:
Gamma ⊢(n) s : A -> Gamma ⊢(S n) s: A.
Proof.
induction 1; eauto.
Qed.
Lemma ordertyping_monotone m n Gamma s A:
m <= n -> Gamma ⊢(m) s : A -> Gamma ⊢(n) s: A.
Proof.
induction 1; eauto using ordertyping_step.
Qed.
Hint Resolve ordertyping_monotone : core.
Lemma ordertyping_soundness n Gamma s A:
Gamma ⊢(n) s : A -> Gamma ⊢ s : A.
Proof.
induction 1; eauto.
Qed.
Lemma ordertyping_completeness Gamma s A:
Gamma ⊢ s : A -> exists n, Gamma ⊢(n) s : A.
Proof.
induction 1.
- exists (ord A); eauto.
- exists (ord (ctype X c)); eauto.
- destruct IHtyping as [n]; exists (max (S (ord A)) n).
econstructor; eauto.
- destruct IHtyping1 as [n], IHtyping2 as [m].
exists (max n m); econstructor; eauto.
Qed.
Lemma vars_ordertyping n x s A Gamma:
x ∈ vars s -> Gamma ⊢(n) s : A -> exists B, nth Gamma x = Some B /\ ord B <= n.
Proof.
intros H % vars_varof; induction 1 in x, H |-*; inv H; eauto.
eapply IHordertyping in H2 as []; eexists; eauto.
Qed.
Lemma vars_ordertyping_nth n x s A B Gamma:
x ∈ vars s -> Gamma ⊢(n) s : A -> nth Gamma x = Some B -> ord B <= n.
Proof.
intros; edestruct vars_ordertyping; eauto.
intuition; congruence.
Qed.
Definition ordertypingSubst n Delta sigma Gamma :=
forall i A, nth Gamma i = Some A -> Delta ⊢(n) sigma i : A.
Notation "Delta ⊩( n ) sigma : Gamma" := (ordertypingSubst n Delta sigma Gamma)
(at level 80, sigma at level 99).
Lemma ordertypingSubst_monotone n m sigma Delta Gamma:
n <= m -> Delta ⊩(n) sigma : Gamma -> Delta ⊩(m) sigma : Gamma.
Proof.
intros H H' i A H1; eapply ordertyping_monotone; eauto.
Qed.
Lemma ordertypingSubst_soundness n Delta (sigma: fin -> exp X) Gamma:
Delta ⊩(n) sigma : Gamma -> Delta ⊩ sigma : Gamma.
Proof.
intros ????; eapply ordertyping_soundness; eauto.
Qed.
Lemma ordertypingSubst_complete Delta sigma Gamma:
Delta ⊩ sigma : Gamma -> exists n, Delta ⊩(n) sigma : Gamma.
Proof.
induction Gamma as [| A Gamma IH] in sigma |-* .
- intros _. exists 0. intros []?; cbn; discriminate.
- intros ?. specialize (IH (shift >> sigma)).
mp IH; [intros ???; eauto|].
specialize (H 0 A); mp H; eauto.
eapply ordertyping_completeness in H.
destruct IH as [n], H as [m].
exists (max n m); intros [|x]B; cbn; [injection 1 as ->|intros].
all: eapply ordertyping_monotone.
2, 4: eauto. all: eauto.
Qed.
(* ** Preservation Order Typing *)
Section PreservationOrdertyping.
Lemma ordertyping_weak_preservation_under_renaming Gamma n s A delta Delta:
Gamma ⊢(n) s : A ->
(forall x A, nth Gamma x = Some A -> x ∈ vars s -> nth Delta (delta x) = Some A) ->
Delta ⊢( n) ren delta s : A.
Proof.
induction s in delta, Gamma, Delta, A |-*; cbn -[vars]; intros; inv H; eauto.
- econstructor. eapply IHs; eauto.
intros [] ? ?; cbn -[vars] in *; intuition.
- econstructor; [eapply IHs1|eapply IHs2]; eauto.
Qed.
Lemma ordertyping_preservation_under_renaming n delta Gamma Delta s A:
Gamma ⊢(n) s : A -> Delta ⊫ delta : Gamma -> Delta ⊢(n) ren_exp delta s : A.
Proof.
intros; eapply ordertyping_weak_preservation_under_renaming; eauto.
Qed.
Lemma ordertyping_weak_preservation_under_substitution n sigma Gamma Delta s A:
Gamma ⊢(n) s : A ->
(forall i A, i ∈ vars s -> nth Gamma i = Some A -> Delta ⊢(n) sigma i : A) ->
Delta ⊢(n) sigma • s : A.
Proof.
induction 1 in sigma, Delta |-*; intros H'; cbn [subst_exp]; subst; eauto.
- econstructor; eauto; eapply IHordertyping.
intros [|m]; cbn; eauto.
+ intros ? H1; injection 1 as <-; econstructor; cbn; eauto.
eapply vars_ordertyping in H1 as []; eauto. intuition.
now injection H1 as ->.
+ intros D H1 H2; unfold funcomp.
eapply ordertyping_preservation_under_renaming; eauto.
now intros i.
- econstructor; [eapply IHordertyping1 | eapply IHordertyping2].
all: intros; eapply H'; eauto.
Qed.
Lemma ordertyping_preservation_under_substitution n sigma Gamma Delta s A:
Gamma ⊢(n) s : A ->
Delta ⊩(n) sigma : Gamma -> Delta ⊢(n) sigma • s : A.
Proof.
intros;
eapply ordertyping_weak_preservation_under_substitution; eauto.
Qed.
Lemma ordertyping_preservation_under_reduction n s s' Gamma A:
s > s' -> Gamma ⊢(n) s : A -> Gamma ⊢(n) s' : A.
Proof.
induction 1 in n, Gamma, A |-*; intros H1; invp @ordertyping; eauto.
inv H3. eapply ordertyping_weak_preservation_under_substitution; eauto.
intros []; cbn; eauto.
intros ? _; now injection 1 as ->.
intros D H6 H7. eapply vars_ordertyping in H6 as [B]; eauto.
intuition. econstructor; intuition.
cbn in H0; rewrite H0 in H7; now injection H7 as ->.
Qed.
Lemma ordertyping_preservation_under_steps n (s s': exp X) (Gamma: ctx) A:
s >* s' -> Gamma ⊢(n) s : A -> Gamma ⊢(n) s' : A.
Proof.
induction 1 in Gamma, A |-*;
eauto using ordertyping_preservation_under_reduction.
Qed.
End PreservationOrdertyping.
Lemma weakening_ordertyping_app n Gamma Delta s A:
Gamma ⊢(n) s : A -> Gamma ++ Delta ⊢(n) s : A.
Proof.
intros H; replace s with (ren id s) by now asimpl.
eapply ordertyping_preservation_under_renaming; eauto.
intros i B H'; unfold id.
rewrite nth_error_app1; eauto.
eapply nth_error_Some_lt; eauto.
Qed.
End OrderTyping.
Notation "Gamma '⊢(' n ')' s ':' A" :=
(ordertyping n Gamma s A) (at level 80, s at level 99).
Notation "Delta ⊩( n ) sigma : Gamma" := (ordertypingSubst n Delta sigma Gamma) (at level 80, sigma at level 99).
#[export] Hint Constructors ordertyping : core.
Hint Rewrite ord_arr ord'_app ord'_rev : simplify.
#[export] Hint Resolve ord'_cons ord'_in : core.
#[export] Hint Resolve vars_ordertyping_nth ordertyping_monotone ordertyping_step ordertyping_soundness : core.
#[export] Hint Resolve
ordertyping_preservation_under_renaming
ordertyping_preservation_under_substitution : core.
#[export] Hint Resolve ord_target ord_target' : core.
Require Import List Arith Lia.
From Undecidability.HOU Require Import std.std.
From Undecidability.HOU.calculus Require Import
prelim terms syntax semantics typing.
Set Default Proof Using "Type".
(* * Order Typing *)
Section OrderTyping.
Context {X: Const}.
Definition ctx := list type.
Implicit Types (s t: exp X) (n m: nat) (Gamma Delta Sigma: ctx)
(x y: fin) (c d: X) (A B: type)
(sigma tau: fin -> exp X) (delta xi: fin -> fin).
(* ** Order of Types *)
Section Order.
Fixpoint ord A :=
match A with
| typevar beta => 1
| A → B => max (S (ord A)) (ord B)
end.
Lemma ord_1 A: 1 <= ord A.
Proof.
induction A; cbn [ord]; eauto.
transitivity (S (ord A1)); eauto using Nat.max_lub_l.
Qed.
Lemma ord_arr A B: ord (A → B) = max (S (ord A)) (ord B).
Proof. reflexivity. Qed.
Lemma ord_arr_one A B: ~ ord (A → B) <= 1.
Proof.
intros H; rewrite ord_arr in H; eapply Nat.max_lub_l in H.
rewrite ord_1 with (A := A) in H; lia.
Qed.
Fixpoint ord' Gamma :=
match Gamma with
| nil => 0
| A :: Gamma => max (ord A) (ord' Gamma)
end.
Lemma ord'_app Gamma Gamma': ord' (Gamma ++ Gamma') = max (ord' Gamma) (ord' Gamma').
Proof.
induction Gamma; cbn; eauto.
now rewrite IHGamma, Nat.max_assoc.
Qed.
Lemma ord'_rev L:
ord' (rev L) = ord' L.
Proof.
induction L; cbn; rewrite ?ord'_app; eauto.
simplify; cbn; eauto.
rewrite IHL.
simplify. eapply Nat.max_comm.
Qed.
Lemma ord'_in A Gamma: A ∈ Gamma -> ord A <= ord' Gamma.
Proof.
induction Gamma; cbn in *; intuition; subst; eauto; lia.
Qed.
Lemma ord'_elements n Gamma: (forall A, A ∈ Gamma -> ord A <= n) <-> ord' Gamma <= n.
Proof.
induction Gamma; cbn; intuition; subst; eauto.
all: simplify in *; intuition.
Qed.
Lemma ord'_cons n Gamma A:
ord A < n -> ord' Gamma <= n -> ord' (A :: Gamma) <= n.
Proof.
intros; cbn; eapply Max.max_lub; lia.
Qed.
Lemma order_head Gamma s A B:
Gamma ⊢ s : A -> Gamma ⊢ (head s) : B -> isAtom (head s) -> ord A <= ord B.
Proof.
induction 1; eauto; cbn.
- intros H1 _; inv H1. rewrite H in H2; injection H2 as ->; eauto.
- intros H1; inv H1; eauto.
- cbn in *; intuition.
- intros; rewrite <-IHtyping1; eauto.
rewrite ord_arr; eauto.
Qed.
Lemma ord_target A: ord (target A) <= 1.
Proof. induction A; eauto. Qed.
Lemma ord_target' Gamma: ord' (target' Gamma) <= 1.
Proof.
eapply ord'_elements; unfold target'; intros; mapinj; eauto using ord_target.
Qed.
End Order.
Hint Resolve ord'_cons : core.
(* ** Order Typing *)
Reserved Notation "Gamma '⊢(' n ')' s ':' A" (at level 80, s at level 99).
Inductive ordertyping n Gamma: exp X -> type -> Prop :=
| ordertypingVar x A:
ord A <= n -> nth Gamma x = Some A -> Gamma ⊢(n) (var x) : A
| ordertypingConst c:
ord (ctype X c) <= S n -> Gamma ⊢(n) (const c) : ctype X c
| ordertypingLam s A B:
A :: Gamma ⊢(n) s : B -> Gamma ⊢(n) lambda s : A → B
| ordertypingApp s t A B:
Gamma ⊢(n) s : A → B -> Gamma ⊢(n) t : A -> Gamma ⊢(n) s t : B
where "Gamma '⊢(' n ')' s ':' A" := (ordertyping n Gamma s A).
Hint Constructors ordertyping : core.
Lemma ordertyping_step n Gamma s A:
Gamma ⊢(n) s : A -> Gamma ⊢(S n) s: A.
Proof.
induction 1; eauto.
Qed.
Lemma ordertyping_monotone m n Gamma s A:
m <= n -> Gamma ⊢(m) s : A -> Gamma ⊢(n) s: A.
Proof.
induction 1; eauto using ordertyping_step.
Qed.
Hint Resolve ordertyping_monotone : core.
Lemma ordertyping_soundness n Gamma s A:
Gamma ⊢(n) s : A -> Gamma ⊢ s : A.
Proof.
induction 1; eauto.
Qed.
Lemma ordertyping_completeness Gamma s A:
Gamma ⊢ s : A -> exists n, Gamma ⊢(n) s : A.
Proof.
induction 1.
- exists (ord A); eauto.
- exists (ord (ctype X c)); eauto.
- destruct IHtyping as [n]; exists (max (S (ord A)) n).
econstructor; eauto.
- destruct IHtyping1 as [n], IHtyping2 as [m].
exists (max n m); econstructor; eauto.
Qed.
Lemma vars_ordertyping n x s A Gamma:
x ∈ vars s -> Gamma ⊢(n) s : A -> exists B, nth Gamma x = Some B /\ ord B <= n.
Proof.
intros H % vars_varof; induction 1 in x, H |-*; inv H; eauto.
eapply IHordertyping in H2 as []; eexists; eauto.
Qed.
Lemma vars_ordertyping_nth n x s A B Gamma:
x ∈ vars s -> Gamma ⊢(n) s : A -> nth Gamma x = Some B -> ord B <= n.
Proof.
intros; edestruct vars_ordertyping; eauto.
intuition; congruence.
Qed.
Definition ordertypingSubst n Delta sigma Gamma :=
forall i A, nth Gamma i = Some A -> Delta ⊢(n) sigma i : A.
Notation "Delta ⊩( n ) sigma : Gamma" := (ordertypingSubst n Delta sigma Gamma)
(at level 80, sigma at level 99).
Lemma ordertypingSubst_monotone n m sigma Delta Gamma:
n <= m -> Delta ⊩(n) sigma : Gamma -> Delta ⊩(m) sigma : Gamma.
Proof.
intros H H' i A H1; eapply ordertyping_monotone; eauto.
Qed.
Lemma ordertypingSubst_soundness n Delta (sigma: fin -> exp X) Gamma:
Delta ⊩(n) sigma : Gamma -> Delta ⊩ sigma : Gamma.
Proof.
intros ????; eapply ordertyping_soundness; eauto.
Qed.
Lemma ordertypingSubst_complete Delta sigma Gamma:
Delta ⊩ sigma : Gamma -> exists n, Delta ⊩(n) sigma : Gamma.
Proof.
induction Gamma as [| A Gamma IH] in sigma |-* .
- intros _. exists 0. intros []?; cbn; discriminate.
- intros ?. specialize (IH (shift >> sigma)).
mp IH; [intros ???; eauto|].
specialize (H 0 A); mp H; eauto.
eapply ordertyping_completeness in H.
destruct IH as [n], H as [m].
exists (max n m); intros [|x]B; cbn; [injection 1 as ->|intros].
all: eapply ordertyping_monotone.
2, 4: eauto. all: eauto.
Qed.
(* ** Preservation Order Typing *)
Section PreservationOrdertyping.
Lemma ordertyping_weak_preservation_under_renaming Gamma n s A delta Delta:
Gamma ⊢(n) s : A ->
(forall x A, nth Gamma x = Some A -> x ∈ vars s -> nth Delta (delta x) = Some A) ->
Delta ⊢( n) ren delta s : A.
Proof.
induction s in delta, Gamma, Delta, A |-*; cbn -[vars]; intros; inv H; eauto.
- econstructor. eapply IHs; eauto.
intros [] ? ?; cbn -[vars] in *; intuition.
- econstructor; [eapply IHs1|eapply IHs2]; eauto.
Qed.
Lemma ordertyping_preservation_under_renaming n delta Gamma Delta s A:
Gamma ⊢(n) s : A -> Delta ⊫ delta : Gamma -> Delta ⊢(n) ren_exp delta s : A.
Proof.
intros; eapply ordertyping_weak_preservation_under_renaming; eauto.
Qed.
Lemma ordertyping_weak_preservation_under_substitution n sigma Gamma Delta s A:
Gamma ⊢(n) s : A ->
(forall i A, i ∈ vars s -> nth Gamma i = Some A -> Delta ⊢(n) sigma i : A) ->
Delta ⊢(n) sigma • s : A.
Proof.
induction 1 in sigma, Delta |-*; intros H'; cbn [subst_exp]; subst; eauto.
- econstructor; eauto; eapply IHordertyping.
intros [|m]; cbn; eauto.
+ intros ? H1; injection 1 as <-; econstructor; cbn; eauto.
eapply vars_ordertyping in H1 as []; eauto. intuition.
now injection H1 as ->.
+ intros D H1 H2; unfold funcomp.
eapply ordertyping_preservation_under_renaming; eauto.
now intros i.
- econstructor; [eapply IHordertyping1 | eapply IHordertyping2].
all: intros; eapply H'; eauto.
Qed.
Lemma ordertyping_preservation_under_substitution n sigma Gamma Delta s A:
Gamma ⊢(n) s : A ->
Delta ⊩(n) sigma : Gamma -> Delta ⊢(n) sigma • s : A.
Proof.
intros;
eapply ordertyping_weak_preservation_under_substitution; eauto.
Qed.
Lemma ordertyping_preservation_under_reduction n s s' Gamma A:
s > s' -> Gamma ⊢(n) s : A -> Gamma ⊢(n) s' : A.
Proof.
induction 1 in n, Gamma, A |-*; intros H1; invp @ordertyping; eauto.
inv H3. eapply ordertyping_weak_preservation_under_substitution; eauto.
intros []; cbn; eauto.
intros ? _; now injection 1 as ->.
intros D H6 H7. eapply vars_ordertyping in H6 as [B]; eauto.
intuition. econstructor; intuition.
cbn in H0; rewrite H0 in H7; now injection H7 as ->.
Qed.
Lemma ordertyping_preservation_under_steps n (s s': exp X) (Gamma: ctx) A:
s >* s' -> Gamma ⊢(n) s : A -> Gamma ⊢(n) s' : A.
Proof.
induction 1 in Gamma, A |-*;
eauto using ordertyping_preservation_under_reduction.
Qed.
End PreservationOrdertyping.
Lemma weakening_ordertyping_app n Gamma Delta s A:
Gamma ⊢(n) s : A -> Gamma ++ Delta ⊢(n) s : A.
Proof.
intros H; replace s with (ren id s) by now asimpl.
eapply ordertyping_preservation_under_renaming; eauto.
intros i B H'; unfold id.
rewrite nth_error_app1; eauto.
eapply nth_error_Some_lt; eauto.
Qed.
End OrderTyping.
Notation "Gamma '⊢(' n ')' s ':' A" :=
(ordertyping n Gamma s A) (at level 80, s at level 99).
Notation "Delta ⊩( n ) sigma : Gamma" := (ordertypingSubst n Delta sigma Gamma) (at level 80, sigma at level 99).
#[export] Hint Constructors ordertyping : core.
Hint Rewrite ord_arr ord'_app ord'_rev : simplify.
#[export] Hint Resolve ord'_cons ord'_in : core.
#[export] Hint Resolve vars_ordertyping_nth ordertyping_monotone ordertyping_step ordertyping_soundness : core.
#[export] Hint Resolve
ordertyping_preservation_under_renaming
ordertyping_preservation_under_substitution : core.
#[export] Hint Resolve ord_target ord_target' : core.