Started merging zero and next into a one and only proof constructor, so normal forms are now unique.

Added a lot of relations on lists in order to study different kinds of morphisms
2023-05-30 14:02:01 +02:00 · 2023-05-30 14:02:01 +02:00 · 422dcf67f0
commit 422dcf67f0
parent 8d1df370ca
3 changed files with 153 additions and 42 deletions
--- a/ListUtil.agda
+++ b/ListUtil.agda
@ -13,7 +13,20 @@ module ListUtil where
      B : T


-  -- Definition of sublists
+  -- Definition of list appartenance
+  -- The definition uses reflexivity and never any kind of equality
+  infix 3 _∈_
+  data _∈_ : T → List T → Prop where
+    zero∈ : A ∈ A ∷ L
+    next∈ : A ∈ L → A ∈ B ∷ L
+
+  {- RELATIONS BETWEEN LISTS -}
+
+  -- We have the following relations
+  --        ↗ ⊂⁰ ↘
+  -- ⊆ → ⊂ → ⊂⁺ → ∈*
+  infix 4 _⊆_ _⊂_ _⊂⁺_ _⊂⁰_ _∈*_
+  {- ⊆ : We can remove elements but only from the head of the list -}
  -- Similar definition : {L L' : List T} → L ⊆ L' ++ L
  data _⊆_ : List T → List T → Prop where
    zero⊆ : L ⊆ L
@ -25,3 +38,54 @@ module ListUtil where
  retro⊆ {L' = B ∷ L'} zero⊆ = next⊆ zero⊆
  retro⊆ {L' = B ∷ L'} (next⊆ h) = next⊆ (retro⊆ h)

+  {- ⊂ : We can remove elements anywhere on the list, no duplicates, no reordering -}
+  data _⊂_ : List T → List T → Prop where
+    zero⊂ : [] ⊂ L
+    both⊂ : L ⊂ L' → (A ∷ L) ⊂ (A ∷ L')
+    next⊂ : L ⊂ L' → L ⊂ (A ∷ L')
+    
+  {- ⊂⁰ : We can remove elements and reorder the list, as long as we don't duplicate the elements -}
+  -----> We do not have unicity of derivation ([A,A] ⊂⁰ [A,A] can be prove by identity or by swapping its two elements
+  --> We could do with some counting function, but ... it would not be nice, would it ?
+  data _⊂⁰_ : List T → List T → Prop where
+    zero⊂⁰ : _⊂⁰_ {T} [] []
+    next⊂⁰ : L ⊂⁰ L' → L ⊂⁰ A ∷ L'
+    both⊂⁰ : L ⊂⁰ L' → A ∷ L ⊂⁰ A ∷ L'
+    swap⊂⁰ : L ⊂⁰ A ∷ B ∷ L' → L ⊂⁰ B ∷ A ∷ L'
+    error  : L ⊂⁰ L'
+    -- TODOTODOTODOTODO Fix this definition
+  {- ⊂⁺ : We can remove and duplicate elements, as long as we don't change the order -}
+  data _⊂⁺_ : List T → List T → Prop where
+    zero⊂⁺ : _⊂⁺_ {T} [] []
+    next⊂⁺ : L ⊂⁺ L' → L ⊂⁺ A ∷ L'
+    dup⊂⁺ : A ∷ L ⊂⁺ L' → A ∷ L ⊂⁺ A ∷ L'
+  {- ∈* : We can remove or duplicate elements and we can change their order -}
+  -- The weakest of all relations on lists
+  -- L ∈* L' if all elements of L exists in L' (no consideration for order nor duplication)
+  data _∈*_ : List T → List T → Prop where
+    zero∈* : [] ∈* L
+    next∈* : A ∈ L → L' ∈* L → (A ∷ L') ∈* L
+
+  -- Founding principle
+  mon∈∈* : A ∈ L → L ∈* L' → A ∈ L'
+  mon∈∈* zero∈ (next∈* x hl) = x
+  mon∈∈* (next∈ ha) (next∈* x hl) = mon∈∈* ha hl
+
+  -- We show that the relation is reflexive and is implied by ⊆
+  refl∈* : L ∈* L
+  ⊆→∈* : L ⊆ L' → L ∈* L'
+  refl∈* {L = []} = zero∈*
+  refl∈* {L = x ∷ L} = next∈* zero∈ (⊆→∈* (next⊆ zero⊆))
+  ⊆→∈* zero⊆ = refl∈*
+  ⊆→∈* {L = []} (next⊆ h) = zero∈*
+  ⊆→∈* {L = x ∷ L} (next⊆ h) = next∈* (next∈ (mon∈∈* zero∈ (⊆→∈* h))) (⊆→∈* (retro⊆ (next⊆ h)))
+
+  -- Allows to grow ∈* to the right
+  right∈* : L ∈* L' → L ∈* (A ∷ L')
+  right∈* zero∈* = zero∈*
+  right∈* (next∈* x h) = next∈* (next∈ x) (right∈* h)
+
+  -- Allows to grow ∈* from both sides
+  both∈* : L ∈* L' → (A ∷ L) ∈* (A ∷ L')
+  both∈* zero∈* = next∈* zero∈ zero∈*
+  both∈* (next∈* x h) = next∈* zero∈ (next∈* (next∈ x) (right∈* h))
--- a/PropositionalKripke.agda
+++ b/PropositionalKripke.agda
@ -120,3 +120,28 @@ module PropositionalKripke (PV : Set) where
    ⊢→⊩ᶠ {F ⇒ F₁} h {Γ'} iq hF = ⊢→⊩ᶠ {F₁} (app {Γ'} {F} {F₁} (halftran⊢⁰⁺⁰ iq h) (⊩ᶠ→⊢ hF))
    ⊩ᶠ→⊢ {Var x} h = neu⁰ h
    ⊩ᶠ→⊢ {F ⇒ F₁} {Γ} h = lam (⊩ᶠ→⊢ (h (addhyp⊢⁰⁺ refl⊢⁰⁺) (⊢→⊩ᶠ {F} {F ∷ Γ} zero)))
+
+  module OtherProofs where
+
+    -- We will try to define the Kripke models using the following embeddings
+
+    -- Strongest is using the ⊢⁺ relation directly
+
+    -- -> See module CompletenessProof
+
+    -- We can also use the relation ⊢⁰⁺, which is compatible with ⊢⁰ and ⊢*
+
+    -- -> See module NormalizationProof
+
+    
+  
+    {- Renamings -}
+
+    {- Weakening anywhere, order preserving, duplication authorized -}
+
+    {- Weakening anywhere, no duplication, order preserving -}
+    
+
+    {- Weakening at the end -}
+
+    -- This is exactly our relation ⊆ 
--- a/PropositionalLogic.agda
+++ b/PropositionalLogic.agda
@ -25,6 +25,7 @@ module PropositionalLogic (PV : Set) where
      G   : Form
      Γ   : Con
      Γ'  : Con
+      Γ'' : Con
      x   : PV


@ -32,12 +33,21 @@ module PropositionalLogic (PV : Set) where
  {--- DEFINITION OF ⊢ ---}
  
  data _⊢_ : Con → Form → Prop where
-    zero : (A ∷ Γ) ⊢ A
-    next : Γ ⊢ A → (B ∷ Γ) ⊢ A
+    zero : A ∈ Γ → Γ ⊢ A
    lam : (A ∷ Γ) ⊢ B → Γ ⊢ (A ⇒ B)
    app : Γ ⊢ (A ⇒ B) → Γ ⊢ A → Γ ⊢ B
-
  infix 5 _⊢_
+  
+  zero⊢ : (A ∷ Γ) ⊢ A
+  zero⊢ = zero zero∈
+  one⊢ : (B ∷ A ∷ Γ) ⊢ A
+  one⊢ = zero (next∈ zero∈)
+
+  -- We can add hypotheses to a proof
+  addhyp⊢ : Γ ∈* Γ' → Γ ⊢ A → Γ' ⊢ A
+  addhyp⊢ s (zero x) = zero (mon∈∈* x s)
+  addhyp⊢ s (lam h) = lam (addhyp⊢ (both∈* s) h)
+  addhyp⊢ s (app h h₁) = app (addhyp⊢ s h) (addhyp⊢ s h₁)

  -- Extension of ⊢ to contexts
  _⊢⁺_ : Con → Con → Prop
@ -45,28 +55,32 @@ module PropositionalLogic (PV : Set) where
  Γ ⊢⁺ (F ∷ Γ') = (Γ ⊢ F) ∧ (Γ ⊢⁺ Γ')
  infix 5 _⊢⁺_

+  -- We show that the relation respects ∈*
+
+  mon∈*⊢⁺ : Γ' ∈* Γ → Γ ⊢⁺ Γ'
+  mon∈*⊢⁺ zero∈* = tt
+  mon∈*⊢⁺ (next∈* x h) = ⟨ (zero x) , (mon∈*⊢⁺ h) ⟩
+
  -- The relation respects ⊆
  mon⊆⊢⁺ : Γ' ⊆ Γ → Γ ⊢⁺ Γ'
-  mon⊆⊢⁺ {[]} sub = tt
-  mon⊆⊢⁺ {x ∷ Γ} zero⊆ = ⟨ zero , mon⊆⊢⁺ (next⊆ zero⊆) ⟩
-  mon⊆⊢⁺ {x ∷ Γ} (next⊆ sub) = ⟨ (next (proj₁ (mon⊆⊢⁺ sub)) ) , mon⊆⊢⁺ (next⊆ (retro⊆ sub)) ⟩
+  mon⊆⊢⁺ h = mon∈*⊢⁺ (⊆→∈* h)

  -- The relation is reflexive
  refl⊢⁺ : Γ ⊢⁺ Γ
  refl⊢⁺ {[]} = tt
-  refl⊢⁺ {x ∷ Γ} = ⟨ zero , mon⊆⊢⁺ (next⊆ zero⊆) ⟩
-
-  -- We can add hypotheses to the left 
-  addhyp⊢⁺ : Γ ⊢⁺ Γ' → (A ∷ Γ) ⊢⁺ Γ'
-  addhyp⊢⁺ {Γ' = []} h = tt
-  addhyp⊢⁺ {Γ' = A ∷ Γ'} h = ⟨ next (proj₁ h) , addhyp⊢⁺ (proj₂ h) ⟩
+  refl⊢⁺ {x ∷ Γ} = ⟨ zero⊢ , mon⊆⊢⁺ (next⊆ zero⊆) ⟩

+  -- We can add hypotheses to to a proof
+  addhyp⊢⁺ : Γ ∈* Γ' → Γ ⊢⁺ Γ'' → Γ' ⊢⁺ Γ''
+  addhyp⊢⁺ {Γ'' = []} s h = tt
+  addhyp⊢⁺ {Γ'' = x ∷ Γ''} s ⟨ Γx , ΓΓ'' ⟩ = ⟨ addhyp⊢ s Γx , addhyp⊢⁺ s ΓΓ'' ⟩
+  
  -- The relation respects ⊢
  halftran⊢⁺ : {Γ Γ' : Con} → {F : Form} → Γ ⊢⁺ Γ' → Γ' ⊢ F → Γ ⊢ F
-  halftran⊢⁺ h⁺ zero = proj₁ h⁺
-  halftran⊢⁺ h⁺ (next h) = halftran⊢⁺ (proj₂ h⁺) h
-  halftran⊢⁺ h⁺ (lam h) = lam (halftran⊢⁺ ⟨ zero , addhyp⊢⁺ h⁺ ⟩ h)
-  halftran⊢⁺ h⁺ (app h h') = app (halftran⊢⁺ h⁺ h) (halftran⊢⁺ h⁺ h')
+  halftran⊢⁺ {Γ' = F ∷ Γ'} h⁺ (zero zero∈) = proj₁ h⁺
+  halftran⊢⁺ {Γ' = F ∷ Γ'} h⁺ (zero (next∈ x)) = halftran⊢⁺ (proj₂ h⁺) (zero x)
+  halftran⊢⁺ h⁺ (lam h) = lam (halftran⊢⁺ ⟨ (zero zero∈) , (addhyp⊢⁺ (right∈* refl∈*) h⁺) ⟩ h)
+  halftran⊢⁺ h⁺ (app h h₁) = app (halftran⊢⁺ h⁺ h) (halftran⊢⁺ h⁺ h₁)

  -- The relation is transitive
  tran⊢⁺ : {Γ Γ' Γ'' : Con} → Γ ⊢⁺ Γ' → Γ' ⊢⁺ Γ'' → Γ ⊢⁺ Γ''
@ -81,8 +95,7 @@ module PropositionalLogic (PV : Set) where
  -- ⊢* are normal forms
  mutual
    data _⊢⁰_ : Con → Form → Prop where
-      zero : (A ∷ Γ) ⊢⁰ A
-      next : Γ ⊢⁰ A → (B ∷ Γ) ⊢⁰ A
+      zero :  A ∈ Γ → Γ ⊢⁰ A
      app : Γ ⊢⁰ (A ⇒ B) → Γ ⊢* A → Γ ⊢⁰ B
    data _⊢*_ : Con → Form → Prop where
      neu⁰ : Γ ⊢⁰ Var x → Γ ⊢* Var x
@ -93,42 +106,53 @@ module PropositionalLogic (PV : Set) where
  -- Both are tighter than ⊢
  ⊢⁰→⊢ : Γ ⊢⁰ F → Γ ⊢ F
  ⊢*→⊢ : Γ ⊢* F → Γ ⊢ F
-  ⊢⁰→⊢ zero = zero
-  ⊢⁰→⊢ (next h) = next (⊢⁰→⊢ h)
+  ⊢⁰→⊢ (zero h) = zero h
  ⊢⁰→⊢ (app h x) = app (⊢⁰→⊢ h) (⊢*→⊢ x)
  ⊢*→⊢ (neu⁰ x) = ⊢⁰→⊢ x
  ⊢*→⊢ (lam h) = lam (⊢*→⊢ h)

+  -- We can add hypotheses to a proof
+  addhyp⊢⁰ : Γ ∈* Γ' → Γ ⊢⁰ A → Γ' ⊢⁰ A
+  addhyp⊢* : Γ ∈* Γ' → Γ ⊢* A → Γ' ⊢* A
+  addhyp⊢⁰ s (zero x) = zero (mon∈∈* x s)
+  addhyp⊢⁰ s (app h h₁) = app (addhyp⊢⁰ s h) (addhyp⊢* s h₁)
+  addhyp⊢* s (neu⁰ x) = neu⁰ (addhyp⊢⁰ s x)
+  addhyp⊢* s (lam h) = lam (addhyp⊢* (both∈* s) h)
+
  -- Extension of ⊢⁰ to contexts
  -- i.e. there is a neutral proof for any element
  _⊢⁰⁺_ : Con → Con → Prop
  Γ ⊢⁰⁺ [] = ⊤
  Γ ⊢⁰⁺ (F ∷ Γ') = (Γ ⊢⁰ F) ∧ (Γ ⊢⁰⁺ Γ')
  infix 5 _⊢⁰⁺_
-  
+
+  -- The relation respects ∈*
+
+  mon∈*⊢⁰⁺ : Γ' ∈* Γ → Γ ⊢⁰⁺ Γ'
+  mon∈*⊢⁰⁺ zero∈* = tt
+  mon∈*⊢⁰⁺ (next∈* x h) = ⟨ (zero x) , (mon∈*⊢⁰⁺ h) ⟩
+
  -- The relation respects ⊆
  mon⊆⊢⁰⁺ : Γ' ⊆ Γ → Γ ⊢⁰⁺ Γ'
-  mon⊆⊢⁰⁺ {[]} sub = tt
-  mon⊆⊢⁰⁺ {x ∷ Γ} zero⊆ = ⟨ zero , mon⊆⊢⁰⁺ (next⊆ zero⊆) ⟩
-  mon⊆⊢⁰⁺ {x ∷ Γ} (next⊆ sub) = ⟨ (next (proj₁ (mon⊆⊢⁰⁺ sub)) ) , mon⊆⊢⁰⁺ (next⊆ (retro⊆ sub)) ⟩
+  mon⊆⊢⁰⁺ h = mon∈*⊢⁰⁺ (⊆→∈* h)

  -- This relation is reflexive
  refl⊢⁰⁺ : Γ ⊢⁰⁺ Γ
  refl⊢⁰⁺ {[]} = tt
-  refl⊢⁰⁺ {x ∷ Γ} = ⟨ zero , mon⊆⊢⁰⁺ (next⊆ zero⊆) ⟩
+  refl⊢⁰⁺ {x ∷ Γ} = ⟨ zero zero∈ , mon⊆⊢⁰⁺ (next⊆ zero⊆) ⟩

  -- A useful lemma, that we can add hypotheses 
-  addhyp⊢⁰⁺ : Γ ⊢⁰⁺ Γ' → (A ∷ Γ) ⊢⁰⁺ Γ'
-  addhyp⊢⁰⁺ {Γ' = []} h = tt
-  addhyp⊢⁰⁺ {Γ' = A ∷ Γ'} h = ⟨ next (proj₁ h) , addhyp⊢⁰⁺ (proj₂ h) ⟩
+  addhyp⊢⁰⁺ : Γ ∈* Γ' → Γ ⊢⁰⁺ Γ'' → Γ' ⊢⁰⁺ Γ''
+  addhyp⊢⁰⁺ {Γ'' = []} s h = tt
+  addhyp⊢⁰⁺ {Γ'' = A ∷ Γ'} s ⟨ Γx , ΓΓ'' ⟩ = ⟨ addhyp⊢⁰ s Γx , addhyp⊢⁰⁺ s ΓΓ'' ⟩

  -- The relation preserves ⊢⁰ and ⊢*
  halftran⊢⁰⁺* : {Γ Γ' : Con} → {F : Form} → Γ ⊢⁰⁺ Γ' → Γ' ⊢* F → Γ ⊢* F
  halftran⊢⁰⁺⁰ : {Γ Γ' : Con} → {F : Form} → Γ ⊢⁰⁺ Γ' → Γ' ⊢⁰ F → Γ ⊢⁰ F
  halftran⊢⁰⁺* h⁺ (neu⁰ x) = neu⁰ (halftran⊢⁰⁺⁰ h⁺ x)
-  halftran⊢⁰⁺* h⁺ (lam h) = lam (halftran⊢⁰⁺* ⟨ zero , addhyp⊢⁰⁺ h⁺ ⟩ h)
-  halftran⊢⁰⁺⁰ h⁺ zero = proj₁ h⁺
-  halftran⊢⁰⁺⁰ h⁺ (next h) = halftran⊢⁰⁺⁰ (proj₂ h⁺) h
+  halftran⊢⁰⁺* h⁺ (lam h) = lam (halftran⊢⁰⁺* ⟨ zero zero∈ , addhyp⊢⁰⁺ (right∈* refl∈*) h⁺ ⟩ h)
+  halftran⊢⁰⁺⁰ {Γ' = x ∷ Γ'} h⁺ (zero zero∈) = proj₁ h⁺
+  halftran⊢⁰⁺⁰ {Γ' = x ∷ Γ'} h⁺ (zero (next∈ h)) = halftran⊢⁰⁺⁰ (proj₂ h⁺) (zero h)
  halftran⊢⁰⁺⁰ h⁺ (app h h') = app (halftran⊢⁰⁺⁰ h⁺ h) (halftran⊢⁰⁺* h⁺ h')

  -- The relation is transitive
@ -152,8 +176,8 @@ module PropositionalLogic (PV : Set) where
  ⟦ A ∷ Γ ⟧ᶜ ρ = (⟦ A ⟧ᶠ ρ) ∧ (⟦ Γ ⟧ᶜ ρ)

  ⟦_⟧ᵈ : Γ ⊢ A → {ρ : Env} → ⟦ Γ ⟧ᶜ ρ → ⟦ A ⟧ᶠ ρ
-  ⟦ zero ⟧ᵈ p = proj₁ p
-  ⟦ next th ⟧ᵈ p = ⟦ th ⟧ᵈ (proj₂ p)
+  ⟦_⟧ᵈ {x ∷ Γ} (zero zero∈) p = proj₁ p
+  ⟦_⟧ᵈ {x ∷ Γ} (zero (next∈ h)) p = ⟦ zero h ⟧ᵈ (proj₂ p)
  ⟦ lam th ⟧ᵈ = λ pₐ p₀ → ⟦ th ⟧ᵈ ⟨ p₀ , pₐ ⟩
  ⟦ app th₁ th₂ ⟧ᵈ = λ p → ⟦ th₁ ⟧ᵈ p (⟦ th₂ ⟧ᵈ p)

@ -169,8 +193,7 @@ module PropositionalLogic (PV : Set) where
    app : ⊢sk (A ⇒ B) → ⊢sk A → ⊢sk B

  data _⊢skC_ : Con → Form → Prop where
-    zero : (A ∷ Γ) ⊢skC A
-    next : Γ ⊢skC A → (B ∷ Γ) ⊢skC A
+    zero : A ∈ Γ → Γ ⊢skC A
    SS : Γ ⊢skC ((A ⇒ B ⇒ C) ⇒ (A ⇒ B) ⇒ A ⇒ C)
    KK : Γ ⊢skC (A ⇒ B ⇒ A)
    app : Γ ⊢skC (A ⇒ B) → Γ ⊢skC A → Γ ⊢skC B
@ -180,8 +203,8 @@ module PropositionalLogic (PV : Set) where
  ⊢⇔⊢sk : ([] ⊢ A) ⇔ ⊢sk A
  
  ⊢sk→⊢ :  ⊢sk A → ([] ⊢ A)
-  ⊢sk→⊢ SS = lam (lam (lam ( app (app (next (next zero)) zero) (app (next zero) zero))))
-  ⊢sk→⊢ KK = lam (lam (next zero))
+  ⊢sk→⊢ SS = lam (lam (lam ( app (app (zero (next∈ (next∈ zero∈))) (zero zero∈)) (app (zero (next∈ zero∈)) (zero zero∈)))))
+  ⊢sk→⊢ KK = lam (lam (zero (next∈ zero∈)))
  ⊢sk→⊢ (app x x₁) = app (⊢sk→⊢ x) (⊢sk→⊢ x₁)

  skC→sk : [] ⊢skC A → ⊢sk A
@ -193,15 +216,14 @@ module PropositionalLogic (PV : Set) where
  lam-sk : (A ∷ Γ) ⊢skC B → Γ ⊢skC (A ⇒ B)
  lam-sk-zero : Γ ⊢skC (A ⇒ A)
  lam-sk-zero {A = A} = app (app SS KK) (KK {B = A})
-  lam-sk zero = lam-sk-zero
-  lam-sk (next x) = app KK x
+  lam-sk (zero zero∈) = lam-sk-zero
+  lam-sk (zero (next∈ h)) = app KK (zero h)
  lam-sk SS = app KK SS
  lam-sk KK = app KK KK
  lam-sk (app x₁ x₂) = app (app SS (lam-sk x₁)) (lam-sk x₂)

  ⊢→⊢skC : Γ ⊢ A → Γ ⊢skC A
-  ⊢→⊢skC zero = zero
-  ⊢→⊢skC (next x) = next (⊢→⊢skC x)
+  ⊢→⊢skC (zero h) = zero h
  ⊢→⊢skC (lam x) = lam-sk (⊢→⊢skC x)
  ⊢→⊢skC (app x x₁) = app (⊢→⊢skC x) (⊢→⊢skC x₁)