Use 'data' instead of aliases to prove reasoning properties
Signed-off-by: Danila Fedorin <danila.fedorin@gmail.com>
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@ -83,13 +83,15 @@ _map_ f fn s = let (s' , (t₁ , s≼s')) = f s in (s' , (fn s' t₁ , s≼s'))
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DependentPredicate : (S → Set s) → Set (lsuc s)
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DependentPredicate T = ∀ (s₁ : S) → T s₁ → Set s
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Both : {T₁ T₂ : S → Set s} → DependentPredicate T₁ → DependentPredicate T₂ →
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DependentPredicate (T₁ ⊗ T₂)
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Both P Q = (λ { s (t₁ , t₂) → (P s t₁ × Q s t₂) })
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data Both {T₁ T₂ : S → Set s}
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(P : DependentPredicate T₁)
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(Q : DependentPredicate T₂) : DependentPredicate (T₁ ⊗ T₂) where
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MkBoth : ∀ {s : S} {t₁ : T₁ s} {t₂ : T₂ s} → P s t₁ → Q s t₂ → Both P Q s (t₁ , t₂)
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And : {T : S → Set s} → DependentPredicate T → DependentPredicate T →
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DependentPredicate T
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And P Q = (λ { s t → (P s t × Q s t) })
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data And {T : S → Set s}
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(P : DependentPredicate T)
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(Q : DependentPredicate T) : DependentPredicate T where
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MkAnd : ∀ {s : S} {t : T s} → P s t → Q s t → And P Q s t
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-- Since monotnic functions keep adding on to the state, proofs of
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-- predicates over their outputs go stale fast (they describe old values of
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@ -101,48 +103,82 @@ record MonotonicPredicate {T : S → Set s} {{ r : Relaxable T }} (P : Dependent
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field relaxPredicate : ∀ (s₁ s₂ : S) (t₁ : T s₁) (s₁≼s₂ : s₁ ≼ s₂) →
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P s₁ t₁ → P s₂ (Relaxable.relax r s₁≼s₂ t₁)
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instance
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BothMonotonic : ∀ {T₁ : S → Set s} {T₂ : S → Set s}
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{{ _ : Relaxable T₁ }} {{ _ : Relaxable T₂ }}
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{P : DependentPredicate T₁} {Q : DependentPredicate T₂}
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{{_ : MonotonicPredicate P}} {{_ : MonotonicPredicate Q}} →
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MonotonicPredicate (Both P Q)
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BothMonotonic {{_}} {{_}} {{P-Mono}} {{Q-Mono}} = record
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{ relaxPredicate = (λ { s₁ s₂ (t₁ , t₂) s₁≼s₂ (MkBoth p q) →
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MkBoth (MonotonicPredicate.relaxPredicate P-Mono s₁ s₂ t₁ s₁≼s₂ p)
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(MonotonicPredicate.relaxPredicate Q-Mono s₁ s₂ t₂ s₁≼s₂ q)})
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}
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AndMonotonic : ∀ {T : S → Set s} {{ _ : Relaxable T }}
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{P : DependentPredicate T} {Q : DependentPredicate T}
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{{_ : MonotonicPredicate P}} {{_ : MonotonicPredicate Q}} →
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MonotonicPredicate (And P Q)
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AndMonotonic {{_}} {{P-Mono}} {{Q-Mono}} = record
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{ relaxPredicate = (λ { s₁ s₂ t s₁≼s₂ (MkAnd p q) →
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MkAnd (MonotonicPredicate.relaxPredicate P-Mono s₁ s₂ t s₁≼s₂ p)
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(MonotonicPredicate.relaxPredicate Q-Mono s₁ s₂ t s₁≼s₂ q)})
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}
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-- A MonotonicState "monad" m has a certain property if its ouputs satisfy that
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-- property for all inputs.
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always : ∀ {T : S → Set s} → DependentPredicate T → MonotonicState T → Set s
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always P m = ∀ s₁ → let (s₂ , t , _) = m s₁ in P s₂ t
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data Always {T : S → Set s} (P : DependentPredicate T) (m : MonotonicState T) : Set s where
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MkAlways : (∀ s₁ → let (s₂ , t , _) = m s₁ in P s₂ t) → Always P m
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infixr 4 _⟨⊗⟩-reason_
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_⟨⊗⟩-reason_ : ∀ {T₁ T₂ : S → Set s} {{ _ : Relaxable T₁ }}
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{P : DependentPredicate T₁} {Q : DependentPredicate T₂}
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{{P-Mono : MonotonicPredicate P}}
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{m₁ : MonotonicState T₁} {m₂ : MonotonicState T₂} →
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always P m₁ → always Q m₂ → always (Both P Q) (m₁ ⟨⊗⟩ m₂)
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_⟨⊗⟩-reason_ {{P-Mono = P-Mono}} {m₁ = m₁} {m₂ = m₂} aP aQ s
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Always P m₁ → Always Q m₂ → Always (Both P Q) (m₁ ⟨⊗⟩ m₂)
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_⟨⊗⟩-reason_ {P = P} {Q = Q} {{P-Mono = P-Mono}} {m₁ = m₁} {m₂ = m₂} (MkAlways aP) (MkAlways aQ) =
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MkAlways impl
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where
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impl : ∀ s₁ → let (s₂ , t , _) = (m₁ ⟨⊗⟩ m₂) s₁ in (Both P Q) s₂ t
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impl s
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with p ← aP s
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with (s' , (t₁ , s≼s')) ← m₁ s
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with q ← aQ s'
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with (s'' , (t₂ , s'≼s'')) ← m₂ s' =
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(MonotonicPredicate.relaxPredicate P-Mono _ _ _ s'≼s'' p , q)
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MkBoth (MonotonicPredicate.relaxPredicate P-Mono _ _ _ s'≼s'' p) q
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infixl 4 _update-reason_
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_update-reason_ : ∀ {T : S → Set s} {{ r : Relaxable T }} →
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{P : DependentPredicate T} {Q : DependentPredicate T}
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{{P-Mono : MonotonicPredicate P}}
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{m : MonotonicState T} {mod : ∀ (s : S) → T s → Σ S (λ s' → s ≼ s')} →
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always P m → (∀ (s : S) (t : T s) →
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Always P m → (∀ (s : S) (t : T s) →
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let (s' , s≼s') = mod s t
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in P s t → Q s' (Relaxable.relax r s≼s' t)) →
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always (And P Q) (m update mod)
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_update-reason_ {{r = r}} {{P-Mono = P-Mono}} {m = m} {mod = mod} aP modQ s
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Always (And P Q) (m update mod)
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_update-reason_ {{r = r}} {P = P} {Q = Q} {{P-Mono = P-Mono}} {m = m} {mod = mod} (MkAlways aP) modQ =
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MkAlways impl
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where
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impl : ∀ s₁ → let (s₂ , t , _) = (m update mod) s₁ in (And P Q) s₂ t
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impl s
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with p ← aP s
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with (s' , (t , s≼s')) ← m s
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with q ← modQ s' t p
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with (s'' , s'≼s'') ← mod s' t =
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(MonotonicPredicate.relaxPredicate P-Mono _ _ _ s'≼s'' p , q)
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MkAnd (MonotonicPredicate.relaxPredicate P-Mono _ _ _ s'≼s'' p) q
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infixl 4 _map-reason_
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_map-reason_ : ∀ {T₁ T₂ : S → Set s}
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{P : DependentPredicate T₁} {Q : DependentPredicate T₂}
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{m : MonotonicState T₁}
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{f : ∀ (s : S) → T₁ s → T₂ s} →
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always P m → (∀ (s : S) (t₁ : T₁ s) (t₂ : T₂ s) → P s t₁ → Q s t₂) →
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always Q (m map f)
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_map-reason_ {m = m} {f = f} aP P⇒Q s
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Always P m → (∀ (s : S) (t₁ : T₁ s) (t₂ : T₂ s) → P s t₁ → Q s t₂) →
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Always Q (m map f)
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_map-reason_ {P = P} {Q = Q} {m = m} {f = f} (MkAlways aP) P⇒Q =
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MkAlways impl
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where
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impl : ∀ s₁ → let (s₂ , t , _) = (m map f) s₁ in Q s₂ t
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impl s
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with p ← aP s
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with (s' , (t₁ , s≼s')) ← m s = P⇒Q s' t₁ (f s' t₁) p
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