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lem-id∘ : {Γ Δ : Con}(σ : Γ ─→ Δ) -> id ∘ σ == σ
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lem-id∘ (el < σ , pσ >) = eq \x -> ref
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lem-∘id : {Γ Δ : Con}(σ : Γ ─→ Δ) -> σ ∘ id == σ
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lem-∘id (el < σ , pσ >) = eq \x -> ref
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lem-∘assoc : {Γ Δ Θ Ξ : Con}(σ : Θ ─→ Ξ)(δ : Δ ─→ Θ)(θ : Γ ─→ Δ) ->
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(σ ∘ δ) ∘ θ == σ ∘ (δ ∘ θ)
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lem-∘assoc (el < σ , pσ >) (el < δ , pδ >) (el < θ , pθ >) = eq \x -> ref
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lem-/∘ : {Γ Δ Θ : Con}(A : Type Γ)(σ : Δ ─→ Γ)(δ : Θ ─→ Δ) ->
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A / σ ∘ δ =Ty A / σ / δ
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lem-/∘ A (el < _ , _ >) (el < _ , _ >) = eqTy \x -> refS
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lem-//id : {Γ : Con}{A : Type Γ}{u : Elem Γ A} -> u // id =El castElem lem-/id u
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lem-//id {Γ}{A}{elem (el < u , pu >)} = eqEl (eq prf)
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=== _ << u (refS << x) by pu (sym (ref<< x))
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=== _ << u (refS << x) by pfi _ _ _
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where open module C11 = Chain _==_ (ref {_}) (trans {_})
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lem-//∘ : {Γ Δ Θ : Con}{A : Type Γ}(u : Elem Γ A)(σ : Δ ─→ Γ)(δ : Θ ─→ Δ) ->
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u // σ ∘ δ =El castElem (lem-/∘ A σ δ) (u // σ // δ)
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lem-//∘ {Γ}{Δ}{Θ} (elem (el < u , pu >)) σ'@(el < σ , _ >) δ'@(el < δ , _ >) = eqEl (eq prf)
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=== _ << u (σ (δ (refS << x))) by pu (p─→ σ' (p─→ δ' (sym (ref<< x))))
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=== _ << u (σ (δ (refS << x))) by pfi _ _ _
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where open module C12 = Chain _==_ (ref {_}) (trans {_})
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lem-wk∘σ,,u : {Γ Δ : Con}{A : Type Γ}(σ : Δ ─→ Γ)(u : Elem Δ (A / σ)) ->
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lem-wk∘σ,,u (el < σ , pσ >) (elem (el < u , pu >)) = eq \x -> ref
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lem-/wk∘σ,,u : {Γ Δ : Con}(A : Type Γ)(σ : Δ ─→ Γ)(u : Elem Δ (A / σ)) ->
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A / wk / (σ ,, u) =Ty A / σ
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lem-/wk∘σ,,u A (el < σ , pσ >) (elem (el < u , pu >)) = eqTy \x -> refS
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lem-vz/σ,,u : {Γ Δ : Con}{A : Type Γ}(σ : Δ ─→ Γ)(u : Elem Δ (A / σ)) ->
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vz // (σ ,, u) =El castElem (lem-/wk∘σ,,u A σ u) u
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lem-vz/σ,,u (el < σ , pσ >) (elem (el < u , pu >)) = eqEl (eq \x -> prf x)
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prf : (x : El _) -> u x == _ << u (refS << x)
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=== _ << u (refS << x) by pu (sym (ref<< x))
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=== _ << u (refS << x) by pfi _ _ _
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where open module C15 = Chain _==_ (ref {_}) (trans {_})
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lem-σ,,u∘ : {Γ Δ Θ : Con}{A : Type Γ}
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(σ : Δ ─→ Γ)(u : Elem Δ (A / σ))(δ : Θ ─→ Δ) ->
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(σ ,, u) ∘ δ == (σ ∘ δ ,, castElem (lem-/∘ A σ δ) (u // δ))
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lem-σ,,u∘ (el < σ , _ >) (elem (el < u , pu >)) δ'@(el < δ , _ >) =
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eq \x -> eq < ref , prf x >
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prf : (x : El _) -> u (δ x) == _ << _ << u (δ (refS << x))
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=== _ << u (δ (refS << x)) by pu (p─→ δ' (sym (ref<< x)))
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=== _ << _ << u (δ (refS << x)) by sym (casttrans _ _ _ _)
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where open module C15 = Chain _==_ (ref {_}) (trans {_})
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lem-wk,,vz : {Γ : Con}{A : Type Γ} -> (wk ,, vz) == id {Γ , A}
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lem-wk,,vz {Γ}{A} = eq prf
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prf : (x : El (Γ , A)) -> _
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prf (el < x , y >) = ref
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lem-Π/ : {Γ Δ : Con}{A : Type Γ}(B : Type (Γ , A))(σ : Δ ─→ Γ) ->
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Π A B / σ =Ty Π (A / σ) (B / (σ ∘ wk ,, castElem (lem-/∘ A σ wk) vz))
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lem-Π/ B (el < σ , pσ >) =
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eqTy \x -> eqS < refS , (\y -> pFam B (eq < ref , prf x y >)) >
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postulate prf : (x : El _)(y : El _) -> y == _ << _ << _ << _ << y
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lem-β : {Γ : Con}{A : Type Γ}{B : Type (Γ , A)}
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(v : Elem (Γ , A) B)(u : Elem Γ A) ->
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(ƛ v) ∙ u =El v // [ u ]
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lem-β {Γ}{A}{B} (elem (el < v , pv >)) (elem (el < u , pu >)) = eqEl (eq \x -> prf x _ _)
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prf : (x : El Γ)(q : _ =S _)(p : _ =S _) ->
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p << v (el < x , u x >) == v (el < x , q << u (refS << x) >)
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chain> p << v (el < x , u x >)
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=== p << q0 << v (el < x , q1 << u (refS << x) >)
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by p<< p (pv (eqSnd (pu (sym (ref<< x)))))
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=== q2 << v (el < x , q1 << u (refS << x) >)
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by sym (trans<< p q0 _)
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=== q2 << q3 << v (el < x , q << u (refS << x) >)
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by p<< q2 (pv (eqSnd (pfi q1 q _)))
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=== v (el < x , q << u (refS << x) >)
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open module C17 = Chain _==_ (ref {_}) (trans {_})