68 lines
3.4 KiB
Text
68 lines
3.4 KiB
Text
-- Copyright (c) 2014 Microsoft Corporation. All rights reserved.
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-- Released under Apache 2.0 license as described in the file LICENSE.
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-- Author: Leonardo de Moura, Jeremy Avigad, Floris van Doorn
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import logic.inhabited logic.cast
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open inhabited eq.ops
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structure sigma {A : Type} (B : A → Type) :=
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dpair :: (dpr1 : A) (dpr2 : B dpr1)
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notation `Σ` binders `,` r:(scoped P, sigma P) := r
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namespace sigma
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universe variables u v
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variables {A A' : Type.{u}} {B : A → Type.{v}} {B' : A' → Type.{v}}
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theorem dpair_eq {a₁ a₂ : A} {b₁ : B a₁} {b₂ : B a₂} (H₁ : a₁ = a₂) (H₂ : eq.rec_on H₁ b₁ = b₂) :
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dpair a₁ b₁ = dpair a₂ b₂ :=
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dcongr_arg2 dpair H₁ H₂
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theorem dpair_heq {a : A} {a' : A'} {b : B a} {b' : B' a'}
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(HB : B == B') (Ha : a == a') (Hb : b == b') : dpair a b == dpair a' b' :=
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hcongr_arg4 @dpair (heq.type_eq Ha) HB Ha Hb
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protected theorem equal {p₁ p₂ : Σa : A, B a} :
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∀(H₁ : dpr1 p₁ = dpr1 p₂) (H₂ : eq.rec_on H₁ (dpr2 p₁) = dpr2 p₂), p₁ = p₂ :=
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destruct p₁ (take a₁ b₁, destruct p₂ (take a₂ b₂ H₁ H₂, dpair_eq H₁ H₂))
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protected theorem hequal {p : Σa : A, B a} {p' : Σa' : A', B' a'} (HB : B == B') :
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∀(H₁ : dpr1 p == dpr1 p') (H₂ : dpr2 p == dpr2 p'), p == p' :=
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destruct p (take a₁ b₁, destruct p' (take a₂ b₂ H₁ H₂, dpair_heq HB H₁ H₂))
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protected definition is_inhabited [instance] (H₁ : inhabited A) (H₂ : inhabited (B (default A))) :
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inhabited (sigma B) :=
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inhabited.destruct H₁ (λa, inhabited.destruct H₂ (λb, inhabited.mk (dpair (default A) b)))
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theorem eq_rec_dpair_commute {C : Πa, B a → Type} {a a' : A} (H : a = a') (b : B a) (c : C a b) :
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eq.rec_on H (dpair b c) = dpair (eq.rec_on H b) (eq.rec_on (dcongr_arg2 C H rfl) c) :=
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eq.drec_on H (dpair_eq rfl (!eq.rec_on_id⁻¹))
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variables {C : Πa, B a → Type} {D : Πa b, C a b → Type}
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definition dtrip (a : A) (b : B a) (c : C a b) := dpair a (dpair b c)
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definition dquad (a : A) (b : B a) (c : C a b) (d : D a b c) := dpair a (dpair b (dpair c d))
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definition dpr1' (x : Σ a, B a) := dpr1 x
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definition dpr2' (x : Σ a b, C a b) := dpr1 (dpr2 x)
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definition dpr3 (x : Σ a b, C a b) := dpr2 (dpr2 x)
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definition dpr3' (x : Σ a b c, D a b c) := dpr1 (dpr2 (dpr2 x))
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definition dpr4 (x : Σ a b c, D a b c) := dpr2 (dpr2 (dpr2 x))
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theorem dtrip_eq {a₁ a₂ : A} {b₁ : B a₁} {b₂ : B a₂} {c₁ : C a₁ b₁} {c₂ : C a₂ b₂}
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(H₁ : a₁ = a₂) (H₂ : eq.rec_on H₁ b₁ = b₂) (H₃ : cast (dcongr_arg2 C H₁ H₂) c₁ = c₂) :
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dtrip a₁ b₁ c₁ = dtrip a₂ b₂ c₂ :=
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dcongr_arg3 dtrip H₁ H₂ H₃
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theorem ndtrip_eq {A B : Type} {C : A → B → Type} {a₁ a₂ : A} {b₁ b₂ : B}
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{c₁ : C a₁ b₁} {c₂ : C a₂ b₂} (H₁ : a₁ = a₂) (H₂ : b₁ = b₂)
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(H₃ : cast (congr_arg2 C H₁ H₂) c₁ = c₂) :
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dtrip a₁ b₁ c₁ = dtrip a₂ b₂ c₂ :=
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hdcongr_arg3 dtrip H₁ (heq.from_eq H₂) H₃
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theorem ndtrip_equal {A B : Type} {C : A → B → Type} {p₁ p₂ : Σa b, C a b} :
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∀(H₁ : dpr1 p₁ = dpr1 p₂) (H₂ : dpr2' p₁ = dpr2' p₂)
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(H₃ : eq.rec_on (congr_arg2 C H₁ H₂) (dpr3 p₁) = dpr3 p₂), p₁ = p₂ :=
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destruct p₁ (take a₁ q₁, destruct q₁ (take b₁ c₁, destruct p₂ (take a₂ q₂, destruct q₂
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(take b₂ c₂ H₁ H₂ H₃, ndtrip_eq H₁ H₂ H₃))))
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end sigma
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