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import logic
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namespace setoid
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inductive setoid : Type :=
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mk_setoid: Π (A : Type), (A → A → Prop) → setoid
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definition carrier (s : setoid)
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:= setoid.rec (λ a eq, a) s
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2014-07-22 09:43:18 -07:00
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definition eqv {s : setoid} : carrier s → carrier s → Prop
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:= setoid.rec (λ a eqv, eqv) s
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2014-10-21 15:27:45 -07:00
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infix `≈` := eqv
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2015-01-24 20:23:21 -08:00
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attribute carrier [coercion]
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inductive morphism (s1 s2 : setoid) : Type :=
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mk_morphism : Π (f : s1 → s2), (∀ x y, x ≈ y → f x ≈ f y) → morphism s1 s2
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2014-09-04 15:03:59 -07:00
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end setoid
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