28 lines
627 B
Text
28 lines
627 B
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
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import logic.classes.decidable logic.classes.inhabited
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open decidable
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namespace unit
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inductive unit : Type :=
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star : unit
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notation `⋆`:max := star
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theorem unit_eq (a b : unit) : a = b :=
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unit_rec (unit_rec (refl ⋆) b) a
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theorem unit_eq_star (a : unit) : a = star :=
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unit_eq a star
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theorem unit_inhabited [instance] : inhabited unit :=
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inhabited_mk ⋆
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theorem decidable_eq [instance] (a b : unit) : decidable (a = b) :=
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inl (unit_eq a b)
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end unit
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