29 lines
728 B
Text
29 lines
728 B
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/-
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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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Module: data.unit
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Author: Leonardo de Moura
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-/
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import logic.eq logic.subsingleton
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namespace unit
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notation `⋆` := star
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protected theorem equal (a b : unit) : a = b :=
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rec_on a (rec_on b rfl)
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theorem eq_star (a : unit) : a = star :=
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equal a star
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protected theorem subsingleton [instance] : subsingleton unit :=
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subsingleton.intro (λ a b, equal a b)
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protected definition is_inhabited [instance] : inhabited unit :=
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inhabited.mk unit.star
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protected definition has_decidable_eq [instance] : decidable_eq unit :=
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take (a b : unit), decidable.inl (equal a b)
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end unit
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