lean2/library/standard/data/unit.lean
2014-08-20 18:04:31 -07:00

25 lines
568 B
Text

-- Copyright (c) 2014 Microsoft Corporation. All rights reserved.
-- Released under Apache 2.0 license as described in the file LICENSE.
-- Author: Leonardo de Moura
import logic.classes.decidable logic.classes.inhabited
using decidable
namespace unit
inductive unit : Type :=
| star : unit
notation `⋆`:max := star
theorem unit_eq (a b : unit) : a = b :=
unit_rec (unit_rec (refl ⋆) b) a
theorem unit_inhabited [instance] : inhabited unit :=
inhabited_mk ⋆
theorem decidable_eq [instance] (a b : unit) : decidable (a = b) :=
inl (unit_eq a b)
end unit