26 lines
860 B
Text
26 lines
860 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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-- Authors: Leonardo de Moura, Jeremy Avigad
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import logic.core.connectives
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inductive inhabited (A : Type) : Type :=
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mk : A → inhabited A
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namespace inhabited
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definition destruct [protected] {A : Type} {B : Type} (H1 : inhabited A) (H2 : A → B) : B :=
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inhabited.rec H2 H1
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definition Prop_inhabited [instance] : inhabited Prop :=
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mk true
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definition fun_inhabited [instance] (A : Type) {B : Type} (H : inhabited B) : inhabited (A → B) :=
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destruct H (λb, mk (λa, b))
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definition dfun_inhabited [instance] (A : Type) {B : A → Type} (H : Πx, inhabited (B x)) : inhabited (Πx, B x) :=
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mk (λa, destruct (H a) (λb, b))
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definition default (A : Type) {H : inhabited A} : A := destruct H (take a, a)
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end inhabited
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