fix(library/logic/axioms/prop_decidable): fixes #704

This commit is contained in:
Leonardo de Moura 2015-06-26 19:14:36 -07:00
parent 1886b71c17
commit 97b3fd45ce
3 changed files with 8 additions and 2 deletions

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@ -8,13 +8,13 @@ Excluded middle + Hilbert implies every proposition is decidable.
import logic.axioms.prop_complete logic.axioms.hilbert data.sum
open decidable inhabited nonempty sum
theorem decidable_inhabited [instance] (a : Prop) : inhabited (decidable a) :=
theorem decidable_inhabited [instance] [priority 0] (a : Prop) : inhabited (decidable a) :=
inhabited_of_nonempty
(or.elim (em a)
(assume Ha, nonempty.intro (inl Ha))
(assume Hna, nonempty.intro (inr Hna)))
theorem prop_decidable [instance] (a : Prop) : decidable a :=
theorem prop_decidable [instance] [priority 0] (a : Prop) : decidable a :=
arbitrary (decidable a)
theorem type_decidable (A : Type) : A + (A → false) :=

4
tests/lean/704.lean Normal file
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@ -0,0 +1,4 @@
import classical
eval if true then 1 else 0
attribute prop_decidable [priority 0]
eval if true then 1 else 0

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@ -0,0 +1,2 @@
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