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fix(library/data/set/equinumerosity): add missing 'using'

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Leonardo de Moura 2016-02-29 13:29:03 -08:00
parent bf60999ede
commit 79ba2638b7
1 changed files with 3 additions and 2 deletions
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library/data/set/equinumerosity.lean
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@ -111,14 +111,15 @@ open set
noncomputable definition h x := if x ∈ Union U then f x else ginv x
lemma h_maps_to : maps_to h A B :=
using f_maps_to dfltB,
take a,
suppose a ∈ A,
show h a ∈ B, from
by_cases
(suppose a ∈ Union U,
by rewrite [↑h, if_pos this]; exact f_maps_to `a ∈ A`)
begin rewrite [↑h, if_pos this], exact f_maps_to `a ∈ A` end)
(suppose a ∉ Union U,
by rewrite [↑h, if_neg this]; exact ginv_maps_to `a ∈ A`)
begin rewrite [↑h, if_neg this], exact ginv_maps_to `a ∈ A` end)
/- h is injective -/