14 lines
503 B
Text
14 lines
503 B
Text
--import data.set.basic
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open tactic
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constant union_is_assoc {α} : is_associative (set α) (∪)
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constant union_is_comm {α} : is_commutative (set α) (∪)
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attribute [instance] union_is_assoc union_is_comm
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section
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universe variable u
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variables {α : Type u}
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example (a b c d₁ d₂ e₁ e₂ : set α) (f : set α → set α → set α) : b ∪ a = d₁ ∪ d₂ → b ∪ c = e₂ ∪ e₁ → f (a ∪ b ∪ c) (a ∪ b ∪ c) = f (c ∪ d₂ ∪ d₁) (e₂ ∪ a ∪ e₁) :=
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by cc
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end
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