20 lines
409 B
Text
20 lines
409 B
Text
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universes u
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def f {α : Type u} [BEq α] (xs : List α) (y : α) : α := do
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for x in xs do
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if x == y then
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return x
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return y
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structure S :=
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(key val : Nat)
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instance : BEq S :=
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⟨fun a b => a.key == b.key⟩
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theorem ex1 : f (α := S) [⟨1, 2⟩, ⟨3, 4⟩, ⟨5, 6⟩] ⟨3, 0⟩ = ⟨3, 4⟩ :=
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rfl
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theorem ex2 : f (α := S) [⟨1, 2⟩, ⟨3, 4⟩, ⟨5, 6⟩] ⟨4, 10⟩ = ⟨4, 10⟩ :=
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rfl
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