12 lines
278 B
Text
12 lines
278 B
Text
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import standard
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hypothesis I : Type
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definition F (X : Type) : Type := (X → Prop) → Prop
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hypothesis unfold : I → F I
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hypothesis fold : F I → I
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hypothesis iso1 : ∀x, fold (unfold x) = x
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variable sorry {A : Type} : A
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theorem iso2 : ∀x, fold (unfold x) = x
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:= sorry
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