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15 include "basics/logic.ma".
17 axiom boh: (False → False) = True.
19 definition J: False → False ≝ λf. match f in False with [ ].
21 definition I2: True ≝ match boh with [ refl ⇒ J ].
23 let rec err (u: True): False ≝ match u with [ I ⇒ err I2 ].
25 lemma oops: False ≝ err I.