lean4-htt/tests/lean/run/decClassical.lean
2020-12-16 10:45:49 -08:00

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Text

open Classical
theorem ex : if (fun x => x + 1) = (fun x => x + 2) then False else True := by
have (fun x => x + 1) ≠ (fun x => x + 2) by
intro h
have 1 = 2 from congrFun h 0
exact absurd this decide!
rw ifNeg this
exact True.intro
def tst (x : Nat) : Bool :=
if 1 < 2 then true else false