lean2/tests/lean/run/ppbeta.lean

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import data.int
open [coercions] [classes] int
open [coercions] nat
definition lt1 (a b : int) := int.le (int.add a 1) b
infix `<` := lt1
infixl `+` := int.add
theorem lt_add_succ2 (a : int) (n : nat) : a < a + nat.succ n :=
int.le.intro (show a + 1 + n = a + nat.succ n, from sorry)