lean2/tests/lean/run/imp_curly.lean

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import data.nat.basic
open nat
theorem zero_left (n : ) : 0 + n = n :=
nat.induction_on n
!add.zero_right
(take m IH, show 0 + succ m = succ m, from
calc
0 + succ m = succ (0 + m) : add.succ_right
... = succ m : IH)