lean2/tests/lean/run/rewrite12.lean

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import data.nat
open nat algebra
variables (f : nat → nat → nat → nat) (a b c : nat)
example (H₁ : a = b) (H₂ : f b a b = 0) : f a a a = 0 :=
by rewrite [H₁ at -{2}, H₂]
example (H₁ : a = b) (H₂ : f b a b = 0) (H₃ : c = f a a a) : c = 0 :=
by rewrite [H₁ at H₃ -{2}, H₂ at H₃, H₃]