lean2/tests/lean/run/tactic16.lean

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import logic data.string
using tactic
variable A : Type.{1}
variable f : A → A → A
theorem tst {a b c : A} (H1 : a = b) (H2 : b = c) : f a (f b b) = f b (f c c)
:= by discard (apply (subst H1)) 3; -- discard the first 3 solutions produced by apply
trace "after subst H1";
apply (subst H2);
apply refl