lean2/tests/lean/run/tactic11.lean
2015-04-27 15:06:16 -07:00

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Text

import logic
theorem tst (a b : Prop) (H : a ↔ b) : b ↔ a
:= have H1 [visible] : a → b, -- We need to mark H1 as fact, otherwise it is not visible by tactics
from iff.elim_left H,
by apply iff.intro;
intro Hb;
apply (iff.elim_right H Hb);
intro Ha;
apply (H1 Ha)
theorem tst2 (a b : Prop) (H : a ↔ b) : b ↔ a
:= have H1 [visible] : a → b,
from iff.elim_left H,
begin
apply iff.intro,
intro Hb;
apply (iff.elim_right H Hb),
intro Ha;
apply (H1 Ha)
end