2014-07-02 21:09:01 +00:00
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import standard
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using tactic
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2014-06-30 07:51:11 +00:00
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theorem tst (a b : Bool) (H : a ↔ b) : b ↔ a
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2014-07-02 21:09:01 +00:00
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:= have H1 [fact] : a → b, -- We need to mark H1 as fact, otherwise it is not visible by tactics
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from iff_elim_left H,
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2014-07-04 17:10:05 +00:00
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by apply iff_intro;
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apply (assume Hb, iff_mp_right H Hb);
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apply (assume Ha, H1 Ha)
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