9 lines
203 B
Text
9 lines
203 B
Text
import standard
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using tactic
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theorem tst (a b : Prop) (H : a ↔ b) : b ↔ a
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:= by apply iff_intro;
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apply (assume Hb, iff_elim_right H Hb);
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apply (assume Ha, iff_elim_left H Ha)
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check tst
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