9 lines
299 B
Text
9 lines
299 B
Text
import logic
|
|
open tactic
|
|
|
|
theorem tst (a b : Prop) (H : a ↔ b) : b ↔ a
|
|
:= have H1 [fact] : 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;
|
|
apply (assume Hb, iff_elim_right H Hb);
|
|
apply (assume Ha, H1 Ha)
|