9 lines
303 B
Text
9 lines
303 B
Text
import standard
|
|
using tactic
|
|
|
|
theorem tst (a b : Bool) (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 ⟦ iff_intro ⟧;
|
|
⟦ assume Hb, iff_mp_right H Hb ⟧;
|
|
⟦ assume Ha, H1 Ha ⟧
|