definition hide ≝ λT:Type.λx:T.x.
notation < "\blacksquare" non associative with precedence 50 for @{'hide}.
-interpretation "hide" 'hide = (hide _ _).
-interpretation "hide2" 'hide = (hide _ _ _).
+interpretation "hide" 'hide = (hide ? ?).
+interpretation "hide2" 'hide = (hide ? ? ?).
definition inject ≝ λP.λa:nat.λp:P a. ex_introT ? P ? p.
coercion inject 0 1.