+(* unifying the type of (y ?) with (Q x) we instantiate ? to x
+axiom foo:
+ ∀P:Type.∀Q:P→Type.∀f:∀x:P.Q x→P→P.∀x:P.∀y:∀x.Q x.
+ (λw.(f w (y w) x = (id ? f) x (hole ? (y x)) x)) (hole ? x).
+*)
+
+alias num (instance 0) = "natural number".
+axiom foo: (100+111) = (100+110).
+
+
+ (id ?(id ?(id ?(id ? (100+100))))) =
+ (id ?(id ?(id ?(id ? (99+100))))).[3:
+ apply (refl_eq nat (id ?(id ?(id ?(id ? (98+102+?))))));
+
+axiom foo: (λx,y.(λz. z (x+y) + z x) (λw:nat.hole ? w)) = λx,y.x. (* OK *)