import logic data.unit structure point (A : Type) (B : Type) := mk :: (x : A) (y : B) check point.eta example (p : point num num) : point.mk (point.x p) (point.y p) = p := point.eta p inductive color := red, green, blue structure color_point (A : Type) (B : Type) extends point A B := mk :: (c : color)