I've put together a small package for lazifying record types. There's a "classy" version in Data.Lazify and a Generic-only version in Data.Lazify.Generic. A few examples are below. I'd love to hear comments on what looks good and what should be changed before I make the first release. As usual, names are the hardest part. Note especially that the operator ($~) is defined in *both* Data.Lazify and Data.Lazify.Generic, and that no operator corresponds to genericLazify. Hrmm mumble. lazify (1, 2) = (1, 2) lazify undefined = (_|_, _|_, _|_) lazify undefined = Sum (_|_, _|_, _|_) genericLazify (1,2) = (1,2) genericLazify undefined = (_|_, _|_, _|_) genericLazify (Sum (MyCon x y)) = ... oops, MyType isn't an instance of Lazifiable lazifyGeneric (1,2) = (1,2) lazifyGeneric undefined = (_|_, _|_, _|_) lazifyGeneric (Sum (MyCon x y)) = Sum (MyCon x y) Thanks in advance, David