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