I'm pleased to announce my first genuinely original Hackage package: notcpp-0.0.1! http://hackage.haskell.org/package/notcpp This was inspired after someone submitted a patch to another of my packages, applicative-quoters, to improve behaviour on later GHC versions by using the new lookupValueName function where appropriate. The patch used CPP to determine if the package versions were such that lookupValueName would exist. But I never liked using CPP: it completely defeats haskell-src-exts and hence things like SourceGraph, and anyway it's not designed for Haskell and doesn't at all understand its structure, or fit with its syntax. With a little thought, I wondered if creative use of template haskell might not achieve the same goal. It turned out it did, and emboldened with this knowledge I set out to write a new package making this technique available to others. Along the way, a second technique occurred to me along the way that this could provide a hack fix for particularly nasty orphan instances; provide the class name, type, and method definitions, and my code detects if an instance exists. If so, it throws away your hard work and uses that; if not it synthesises (crudely, and probably inaccurately in some cases) an instance from your information and includes it in your code. One way or another, the instance will exist. I should emphasise that the way this is done is strange, and I have possibly hit a GHC bug or two, so I invite people to test, to -ddump-splices and make sure the package is behaving, and to let me know what they discover :) I'm off to fetch a GHC HEAD and see if it is any more co-operative. Ben Millwood (second attempt at sending this, since the first was from an address not subscribed the the list, whoops)