If you aren't using a boilerplate removal library, and are working with haskell-src-exts, then you are very probably doing it wrong!
Oh? Why is that?
By wrong I don't mean "incorrect results", I mean hideously ugly. Take the example of stripping out all type signatures in patterns, since you want to get rid of that extension. Without a boilerplate removal library that would take ~100 lines of code, perhaps more, and be very sensitive to which extensions your parser supported. With Uniplate I can write: import Data.Generics.Uniplate.Data removePatternSigs = transformBi f where f (PatTypeSig _ x _) = x f x = x If I didn't use Uniplate, I'd find the extra syntax extensions in HSE to be very annoying. Since I do use Uniplate, I only need to think about them when I'm working with them - so I transparently support them, and when I do need them, they're already there. I'm using Uniplate as an example since I think it's the nicest boilerplate removal library, but I'm biased, and any boilerplate removal library should be able to do similar tricks. Thanks, Neil