[Haskell-cafe] How to check if two Haskell files are the same?

Hi, I would like to write a Haskell pretty-printer, using standard libraries for that. How can I check if the original and the pretty-printed versions are the same? For instance, is there a file generated by GHC at the compilation pipe that is always guaranteed to have the same MD5 hash when it comes from equivalent source? Thanks, Maurício