anchor.diff:  # generic builder for Cabal packages
   
  -attrs :
  +{stdenv, fetchurl, lib, ghc, enableLibraryProfiling ? false, ...} :
   {
     mkDerivation =
       transform :
  
positive.code:             # default buildInputs are just ghc, if more buildInputs are required
              # buildInputs can be extended by the client by using extraBuildInputs,
              # but often propagatedBuildInputs is preferable anyway
              buildInputs = [attrs.ghc] ++ self.extraBuildInputs;
              extraBuildInputs = [];
  
              # we make sure that propagatedBuildInputs is defined, so that we don't
  
negative.code: 
              # library directories that have to be added to the Cabal files
              extraLibDirs = [];
  
              libraryProfiling =
                if enableLibraryProfiling then ["--enable-library-profiling"]
                                          else ["--disable-library-profiling"];
  
              # compiles Setup and configures
              configurePhase = ''
  