anchor.diff:                ${optionalString (versionOlder "7.8" ghc.version && !self.isLibrary) ''
                   configureFlags+=" --ghc-option=-j$NIX_BUILD_CORES"
                 ''}
  +              ${optionalString self.useCpphs ''
  +                configureFlags+=" --ghc-option=-pgmPcpphs --ghc-option=-optP--cpp"
  +              ''}
   
                 ${optionalString self.stdenv.isDarwin ''
                   configureFlags+=" --with-gcc=clang"
  
positive.code:             extraBuildInputs = self.buildTools ++
                                 (optionals self.doCheck self.testDepends) ++
                                 (optional self.hyperlinkSource hscolour) ++
                                 (if self.pkgconfigDepends == [] then [] else [pkgconfig]) ++
                                 (if self.isLibrary then [] else self.buildDepends ++ self.extraLibraries ++ self.pkgconfigDepends);
  
  
negative.code:             # pass the '--enable-tests' flag to cabal in the configure stage
              # and run any regression test suites the package might have
              doCheck = enableCheckPhase;
  
              # force cpphs instead of the C compiler's preprocessor; sometimes
              # needed due to clang's wacky behavior
              useCpphs = false;
  
              # pass the '--hyperlink-source' flag to ./Setup haddock
              hyperlinkSource = enableHyperlinkSource;
  