anchor.diff:        containers
         extra
         filepath
  +      hakyll
         heist
         hsexif
         hspec
  
positive.code:     # personal utilities
      phocid  = haskellPackages.callPackage ~/proj/phocid {};
  
      # haskell environment
      myHaskellEnv = haskellPackages.ghcWithHoogle (p: with p; [
        cabal-install
  
negative.code:       lens
        mtl
        optparse-applicative
        pandoc
        parsec
        postgresql-simple
        process
  