anchor.diff:        inherit haskellPackages;
         inherit ihaskellExe;
         inherit ihaskellEnv;
  +      inherit ihaskellLabextension;
         inherit jupyterlab;
         inherit ihaskellGhcLibFunc;
         inherit ihaskellKernelFileFunc;
         inherit ihaskellKernelSpecFunc;
  -      inherit ihaskellLabextension;
         inherit ihaskellDataDirFunc;
         inherit ihaskellBuildEnvFunc;
       };
     };
   
     ihaskellBuildEnv = ihaskellBuildEnvFunc {
  -    inherit ihaskellEnv;
  -    inherit jupyterlab;
  -    inherit ihaskellDataDir;
  -    sysPackages = systemPackages nixpkgs;
  +    inherit ihaskellEnv jupyterlab ihaskellDataDir systemPackages;
     };
   
   in ihaskellBuildEnv
  
positive.code:   };
    ihaskellDataDir = ihaskellDataDirFunc ihaskellKernelSpec ihaskellLabextension;
  
    ihaskellBuildEnvFunc = { ihaskellEnv, jupyterlab, sysPackages, ihaskellDataDir }: nixpkgs.buildEnv {
      name = "ihaskell-with-packages";
      buildInputs = [ nixpkgs.makeWrapper ];
      paths = [ ihaskellEnv jupyterlab ];
  
negative.code:       for prg in $out/bin"/"*;do
          if [[ -f $prg && -x $prg ]]; then
            wrapProgram $prg \
              --prefix PATH : "${nixpkgs.lib.makeBinPath ([ihaskellEnv] ++ (systemPackages nixpkgs))}" \
              --prefix JUPYTER_PATH : "${ihaskellDataDir}"
          fi
        done
  