anchor.diff:      rev    = "cc5cdff696aa99e1001124917c3b87b95529c4e3";
       sha256 = "13abrymry4nqyl9gmjrj8lhplbg4xag7x41n89yyw822360d3drh";
     };
  +  gtk2hs = nixpkgs.fetchFromGitHub {
  +    owner  = "gtk2hs";
  +    repo   = "gtk2hs";
  +    rev    = "f066503df2c6d8d57e06630615d2097741d09d39";
  +    sha256 = "1drqwz5ry8i9sv34kkywl5hj0p4yffbjgzb5fgpp4dzdgfxl0cqk";
  +  };
     displays = self: builtins.listToAttrs (
       map
         (display: { name = display; value = self.callCabal2nix display "${ihaskell-display-src}/${display}" {}; })
  
positive.code:           export GHC_PACKAGE_PATH=$PWD/dist/package.conf.inplace/:$GHC_PACKAGE_PATH
          '';
        });
        ghc-parser        = self.callCabal2nix "ghc-parser"     ghc-parser-src     {};
        ipython-kernel    = self.callCabal2nix "ipython-kernel" ipython-kernel-src {};
        shelly = nixpkgs.haskell.lib.doJailbreak super.shelly;
  
        plot              = self.callCabal2nix "plot"               plot             { inherit cairo pango; };
  
        Chart             = super.callHackage "Chart" "1.8.2" {};
        Chart-cairo       = super.callHackage "Chart-cairo" "1.8.2" {};
        cairo             = super.callHackage "cairo" "0.13.3.0" {};
        cubicbezier       = super.callHackage "cubicbezier" "0.6.0.4" {};
        diagrams          = super.callHackage "diagrams" "1.4" {};
        diagrams-cairo    = super.callHackage "diagrams-cairo" "1.4" {};
        diagrams-contrib  = super.callHackage "diagrams-contrib" "1.4.1" {};
        diagrams-core     = super.callHackage "diagrams-core" "1.4.0.1" {};
  
negative.code:       diagrams-svg      = super.callHackage "diagrams-svg" "1.4.1" {};
        dual-tree         = super.callHackage "dual-tree" "0.2.1" {};
        fast-math         = super.callHackage "fast-math" "1.0.2" {};
        gtk2hs-buildtools = super.callHackage "gtk2hs-buildtools" "0.13.3.0" {};
        magic             = super.callHackage "magic" "1.1" {};
        mfsolve           = super.callHackage "mfsolve" "0.3.2.0" {};
        statestack        = super.callHackage "statestack" "0.2.0.5" {};
        static-canvas     = super.callHackage "static-canvas" "0.2.0.3" {};
        svg-builder       = super.callHackage "svg-builder" "0.1.0.2" {};
  