anchor.diff:      overrides = self: super:
         let guardGhcjs = p: if self.ghc.isGhcjs or false then null else p;
          in {
  +            pact = pkgs.haskell.lib.addBuildDepend super.pact pkgs.z3;
               aeson = self.callHackage "aeson" "1.1.2.0" {};
               blake2 = guardGhcjs super.blake2;
               haskeline = guardGhcjs super.haskeline;
  
positive.code: { rpRef ? "ea3c9a1536a987916502701fb6d319a880fdec96", rpSha ?  "0339ds5xa4ymc7xs8nzpa4mvm09lzscisdgpdfc6rykwhbgw9w2a" }:
  
  let rp = (import <nixpkgs> {}).fetchFromGitHub {
             owner = "mightybyte";
             repo = "reflex-platform";
             rev = rpRef;
             sha256 = rpSha;
  
negative.code:            ["result" "dist" "dist-ghcjs" ".git"]))
          ./.;
      };
      toolOverrides = ghc: super: {
        z3 = pkgs.z3;
      };
      shells = {
        ghc = ["pact"];
        # ghcjs = ["pact"];
  