anchor.diff:      ${builtBinary}/bin/$name
     '';
   
  +  # Overrides the lib.commitIdFromGitRepo function in nixpkgs
     commitIdFromGitRepo = import ./nix/commit-id.nix { inherit lib; };
   
     # Plucks all the cardano-sl packages from the haskellPackages set,
  
positive.code:   # applied to the given args.
    importPkgs = args: import fetchNixPkgs ({ overlays = [ (import ./nix/overlays/jemalloc.nix) ]; } // args);
  
    maybeEnv = env: default:
      let
        result = builtins.getEnv env;
  
negative.code: 
    # Generates an attrset for the three cardano-sl networks by applying
    # the given function to each environment.
    #
    # Example:
    #   forEnvironments ({ environment, confKey, ... }: "key for ${environment} is ${confKey}")
    #   => { demo = "key for demo is dev";
    #        mainnet = "key for mainnet is mainnet_full";
    #        staging = "key for staging is mainnet_dryrun_full";
    #        testnet = "key for testnet is testnet_full"; }
    forEnvironments = f: lib.mapAttrs
      (name: env: f (env // { environment = name; }))
      environments;
  
    runHaskell = name: hspkgs: deps: env: code: let
      ghc = hspkgs.ghcWithPackages deps;
  