anchor.diff: -{ stdenv, fetchurl, pkgconfig, autoreconfHook, openssl, db48, boost, zeromq, rapidcheck
  +{ stdenv, fetchurl, pkgconfig, autoreconfHook, openssl, db48, boost, zeromq, rapidcheck, hexdump
   , zlib, miniupnpc, qtbase ? null, qttools ? null, wrapQtAppsHook ? null, utillinux, python3, qrencode, libevent
   , withGui }:
   
  
positive.code:     homepage = http://www.bitcoin.org/;
      maintainers = with maintainers; [ roconnor AndersonTorres ];
      license = licenses.mit;
      # bitcoin needs hexdump to build, which doesn't seem to build on darwin at the moment.
      platforms = platforms.linux;
    };
  }
  
negative.code: 
    nativeBuildInputs =
      [ pkgconfig autoreconfHook ]
      ++ optional stdenv.isDarwin hexdump
      ++ optional withGui wrapQtAppsHook;
    buildInputs = [ openssl db48 boost zlib zeromq
                    miniupnpc libevent]
  