anchor.diff:  , enableFfmpeg ? false, ffmpeg
   , enableGStreamer ? false, gst_all_1
   , enableEigen ? false, eigen
  -, enableCuda ? false, cudatoolkit, gcc49
  +, enableCuda ? false, cudatoolkit, gcc5
   }:
   
   let
  
positive.code:     rev = version;
      sha256 = "1l0w12czavgs0wzw1c594g358ilvfg2fn32cn8z7pv84zxj4g429";
    };
  
    preConfigure =
      let ippicvVersion = "20151201";
  
negative.code: { lib, stdenv, fetchurl, fetchpatch, fetchFromGitHub, cmake, pkgconfig, unzip
  , zlib
  , enableIpp ? false
  , enableContrib ? false
  