anchor.diff:  let
     pname = "shogun";
     version = "6.1.4";
  +
     rxcppVersion = "4.0.0";
     gtestVersion = "1.8.0";
  +
     srcs = {
       toolbox = fetchFromGitHub {
         owner = pname + "-toolbox";
  
positive.code: { stdenv, lib, fetchFromGitHub, fetchpatch, fetchurl, cmake, ctags, swig
  # data, compression
  , bzip2, curl, hdf5, json_c, xz, lzo, protobuf, snappy
  # maths
  , blas, lapack, eigen, nlopt, lp_solve, colpack, glpk
  # libraries
  , libarchive, libxml2
  # extra support
  , pythonSupport ? true, pythonPackages ? null
  , opencvSupport ? false, opencv ? null
  , withSvmLight ? false
  }:
  
  
negative.code: in
  
  stdenv.mkDerivation rec {
    inherit pname version;
  
    src = srcs.toolbox;
  
    patches = [
      (fetchpatch {
  