anchor.diff:    pythonPackages = python27Packages;
   in stdenv.mkDerivation rec {
     name = "freecad-${version}";
  -  version = "0.17";
  +  version = "0.18.1";
   
     src = fetchurl {
       url = "https://github.com/FreeCAD/FreeCAD/archive/${version}.tar.gz";
  -    sha256 = "1yv6abdzlpn4wxy315943xwrnbywxqfgkjib37qwfvbb8y9p60df";
  +    sha256 = "0lamrs84zv99v4z7yi6d9amjmnh7r6frairc2aajgfic380720bc";
     };
   
     buildInputs = [ cmake coin3d xercesc ode eigen qt4 opencascade gts
  
positive.code:   postInstall = ''
      wrapProgram $out/bin/FreeCAD --prefix PYTHONPATH : $PYTHONPATH \
        --set COIN_GL_NO_CURRENT_CONTEXT_CHECK 1
  
      mkdir -p $out/share/mime/packages
      cat << EOF > $out/share/mime/packages/freecad.xml
      <?xml version="1.0" encoding="UTF-8"?>
      <mime-info xmlns='http://www.freedesktop.org/standards/shared-mime-info'>
        <mime-type type="application/x-extension-fcstd">
          <sub-class-of type="application/zip"/>
          <comment>FreeCAD Document</comment>
          <glob pattern="*.fcstd"/>
        </mime-type>
      </mime-info>
      EOF
  
      mkdir -p $out/share/applications
      cp $desktopItem/share/applications/* $out/share/applications/
      for entry in $out/share/applications/*.desktop; do
        substituteAllInPlace $entry
      done
    '';
  
    desktopItem = makeDesktopItem {
      name = "freecad";
      desktopName = "FreeCAD";
      genericName = "CAD Application";
      comment = meta.description;
      exec = "@out@/bin/FreeCAD %F";
      categories = "Science;Education;Engineering;";
      startupNotify = "true";
      mimeType = "application/x-extension-fcstd;";
      extraEntries = ''
        Path=@out@/share/freecad
      '';
    };
  
    meta = with stdenv.lib; {
      description = "General purpose Open Source 3D CAD/MCAD/CAx/CAE/PLM modeler";
      homepage = https://www.freecadweb.org/;
  
negative.code:   ] ++ (with pythonPackages; [
      matplotlib pycollada pyside pysideShiboken pysideTools pivy python boost
    ]);
  
    enableParallelBuilding = true;
  
  