anchor.diff:  
   assert ncursesSupport      -> ncurses != null;
   
  -assert x11Support          -> xlibsWrapper != null;
   assert xdamageSupport      -> x11Support && libXdamage != null;
   assert imlib2Support       -> x11Support && imlib2     != null;
   assert luaSupport          -> lua != null;
  
positive.code:                             , docbook_xsl ? null , docbook_xml_dtd_44 ? null
  
  , ncursesSupport      ? true      , ncurses       ? null
  , x11Support          ? true      , xlibsWrapper           ? null
  , xdamageSupport      ? x11Support, libXdamage    ? null
  , doubleBufferSupport ? x11Support
  , imlib2Support       ? x11Support, imlib2        ? null
  
negative.code:   buildInputs = [ glib libXinerama ]
      ++ optionals docsSupport        [ docbook2x docbook_xsl docbook_xml_dtd_44 libxslt man less ]
      ++ optional  ncursesSupport     ncurses
      ++ optionals x11Support         [ freetype xorg.libICE xorg.libX11 xorg.libXext xorg.libXft xorg.libSM ]
      ++ optional  xdamageSupport     libXdamage
      ++ optional  imlib2Support      imlib2
      ++ optional  luaSupport         lua
  