anchor.diff:    '';
   
     meta = {
  -    description = "A program for visualising graphs";
  -    homepage = http://www.graphviz.org/;
  +    homepage = "http://www.graphviz.org/";
  +    description = "open source graph visualization software"
  +
  +    longDescription = ''
  +      Graphviz is open source graph visualization software. Graph
  +      visualization is a way of representing structural information as
  +      diagrams of abstract graphs and networks. It has important
  +      applications in networking, bioinformatics, software engineering,
  +      database and web design, machine learning, and in visual
  +      interfaces for other technical domains.
  +    '';
  +
  +    platforms = stdenv.lib.platforms.linux;
  +    maintainers = [ stdenv.lib.maintainers.simons ];
     };
   }
  
positive.code: { stdenv, fetchurl, pkgconfig, libpng, libjpeg, expat, libXaw
  , yacc, libtool, fontconfig, pango, gd, xlibs
  }:
  
  stdenv.mkDerivation rec {
  
negative.code: 
    buildInputs =
      [ pkgconfig libpng libjpeg expat libXaw yacc libtool fontconfig
        pango gd gts
      ] ++ stdenv.lib.optionals (xlibs != null) [ xlibs.xlibs xlibs.libXrender ];
  
    configureFlags =
      [ "--with-pngincludedir=${libpng}/include"
        "--with-pnglibdir=${libpng}/lib"
  