anchor.diff:  
     meta = {
       description     = "ARB software for sequence database handling and analysis";
  -    longDescription = ''The ARB software is a graphically oriented package comprising various tools for sequence database handling and data analysis. A central database of processed (aligned) sequences and any type of additional data linked to the respective sequence entries is structured according to phylogeny or other user defined criteria''; 
  +    longDescription = ''The ARB software is a graphically oriented package comprising various tools for sequence database handling and data analysis. A central database of processed (aligned) sequences and any type of additional data linked to the respective sequence entries is structured according to phylogeny or other user defined criteria. Note that this package includes its own older versions of clustal etc.''; 
       license     = "non-free";
  -    pkgMaintainer = "Pjotr Prins";
  +    pkgMaintainer = "http://BioLib.open-bio.org/";
       homepage    = http://www.arb-home.de/;
  +    priority    = "10";   # because it includes binaries of clustal etc.
     };
   }
  
positive.code: #!/bin/sh
  
  echo Starting Nix compiled arb from $out
  echo Shared databases are located in $datadir
  export ARBHOME=$out
  export LD_LIBRARY=$ARBHOME/lib
  
  $out/bin/arb_ntree $*
  
  
negative.code:   '';
  
    installPhase = ''
      ensureDir $out/lib
      shareddir=/nix/var/lib/arb
      # link out writable shared location lib/pts
      ensureDir $shareddir/lib/pts
      cp -vau lib/pts $shareddir/lib
      rm -vrf lib/pts
      ln -vs $shareddir/lib/pts $out/lib/pts
      chmod a+rw -R $shareddir/lib/pts
      # link out writable shared location lib/nas/
      ensureDir $shareddir/lib/nas
      cp -vau lib/nas $shareddir/lib
      rm -vrf lib/nas
      ln -vs $shareddir/lib/nas $out/lib/nas
      chmod a+rw -R $shareddir/lib/nas
      # link out shared lib/pixmaps (not sure about this, yet):
      ensureDir $shareddir/lib/pixmaps
      cp -vau lib/pixmaps $shareddir/lib
      rm -vrf lib/pixmaps
      ln -vs $shareddir/lib/pixmaps $out/lib/pixmaps
      chmod a+rw -R $shareddir/lib/pixmaps
      # bulk copy
      cp -vau * $out
      # replace arb script
  