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:   '';
  
    installPhase = ''
      datadir=/nix/var/lib/arb
      ensureDir $out/lib
      # link out shared location
      ensureDir $datadir/lib/pts
      chmod a+rwx $datadir/lib/pts
      # cp -vau lib/pts $datadir/lib
      rm -vrf lib/pts
      ln -vs $datadir/lib/pts $out/lib/pts
      # link out shared location
      ensureDir $datadir/lib/nas
      cp -vau lib/nas $datadir/lib
      rm -vrf lib/nas
      ln -vs $datadir/lib/nas $out/lib/nas
      # bulk copy
      cp -vau * $out
      # replace arb script
  
negative.code: #!/bin/sh
  
  echo Starting Nix compiled arb from $out
  echo Shared databases are located in $shareddir
  # sometimes local profiles override these:
  export ARBHOME=$out
  export LD_LIBRARY=$ARBHOME/lib   
  
  $out/bin/arb_ntree $*
  
  