anchor.diff:  { stdenv
   , fetchurl
  +, lib
   }:
   
   stdenv.mkDerivation rec {
  
positive.code:     makeFlagsArray+=("prefix=$out")
    '';
  
    meta = with stdenv.lib; {
      description = "Library for asynchronous I/O in Linux";
      homepage = http://lse.sourceforge.net/io/aio.html;
      license = licenses.lgpl21;
  
negative.code: 
    src = fetchurl {
      url = "https://fedorahosted.org/releases/l/i/libaio/${name}.tar.gz";
      multihash = "QmPxxZxeCD1Dmgkbtr8DFwyBDEU7tY9E7cpP2tXVWJAedE";
      sha256 = "0zjzfkwd1kdvq6zpawhzisv7qbq1ffs343i5fs9p498pcf7046g0";
    };
  
  